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, Data samples Year Species√s [GeV ] ∫LdtN tot (sampled) Run12000Au - Au1301 µb M Run22001/02 Au - Au20024 µb M Au - Au19 < 1 M p - p pb B Run32002/03 d - Au nb B p - p pb B Run42003/04 Au - Au µb B Au - Au62.49 µb M Run52005 Cu - Cu2003 nb B Cu - Cu nb B Cu - Cu µb -1 9 M p - p pb B Run p - p pb B p - p pb B Run-72007Au - Au µb B Run-82007/08 d - Au20080 nb B p - p pb B Au - Au9.2 few k Published: arXiv: arXiv: Phys. Rev. Lett. 99, (2007) Phys. Rev. C 72, (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, 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, 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 p T 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 90 o

Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10, K + K – mode K + K – (two K ID) SystemN evt p T (GeV/c)Method p+p – 7.0no PID – 4.5one K PID d+Au – 5.1no PID Au+Au – 7.0no PID – 3.95two K PID Peak examples are shown for p+p data at √s= 200GeV

Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10, e + e – mode Central arm acceptance: |  | < 0.35 Δ  = 2 x 90 o Tracking: Use of both arms and two arms decays to increase statistics and low p T 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, 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 RICH e/π=1000 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, Combinatorial background Event Ne – Ne + e–e– e+e+ e–e– e+e+ e–e– e+e+ e–e– M e + e – M e + e + M e – e – M e + e + M e – e – SubtractionNormalization π 0  γ e + e – γ  e + e – Combinatorial Background Subtraction: PRC81, (2010) = 2√

Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10, e + e – mode p+p Au+Au d+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, 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, μ + μ – mode Muon arm acceptances: -2.4<  < <  < 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, Line shape modification Phys. Rev., C63 (2001) Chiral 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 collisions At low p T. In di-lepton channel The data is measured in: The MB AuAu collisions At average p T In hadronic channel I do not have results on e + e – in p+p But one does not expect large signal there

Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10, p+p 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 p T, 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 p T range from to 7 GeV/c

Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10, Integrated Yields in 200GeV dN/dy and : 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: Stat model calculation from EPJC66, 377 (2010) dN/dy and of φ-meson are directly measured in p+p

Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10, 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 p T : The departures depends on species and centralities. Consistent with recombination models. Low p T : No significant change in slope. Support an expectation of a lesser radial flow for φ- meson. PHENIX provides full set of 200 GeV in K + K –

Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10, GeV in e + e – d+Au: Covering the entire p T 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, Integrated Yields in Integrated parameters: Due to p T 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 N part but clearly depends on √s NN The yield per participant: Clear increase from p+p to central AuAu in both measured the increase is approximately by a factor of 3 Yields increase with N part. Slopes remain the same.

Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10, GeV Spectra: 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, 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 R AA 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, Flow Results: 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 v 2 of the φ- meson scales with the number of quarks the vs. kE T /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, GeV Run3: Preliminary PHENIX results left room for some increase of the RdA at high p T. 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 200 GeV are weak if any.

Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10, GeV The result is new and promising, work on it continues. Au d 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-p T )

Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10, & 62 GeV R AA in CuCu and AuAu shows similar suppression for close N part The same behavior is measured for all other particles in these systems

Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10, 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+Au 62 GeV, 200 GeV RAA, flow the φ-meson behaves consistently with all other mesons in the full p T 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, R 200 GeV In 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 R AA ’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 π 0 Closer to central: The difference between the two particles grows up at intermediate p T ’s. In the most peripheral: φ shows no enhancement, however it is not suppressed by ~0.8 like π 0 φ-meson suppression is far from being understood. We need low and high p T 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, Nuclear Modification Factor

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

Part I. Detector

Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10, The PHENIX detector Pioneering 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 Tm Increase in tracking resolution “+ –” mode ∫Bdl = 0.43 Tm Creating zero-field region Central arm acceptance: |  | < 0.35 Δ  = 2 x 90 o

Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10, The PHENIX detector Pioneering High Energy Nuclear Interaction eXperiment Global detectors: BBC / ZDC: trigger, vertex, timing, centrality. ε trigger = 50%… 92% σ vertex = 0.5cm… 2cm Tracking System: DC / PC1: momentum, pattern recognition. dp T /p T ≈ 1.0%p T + 0.7% Pattern recognition: DC / PC1 + PC2 + PC3/EMCal: events structure, fake rejection ε occupancy = 100%… 85% Calorimetry: PbSc / PbGl: EM component, σ E /E ≈ 8.1%/√E + 3.0% Central arm acceptance: |  | < 0.35 Δ  = 2 x 90 o

Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10, The PHENIX detector Pioneering High Energy Nuclear Interaction eXperiment Time of Flight: Scintillating slabs: p/K < 4.5 GeV/c π/K < 2.5 GeV/c σ ToF ≈ 100 ps Calorimetry: PbSc: ToF σ ToF ≈ 500 ps PbSc/PbGl: Shower shape, E/p eID: RICH PMT/CO 2 : e/π > 1000 Other (not used) RPC ToF Aerogel HBD Central arm acceptance: |  | < 0.35 Δ  = 2 x 90 o

Sasha Milov, WISH-2010, Catania: "Measurement of φ..." Aug,10, The PHENIX detector Pioneering 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 90 o