CMS PAPER CFT-09-010

CMS Paper

2009/12/29

Performance Study of the CMS Barrel Resistive PlateChambers with Cosmic Rays

The CMS Collaboration∗

Abstract

In October and November 2008, the CMS collaboration conducted a programme ofcosmic ray data taking, which has recorded about 270 million events. The ResistivePlate Chamber system, which is part of the CMS muon detection system, was suc-cessfully operated in the full barrel. More than 98 % of the channels were operationalduring the exercise with typical detection efficiency of 90 %. In this paper, the perfor-mance of the detector during these dedicated runs is reported.

∗See Appendix A for the list of collaboration members

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1 IntroductionThe primary goal of the Compact Muon Solenoid (CMS) experiment [1] is to explore parti-cle physics at the TeV energy scale exploiting the collisions between protons delivered by theLarge Hadron Collider (LHC) [2]. The Resistive Plate Chamber (RPC) system [3] is part of themuon detection system and is used for triggering purposes. RPCs have been chosen because oftheir good time resolution (about 2 ns) and high granularity, which permit a fast and efficienttriggering of muons over large areas.

During October-November 2008, the CMS Collaboration conducted a month-long data-takingexercise known as the Cosmic Run At Four Tesla (CRAFT), with the goal of commissioning theexperiment for extended operation [4]. With all installed detector systems participating, CMSrecorded 270 million cosmic-ray-triggered events with the solenoid at a central flux density of3.8 T.

The muon system is composed of a central barrel (in the pseudo-rapidity window |η| < 1.04)and two closing endcaps (1.04 < |η| < 2.4). The RPCs participated in the CRAFT data takingwith the full barrel and half of the endcaps in operation. Part of the endcaps was not operationalbecause the readout electronics was not yet available.

For the RPC system, the CRAFT 2008 exercise has permitted the check of the full data takingchain, from the detector up to the data acquisition boards, and the confirmation of the detec-tor performance established during the quality control phase [5], also in presence of the CMSmagnetic field. The exercise was also a useful benchmark to complete the commissioning ofthe endcap part of the RPC system.

This paper is focused on the barrel RPC system performance. Sections 2 and 3 describe the RPCsystem layout, and the operation and monitoring procedures during the CRAFT exercise, re-spectively. In Section 4, the readout electronics is presented and the synchronization procedureis described. Section 5 deals with the barrel RPC performance, in terms of cluster size, positionresolution and detection efficiency.

2 RPC system layoutThe central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diame-ter. The silicon pixel and strip tracker, the crystal electromagnetic calorimeter (ECAL) and thebrass-scintillator hadronic calorimeter (HCAL) are located within the solenoidal field volume.Muons are measured in gas ionization detectors embedded in the steel return yoke. CMS usesa right-handed coordinate system, with the origin at the nominal collision point, the x-axispointing to the centre of the LHC, the y-axis pointing up (perpendicular to the LHC plane),and the z-axis along the anticlockwise-beam direction. The polar angle, θ, is measured fromthe positive z-axis, the azimuthal angle, φ, is measured in the x-y plane.

The RPC detectors are employed in CMS as a dedicated trigger system in both the barrel andin the endcap regions. They complement the muon tracking system: drift tubes (DT) [6] in thebarrel and cathode strip chambers (CSC) [7] in the endcaps.

From the geometrical point of view, the muon system is divided into five wheels in the barreland three disks in each endcap. Each barrel wheel is divided in 12 sectors, covering the fullazimuthal dimension (see Fig. 1). Each sector consists of four layers of DTs and six layers ofRPCs, with a total of 480 RPC stations of average area of 12 m2. The two innermost DT layersare sandwiched between RPC layers (RB1in and RB1out for the innermost DT layer, RB2in and

2 2 RPC system layout

RB2out for the second one). The third and fourth DT layers are complemented with a singleRPC layer, placed on their inner side (RB3 and RB4). A detailed description of the muon systemgeometry can be found in Ref. [1].

Figure 1: Transverse view of the muon system layout in the barrel region, showing the positionsof the DT and RPC stations.

Each barrel RPC station is mechanically composed of two or three adjacent RPC units, called“rolls”, making a total of 1020 rolls for the barrel RPC system. Figure 2 shows a schematiclayout of a RPC station composed by two rolls. The CMS RPC rolls are double RPC units,where each unit is composed of two bakelite electrodes, each 2 mm thick, and a 2 mm wide gasgap. Readout strips, which are oriented along the beam direction, are placed between the twoRPC units, with an independent electronic channel for each strip. The total readout system ofthe barrel RPC detector consists of 68 136 channels.

The strip location defines a point in the local reference frame of the RPC with a precision givenby the strip width, ranging from 2.3 cm, for the innermost RB1in layer, to 4.1 cm, for the RB4layer (see Table 1). The strip signals are discriminated and shaped into 100 ns digital pulses byfront-end boards with programmable discriminator thresholds.

The RPC detectors, which work in saturated avalanche mode, use a three-component, non-flammable gas mixture composed of 96.2 % C2H2F4 (R134a), 3.5 % isobutane (C4H10) and 0.3 %SF6. Water vapour is added to obtain a mixture with a relative humidity of 40–50 %, in orderto maintain a constant bakelite resistivity and, thus, avoid a degradation of RPC performanceunder high background conditions. The large volume of the total RPC system (18 m3) and theuse of a rather expensive gas mixture impose the use of a gas recirculation system. This systemconsists of the following modules: the primary supply, the mixer, the humidifier, the closed-loop circulators, the gas distributors to the chambers, the purifiers, and the pump. The purifier

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Figure 2: Schematic layout of a RPC station composed of two rolls.

system is made of a set of filters designed to remove contaminants from the gas mixture. Thesystem operates with a fraction of fresh gas mixture in the range from 10 % to 2 %. This is thefirst time that such a large RPC system is operated with a closed loop gas system.

3 Detector operation and monitoringThe effective working voltage, Veff, relevant for the charge avalanche production inside theRPC, depends on environmental parameters such as gas temperature (T) and pressure (P),according to Eq. 1 [8]

Veff = V ×P0

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TT0

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where Veff is the effective voltage, V is the applied power voltage, and P0 = 1010 mbar andT0 = 293 K are the reference pressure and temperature, respectively. Only the effective voltageis relevant when comparing detector performance in different sites and run conditions.

The CMS RPCs have been extensively tested at the production sites and their physics perfor-mance was studied [3, 5]. During 2006, a small fraction of the RPC system was calibrated andoperated [9]. In both cases, it was found that 95 % of the maximum plateau efficiency is reachedat an effective voltage of 9.6 kV, corresponding to an average applied voltage of 9.2 kV for thepressure conditions in the CMS cavern.

For the CRAFT 2008 exercise, the operating voltage was set to 9.2 kV and the electronic thresh-olds of the readout system were set to 230 mV, corresponding to an induced charge of 180 fC.These operating conditions are conservative and do not permit the detector to reach its max-imum efficiency. This approach was chosen to maintain low noise levels and safe operatingconditions, since this was the first time that the full system was operated. Following extensivepast studies [10], the working conditions were maintained within strict ranges: temperaturelower than 24 ◦C, humidity in the range 40–50 % and fraction of O2 below 300 ppm.

These parameters were monitored and controlled by the Detector Control System (DCS) [11].Their values were stored in a database and used, offline, to study the system stability.

4 3 Detector operation and monitoring

3.1 Temperature

Out of the 480 RPC stations, 310 are equipped with a temperature probe installed inside themechanical frame. Figure 3 shows in the left plot the temperature distribution of those barrelstations at the end of the CRAFT period (averaged over one day) and on the right plot itsaverage vs. time. The system temperature was maintained below 24 ◦C during the full CRAFTperiod, in order to guarantee proper RPC operation. Clear variations are observed when theelectronics of CMS is switched on or off. The steep increase seen at the start of the CRAFTexercise, when all the detectors were fully operating, is a consequence of the non optimizedcooling of the system. A special effort was dedicated to increase the cooling circuit capabilityafter the end of the CRAFT exercise. The temperature of the input cooling water has beenreduced by one degree in order to guarantee a constant stable temperature lower than 24 ◦C,as confirmed in 2009, during long cosmic rays data taking periods.

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Figure 3: RPC temperature, as measured by the probes installed inside the stations. Left side:distribution of RPC temperature taken at the end of the CRAFT period and averaged over onefull day of data taking. Right side: Average RPC temperature as a function of time. Each pointrepresents the temperature averaged over 4 hours and over all barrel stations. The increase andthe variations of the temperature are triggered by the start of the CMS electronics.

3.2 Currents

The currents drawn by the RPCs, I, are strongly affected by variations of the environmentalconditions. A sudden current increase could also indicate a malfunctioning of the detector.Therefore, a careful and continuous monitoring of the currents is performed. Each RPC stationis powered by a separate high voltage supply. The current drawn in each RPC station is readout and stored through the DCS. Figure 4 shows in the left plot the I distribution at an oper-ating voltage of 9.2 kV, for the 480 barrel stations, at the end of the CRAFT period. Only for11 stations the value of I is larger than 3 µA. During the CRAFT exercise, ten units out of 2040were disconnected because of problems with the high voltage connections, leaving the corre-sponding rolls working in single gap mode. Figure 4 right plot shows that the average currentdrawn by the stations was around 1 µA and stable in time. No correlation is observed betweenthe mean current values and the temperature variations, in the operating range.

3.3 Counting rates

The RPC noise rate is carefully monitored, since abnormal values in some parts of the detectorcan result in high fake muon trigger rates. At the beginning of each run, dedicated calibrationdata were taken and analysed to identify and mask noisy readout channels with rates above

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Figure 4: Distribution of the current drawn by the RPCs. Left plot shows the average over onefull day of data taking at the end of the CRAFT period. The plot has no overflow. Right plot:average current as a function of time. Each point is the average current over 4 hours and overall barrel stations. The operating voltage is 9.2 kV.

100 Hz/cm2. This value was chosen because it corresponds to the limit that the trigger systemcan sustain. The total number of masked and dead channels was stable during the CRAFTperiod, at about 1 % of the total number of channels in both cases.

The average noise per second and per cm2 is computed for each roll by adding the contributionsfrom all non-masked channels. The distribution of the number of rolls as a function of theaverage noise is shown in Fig. 5, for one specific run. Only 3 % of the rolls have an averagenoise rate greater than 1 Hz/cm2.

Although the average noise rate is very low, a problem related to events with correlated noiseon several layers has been detected few times per day affecting about 10−3 of the total datataking time during the CRAFT exercise. A special effort has been made to understand thesensitivity of the RPCs to external noise sources. The detector grounding has been improvedwhere possible, and further studies are in progress. Preliminary analyses have demonstratedthat the fake trigger rate is reduced by two orders of magnitude when the LHC trigger algo-rithm is used instead of the dedicated cosmic ray trigger employed during the CRAFT exercise.The LHC trigger algorithm requires more stringent constraints on the incoming muon directionand is less sensitive to the detector noise.

