measurement of the φ -meson production in the rhi collisions with the phenix detector at rhic
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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.
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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e+e– mode
Central arm acceptance: || < 0.35 Δ = 2 x 90o
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.
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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– –>
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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”
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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.
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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)
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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–
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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.
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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.
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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…
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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)
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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)
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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.
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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)
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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.
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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Nuclear Modification Factor
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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HBD peaks
Part I. Detector
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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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
Central arm acceptance: || < 0.35 Δ = 2 x 90o
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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The PHENIX detectorPioneering High Energy Nuclear Interaction eXperiment
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%
Central arm acceptance: || < 0.35 Δ = 2 x 90o
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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The PHENIX detectorPioneering High Energy Nuclear Interaction eXperiment
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
Central arm acceptance: || < 0.35 Δ = 2 x 90o
Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10,2010
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The PHENIX detectorPioneering High Energy Nuclear Interaction eXperiment
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
Central arm acceptance: || < 0.35 Δ = 2 x 90o
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