measurement of the φ -meson production in the rhi collisions with the phenix detector at rhic

Measurement of the φ-meson production in the RHI Collisions with

the PHENIX detector at RHIC

Sasha Milov

Weizmann Institute of Science

for the PHENIX Collaboration

Part I. Analysis

Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010

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Data samples

Year Species √s [GeV ] ∫Ldt Ntot (sampled)

Run1 2000 Au - Au 130 1 µb-1 10 M

Run2 2001/02Au - Au 200 24 µb-1 170 MAu - Au 19 < 1 M

p - p 200 0.15 pb-1 3.7 B

Run3 2002/03d - Au 200 2.74 nb-1 5.5 Bp - p 200 0.35 pb-1 6.6 B

Run4 2003/04Au - Au 200 241 µb-1 1.5 BAu - Au 62.4 9 µb-1 58 M

Run5 2005

Cu - Cu 200 3 nb-1 8.6 BCu - Cu 62.4 0.19 nb-1 0.4 BCu - Cu 22.4 2.7 µb-1 9 M

p - p 200 3.8 pb-1 85 B

Run-6 2006p - p 200 10.7 pb-1 233 Bp - p 62.4 0.1 pb-1 28 B

Run-7 2007 Au - Au 200 813 µb-1 5.1 B

Run-8 2007/08d - Au 200 80 nb-1 160 Bp - p 200 5.2 pb-1 115 B

Au - Au 9.2 few k

Published: arXiv:1005.3674arXiv:1004.3532Phys. Rev. Lett. 99, 052301 (2007)Phys. Rev. C 72, 014903 (2005)

Preliminary

M. Naglis, Φ meson production in p+p, d+Au and Au+Au collisions at RHIC using the PHENIX detector. PhD thesis, WIS, 2009.

D. Sharma, - and φ-meson production in p+p and d+Au collisions at RHIC energies, using the PHENIX Detector. PhD thesis, WIS, 2010.


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K+K– mode ToF-ToF configuration:

Provides the cleanest sample, but is limited both in acceptance an in momentum.

ToF-EMCToF configuration:This configuration was used only in run2 analysis because it is limited in pT of the particles.

ToF-noPID configuration:Provides larger acceptance on expense of worse S/B ratio, but increases overall significance and momentum reach

noPID+ matching:Allows cleaning the sample and make systematic studies

noPID-noPID configuration:Getting even larger acceptance

Central arm acceptance: || < 0.35 Δ = 2 x 90o


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K+K– mode K+ K– (two K ID)

System Nevt pT (GeV/c) Method

p+p 1.44 109 1.3 – 7.0 no PID1.50 109 0.9 – 4.5 one K PID

d+Au 63 106 1.45 – 5.1 no PIDAu+Au 824 106 2.45 – 7.0 no PID

722 106 1.1 – 3.95 two K PID

Peak examples are shown for p+p data at √s=200GeV


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e+e– mode


Tracking:Use of both arms and two arms decays to increase statistics and low pT coverage.

Electron Identification:RICH + EMCal (both technologies) to increase coverage and reduce systematic errors.

Combinatorial Background Subtraction:Based on mixing technique using pairs from different events. Events must be similar in vertex and centrality.

Dalitz pair rejection:Not yet used, but will be possible with HBD data from runs 2009, 2010.


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Electron identification Purity

Upper curve: all tracks

Middle curve: e+e– identified by RICH

Lower curve: Random coincidence.

E/p cut increases electron sample purity by additional factor of 10.

Upper curve: pairs from where only one track is identified as e+ or e–

coming from Dalitzes and conversions

Middle curve: pairs open up in the plane orthogonal to magnetic field (remove Dalitzes)

Lower curve: Pairs where the second track was not identified as an electron.

Efficiency

Mass corresponding to the beam-pipe radius

RIC

H e

/π=1

000

EMCal e/π=10

Pool of electrons

from same event

category:

centrality, reaction plane, vertex


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Combinatorial background Event Ne– Ne+

e– e+

e– e+

e–

e+

e–

M e+e–

M e+e–

M e+e+ M e–e–

M e+e+ M e–e–

Subtraction Normalization

π0 γ e+e–

γ e+e–

Combinatorial Background Subtraction: PRC81, 034911 (2010)

<N±> = 2√<N++><N– –>


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e+e– mode

p+p

Au+Aud+Au

In p+p:Combinatorial Background Subtraction was not used, because the S/B ration is relatively high ~ 5:1.

