Status Report of The CMS Experiment

Christos Leonidopoulos

CERN-PHon behalf of the CMS Collaboration

102nd LHCC Meeting, CERN7 July 2010

The Collaboration

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AACHEN-1, AACHEN-3A, AACHEN-3B, ADANA-CUKUROVA, ANKARA-METU, ANTWERPEN, ATHENS, ATOMKI, AUCKLAND, BARI, BEIJING-IHEP, BOGAZICI, BOLOGNA, BOSTON-UNIV, BRISTOL, BROWN-UNIV, BRUNEL, BRUSSEL-VUB, BRUXELLES-ULB, BUDAPEST, CALTECH, CANTERBURY, CARNEGIE-MELLON, CATANIA, CCCS-UWE, CERN, CHANDIGARH, CHEJU, ILLINOIS-CHICAGO, CHONNAM, CHUNGBUK, CHUNGLI-NCU, COLORADO, CORNELL, DEBRECEN-IEP, DELHI-UNIV, DEMOKRITOS, DESY, DONGSHIN, DUBLIN-UCD, DUBNA, EINDHOVEN, FAIRFIELD, FERMILAB, FIRENZE, FLORIDA-FIU, FLORIDA-STATE, FLORIDA-TECH, FLORIDA-UNIV, FRASCATI, GENOVA, GHENT, HAMBURG-UNIV, HEFEI-USTC, HELSINKI-HIP, HELSINKI-UNIV, HEPHY, IOANNINA, IOWA, IPM, ISLAMABAD-NCP, JOHNS-HOPKINS, KANGWON, KANSAS-STATE, KANSAS-UNIV, KARLSRUHE-IEKP, KHARKOV-ISC, KHARKOV-KIPT, KHARKOV-KSU, KONKUK-UNIV, KOREA-UNIV, KYUNGPOOK, LAPP, LAPPEENRANTA-LUT, LIP, LIVERMORE, LONDON-IC, LOUVAIN, LYON, MADRID-CIEMAT, MADRID-UNIV, MARYLAND, MEXICO-IBEROAM, MEXICO-IPN, MEXICO-PUEBLA, MEXICO-UASLP, MILANO-BICOCCA, MINNESOTA, MINSK-INP, MINSK-NCPHEP, MINSK-RIAPP, MINSK-UNIV, MISSISSIPPI, MIT, MONS, MOSCOW-INR, MOSCOW-ITEP, MOSCOW-LEBEDEV, MOSCOW-MSU, MOSCOW-RDIPE, MUMBAI-BARC, MYASISHCHEV, NAPOLI, NEBRASKA, NICOSIA-UNIV, NORTHEASTERN, NORTHWESTERN, NOTRE DAME, NUST, OHIO-STATE, OVIEDO, PADOVA, PAVIA, PEKING-UNIV, PERUGIA, PISA, POLYTECHNIQUE, PRINCETON, PROTVINO, PSI, PUERTO RICO, PURDUE, PURDUE-CALUMET, RAL, RICE, RIE, RIO-CBPF, RIO-UERJ, ROCHESTER, ROCKEFELLER, ROMA-1, RUTGERS, SACLAY, SANTANDER, SAO PAULO, SEONAM, SEOUL-EDU, SEOUL-SNU, SHANGHAI-IC, SKK-UNIV, SOFIA-CLMI, SOFIA-INRNE, SOFIA-UNIV, SPLIT-FESB, SPLIT-UNIV, ST-PETERSBURG, STRASBOURG, SUNY-BUFFALO, TAIPEI-NTU, TALLINN, TASHKENT, TBILISI-IHEPI, TBILISI-IPAS, TENNESSEE, TEXAS-TAMU, TEXAS-TECH, TIFR-EHEP, TIFR-HECR, TORINO, TRIESTE, UCDAVIS, UCLA, UC RIVERSIDE, UC SANTA BARBARA, UC SAN DIEGO, UNIANDES, VANDERBILT, VILNIUS-ACADEMY, VILNIUS-UNIV, VINCA, VIRGINIA-TECH, VIRGINIA-UNIV, WARSAW-IEP, WARSAW-INS, WARSAW-ISE, WAYNE, WISCONSIN, WONKWANG, YEREVAN, ZAGREB-RUDJER, ZURICH-ETH, ZURICH-UNIV

• 182 Institutions • 3000 scientists and engineers• 2000 Authors

Reminder: we went from this…3.8T Superconducting Solenoid

All Silicon Tracker (Pixels and Microstrips)

Lead tungstate E/M Calorimeter (ECAL)

Redundant Muon System(RPCs, Drift Tubes,

Cathode Strip Chambers)