3.4 Gas monitoring

The mixture composition and its quality are monitored by two independent devices. The GasQuality Monitor [12, 13] performs chemical analyses (mainly gas chromatography, pH and flu-oride monitoring). The Gas Gain Monitor [14], is based on the monitoring of the performanceof three sets of 50 × 50 cm2 single gap RPCs, each supplied with a different gas mixture (freshgas, and gas from the recirculating system, before and after the purifiers).

During the CRAFT exercise, the gas system was operated continuously with a fraction of 8 %of fresh mix. The lifetime of the purifiers before regeneration was about 36 hours betweenregenerations of first stage purifier, to remove water from gas mixture humidity, and one weekbetween regenerations of second stage purifier, to remove air contamination. The full systemwas running smoothly during the operation. The downtime due to gas system stops was lessthan 1 %.

6 4 Synchronization of RPC data

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Figure 5: Example distribution of the number of rolls as a function of the average noise inthe roll, for a given data taking run. Channels exceeding 100 Hz/cm2 are masked and do notcontribute to the average noise. The operating voltage is 9.2 kV.

4 Synchronization of RPC dataMuon signals detected by the RPC chambers and transmitted by the readout electronics mustarrive in dedicated electronic boards at a specified time, in order to correctly contribute to thetrigger decisions. In addition, RPC data sent to the CMS Data Acquisition system (DAQ) andRPC trigger information must be associated to the right LHC bunch crossing (BX: 25 ns timeinterval).

The different steps of data transmission in the RPC system are described in detail in Ref. [15].After pulse discrimination in the front end boards, the data are transmitted asynchronously tothe Link Boards situated on the CMS detector, where zero-suppression is performed. The dataare then sent through optical fibres to the CMS counting room, in the underground cavern,where RPC muon trigger objects are identified, as part of the CMS Level-1 trigger system, andsent to the Global Muon Trigger. In parallel, the data are sent to the CMS DAQ system. Toensure integration with CMS, the RPC readout and trigger systems work in synchronous modeusing the CMS Timing, Trigger and Control (TTC) system [16].

The TTC signals (including clock and reference bunch crossing identification) are distributed tothe Link Boards, where the signals from the detector are synchronized with the LHC clock. Thedata are assigned to the proper bunch crossing according to a time window determined by thelength of the TTC fibres, the muon time of flight, and the signal propagation and transmissiontimes along the strips, cables and electronics.

The RPC readout [17] is designed to send data from up to 8 consecutive bunch crossings (BXs)to the DAQ system: the trigger BX plus 3 pre- and 4 post-trigger BXs. During the CRAFTexercise, only 7 BXs were transmitted to the DAQ (±3 BXs around the triggered event).

The timing setups of the system are different for the LHC beam mode and for the cosmic ray

7

runs. In beam mode the synchronization is driven by beam collisions, which are fixed in phasewith respect to the LHC clock, while in the cosmic mode this phase is arbitrary: cosmic raysarrive randomly with respect to the LHC clock. The synchronizations of the upper and lowerparts of the detector differ significantly in the two modes, due to the asymmetric phi distribu-tion of the cosmic rays.

In order to optimize the data synchronization, initial delays were estimated, based on the lengthof cables and fibres. The bottom-central part of the detector was chosen as a reference, and de-lays of data from other parts of the detector were fine-tuned to optimize the data alignmentin time. The same timing was kept for the full CRAFT period. As an illustration of the RPCsynchronization during the CRAFT exercise, Fig. 6 presents a typical example of the time dis-tribution of the data coming from individual RPCs. The time is counted with respect to thebunch crossing assigned by the RPC Level-1 global trigger logic, based on the coincidence ofat least 3 chambers along a muon trajectory. The peak in the central bin corresponds to datawhich are synchronous with the RPC Level-1 trigger. The spread to the two neighbouring binsis caused mainly by the arbitrary choice of the synchronization phase, relevant only for cosmicray runs. The spread over the other bins is due to the non-perfect synchronization of contribut-ing triggers, and to a background caused by Link Boards connected to the most noisy electronicchannels.

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Figure 6: Typical time distribution (in bunch crossing units of 25 ns) of the data coming fromindividual RPCs with respect to the RPC global trigger time. The dashed line shows the back-ground caused by the 10 over 1020 Link Boards connected to the most noisy channels.

In view of the good quality of the present data, much better synchronization is expected forLHC runs.

5 Detector performanceThe performance of the RPC system has been studied by making use of the local DT hit recon-struction [6]. The three innermost DT layers are able to locally reconstruct three dimensionalmuon track segments with up to eight hits in the rφ plane and up to four hits in the rz plane.

8 5 Detector performance

The outermost DT layer provides a segment in the rφ plane.

The extrapolation of a DT track segment onto an RPC plane allows the study of the local RPCperformance, by searching for RPC channels over threshold in a small region around the impactpoint. Previous studies [9] have shown that a range of ± 2 strips between the extrapolatedimpact point and the closest firing strip is adequate.

In addition, the CRAFT exercise led to the identification of 15 swapped readout cables out of atotal of 4720, and a few cases of RPC to DT misalignments at the level of more than 1 cm.

In the following sub-sections the results on cluster size, position resolution and detection effi-ciency are reported for the whole barrel system. The RPC cluster size and the position resolu-tion are studied separately for layers with different strip pitches. No special selection is appliedto the DT track segments used for the extrapolation, except for the requirement that no othersegment is reconstructed in the DT station. This condition is imposed to reject multiple muonevents and other possible ambiguous topologies. Moreover, only pointing segments in the rφplane have been used in these analyses. A pointing track segment in the rφ plane is defined asa segment within an angle of ± 20 degrees around the normal to the RPC layer, in the planeperpendicular to the strip direction. All the figures have been produced by analysing a run ofabout 2 million events, representative of the full CRAFT period.

5.1 Cluster size

A cluster is defined as a consecutive set of strips, each of them collecting an induced chargeabove the discrimination threshold of 180 fC. The number of strips in the cluster is called thecluster size.

The cluster size depends on the RPC strip pitch, on the impact point position with respect tothe strip, and on the track crossing angle. Figure 7 shows the cluster size distribution for theRB1in layers, for pointing muons. The different strip pitches and the average cluster sizes aregiven for all layers in Table 1. The fractions of events having cluster sizes corresponding to 1,2, 3 or more than 3 strips are shown for different layers in Fig. 8.

Table 1: Strip pitch and average cluster size, counted as the number of strips, for pointing tracksegments, with operating voltage of 9.2 kV.

RPC layer strip pitch (cm) average cluster sizeRB1in 2.3 1.52RB1out 2.5 1.46RB2in 2.8 1.41RB2out 3.0 1.38RB3 3.5 1.31RB4 4.1 1.25

The number of firing strips for a crossing muon is a function of the local impact point positionwith respect to the RPC strip. The distribution in Fig. 9 shows the deviation, ∆, measured instrip pitch units, between the impact point and the cluster centre for the RB1in layer, in a localreference frame. In this local frame the fired strip is between 0 and 1 for events with clustersize of 1, the two fired strips are between −1 and 1 for events with cluster size of 2, and thethree fired strips are between−1 and 2 for events with cluster size of 3. The three distributions,normalized to the same area, are overlayed. Events with cluster size of 1 are more frequent fortracks crossing the RPC layer close to the middle of a strip, while the fraction of events with acluster size of 2 increases for muons close to the edge between two adjacent strips.

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Figure 8: Relative population of reconstructed clusters with size equal to 1, 2, 3 and more than3 strips, for each RPC layer.

10 5 Detector performance

In addition, the cluster size depends on the muon incident angle with respect to the RPC sur-face, in the plane orthogonal to the strip direction. This is visible in Fig. 10, which presents thedependence of the average cluster size on the absolute value of the tangent of the angle α, de-fined as the angle between the muon direction and the normal to the RPC surface in the planeperpendicular to the strip direction, for the RB1in layer. This dependence is due both to theincreased path length in the crossed gas gap and to the RPC double gap structure where twoindependent avalanches develop in the two gas gaps, 6 mm apart, which may induce signalson different strips, increasing the cluster size.

It should be noted that, because of the bending of muon trajectories due to the magnetic field,low momentum muons coming from the interaction point, during LHC runs, may cross theRPC detectors with relatively large angles. Cosmic muons are very useful to study these topolo-gies since they cross the detector at all possible angles, depending on the sector.

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Figure 9: Distribution of the track impact point for the RB1in layer in a local reference frame,for events with cluster size of 1, 2 and 3, in units of strip pitch. The local frame, described bythe drawing under the plot, is defined in such a way that the fired strip is between 0 and 1 forevents with cluster size of 1, the two fired strips are between −1 and 1 for events with clustersize of 2, and the three fired strips are between −1 and 2 for events with cluster size of 3. Thethree distributions are normalized to the same unit area.

5.2 Position resolution

The centre of a cluster provides a measurement of the position of the muon track crossing point,in the rφ plane. In order to study the RPC position resolution, the cluster centre is comparedto the extrapolated point of the DT segment onto the RPC layer. The distribution of the off-setbetween the position of the track crossing point onto the surface separating the two gaps andthe cluster centre, named residual, is computed for every roll, providing an estimate of therelative DT and RPC alignment.

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Figure 10: Average cluster size as a function of the absolute value of the tangent of the angle α,defined as the angle between the track direction and the normal to the RPC surface in the planeperpendicular to the strip direction, for the RB1in layer and with an operating voltage of 9.2 kV.

Figure 11 presents the distribution of the mean value of the residuals for all barrel rolls. Therelative alignment is of a few millimetres, but two cases of a few centimetres have also been ob-served (not visible on the plot scale). The mean values extracted from the residual distributionshave been used to correct the data offline, in order to improve the position resolution.

Figure 12 shows the residual distribution in cm for the RB1in layer, after having applied thealignment corrections, for events with cluster size lower than four.

The analysis of the RPC residuals has been performed for all layers, corresponding to differentstrip pitches as reported in Table 1, and for events with different cluster sizes. The RMS valuesof the residual distribution are presented in Fig. 13, as a function of the layer, for differentcluster sizes. The trend reflects the variation of the strip pitch and the geometry of the differentRPC layers.

5.3 Detection efficiency

The most important parameter defining the RPC performance is the detection efficiency. TheDT segment extrapolation, presented at the beginning of Section 5, is used to estimate the RPCefficiency, for a full roll.