In d+Au:C.B.S. was used for MB trigger only. For ERT the mixing was done for MB and ERT condition was imposed on it. S/B varies from 10:1 to 1:10 (approx.)

In Au+Au:C.B.S. is the only way to estimate the signal. S/B ration is very low < 1:100

Under the peaks:Correlated background. “The Cocktail”


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Efficiencies

Acceptance:Includes geometry, inactive regions, detector response, analysis cuts.

Trigger efficiency to a triggering (daughter) particle:Measured from MB sample, includes trigger electronics inactive areas

Trigger efficiency to the analyzed (mother) particle:Deduced from the MC and the single particle trigger efficiency.


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μ+μ– mode Muon arm acceptances: -2.4< < -1.2 1.2< < 2.2 Δ = 2π

Sample :So far run8 (d+Au) p+p sample also very promicing

Muon arms:Use acceptance of both muon arms.

CBS:The sample is biased therefore use of CBS is difficult. We used modified method of the CBS

Clear signal form φ and /.

Part IIa. Results

(Spectral widths shapes and yields)


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Line shape modificationPhys. Rev., C63 (2001) 054907Chiral Symmetry Restoration probe:

Due to its short life-time (44 fm/c), the φ is considered a probe of the Chiral Symmetry Restoration The line shaper and/or position of the particle can be different from the vacuum value.

The effect is expected to be seen in:The most central AuAu collisionsAt low pT.In di-lepton channel

The data is measured in:The MB AuAu collisionsAt average pT

In hadronic channel

I do not have results on e+e– in p+pBut one does not expect large signal there


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p+p spectra @ 200 GeV Consistency:

An agreement between different K-ID methods was shown before

K+K– and e+e– results very well agree to each other

Momentum coverage:e+e– mode allows measurement at zero pT, thus providing the integrated yield.

K+K– mode w/o identification extends to 7 GeV/c, limited by statistics.

Self-consistent result in a wide pT range from 0.125 to 7 GeV/c


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Integrated Yields in p+p @ 200GeV

dN/dy and <pT>:First time direct counting of the integrated parameters, no extrapolations or model assumptions

PHENIX / STAR:The numbers are close between the experiments, which is not always the case…

Statistical model agreement:Not clear why the stat. model works in p+p, but it does a good job.

arXiv:1005.3674

Stat model calculation from EPJC66, 377 (2010)

dN/dy and <pT> of φ-meson are directly measured in p+p


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A+A @ 200 GeV in K+K–

Spectra in A+A:Measured above 1GeV/c in full range of centralities and systems.

Fits well to Tsallis function, and departs from exponential.

High pT:The departures depends on species and centralities. Consistent with recombination models.

Low pT:No significant change in slope. Support an expectation of a lesser radial flow for φ-meson.

PHENIX provides full set of measurements @ 200 GeV in K+K–


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d(Au)+Au @ 200 GeV in e+e–

d+Au:Covering the entire pT range form zero to 6 GeV/c in all centrality bins.

Au+Au:The run4 Preliminary data which is of a lesser stat. significance compare to hadronic channel. It will remain so before the HBD results are analyzed.

The lighter systems are measured. The analysis of AuAu data required HBD samples to be analyzed.


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Integrated Yields in A(d)+A @200GeV Integrated parameters:

Due to pT range in K+K– mode the integrated values require assumptions to work them out

In e+e– the result suffers from extremely poor statistics and shall be taken seriously only with the systematic errors.

The slope parameter:T changes very little with increasing Npart but clearly depends on √sNN

The yield per participant:Clear increase from p+p to central AuAu in both measured energies.

@200GeV the increase is approximately by a factor of 3Yields increase with Npart. Slopes remain the same.


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Spectra @ 62GeVSpectra:

PHENIX has Preliminary results on φ-meson production measured in K+K– decay channel at 62 GeV in p+p, CuCu and AuAu systems.

Measurements are done above 1GeV/c and extends to 3-4GeV/c limited by available statistics.

The results exist in full range of centralities and systems.

Full set of data to study the systematics of the φ at lower energy.

Part IIb. Not about physics…


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A factor of 2.

Integrated yield in p+p:Perhaps the only measurement where PHENIX and STAR agree.

Spectra in all systems:Consistently show higher rates measured by STAR reaching a factor of 2 for the same number of participants in Au+Au.