Hermetic (|η|<5.2) Hadron Calorimeter (HCAL)

[scintillators & brass]

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First 7 TeV collisions in CMS – 30 March 2010

…to this

…and this, just three months later

Life did not begin in a vacuumwith the first collisions

One Billion Cosmic Muons

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before collisions

23 JINST papers: March 2010 (Vol. 5)

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Feedback into realistic simulationto help us prepare for collisions

Detector understanding• “Why should we believe that the simulation

correctly describes the detector performance?”• Excellent question!• TeVatron experience: it takes a long time to

commission & understand collider experimentsAccelerator, detector, trigger, background,

underlying event, software: very complicated problems

Claim:• Cosmic runs/beam tests have made a difference• First data distributions agree well with simulation

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CMS is still in the commissioning phase

From data-taking to the plots

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• Hard work, long hours

• Despite early phase and complexity of experiment Unprecedented levels of readiness Very encouraging first results

• But: Always problems seeking solutions Hardest part is ahead of us

Operations

Integrated luminosity

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Since end of M

arch (7

TeV):

100 nb-1 delivere

d (*)

88 nb-1 re

corded (~88%)

• ~3/4 of data recorded arrived in last 10 days• Working hard to integrate full datasets for ICHEP• Most performance plots use only fraction of data

(*) Stable beams only

L≈ 1027-1029 cm-2s-1

L≈ 1030cm-2s-1

Subdetectors status

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MUON-CSC

MUON-DT

MUON-RPC

HCAL BARREL

HCAL ENDCAP

HCAL FORWARD

ECAL BARREL

ECAL END-CAP

PRE-SHOWER

STRIP TRACKER

PIXEL TRACKER

MUON-CSC

MUON-DT

MUON-RPC

HCAL BARREL

HCAL ENDCAP

HCAL FORWARD

ECAL BARREL

ECAL END-CAP

PRE-SHOWER

STRIP TRACKER

PIXEL TRACKER

Series1

98.5

99.8

98.8

99.9

100

99.9

99.3

98.9

99.8

98.1

98.2

Alignment/calibration status, dead/masked channels mirrored in MC

“The Trigger does not determine which Physics Model is Right.

Only which Physics Model is Left.”

DAQ/Trigger

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• L1/DAQ rate: 45 kHz, @<0.5 MB/evt• High-Level Trigger: have successfully deployed

online trigger menus spanning luminosities from 1E27 through 2E30o Very smooth running throughout (200-400 Hz)

• HLT CPU-performance: 49 ms/evto Primary contributors: commissioning

and early analysis triggerso Contingency: factor of 2o Constantly on watch list Overflows taken into

account in the mean

Run 138737

Trigger Performance

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• HLT muon efficiency wrt L1• L1 objects matched to offline

objects• ~90% efficiency at the plateau

• Photon efficiency wrt offline “super clusters”• For barrel & endcaps• Nearly 100% efficient

Predicting trigger rates: MC vs. data

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“Building trigger menus 101”

Predicting trigger rates: MC vs. data

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Monte Carlo:• Only used as a cross-check

at this point• Some trigger paths have

significant cosmic or noise distributions that are not modeled with “baseline” MC

• Still, impressive agreement overall

Using MC to cross-check 4.6E29 rates

Predicting trigger rates: MC vs. data

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Data:• Most triggers exhibit fairly

linear behavior vs. luminosity

• Extrapolation errors minimized by using most recent data to keep the rate non-linearities under control

• Rates of all main players are predicted within ~20%

Using 1.2E29 rates to predict 4.6E29 rates

Calibration Trigger Streams

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• Calibration triggers have access to full L1 rate, and they output small fraction of event

• Feature unique to CMS HLT• Calibration starts online!

Trigger calibration streams

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• Calibration triggers have access to full L1 rate, and they output small fraction of event

• π0 peak reconstructed offline 200 seconds into 7 TeV run

30 March 2010

LHC has delivered

Trigger has accepted

CMS will analyze22

Analysis Activity

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10-20k analysis jobs running on Tier-2s continuously every day of June

Routinely delivering 100k jobs per dayOctober 09

MC Exercise

7 TeV data

Winter Break

Physics production

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3+1 CMS papers since May

• Rise of the particle density at (2.36) 7 TeV steeper than in models• Careful tuning effort of the MC generators is ongoing

“Transverse Momentum and Pseudorapidity Distributions of Charged Hadrons in pp Collisions at √s=7TeV”, submitted to PRL