For each DT track segment extrapolated onto the RPC surface, a roll is considered efficient ifat least one RPC strip is over threshold within ± 2 strips from the extrapolated impact point.Figure 14 shows the efficiency vs. the local impact point on the RPC surface. The pattern due tothe spacers placed on a 10 × 10 cm2 grid is clearly visible. Moreover, a reduction of the overallefficiency is visible in the y coordinate (as defined in the figure) at about 55 cm, where only onegap is present.

The roll efficiency distribution is shown in Fig. 15 for a typical run, taken at the operating volt-

12 5 Detector performance

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Figure 12: Normalized distribution of the residuals in cm, for the RB1in layer (events withcluster size larger than three are not included).

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age of 9.2 kV. The peak of the distribution is about 90 %, while the tail at lower efficiency valuesis due to now known swapped cables, chambers working in single gap mode and chamberswith synchronization problems.

After the end of the CRAFT exercise many improvements have been obtained and the operatingconditions have been optimized. In 2009 the efficiency distribution was around 95 % at 9.4 kV.

6 ConclusionsData collected during the CRAFT 2008 period have been very useful for detector commission-ing. About 98 % of the electronic channels were operational during the exercise. Hardwareproblems such as swapped cables and electronic failures have been identified and fixed. Therelative position of each RPC station with respect to the DT chambers has been measured inthe rφ direction, and the position resolution of the RPC system has been determined. Softwaretools to monitor the system performance have been developed and tuned during the runningperiod. The performance of the barrel system has been measured from data. The results showa good stability of the detector and an efficiency around 90 % at the operating voltage of 9.2 kV.Many improvements have been made after the CRAFT 2008 exercise. The temperature of theinput cooling water has been reduced by one degree. Hardware failures have been fixed, theworking voltage and the electronic threshold have been optimized, and the synchronizationof the RPC barrel signals has been improved. Although more systematic studies are still inprogress, the RPC barrel system is ready for LHC beam collisions.

14 6 Conclusions

Gas gap

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every 10 cm

Figure 14: Efficiency of an RB1in roll as a function of the x and y coordinates (as defined in thefigure) of the extrapolated track impact point. The lower efficiency spots are due to the deadregions induced by spacers on a 10× 10 cm2 grid. An efficiency reduction is also visible for they coordinate at about 55 cm, where only a single gap is present.

AcknowledgementsWe thank the technical and administrative staff at CERN and other CMS Institutes, and ac-knowledge support from: FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ,and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIEN-CIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia);Academy of Finland, ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG,and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India);IPM (Iran); SFI (Ireland); INFN (Italy); NRF (Korea); LAS (Lithuania); CINVESTAV, CONA-CYT, SEP, and UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR(Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE (Russia); MSTDS (Serbia);MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAKand TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA). Individuals have receivedsupport from the Marie-Curie IEF program (European Union); the Leventis Foundation; the A.P. Sloan Foundation; and the Alexander von Humboldt Foundation.

15

Entries 1020

Mean 86.29

RMS 14.61

efficiency (%)10 20 30 40 50 60 70 80 90 100

num

ber

of r

olls

0

50

100

150

200

250Entries 1020

Mean 86.29

RMS 14.61CMS 2008

Figure 15: Efficiency distribution for barrel rolls, at an operating voltage of 9.2 kV. The tail atlower efficiency values is due to now known swapped cables, chambers working in single gapmode and chambers with synchronization problems.

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16 6 Conclusions

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17

A The CMS CollaborationYerevan Physics Institute, Yerevan, ArmeniaS. Chatrchyan, V. Khachatryan, A.M. Sirunyan

Institut fur Hochenergiephysik der OeAW, Wien, AustriaW. Adam, B. Arnold, H. Bergauer, T. Bergauer, M. Dragicevic, M. Eichberger, J. Ero, M. Friedl,R. Fruhwirth, V.M. Ghete, J. Hammer1, S. Hansel, M. Hoch, N. Hormann, J. Hrubec, M. Jeitler,G. Kasieczka, K. Kastner, M. Krammer, D. Liko, I. Magrans de Abril, I. Mikulec, F. Mittermayr,B. Neuherz, M. Oberegger, M. Padrta, M. Pernicka, H. Rohringer, S. Schmid, R. Schofbeck,T. Schreiner, R. Stark, H. Steininger, J. Strauss, A. Taurok, F. Teischinger, T. Themel, D. Uhl,P. Wagner, W. Waltenberger, G. Walzel, E. Widl, C.-E. Wulz

National Centre for Particle and High Energy Physics, Minsk, BelarusV. Chekhovsky, O. Dvornikov, I. Emeliantchik, A. Litomin, V. Makarenko, I. Marfin,V. Mossolov, N. Shumeiko, A. Solin, R. Stefanovitch, J. Suarez Gonzalez, A. Tikhonov

Research Institute for Nuclear Problems, Minsk, BelarusA. Fedorov, A. Karneyeu, M. Korzhik, V. Panov, R. Zuyeuski

Research Institute of Applied Physical Problems, Minsk, BelarusP. Kuchinsky

Universiteit Antwerpen, Antwerpen, BelgiumW. Beaumont, L. Benucci, M. Cardaci, E.A. De Wolf, E. Delmeire, D. Druzhkin, M. Hashemi,X. Janssen, T. Maes, L. Mucibello, S. Ochesanu, R. Rougny, M. Selvaggi, H. Van Haevermaet,P. Van Mechelen, N. Van Remortel

Vrije Universiteit Brussel, Brussel, BelgiumV. Adler, S. Beauceron, S. Blyweert, J. D’Hondt, S. De Weirdt, O. Devroede, J. Heyninck, A. Ka-logeropoulos, J. Maes, M. Maes, M.U. Mozer, S. Tavernier, W. Van Doninck1, P. Van Mulders,I. Villella

Universite Libre de Bruxelles, Bruxelles, BelgiumO. Bouhali, E.C. Chabert, O. Charaf, B. Clerbaux, G. De Lentdecker, V. Dero, S. Elgammal,A.P.R. Gay, G.H. Hammad, P.E. Marage, S. Rugovac, C. Vander Velde, P. Vanlaer, J. Wickens

Ghent University, Ghent, BelgiumM. Grunewald, B. Klein, A. Marinov, D. Ryckbosch, F. Thyssen, M. Tytgat, L. Vanelderen,P. Verwilligen

Universite Catholique de Louvain, Louvain-la-Neuve, BelgiumS. Basegmez, G. Bruno, J. Caudron, C. Delaere, P. Demin, D. Favart, A. Giammanco,G. Gregoire, V. Lemaitre, O. Militaru, S. Ovyn, K. Piotrzkowski1, L. Quertenmont, N. Schul

Universite de Mons, Mons, BelgiumN. Beliy, E. Daubie

Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, BrazilG.A. Alves, M.E. Pol, M.H.G. Souza

Universidade do Estado do Rio de Janeiro, Rio de Janeiro, BrazilW. Carvalho, D. De Jesus Damiao, C. De Oliveira Martins, S. Fonseca De Souza, L. Mundim,V. Oguri, A. Santoro, S.M. Silva Do Amaral, A. Sznajder

Instituto de Fisica Teorica, Universidade Estadual Paulista, Sao Paulo, Brazil

18 A The CMS Collaboration

T.R. Fernandez Perez Tomei, M.A. Ferreira Dias, E. M. Gregores2, S.F. Novaes

Institute for Nuclear Research and Nuclear Energy, Sofia, BulgariaK. Abadjiev1, T. Anguelov, J. Damgov, N. Darmenov1, L. Dimitrov, V. Genchev1, P. Iaydjiev,S. Piperov, S. Stoykova, G. Sultanov, R. Trayanov, I. Vankov

University of Sofia, Sofia, BulgariaA. Dimitrov, M. Dyulendarova, V. Kozhuharov, L. Litov, E. Marinova, M. Mateev, B. Pavlov,P. Petkov, Z. Toteva1

Institute of High Energy Physics, Beijing, ChinaG.M. Chen, H.S. Chen, W. Guan, C.H. Jiang, D. Liang, B. Liu, X. Meng, J. Tao, J. Wang, Z. Wang,Z. Xue, Z. Zhang

State Key Lab. of Nucl. Phys. and Tech., Peking University, Beijing, ChinaY. Ban, J. Cai, Y. Ge, S. Guo, Z. Hu, Y. Mao, S.J. Qian, H. Teng, B. Zhu

Universidad de Los Andes, Bogota, ColombiaC. Avila, M. Baquero Ruiz, C.A. Carrillo Montoya, A. Gomez, B. Gomez Moreno, A.A. OcampoRios, A.F. Osorio Oliveros, D. Reyes Romero, J.C. Sanabria

Technical University of Split, Split, CroatiaN. Godinovic, K. Lelas, R. Plestina, D. Polic, I. Puljak

University of Split, Split, CroatiaZ. Antunovic, M. Dzelalija

Institute Rudjer Boskovic, Zagreb, CroatiaV. Brigljevic, S. Duric, K. Kadija, S. Morovic

University of Cyprus, Nicosia, CyprusR. Fereos, M. Galanti, J. Mousa, A. Papadakis, F. Ptochos, P.A. Razis, D. Tsiakkouri, Z. Zinonos

National Institute of Chemical Physics and Biophysics, Tallinn, EstoniaA. Hektor, M. Kadastik, K. Kannike, M. Muntel, M. Raidal, L. Rebane

Helsinki Institute of Physics, Helsinki, FinlandE. Anttila, S. Czellar, J. Harkonen, A. Heikkinen, V. Karimaki, R. Kinnunen, J. Klem, M.J. Ko-rtelainen, T. Lampen, K. Lassila-Perini, S. Lehti, T. Linden, P. Luukka, T. Maenpaa, J. Nysten,E. Tuominen, J. Tuominiemi, D. Ungaro, L. Wendland

Lappeenranta University of Technology, Lappeenranta, FinlandK. Banzuzi, A. Korpela, T. Tuuva

Laboratoire d’Annecy-le-Vieux de Physique des Particules, IN2P3-CNRS, Annecy-le-Vieux,FranceP. Nedelec, D. Sillou

DSM/IRFU, CEA/Saclay, Gif-sur-Yvette, FranceM. Besancon, R. Chipaux, M. Dejardin, D. Denegri, J. Descamps, B. Fabbro, J.L. Faure, F. Ferri,S. Ganjour, F.X. Gentit, A. Givernaud, P. Gras, G. Hamel de Monchenault, P. Jarry, M.C. Lemaire,E. Locci, J. Malcles, M. Marionneau, L. Millischer, J. Rander, A. Rosowsky, D. Rousseau,M. Titov, P. Verrecchia

Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, FranceS. Baffioni, L. Bianchini, M. Bluj3, P. Busson, C. Charlot, L. Dobrzynski, R. Granier de Cas-sagnac, M. Haguenauer, P. Mine, P. Paganini, Y. Sirois, C. Thiebaux, A. Zabi