Ratios:Yet the ratios to p+p like RAA and dN/dy look more or less the same.

PHENIX takes it very seriously. With a variety of samples, decay modes and techniques, we give the φ-meson “a very special treatment”.

We hope STAR does the same.

Compiled by M.Naglis

Part IIc. Results

(Flow)


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FlowResults:

PHENIX published results of run4 and has preliminary analysis of run7 flow of φ-meson in AuAu at 200 GeV. The results are consistent.

Scaling:Elliptic flow v2 of the φ-meson scales with the number of quarks the vs. kET/q similar to the scaling observed for all the measured particles.

Flow of the φ is crucial for establishing the validity of the flow scaling with the number of quarks.

Part IIc. Results

(Nuclear Modification Factor)


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RdA @ 200 GeV Run3:

Preliminary PHENIX results left room for some increase of the RdA at high pT. Although the data was also consistent with the flat behavior the trend was suggestive.

Run8:Final results published by PHENIX show no increase.

The new results extend to 7 GeV/c and above 1 GeV/c the behavior of φ-meson is consistent with the trends shown by other mesons.

Cold Nuclear Matter effects in φ-meson production @ 200 GeV are weak if any.


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RdA @ 200 GeV

The result is new and promising, work on it continues.

First look: φ is suppressed in d-going direction, In Au-going direction the ration is constant like at mid-rapidity (we are looking at rather high-pT)


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Cu+Cu @ 200 & 62 GeV

RAA in CuCu and AuAu shows similar suppression for close Npart The same behavior is measured for all other particles in these systems


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Almost a summary

At mid-rapidity, in all decay modes, in all systems, at all energies, in all parameters we measured:

K+K–, e+e–

p+p, d+Au, Cu+Cu, Au+Au62 GeV, 200 GeVRAA, flowthe φ-meson behaves consistently with all other mesons in the full pT range of our measurements.

The values seems to show different behavior are the integrated yields per participant, significantly increasing from p+p to the most central Au+Au events.


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RAA @ 200 GeVIn the most central:

At pT <2GeV/c suppression of φ are K similar suggesting the flavor content dependence.The difference grows even more, however >5GeV/c the RAA’s are comparable at present statistics.That however is in contradiction to the -meson trend which has ~50% strange quark content and behaves similar to π0

Closer to central:The difference between the two particles grows up at intermediate pT’s.

In the most peripheral:φ shows no enhancement, however it is not suppressed by ~0.8 like π0

φ-meson suppression is far from being understood. We need low and high pT data and other s-quark particles to complete the picture.

Part III. Instead of a summary

BACKUP


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Nuclear Modification Factor


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HBD peaks

Part I. Detector


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The PHENIX detectorPioneering High Energy Nuclear Interaction eXperiment

Magnetic Field:Outer coils:∫Bdl = 0.78 Tm

Polarity can change for systematic studies and field configuration with Inner coil.

Inner coil:“+ +” mode ∫Bdl = 1.04 TmIncrease in tracking resolution

“+ –” mode ∫Bdl = 0.43 TmCreating zero-field region



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Global detectors:BBC / ZDC: trigger, vertex, timing, centrality.εtrigger = 50%… 92%σvertex = 0.5cm… 2cm

Tracking System:DC / PC1: momentum, pattern recognition.dpT/pT ≈ 1.0%•pT + 0.7%

Pattern recognition:DC / PC1 + PC2 + PC3/EMCal: events structure, fake rejectionεoccupancy = 100%… 85%

Calorimetry:PbSc / PbGl: EM component, σE/E ≈ 8.1%/√E + 3.0%



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Time of Flight:Scintillating slabs: p/K < 4.5 GeV/cπ/K < 2.5 GeV/cσToF ≈ 100 ps

Calorimetry:PbSc: ToF σToF ≈ 500 psPbSc/PbGl: Shower shape, E/p

eID:RICH PMT/CO2:e/π > 1000

Other (not used)RPC ToFAerogelHBD



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Triggers:Minimum Biased: 1 or more hits on each side

ERT gamma:∑2x2(4x4) EMCal towers must exceed threshold

ERT electron:The same in coincidence with RICH hit


measurement of the φ -meson production in the rhi collisions with the phenix detector at rhic

Documents

p p data

au au200813 b

d au collisions

p p20010

pidau au

pidd au

tofnopid configuration

phenix detector