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CMS paper at 7TeV

Detector & Physics PerformanceCalorimetry Jets

Tracking b-tagging

Muon EWK/Onia

Particle

Flow Electron EWK/Onia

Detector & Physics PerformanceCalorimetry Jets

Tracking b-tagging

Muon EWK/Onia

Particle

Flow Electron EWK/Onia

1.46M of π0 → γγPT(γ) > 0.4 GeV, PT(pair) > 1 GeV

MC based correction applied according to cluster η and energy

0.43 nb-1 1.46M π0

0.43 nb-1 25.5k η

25.5K η → γγPT(γ) > 0.5 GeV, PT(pair) > 2.5 GeV

Calorimetry: π0 and η → γγ

• Statistics refer to < 0.5 nb-1

• Very useful tool to intercalibrate the crystals• Good agreement in width and Signal/Background ratio• Masses agree with expectations to within 1% 29

DATA

DATA

MC

MC

Calorimetry: Missing ET

Calorimetric MET (GeV)

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• Jets reconstructed with the anti-kT R=0.5 algorithm• Dijet selection : Jet PΤ > 25 GeV, Δφ > 2.1, |η| < 3• Loose ID cuts on number of components and neutral/charged energy fraction

Detector & Physics PerformanceCalorimetry Jets

Tracking b-tagging

Muon EWK/Onia

Particle

Flow Electron EWK/Onia

Calorimetric di-jet events

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Dijet m

ass

Δφ(j1, j2)

# of Calo Towers

Fraction of EM energy in Calo-Jets

Detector & Physics PerformanceCalorimetry Jets

Tracking b-tagging

Muon EWK/Onia

Particle

Flow Electron EWK/Onia

Tracking distributions

Muon distributions

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“Global Muons”: matched tracks from Muon system and Tracker

Global Muons

• η and pT distributions dominated by light hadron decay muons (red)• good agreement with MC prediction, including o heavy flavor decays (blue)o punch-through (black)o fakes (green)

Global Muons

pT spectrum

η distribution φ distribution

Tracking distributions

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η distribution φ distribution

Tracker Material Budget

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η distribution φ distribution

Tracker Material Budget

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pixel cluster charge

Tomography

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Detector & Physics PerformanceCalorimetry Jets

Tracking b-tagging

Muon EWK/Onia

Particle

Flow Electron EWK/Onia

3D impact parameter value and significance all tracks with pT> 1GeV belonging to jets with pT >

40 GeV and |η| < 1.5 - PFlow Jets anti-kT R=0.5)

Excellent alignment and general tracking performance

b-tagging 3D IP significance

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42Two b-jets candidate

b-tagging example

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CMS experiment at LHC, CERNRun 136100 / Event 2568584382010-25-5 03:43:48 CEDTB- → J/yK- candidate

CMS experiment at LHC, CERNRun 136100 / Event 2568584382010-25-5 03:43:48 CEDTB- → J/yK- candidate

All other tracks: pT > 1.0 GeV/c

2

2

GeV/ 135.3

GeV/ 268.5

cM

cKM

Detector & Physics PerformanceCalorimetry Jets

Tracking b-tagging

Muon EWK/Onia

Particle

Flow Electron EWK/Onia

Particle Flow• Particle Flow: Full Event reconstruction

Topological matching between charged particle momenta measured with tracker with clusters in calorimeter Corrects for energy loss along trajectories Better precision, full event info

• High-level object: requires holistic detector view Excellent tracker High E/M calorimeter granularity (0.017 × 0.017) Strong magnetic field to separate tracks

• CMS very well suited for P-Flow reconstruction 46

Particle Flow MET

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Particle Flow MET

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Laser forgotten on

Need cleaning strategies developed based on timing constraints

Particle Flow MET

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Comparison between calorimetric and Particle-Flow MET(Minimum bias events)

Detector & Physics PerformanceCalorimetry Jets

Tracking b-tagging

Muon EWK/Onia

Particle

Flow Electron EWK/Onia

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J/ψ → μ+μ−

Ongoing studies:• Momentum scale corrections by studying mass as a function of η, pT (material budget)• Efficiency studies with tag-n-probe• Flight distance with determination of prompt and b→J/ψ + Χ

terms

Signal events: 4150 ± 222Sigma: 43.1 ± 1.9 (stat.) MeVM

0 : 3.094 ± 0.001 (stat.) GeV

S/B= 5.2χ2/Νdof = 1.0

56 nb-1

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J/ψ → μ+μ− : The Best Of

Selection of central (barrel), high-quality dimuons:• Resolution: 43.1 MeV → 21.0 MeV

56 nb-1

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J/ψ → μ+μ− plus friends

60 nb-1

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J/ψ → μ+μ− plus friends

Not enough statistics to disentangle all resonances (yet)