19

Institut Pluridisciplinaire Hubert Curien, Universite de Strasbourg, Universite de HauteAlsace Mulhouse, CNRS/IN2P3, Strasbourg, FranceJ.-L. Agram4, A. Besson, D. Bloch, D. Bodin, J.-M. Brom, E. Conte4, F. Drouhin4, J.-C. Fontaine4,D. Gele, U. Goerlach, L. Gross, P. Juillot, A.-C. Le Bihan, Y. Patois, J. Speck, P. Van Hove

Universite de Lyon, Universite Claude Bernard Lyon 1, CNRS-IN2P3, Institut de PhysiqueNucleaire de Lyon, Villeurbanne, FranceC. Baty, M. Bedjidian, J. Blaha, G. Boudoul, H. Brun, N. Chanon, R. Chierici, D. Contardo,P. Depasse, T. Dupasquier, H. El Mamouni, F. Fassi5, J. Fay, S. Gascon, B. Ille, T. Kurca, T. LeGrand, M. Lethuillier, N. Lumb, L. Mirabito, S. Perries, M. Vander Donckt, P. Verdier

E. Andronikashvili Institute of Physics, Academy of Science, Tbilisi, GeorgiaN. Djaoshvili, N. Roinishvili, V. Roinishvili

Institute of High Energy Physics and Informatization, Tbilisi State University, Tbilisi,GeorgiaN. Amaglobeli

RWTH Aachen University, I. Physikalisches Institut, Aachen, GermanyR. Adolphi, G. Anagnostou, R. Brauer, W. Braunschweig, M. Edelhoff, H. Esser, L. Feld,W. Karpinski, A. Khomich, K. Klein, N. Mohr, A. Ostaptchouk, D. Pandoulas, G. Pierschel,F. Raupach, S. Schael, A. Schultz von Dratzig, G. Schwering, D. Sprenger, M. Thomas, M. Weber,B. Wittmer, M. Wlochal

RWTH Aachen University, III. Physikalisches Institut A, Aachen, GermanyO. Actis, G. Altenhofer, W. Bender, P. Biallass, M. Erdmann, G. Fetchenhauer1, J. Frangenheim,T. Hebbeker, G. Hilgers, A. Hinzmann, K. Hoepfner, C. Hof, M. Kirsch, T. Klimkovich,P. Kreuzer1, D. Lanske†, M. Merschmeyer, A. Meyer, B. Philipps, H. Pieta, H. Reithler,S.A. Schmitz, L. Sonnenschein, M. Sowa, J. Steggemann, H. Szczesny, D. Teyssier, C. Zeidler

RWTH Aachen University, III. Physikalisches Institut B, Aachen, GermanyM. Bontenackels, M. Davids, M. Duda, G. Flugge, H. Geenen, M. Giffels, W. Haj Ahmad, T. Her-manns, D. Heydhausen, S. Kalinin, T. Kress, A. Linn, A. Nowack, L. Perchalla, M. Poettgens,O. Pooth, P. Sauerland, A. Stahl, D. Tornier, M.H. Zoeller

Deutsches Elektronen-Synchrotron, Hamburg, GermanyM. Aldaya Martin, U. Behrens, K. Borras, A. Campbell, E. Castro, D. Dammann, G. Eckerlin,A. Flossdorf, G. Flucke, A. Geiser, D. Hatton, J. Hauk, H. Jung, M. Kasemann, I. Katkov,C. Kleinwort, H. Kluge, A. Knutsson, E. Kuznetsova, W. Lange, W. Lohmann, R. Mankel1,M. Marienfeld, A.B. Meyer, S. Miglioranzi, J. Mnich, M. Ohlerich, J. Olzem, A. Parenti,C. Rosemann, R. Schmidt, T. Schoerner-Sadenius, D. Volyanskyy, C. Wissing, W.D. Zeuner1

University of Hamburg, Hamburg, GermanyC. Autermann, F. Bechtel, J. Draeger, D. Eckstein, U. Gebbert, K. Kaschube, G. Kaussen,R. Klanner, B. Mura, S. Naumann-Emme, F. Nowak, U. Pein, C. Sander, P. Schleper, T. Schum,H. Stadie, G. Steinbruck, J. Thomsen, R. Wolf

Institut fur Experimentelle Kernphysik, Karlsruhe, GermanyJ. Bauer, P. Blum, V. Buege, A. Cakir, T. Chwalek, W. De Boer, A. Dierlamm, G. Dirkes,M. Feindt, U. Felzmann, M. Frey, A. Furgeri, J. Gruschke, C. Hackstein, F. Hartmann1,S. Heier, M. Heinrich, H. Held, D. Hirschbuehl, K.H. Hoffmann, S. Honc, C. Jung, T. Kuhr,T. Liamsuwan, D. Martschei, S. Mueller, Th. Muller, M.B. Neuland, M. Niegel, O. Oberst,A. Oehler, J. Ott, T. Peiffer, D. Piparo, G. Quast, K. Rabbertz, F. Ratnikov, N. Ratnikova, M. Renz,C. Saout1, G. Sartisohn, A. Scheurer, P. Schieferdecker, F.-P. Schilling, G. Schott, H.J. Simonis,

20 A The CMS Collaboration

F.M. Stober, P. Sturm, D. Troendle, A. Trunov, W. Wagner, J. Wagner-Kuhr, M. Zeise, V. Zhukov6,E.B. Ziebarth

Institute of Nuclear Physics ”Demokritos”, Aghia Paraskevi, GreeceG. Daskalakis, T. Geralis, K. Karafasoulis, A. Kyriakis, D. Loukas, A. Markou, C. Markou,C. Mavrommatis, E. Petrakou, A. Zachariadou

University of Athens, Athens, GreeceL. Gouskos, P. Katsas, A. Panagiotou1

University of Ioannina, Ioannina, GreeceI. Evangelou, P. Kokkas, N. Manthos, I. Papadopoulos, V. Patras, F.A. Triantis

KFKI Research Institute for Particle and Nuclear Physics, Budapest, HungaryG. Bencze1, L. Boldizsar, G. Debreczeni, C. Hajdu1, S. Hernath, P. Hidas, D. Horvath7, K. Kra-jczar, A. Laszlo, G. Patay, F. Sikler, N. Toth, G. Vesztergombi

Institute of Nuclear Research ATOMKI, Debrecen, HungaryN. Beni, G. Christian, J. Imrek, J. Molnar, D. Novak, J. Palinkas, G. Szekely, Z. Szillasi1,K. Tokesi, V. Veszpremi

University of Debrecen, Debrecen, HungaryA. Kapusi, G. Marian, P. Raics, Z. Szabo, Z.L. Trocsanyi, B. Ujvari, G. Zilizi

Panjab University, Chandigarh, IndiaS. Bansal, H.S. Bawa, S.B. Beri, V. Bhatnagar, M. Jindal, M. Kaur, R. Kaur, J.M. Kohli,M.Z. Mehta, N. Nishu, L.K. Saini, A. Sharma, A. Singh, J.B. Singh, S.P. Singh

University of Delhi, Delhi, IndiaS. Ahuja, S. Arora, S. Bhattacharya8, S. Chauhan, B.C. Choudhary, P. Gupta, S. Jain, S. Jain,M. Jha, A. Kumar, K. Ranjan, R.K. Shivpuri, A.K. Srivastava

Bhabha Atomic Research Centre, Mumbai, IndiaR.K. Choudhury, D. Dutta, S. Kailas, S.K. Kataria, A.K. Mohanty, L.M. Pant, P. Shukla, A. Top-kar

Tata Institute of Fundamental Research - EHEP, Mumbai, IndiaT. Aziz, M. Guchait9, A. Gurtu, M. Maity10, D. Majumder, G. Majumder, K. Mazumdar,A. Nayak, A. Saha, K. Sudhakar

Tata Institute of Fundamental Research - HECR, Mumbai, IndiaS. Banerjee, S. Dugad, N.K. Mondal

Institute for Studies in Theoretical Physics & Mathematics (IPM), Tehran, IranH. Arfaei, H. Bakhshiansohi, A. Fahim, A. Jafari, M. Mohammadi Najafabadi, A. Moshaii,S. Paktinat Mehdiabadi, S. Rouhani, B. Safarzadeh, M. Zeinali

University College Dublin, Dublin, IrelandM. Felcini

INFN Sezione di Bari a, Universita di Bari b, Politecnico di Bari c, Bari, ItalyM. Abbresciaa ,b, L. Barbonea, F. Chiumaruloa, A. Clementea, A. Colaleoa, D. Creanzaa,c,G. Cuscelaa, N. De Filippisa, M. De Palmaa,b, G. De Robertisa, G. Donvitoa, F. Fedelea, L. Fiorea,M. Francoa, G. Iasellia,c, N. Lacalamitaa, F. Loddoa, L. Lusitoa,b, G. Maggia,c, M. Maggia,N. Mannaa,b, B. Marangellia ,b, S. Mya ,c, S. Natalia ,b, S. Nuzzoa,b, G. Papagnia, S. Piccolomoa,G.A. Pierroa, C. Pintoa, A. Pompilia ,b, G. Pugliesea ,c, R. Rajana, A. Ranieria, F. Romanoa,c,

21

G. Rosellia,b, G. Selvaggia ,b, Y. Shindea, L. Silvestrisa, S. Tupputia ,b, G. Zitoa

INFN Sezione di Bologna a, Universita di Bologna b, Bologna, ItalyG. Abbiendia, W. Bacchia ,b, A.C. Benvenutia, M. Boldinia, D. Bonacorsia, S. Braibant-Giacomellia,b, V.D. Cafaroa, S.S. Caiazzaa, P. Capiluppia,b, A. Castroa ,b, F.R. Cavalloa,G. Codispotia,b, M. Cuffiania,b, I. D’Antonea, G.M. Dallavallea,1, F. Fabbria, A. Fanfania ,b,D. Fasanellaa, P. Giacomellia, V. Giordanoa, M. Giuntaa ,1, C. Grandia, M. Guerzonia,S. Marcellinia, G. Masettia,b, A. Montanaria, F.L. Navarriaa,b, F. Odoricia, G. Pellegrinia,A. Perrottaa, A.M. Rossia,b, T. Rovellia ,b, G. Sirolia ,b, G. Torromeoa, R. Travaglinia ,b

INFN Sezione di Catania a, Universita di Catania b, Catania, ItalyS. Albergoa,b, S. Costaa,b, R. Potenzaa,b, A. Tricomia,b, C. Tuvea

INFN Sezione di Firenze a, Universita di Firenze b, Firenze, ItalyG. Barbaglia, G. Broccoloa,b, V. Ciullia ,b, C. Civininia, R. D’Alessandroa ,b, E. Focardia ,b,S. Frosalia,b, E. Galloa, C. Gentaa,b, G. Landia ,b, P. Lenzia,b ,1, M. Meschinia, S. Paolettia,G. Sguazzonia, A. Tropianoa