60 nb-1

• Event selection: Muon id cuts Isolation, pT and MET cuts

• Monte Carlo: Event count normalized to integrated luminosity

W→μν candidate

W± →μ±ν observation

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# of candidate (MT > 50 GeV) = 137

# of expected signal (MT > 50 GeV) = 128

# of expected background (MT > 50 GeV) = 7

37 nb-1

• Event selection: Muon id cuts Loose isolation, pT cuts

• Monte Carlo: Event count normalized to integrated luminosity

Z →μ+μ− observation

Z→μμ candidate

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#of candidate = 25#of expected signal = 24.7 #of expected background = 0.08

60 nb-1

Detector & Physics PerformanceCalorimetry Jets

Tracking b-tagging

Muon EWK/Onia

Particle

Flow Electron EWK/Onia

58

J/ψ → e+e−

• Higher background, tighter selection compared to muon channel• Challenging analysis, Particle-Flow selection crucial• Very promising preliminary results, signal clearly established

Signal events: 132 ± 14Sigma: 98 ± 12 (stat.) MeVM

0 : 3.070± 0.013 (stat.) GeV

37 nb-1

Two event selections: Basic electron ID, no MET cuts More advanced electron ID, cuts

on ET, MET, ΣET

W± →e±ν observation

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173 candidates with MT > 50 GeVMC: Sig=163, Bkg=5

196 candidates with MT > 50 GeVMC: Sig =176, Bkg =11

51 nb-1

• Event selection: Two electrons with ET > 20 GeV

• Monte Carlo: Event count normalized to integrated luminosity

Z →e+e− observation

Z→ee candidate

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52 nb-1

#of candidate = 18#of expected signal = 19 #of expected background = 0.8

Summary

7 TeV collisions: a very exciting run!

• The CMS detector is working according to design First performance results are very encouraging Its behavior can be reproduced in Monte Carlo

simulation Our level of understanding for this early

commissioning phase is very advanced

• The “rediscovery” of the SM has begun • We are setting the grounds for challenging it

as early as the end of 2010

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Epilogue

• The technology of the LHC accelerator and experiments is unprecedented

• Massive amount of work and preparation invested in building and commissioning hardware & software

• But: we do not forget that the real challenges are still ahead (for all of us)

• We should consider this truly exciting period as the beginning of a marathon

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The Beginning of The Journey

Credit for “Da Vinci” drawings: Sergio Cittolin

Credit for material used in this talk: LHC, CMS

Backup

65

The CMS Detector

MUON BARREL

CALORIMETERS

PixelsSilicon Microstrips210 m2 of silicon sensors9.6M (Strip) & 66M (Pixel) channels

ECAL76k scintillating PbWO4 crystals

Cathode Strip Chambers (CSC)Resistive Plate Chambers (RPC)

Drift Tube Chambers (DT)

Resistive Plate Chambers (RPC)

Superconducting Coil, 4 Tesla

Steel YOKE

TRACKER

MUONENDCAPS

HCALPlastic scintillator/brasssandwich

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Muon pT resolution with cosmics1B events of (mostly muon) cosmic events collected make muons the best understood reconstructed object in CMS

Compare muon pT in upper, lower detector halves to evaluate resolution

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12% resolutionat 1 TeV

π0 → γγ η, Φ distributions

Relative calibrationprecision ~ 2%target ~ 0.5% at 10pb-1

π0s and ECAL calibration

π0 and Φ symmetry

ECAL Barrel ECAL Barrel

HLT: CPU performance & pile-up

69

• First look at impact of pileup on CPU-performance

1 coll/bunch

2 coll/bunch

• Have deployed “multiple-vertex” trigger to

facilitate pile-up studies with real data

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J/ψ → μ+μ−

• Run range: 132440-139370• Common selection:

No scraping Tracker Muons of opposite charge Pixel layers >= 2 Tracker hits >= 12 Tracker chi2 < 3 Mu pT > 2.5 Mu segments >=2 Matched L1DoubleMuOpen vertex Prob > 0.05

Run 136100, Event 256858438 • Measured Parameters:

18

mm 11.0

mm 93.1

844.0Prob

GeV/ 3.5

GeV/ 4.3

GeV/ 1.10

GeV/ 6.18)(

GeV/ 135.3

GeV/ 268.5

2

2

2

xyxy

xy

xy

T

T

T

T

LL

L

L

cKp

cp

cp

cBp

cM

cKM

3-trk vertex that is displaced from the PV by 2mm (18s).

Our background is dominated by real J/yDimuon mass in data (points) compared to MC (hist)