INFN Laboratori Nazionali di Frascati, Frascati, ItalyL. Benussi, M. Bertani, S. Bianco, S. Colafranceschi11, D. Colonna11, F. Fabbri, M. Giardoni,L. Passamonti, D. Piccolo, D. Pierluigi, B. Ponzio, A. Russo

INFN Sezione di Genova, Genova, ItalyP. Fabbricatore, R. Musenich

INFN Sezione di Milano-Biccoca a, Universita di Milano-Bicocca b, Milano, ItalyA. Benagliaa, M. Callonia, G.B. Ceratia ,b ,1, P. D’Angeloa, F. De Guioa, F.M. Farinaa, A. Ghezzia,P. Govonia,b, M. Malbertia,b ,1, S. Malvezzia, A. Martellia, D. Menascea, V. Miccioa,b, L. Moronia,P. Negria,b, M. Paganonia ,b, D. Pedrinia, A. Pulliaa ,b, S. Ragazzia ,b, N. Redaellia, S. Salaa,R. Salernoa,b, T. Tabarelli de Fatisa ,b, V. Tancinia,b, S. Taronia ,b

INFN Sezione di Napoli a, Universita di Napoli ”Federico II” b, Napoli, ItalyS. Buontempoa, N. Cavalloa, A. Cimminoa ,b ,1, M. De Gruttolaa,b ,1, F. Fabozzia,12, A.O.M. Iorioa,L. Listaa, D. Lomidzea, P. Nolia ,b, P. Paoluccia, C. Sciaccaa,b

INFN Sezione di Padova a, Universita di Padova b, Padova, ItalyP. Azzia,1, N. Bacchettaa, L. Barcellana, P. Bellana ,b ,1, M. Bellatoa, M. Benettonia, M. Biasottoa ,13,D. Biselloa,b, E. Borsatoa ,b, A. Brancaa, R. Carlina ,b, L. Castellania, P. Checchiaa, E. Contia,F. Dal Corsoa, M. De Mattiaa,b, T. Dorigoa, U. Dossellia, F. Fanzagoa, F. Gasparinia ,b,U. Gasparinia,b, P. Giubilatoa,b, F. Gonellaa, A. Greselea,14, M. Gulminia ,13, A. Kaminskiya ,b,S. Lacapraraa ,13, I. Lazzizzeraa ,14, M. Margonia ,b, G. Marona ,13, S. Mattiazzoa,b, M. Mazzucatoa,M. Meneghellia, A.T. Meneguzzoa,b, M. Michelottoa, F. Montecassianoa, M. Nespoloa,M. Passaseoa, M. Pegoraroa, L. Perrozzia, N. Pozzobona ,b, P. Ronchesea,b, F. Simonettoa,b,N. Tonioloa, E. Torassaa, M. Tosia ,b, A. Triossia, S. Vaninia ,b, S. Venturaa, P. Zottoa,b,G. Zumerlea,b

INFN Sezione di Pavia a, Universita di Pavia b, Pavia, ItalyP. Baessoa,b, U. Berzanoa, S. Bricolaa, M.M. Necchia ,b, D. Paganoa,b, S.P. Rattia,b, C. Riccardia,b,P. Torrea ,b, A. Vicinia, P. Vituloa,b, C. Viviania,b

INFN Sezione di Perugia a, Universita di Perugia b, Perugia, ItalyD. Aisaa, S. Aisaa, E. Babuccia, M. Biasinia,b, G.M. Bileia, B. Caponeria,b, B. Checcuccia, N. Dinua,L. Fanoa, L. Farnesinia, P. Laricciaa,b, A. Lucaronia,b, G. Mantovania ,b, A. Nappia,b, A. Pilusoa,V. Postolachea, A. Santocchiaa,b, L. Servolia, D. Tonoiua, A. Vedaeea, R. Volpea ,b

22 A The CMS Collaboration

INFN Sezione di Pisa a, Universita di Pisa b, Scuola Normale Superiore di Pisa c, Pisa, ItalyP. Azzurria ,c, G. Bagliesia, J. Bernardinia,b, L. Berrettaa, T. Boccalia, A. Boccia ,c, L. Borrelloa,c,F. Bosia, F. Calzolaria, R. Castaldia, R. Dell’Orsoa, F. Fioria,b, L. Foaa ,c, S. Gennaia,c, A. Giassia,A. Kraana, F. Ligabuea ,c, T. Lomtadzea, F. Mariania, L. Martinia, M. Massaa, A. Messineoa ,b,A. Moggia, F. Pallaa, F. Palmonaria, G. Petragnania, G. Petrucciania ,c, F. Raffaellia, S. Sarkara,G. Segneria, A.T. Serbana, P. Spagnoloa ,1, R. Tenchinia ,1, S. Tolainia, G. Tonellia,b ,1, A. Venturia,P.G. Verdinia

INFN Sezione di Roma a, Universita di Roma ”La Sapienza” b, Roma, ItalyS. Baccaroa ,15, L. Baronea,b, A. Bartolonia, F. Cavallaria ,1, I. Dafineia, D. Del Rea ,b, E. DiMarcoa ,b, M. Diemoza, D. Francia,b, E. Longoa,b, G. Organtinia ,b, A. Palmaa ,b, F. Pandolfia ,b,R. Paramattia,1, F. Pellegrinoa, S. Rahatloua ,b, C. Rovellia

INFN Sezione di Torino a, Universita di Torino b, Universita del Piemonte Orientale (No-vara) c, Torino, ItalyG. Alampia, N. Amapanea ,b, R. Arcidiaconoa,b, S. Argiroa,b, M. Arneodoa ,c, C. Biinoa,M.A. Borgiaa,b, C. Bottaa,b, N. Cartigliaa, R. Castelloa ,b, G. Cerminaraa,b, M. Costaa ,b,D. Dattolaa, G. Dellacasaa, N. Demariaa, G. Dugheraa, F. Dumitrachea, A. Grazianoa ,b,C. Mariottia, M. Maronea,b, S. Masellia, E. Migliorea,b, G. Milaa ,b, V. Monacoa ,b, M. Musicha ,b,M. Nervoa ,b, M.M. Obertinoa ,c, S. Oggeroa,b, R. Paneroa, N. Pastronea, M. Pelliccionia ,b,A. Romeroa,b, M. Ruspaa,c, R. Sacchia,b, A. Solanoa,b, A. Staianoa, P.P. Trapania ,b ,1, D. Trocinoa ,b,A. Vilela Pereiraa,b, L. Viscaa,b, A. Zampieria

INFN Sezione di Trieste a, Universita di Trieste b, Trieste, ItalyF. Ambroglinia ,b, S. Belfortea, F. Cossuttia, G. Della Riccaa,b, B. Gobboa, A. Penzoa

Kyungpook National University, Daegu, KoreaS. Chang, J. Chung, D.H. Kim, G.N. Kim, D.J. Kong, H. Park, D.C. Son

Wonkwang University, Iksan, KoreaS.Y. Bahk

Chonnam National University, Kwangju, KoreaS. Song

Konkuk University, Seoul, KoreaS.Y. Jung

Korea University, Seoul, KoreaB. Hong, H. Kim, J.H. Kim, K.S. Lee, D.H. Moon, S.K. Park, H.B. Rhee, K.S. Sim

Seoul National University, Seoul, KoreaJ. Kim

University of Seoul, Seoul, KoreaM. Choi, G. Hahn, I.C. Park

Sungkyunkwan University, Suwon, KoreaS. Choi, Y. Choi, J. Goh, H. Jeong, T.J. Kim, J. Lee, S. Lee

Vilnius University, Vilnius, LithuaniaM. Janulis, D. Martisiute, P. Petrov, T. Sabonis

Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, MexicoH. Castilla Valdez1, A. Sanchez Hernandez

23

Universidad Iberoamericana, Mexico City, MexicoS. Carrillo Moreno

Universidad Autonoma de San Luis Potosı, San Luis Potosı, MexicoA. Morelos Pineda

University of Auckland, Auckland, New ZealandP. Allfrey, R.N.C. Gray, D. Krofcheck

University of Canterbury, Christchurch, New ZealandN. Bernardino Rodrigues, P.H. Butler, T. Signal, J.C. Williams

National Centre for Physics, Quaid-I-Azam University, Islamabad, PakistanM. Ahmad, I. Ahmed, W. Ahmed, M.I. Asghar, M.I.M. Awan, H.R. Hoorani, I. Hussain,W.A. Khan, T. Khurshid, S. Muhammad, S. Qazi, H. Shahzad

Institute of Experimental Physics, Warsaw, PolandM. Cwiok, R. Dabrowski, W. Dominik, K. Doroba, M. Konecki, J. Krolikowski, K. Pozniak16,R. Romaniuk, W. Zabolotny16, P. Zych

Soltan Institute for Nuclear Studies, Warsaw, PolandT. Frueboes, R. Gokieli, L. Goscilo, M. Gorski, M. Kazana, K. Nawrocki, M. Szleper, G. Wrochna,P. Zalewski

Laboratorio de Instrumentacao e Fısica Experimental de Partıculas, Lisboa, PortugalN. Almeida, L. Antunes Pedro, P. Bargassa, A. David, P. Faccioli, P.G. Ferreira Parracho,M. Freitas Ferreira, M. Gallinaro, M. Guerra Jordao, P. Martins, G. Mini, P. Musella, J. Pela,L. Raposo, P.Q. Ribeiro, S. Sampaio, J. Seixas, J. Silva, P. Silva, D. Soares, M. Sousa, J. Varela,H.K. Wohri

Joint Institute for Nuclear Research, Dubna, RussiaI. Altsybeev, I. Belotelov, P. Bunin, Y. Ershov, I. Filozova, M. Finger, M. Finger Jr., A. Golunov,I. Golutvin, N. Gorbounov, V. Kalagin, A. Kamenev, V. Karjavin, V. Konoplyanikov, V. Ko-renkov, G. Kozlov, A. Kurenkov, A. Lanev, A. Makankin, V.V. Mitsyn, P. Moisenz, E. Nikonov,D. Oleynik, V. Palichik, V. Perelygin, A. Petrosyan, R. Semenov, S. Shmatov, V. Smirnov,D. Smolin, E. Tikhonenko, S. Vasil’ev, A. Vishnevskiy, A. Volodko, A. Zarubin, V. Zhiltsov

Petersburg Nuclear Physics Institute, Gatchina (St Petersburg), RussiaN. Bondar, L. Chtchipounov, A. Denisov, Y. Gavrikov, G. Gavrilov, V. Golovtsov, Y. Ivanov,V. Kim, V. Kozlov, P. Levchenko, G. Obrant, E. Orishchin, A. Petrunin, Y. Shcheglov, A. Shchet-kovskiy, V. Sknar, I. Smirnov, V. Sulimov, V. Tarakanov, L. Uvarov, S. Vavilov, G. Velichko,S. Volkov, A. Vorobyev

Institute for Nuclear Research, Moscow, RussiaYu. Andreev, A. Anisimov, P. Antipov, A. Dermenev, S. Gninenko, N. Golubev, M. Kirsanov,N. Krasnikov, V. Matveev, A. Pashenkov, V.E. Postoev, A. Solovey, A. Solovey, A. Toropin,S. Troitsky

Institute for Theoretical and Experimental Physics, Moscow, RussiaA. Baud, V. Epshteyn, V. Gavrilov, N. Ilina, V. Kaftanov†, V. Kolosov, M. Kossov1, A. Krokhotin,S. Kuleshov, A. Oulianov, G. Safronov, S. Semenov, I. Shreyber, V. Stolin, E. Vlasov, A. Zhokin

Moscow State University, Moscow, RussiaE. Boos, M. Dubinin17, L. Dudko, A. Ershov, A. Gribushin, V. Klyukhin, O. Kodolova, I. Lokhtin,S. Petrushanko, L. Sarycheva, V. Savrin, A. Snigirev, I. Vardanyan

24 A The CMS Collaboration

P.N. Lebedev Physical Institute, Moscow, RussiaI. Dremin, M. Kirakosyan, N. Konovalova, S.V. Rusakov, A. Vinogradov

State Research Center of Russian Federation, Institute for High Energy Physics, Protvino,RussiaS. Akimenko, A. Artamonov, I. Azhgirey, S. Bitioukov, V. Burtovoy, V. Grishin1, V. Kachanov,D. Konstantinov, V. Krychkine, A. Levine, I. Lobov, V. Lukanin, Y. Mel’nik, V. Petrov, R. Ryutin,S. Slabospitsky, A. Sobol, A. Sytine, L. Tourtchanovitch, S. Troshin, N. Tyurin, A. Uzunian,A. Volkov

Vinca Institute of Nuclear Sciences, Belgrade, SerbiaP. Adzic, M. Djordjevic, D. Jovanovic18, D. Krpic18, D. Maletic, J. Puzovic18, N. Smiljkovic

Centro de Investigaciones Energeticas Medioambientales y Tecnologicas (CIEMAT),Madrid, SpainM. Aguilar-Benitez, J. Alberdi, J. Alcaraz Maestre, P. Arce, J.M. Barcala, C. Battilana, C. BurgosLazaro, J. Caballero Bejar, E. Calvo, M. Cardenas Montes, M. Cepeda, M. Cerrada, M. ChamizoLlatas, F. Clemente, N. Colino, M. Daniel, B. De La Cruz, A. Delgado Peris, C. Diez Pardos,C. Fernandez Bedoya, J.P. Fernandez Ramos, A. Ferrando, J. Flix, M.C. Fouz, P. Garcia-Abia,A.C. Garcia-Bonilla, O. Gonzalez Lopez, S. Goy Lopez, J.M. Hernandez, M.I. Josa, J. Marin,G. Merino, J. Molina, A. Molinero, J.J. Navarrete, J.C. Oller, J. Puerta Pelayo, L. Romero,J. Santaolalla, C. Villanueva Munoz, C. Willmott, C. Yuste

Universidad Autonoma de Madrid, Madrid, SpainC. Albajar, M. Blanco Otano, J.F. de Troconiz, A. Garcia Raboso, J.O. Lopez Berengueres

Universidad de Oviedo, Oviedo, SpainJ. Cuevas, J. Fernandez Menendez, I. Gonzalez Caballero, L. Lloret Iglesias, H. Naves Sordo,J.M. Vizan Garcia

Instituto de Fısica de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander, SpainI.J. Cabrillo, A. Calderon, S.H. Chuang, I. Diaz Merino, C. Diez Gonzalez, J. Duarte Campder-ros, M. Fernandez, G. Gomez, J. Gonzalez Sanchez, R. Gonzalez Suarez, C. Jorda, P. LobellePardo, A. Lopez Virto, J. Marco, R. Marco, C. Martinez Rivero, P. Martinez Ruiz del Arbol,F. Matorras, T. Rodrigo, A. Ruiz Jimeno, L. Scodellaro, M. Sobron Sanudo, I. Vila, R. VilarCortabitarte

CERN, European Organization for Nuclear Research, Geneva, SwitzerlandD. Abbaneo, E. Albert, M. Alidra, S. Ashby, E. Auffray, J. Baechler, P. Baillon, A.H. Ball,S.L. Bally, D. Barney, F. Beaudette19, R. Bellan, D. Benedetti, G. Benelli, C. Bernet, P. Bloch,S. Bolognesi, M. Bona, J. Bos, N. Bourgeois, T. Bourrel, H. Breuker, K. Bunkowski, D. Campi,T. Camporesi, E. Cano, A. Cattai, J.P. Chatelain, M. Chauvey, T. Christiansen, J.A. CoarasaPerez, A. Conde Garcia, R. Covarelli, B. Cure, A. De Roeck, V. Delachenal, D. Deyrail, S. DiVincenzo20, S. Dos Santos, T. Dupont, L.M. Edera, A. Elliott-Peisert, M. Eppard, M. Favre,N. Frank, W. Funk, A. Gaddi, M. Gastal, M. Gateau, H. Gerwig, D. Gigi, K. Gill, D. Giordano,J.P. Girod, F. Glege, R. Gomez-Reino Garrido, R. Goudard, S. Gowdy, R. Guida, L. Guiducci,J. Gutleber, M. Hansen, C. Hartl, J. Harvey, B. Hegner, H.F. Hoffmann, A. Holzner, A. Honma,M. Huhtinen, V. Innocente, P. Janot, G. Le Godec, P. Lecoq, C. Leonidopoulos, R. Loos,C. Lourenco, A. Lyonnet, A. Macpherson, N. Magini, J.D. Maillefaud, G. Maire, T. Maki,L. Malgeri, M. Mannelli, L. Masetti, F. Meijers, P. Meridiani, S. Mersi, E. Meschi, A. MeynetCordonnier, R. Moser, M. Mulders, J. Mulon, M. Noy, A. Oh, G. Olesen, A. Onnela, T. Orimoto,L. Orsini, E. Perez, G. Perinic, J.F. Pernot, P. Petagna, P. Petiot, A. Petrilli, A. Pfeiffer, M. Pierini,M. Pimia, R. Pintus, B. Pirollet, H. Postema, A. Racz, S. Ravat, S.B. Rew, J. Rodrigues Antunes,

25

G. Rolandi21, M. Rovere, V. Ryjov, H. Sakulin, D. Samyn, H. Sauce, C. Schafer, W.D. Schlatter,M. Schroder, C. Schwick, A. Sciaba, I. Segoni, A. Sharma, N. Siegrist, P. Siegrist, N. Sinanis,T. Sobrier, P. Sphicas22, D. Spiga, M. Spiropulu17, F. Stockli, P. Traczyk, P. Tropea, J. Troska,A. Tsirou, L. Veillet, G.I. Veres, M. Voutilainen, P. Wertelaers, M. Zanetti

Paul Scherrer Institut, Villigen, SwitzerlandW. Bertl, K. Deiters, W. Erdmann, K. Gabathuler, R. Horisberger, Q. Ingram, H.C. Kaestli,S. Konig, D. Kotlinski, U. Langenegger, F. Meier, D. Renker, T. Rohe, J. Sibille23,A. Starodumov24

Institute for Particle Physics, ETH Zurich, Zurich, SwitzerlandB. Betev, L. Caminada25, Z. Chen, S. Cittolin, D.R. Da Silva Di Calafiori, S. Dambach25,G. Dissertori, M. Dittmar, C. Eggel25, J. Eugster, G. Faber, K. Freudenreich, C. Grab, A. Herve,W. Hintz, P. Lecomte, P.D. Luckey, W. Lustermann, C. Marchica25, P. Milenovic26, F. Moort-gat, A. Nardulli, F. Nessi-Tedaldi, L. Pape, F. Pauss, T. Punz, A. Rizzi, F.J. Ronga, L. Sala,A.K. Sanchez, M.-C. Sawley, V. Sordini, B. Stieger, L. Tauscher†, A. Thea, K. Theofilatos,D. Treille, P. Trub25, M. Weber, L. Wehrli, J. Weng, S. Zelepoukine27

Universitat Zurich, Zurich, SwitzerlandC. Amsler, V. Chiochia, S. De Visscher, C. Regenfus, P. Robmann, T. Rommerskirchen,A. Schmidt, D. Tsirigkas, L. Wilke

National Central University, Chung-Li, TaiwanY.H. Chang, E.A. Chen, W.T. Chen, A. Go, C.M. Kuo, S.W. Li, W. Lin

National Taiwan University (NTU), Taipei, TaiwanP. Bartalini, P. Chang, Y. Chao, K.F. Chen, W.-S. Hou, Y. Hsiung, Y.J. Lei, S.W. Lin, R.-S. Lu,J. Schumann, J.G. Shiu, Y.M. Tzeng, K. Ueno, Y. Velikzhanin, C.C. Wang, M. Wang

Cukurova University, Adana, TurkeyA. Adiguzel, A. Ayhan, A. Azman Gokce, M.N. Bakirci, S. Cerci, I. Dumanoglu, E. Eskut,S. Girgis, E. Gurpinar, I. Hos, T. Karaman, T. Karaman, A. Kayis Topaksu, P. Kurt, G. Onengut,G. Onengut Gokbulut, K. Ozdemir, S. Ozturk, A. Polatoz, K. Sogut28, B. Tali, H. Topakli,D. Uzun, L.N. Vergili, M. Vergili

Middle East Technical University, Physics Department, Ankara, TurkeyI.V. Akin, T. Aliev, S. Bilmis, M. Deniz, H. Gamsizkan, A.M. Guler, K. Ocalan, M. Serin, R. Sever,U.E. Surat, M. Zeyrek

Bogazici University, Department of Physics, Istanbul, TurkeyM. Deliomeroglu, D. Demir29, E. Gulmez, A. Halu, B. Isildak, M. Kaya30, O. Kaya30, S. Ozkoru-cuklu31, N. Sonmez32

National Scientific Center, Kharkov Institute of Physics and Technology, Kharkov, UkraineL. Levchuk, S. Lukyanenko, D. Soroka, S. Zub

University of Bristol, Bristol, United KingdomF. Bostock, J.J. Brooke, T.L. Cheng, D. Cussans, R. Frazier, J. Goldstein, N. Grant,M. Hansen, G.P. Heath, H.F. Heath, C. Hill, B. Huckvale, J. Jackson, C.K. Mackay, S. Metson,D.M. Newbold33, K. Nirunpong, V.J. Smith, J. Velthuis, R. Walton

Rutherford Appleton Laboratory, Didcot, United KingdomK.W. Bell, C. Brew, R.M. Brown, B. Camanzi, D.J.A. Cockerill, J.A. Coughlan, N.I. Geddes,K. Harder, S. Harper, B.W. Kennedy, P. Murray, C.H. Shepherd-Themistocleous, I.R. Tomalin,J.H. Williams†, W.J. Womersley, S.D. Worm

26 A The CMS Collaboration

Imperial College, University of London, London, United KingdomR. Bainbridge, G. Ball, J. Ballin, R. Beuselinck, O. Buchmuller, D. Colling, N. Cripps, G. Davies,M. Della Negra, C. Foudas, J. Fulcher, D. Futyan, G. Hall, J. Hays, G. Iles, G. Karapos-toli, B.C. MacEvoy, A.-M. Magnan, J. Marrouche, J. Nash, A. Nikitenko24, A. Papageorgiou,M. Pesaresi, K. Petridis, M. Pioppi34, D.M. Raymond, N. Rompotis, A. Rose, M.J. Ryan,C. Seez, P. Sharp, G. Sidiropoulos1, M. Stettler, M. Stoye, M. Takahashi, A. Tapper, C. Timlin,S. Tourneur, M. Vazquez Acosta, T. Virdee1, S. Wakefield, D. Wardrope, T. Whyntie, M. Wing-ham

Brunel University, Uxbridge, United KingdomJ.E. Cole, I. Goitom, P.R. Hobson, A. Khan, P. Kyberd, D. Leslie, C. Munro, I.D. Reid,C. Siamitros, R. Taylor, L. Teodorescu, I. Yaselli

Boston University, Boston, USAT. Bose, M. Carleton, E. Hazen, A.H. Heering, A. Heister, J. St. John, P. Lawson, D. Lazic,D. Osborne, J. Rohlf, L. Sulak, S. Wu

Brown University, Providence, USAJ. Andrea, A. Avetisyan, S. Bhattacharya, J.P. Chou, D. Cutts, S. Esen, G. Kukartsev, G. Lands-berg, M. Narain, D. Nguyen, T. Speer, K.V. Tsang

University of California, Davis, Davis, USAR. Breedon, M. Calderon De La Barca Sanchez, M. Case, D. Cebra, M. Chertok, J. Conway,P.T. Cox, J. Dolen, R. Erbacher, E. Friis, W. Ko, A. Kopecky, R. Lander, A. Lister, H. Liu,S. Maruyama, T. Miceli, M. Nikolic, D. Pellett, J. Robles, M. Searle, J. Smith, M. Squires, J. Stilley,M. Tripathi, R. Vasquez Sierra, C. Veelken

University of California, Los Angeles, Los Angeles, USAV. Andreev, K. Arisaka, D. Cline, R. Cousins, S. Erhan1, J. Hauser, M. Ignatenko, C. Jarvis,J. Mumford, C. Plager, G. Rakness, P. Schlein†, J. Tucker, V. Valuev, R. Wallny, X. Yang

University of California, Riverside, Riverside, USAJ. Babb, M. Bose, A. Chandra, R. Clare, J.A. Ellison, J.W. Gary, G. Hanson, G.Y. Jeng, S.C. Kao,F. Liu, H. Liu, A. Luthra, H. Nguyen, G. Pasztor35, A. Satpathy, B.C. Shen†, R. Stringer, J. Sturdy,V. Sytnik, R. Wilken, S. Wimpenny

University of California, San Diego, La Jolla, USAJ.G. Branson, E. Dusinberre, D. Evans, F. Golf, R. Kelley, M. Lebourgeois, J. Letts, E. Lipeles,B. Mangano, J. Muelmenstaedt, M. Norman, S. Padhi, A. Petrucci, H. Pi, M. Pieri, R. Ranieri,M. Sani, V. Sharma, S. Simon, F. Wurthwein, A. Yagil

University of California, Santa Barbara, Santa Barbara, USAC. Campagnari, M. D’Alfonso, T. Danielson, J. Garberson, J. Incandela, C. Justus, P. Kalavase,S.A. Koay, D. Kovalskyi, V. Krutelyov, J. Lamb, S. Lowette, V. Pavlunin, F. Rebassoo, J. Ribnik,J. Richman, R. Rossin, D. Stuart, W. To, J.R. Vlimant, M. Witherell

California Institute of Technology, Pasadena, USAA. Apresyan, A. Bornheim, J. Bunn, M. Chiorboli, M. Gataullin, D. Kcira, V. Litvine, Y. Ma,H.B. Newman, C. Rogan, V. Timciuc, J. Veverka, R. Wilkinson, Y. Yang, L. Zhang, K. Zhu,R.Y. Zhu

Carnegie Mellon University, Pittsburgh, USAB. Akgun, R. Carroll, T. Ferguson, D.W. Jang, S.Y. Jun, M. Paulini, J. Russ, N. Terentyev,H. Vogel, I. Vorobiev

27

University of Colorado at Boulder, Boulder, USAJ.P. Cumalat, M.E. Dinardo, B.R. Drell, W.T. Ford, B. Heyburn, E. Luiggi Lopez, U. Nauenberg,K. Stenson, K. Ulmer, S.R. Wagner, S.L. Zang

Cornell University, Ithaca, USAL. Agostino, J. Alexander, F. Blekman, D. Cassel, A. Chatterjee, S. Das, L.K. Gibbons, B. Heltsley,W. Hopkins, A. Khukhunaishvili, B. Kreis, V. Kuznetsov, J.R. Patterson, D. Puigh, A. Ryd, X. Shi,S. Stroiney, W. Sun, W.D. Teo, J. Thom, J. Vaughan, Y. Weng, P. Wittich

Fairfield University, Fairfield, USAC.P. Beetz, G. Cirino, C. Sanzeni, D. Winn

Fermi National Accelerator Laboratory, Batavia, USAS. Abdullin, M.A. Afaq1, M. Albrow, B. Ananthan, G. Apollinari, M. Atac, W. Badgett, L. Bagby,J.A. Bakken, B. Baldin, S. Banerjee, K. Banicz, L.A.T. Bauerdick, A. Beretvas, J. Berryhill,P.C. Bhat, K. Biery, M. Binkley, I. Bloch, F. Borcherding, A.M. Brett, K. Burkett, J.N. Butler,V. Chetluru, H.W.K. Cheung, F. Chlebana, I. Churin, S. Cihangir, M. Crawford, W. Dagenhart,M. Demarteau, G. Derylo, D. Dykstra, D.P. Eartly, J.E. Elias, V.D. Elvira, D. Evans, L. Feng,M. Fischler, I. Fisk, S. Foulkes, J. Freeman, P. Gartung, E. Gottschalk, T. Grassi, D. Green,Y. Guo, O. Gutsche, A. Hahn, J. Hanlon, R.M. Harris, B. Holzman, J. Howell, D. Hufnagel,E. James, H. Jensen, M. Johnson, C.D. Jones, U. Joshi, E. Juska, J. Kaiser, B. Klima, S. Kossiakov,K. Kousouris, S. Kwan, C.M. Lei, P. Limon, J.A. Lopez Perez, S. Los, L. Lueking, G. Lukhanin,S. Lusin1, J. Lykken, K. Maeshima, J.M. Marraffino, D. Mason, P. McBride, T. Miao, K. Mishra,S. Moccia, R. Mommsen, S. Mrenna, A.S. Muhammad, C. Newman-Holmes, C. Noeding,V. O’Dell, O. Prokofyev, R. Rivera, C.H. Rivetta, A. Ronzhin, P. Rossman, S. Ryu, V. Sekhri,E. Sexton-Kennedy, I. Sfiligoi, S. Sharma, T.M. Shaw, D. Shpakov, E. Skup, R.P. Smith†, A. Soha,W.J. Spalding, L. Spiegel, I. Suzuki, P. Tan, W. Tanenbaum, S. Tkaczyk1, R. Trentadue1, L. Up-legger, E.W. Vaandering, R. Vidal, J. Whitmore, E. Wicklund, W. Wu, J. Yarba, F. Yumiceva,J.C. Yun

University of Florida, Gainesville, USAD. Acosta, P. Avery, V. Barashko, D. Bourilkov, M. Chen, G.P. Di Giovanni, D. Dobur,A. Drozdetskiy, R.D. Field, Y. Fu, I.K. Furic, J. Gartner, D. Holmes, B. Kim, S. Klimenko,J. Konigsberg, A. Korytov, K. Kotov, A. Kropivnitskaya, T. Kypreos, A. Madorsky, K. Matchev,G. Mitselmakher, Y. Pakhotin, J. Piedra Gomez, C. Prescott, V. Rapsevicius, R. Remington,M. Schmitt, B. Scurlock, D. Wang, J. Yelton

Florida International University, Miami, USAC. Ceron, V. Gaultney, L. Kramer, L.M. Lebolo, S. Linn, P. Markowitz, G. Martinez, J.L. Ro-driguez

Florida State University, Tallahassee, USAT. Adams, A. Askew, H. Baer, M. Bertoldi, J. Chen, W.G.D. Dharmaratna, S.V. Gleyzer, J. Haas,S. Hagopian, V. Hagopian, M. Jenkins, K.F. Johnson, E. Prettner, H. Prosper, S. Sekmen

Florida Institute of Technology, Melbourne, USAM.M. Baarmand, S. Guragain, M. Hohlmann, H. Kalakhety, H. Mermerkaya, R. Ralich, I. Vo-dopiyanov

University of Illinois at Chicago (UIC), Chicago, USAB. Abelev, M.R. Adams, I.M. Anghel, L. Apanasevich, V.E. Bazterra, R.R. Betts, J. Callner,M.A. Castro, R. Cavanaugh, C. Dragoiu, E.J. Garcia-Solis, C.E. Gerber, D.J. Hofman, S. Kha-latian, C. Mironov, E. Shabalina, A. Smoron, N. Varelas

28 A The CMS Collaboration

The University of Iowa, Iowa City, USAU. Akgun, E.A. Albayrak, A.S. Ayan, B. Bilki, R. Briggs, K. Cankocak36, K. Chung, W. Clarida,P. Debbins, F. Duru, F.D. Ingram, C.K. Lae, E. McCliment, J.-P. Merlo, A. Mestvirishvili,M.J. Miller, A. Moeller, J. Nachtman, C.R. Newsom, E. Norbeck, J. Olson, Y. Onel, F. Ozok,J. Parsons, I. Schmidt, S. Sen, J. Wetzel, T. Yetkin, K. Yi

Johns Hopkins University, Baltimore, USAB.A. Barnett, B. Blumenfeld, A. Bonato, C.Y. Chien, D. Fehling, G. Giurgiu, A.V. Gritsan,Z.J. Guo, P. Maksimovic, S. Rappoccio, M. Swartz, N.V. Tran, Y. Zhang

The University of Kansas, Lawrence, USAP. Baringer, A. Bean, O. Grachov, M. Murray, V. Radicci, S. Sanders, J.S. Wood, V. Zhukova

Kansas State University, Manhattan, USAD. Bandurin, T. Bolton, K. Kaadze, A. Liu, Y. Maravin, D. Onoprienko, I. Svintradze, Z. Wan

Lawrence Livermore National Laboratory, Livermore, USAJ. Gronberg, J. Hollar, D. Lange, D. Wright

University of Maryland, College Park, USAD. Baden, R. Bard, M. Boutemeur, S.C. Eno, D. Ferencek, N.J. Hadley, R.G. Kellogg, M. Kirn,S. Kunori, K. Rossato, P. Rumerio, F. Santanastasio, A. Skuja, J. Temple, M.B. Tonjes, S.C. Ton-war, T. Toole, E. Twedt

Massachusetts Institute of Technology, Cambridge, USAB. Alver, G. Bauer, J. Bendavid, W. Busza, E. Butz, I.A. Cali, M. Chan, D. D’Enterria, P. Everaerts,G. Gomez Ceballos, K.A. Hahn, P. Harris, S. Jaditz, Y. Kim, M. Klute, Y.-J. Lee, W. Li, C. Loizides,T. Ma, M. Miller, S. Nahn, C. Paus, C. Roland, G. Roland, M. Rudolph, G. Stephans, K. Sumorok,K. Sung, S. Vaurynovich, E.A. Wenger, B. Wyslouch, S. Xie, Y. Yilmaz, A.S. Yoon

University of Minnesota, Minneapolis, USAD. Bailleux, S.I. Cooper, P. Cushman, B. Dahmes, A. De Benedetti, A. Dolgopolov, P.R. Dudero,R. Egeland, G. Franzoni, J. Haupt, A. Inyakin37, K. Klapoetke, Y. Kubota, J. Mans, N. Mirman,D. Petyt, V. Rekovic, R. Rusack, M. Schroeder, A. Singovsky, J. Zhang

University of Mississippi, University, USAL.M. Cremaldi, R. Godang, R. Kroeger, L. Perera, R. Rahmat, D.A. Sanders, P. Sonnek, D. Sum-mers

University of Nebraska-Lincoln, Lincoln, USAK. Bloom, B. Bockelman, S. Bose, J. Butt, D.R. Claes, A. Dominguez, M. Eads, J. Keller, T. Kelly,I. Kravchenko, J. Lazo-Flores, C. Lundstedt, H. Malbouisson, S. Malik, G.R. Snow

State University of New York at Buffalo, Buffalo, USAU. Baur, I. Iashvili, A. Kharchilava, A. Kumar, K. Smith, M. Strang

Northeastern University, Boston, USAG. Alverson, E. Barberis, O. Boeriu, G. Eulisse, G. Govi, T. McCauley, Y. Musienko38, S. Muzaf-far, I. Osborne, T. Paul, S. Reucroft, J. Swain, L. Taylor, L. Tuura

Northwestern University, Evanston, USAA. Anastassov, B. Gobbi, A. Kubik, R.A. Ofierzynski, A. Pozdnyakov, M. Schmitt, S. Stoynev,M. Velasco, S. Won

University of Notre Dame, Notre Dame, USAL. Antonelli, D. Berry, M. Hildreth, C. Jessop, D.J. Karmgard, T. Kolberg, K. Lannon, S. Lynch,

29

N. Marinelli, D.M. Morse, R. Ruchti, J. Slaunwhite, J. Warchol, M. Wayne

The Ohio State University, Columbus, USAB. Bylsma, L.S. Durkin, J. Gilmore39, J. Gu, P. Killewald, T.Y. Ling, G. Williams

Princeton University, Princeton, USAN. Adam, E. Berry, P. Elmer, A. Garmash, D. Gerbaudo, V. Halyo, A. Hunt, J. Jones, E. Laird,D. Marlow, T. Medvedeva, M. Mooney, J. Olsen, P. Piroue, D. Stickland, C. Tully, J.S. Werner,T. Wildish, Z. Xie, A. Zuranski

University of Puerto Rico, Mayaguez, USAJ.G. Acosta, M. Bonnett Del Alamo, X.T. Huang, A. Lopez, H. Mendez, S. Oliveros, J.E. RamirezVargas, N. Santacruz, A. Zatzerklyany

Purdue University, West Lafayette, USAE. Alagoz, E. Antillon, V.E. Barnes, G. Bolla, D. Bortoletto, A. Everett, A.F. Garfinkel, Z. Gecse,L. Gutay, N. Ippolito, M. Jones, O. Koybasi, A.T. Laasanen, N. Leonardo, C. Liu, V. Maroussov,P. Merkel, D.H. Miller, N. Neumeister, A. Sedov, I. Shipsey, H.D. Yoo, Y. Zheng

Purdue University Calumet, Hammond, USAP. Jindal, N. Parashar

Rice University, Houston, USAV. Cuplov, K.M. Ecklund, F.J.M. Geurts, J.H. Liu, D. Maronde, M. Matveev, B.P. Padley,R. Redjimi, J. Roberts, L. Sabbatini, A. Tumanov

University of Rochester, Rochester, USAB. Betchart, A. Bodek, H. Budd, Y.S. Chung, P. de Barbaro, R. Demina, H. Flacher, Y. Gotra,A. Harel, S. Korjenevski, D.C. Miner, D. Orbaker, G. Petrillo, D. Vishnevskiy, M. Zielinski

The Rockefeller University, New York, USAA. Bhatti, L. Demortier, K. Goulianos, K. Hatakeyama, G. Lungu, C. Mesropian, M. Yan

Rutgers, the State University of New Jersey, Piscataway, USAO. Atramentov, E. Bartz, Y. Gershtein, E. Halkiadakis, D. Hits, A. Lath, K. Rose, S. Schnetzer,S. Somalwar, R. Stone, S. Thomas, T.L. Watts

University of Tennessee, Knoxville, USAG. Cerizza, M. Hollingsworth, S. Spanier, Z.C. Yang, A. York

Texas A&M University, College Station, USAJ. Asaadi, A. Aurisano, R. Eusebi, A. Golyash, A. Gurrola, T. Kamon, C.N. Nguyen, J. Pivarski,A. Safonov, S. Sengupta, D. Toback, M. Weinberger

Texas Tech University, Lubbock, USAN. Akchurin, L. Berntzon, K. Gumus, C. Jeong, H. Kim, S.W. Lee, S. Popescu, Y. Roh, A. Sill,I. Volobouev, E. Washington, R. Wigmans, E. Yazgan

Vanderbilt University, Nashville, USAD. Engh, C. Florez, W. Johns, S. Pathak, P. Sheldon

University of Virginia, Charlottesville, USAD. Andelin, M.W. Arenton, M. Balazs, S. Boutle, M. Buehler, S. Conetti, B. Cox, R. Hirosky,A. Ledovskoy, C. Neu, D. Phillips II, M. Ronquest, R. Yohay

Wayne State University, Detroit, USAS. Gollapinni, K. Gunthoti, R. Harr, P.E. Karchin, M. Mattson, A. Sakharov

30 A The CMS Collaboration

University of Wisconsin, Madison, USAM. Anderson, M. Bachtis, J.N. Bellinger, D. Carlsmith, I. Crotty1, S. Dasu, S. Dutta, J. Efron,F. Feyzi, K. Flood, L. Gray, K.S. Grogg, M. Grothe, R. Hall-Wilton1, M. Jaworski, P. Klabbers,J. Klukas, A. Lanaro, C. Lazaridis, J. Leonard, R. Loveless, M. Magrans de Abril, A. Mohapatra,G. Ott, G. Polese, D. Reeder, A. Savin, W.H. Smith, A. Sourkov40, J. Swanson, M. Weinberg,D. Wenman, M. Wensveen, A. White

†: Deceased1: Also at CERN, European Organization for Nuclear Research, Geneva, Switzerland2: Also at Universidade Federal do ABC, Santo Andre, Brazil3: Also at Soltan Institute for Nuclear Studies, Warsaw, Poland4: Also at Universite de Haute-Alsace, Mulhouse, France5: Also at Centre de Calcul de l’Institut National de Physique Nucleaire et de Physique desParticules (IN2P3), Villeurbanne, France6: Also at Moscow State University, Moscow, Russia7: Also at Institute of Nuclear Research ATOMKI, Debrecen, Hungary8: Also at University of California, San Diego, La Jolla, USA9: Also at Tata Institute of Fundamental Research - HECR, Mumbai, India10: Also at University of Visva-Bharati, Santiniketan, India11: Also at Facolta’ Ingegneria Universita’ di Roma ”La Sapienza”, Roma, Italy12: Also at Universita della Basilicata, Potenza, Italy13: Also at Laboratori Nazionali di Legnaro dell’ INFN, Legnaro, Italy14: Also at Universita di Trento, Trento, Italy15: Also at ENEA - Casaccia Research Center, S. Maria di Galeria, Italy16: Also at Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland17: Also at California Institute of Technology, Pasadena, USA18: Also at Faculty of Physics of University of Belgrade, Belgrade, Serbia19: Also at Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France20: Also at Alstom Contracting, Geneve, Switzerland21: Also at Scuola Normale e Sezione dell’ INFN, Pisa, Italy22: Also at University of Athens, Athens, Greece23: Also at The University of Kansas, Lawrence, USA24: Also at Institute for Theoretical and Experimental Physics, Moscow, Russia25: Also at Paul Scherrer Institut, Villigen, Switzerland26: Also at Vinca Institute of Nuclear Sciences, Belgrade, Serbia27: Also at University of Wisconsin, Madison, USA28: Also at Mersin University, Mersin, Turkey29: Also at Izmir Institute of Technology, Izmir, Turkey30: Also at Kafkas University, Kars, Turkey31: Also at Suleyman Demirel University, Isparta, Turkey32: Also at Ege University, Izmir, Turkey33: Also at Rutherford Appleton Laboratory, Didcot, United Kingdom34: Also at INFN Sezione di Perugia; Universita di Perugia, Perugia, Italy35: Also at KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary36: Also at Istanbul Technical University, Istanbul, Turkey37: Also at University of Minnesota, Minneapolis, USA38: Also at Institute for Nuclear Research, Moscow, Russia39: Also at Texas A&M University, College Station, USA40: Also at State Research Center of Russian Federation, Institute for High Energy Physics,Protvino, Russia

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