Systematic measurement of light vector mesons at RHIC-PHNEIX Yoshihide Nakamiya Hiroshima University, Japan (for the PHENIX Collaboration) Quark Matter 2008, Variable Energy Cyclotron Centre,Jaipur,India

2Outline Physics motivation PHENIX experiments at RHIC PHENIX experiments at RHIC Improved Analysis Improved Analysis - no PID methods - no PID methods (φ -> K+K-) (φ -> K+K-) - new background subtraction methods - new background subtraction methods (ω->π 0 γγ) (ω->π 0 γγ) Result (φ mesons and ω mesons) Result (φ mesons and ω mesons) - mT & pT slope - mT & pT slope - Results of yield analysis - Results of yield analysis (dN/dy & temperature) (dN/dy & temperature) - Results of Line shape analysis - Results of Line shape analysis Summary Summary

3 Physics Background Acta Phys. Pol. B 31 (2000) 3021 At RHIC Lattice QCD predicts a phase transition to a deconfined partonic matter at a temperature of about 170 MeV.  Heavy-ion collision is the unique method to produce a phase transition at the regime of high energy density and low baryon density (cross over regions).  Several kinds of phase transition has happened in cross over regions. -> What’s order parameter ? chiral condensate ->chiral phase transition quark number susceptibility -> deconfinment plyakov loop ->deconfinment Heavy-ion collisions at RHIC has capability of studying a phase transition In a cross over region. Measurements from various viewpoints Is needed to reveal the property of a partoic matter.

4 Why light vector mesons ? - deconfinement(shape of thermal radiation) -> Spectral function has been changed in a deconfined partonic matter. - chiral phase transition (chiral symmetry restoration) -> Mass modification will be expected to happen in the deconfined partonic matter. - Hydrodynamic calculation expects that duration time of a deconfined matter is about 10 fm/c. -> Short lived vector mesons are desirable as the target of measurement （ τ QGP = 10 fm/c, τ φ = 46 fm/c, τ ω = 23 fm/c, τ ρ = 1.3 fm/c) Measurement of mass state for light & short lived mesons are suitable for the study of the partonic matter. ⇒ φ and ω mesons can be measured in PHNIX. R. Rapp J. Phys G31 (2005) S217

5 Experimental setup RHIC perspective PHENIX overview PHENIX spectrometer BBC & ZDC : Event trigger, Collision vertex, Centrality Acceptance ⇒ pseud-rapidity range : |η| < 0.35 azimuthal angle : 2x90 degree(2 arms) DC & PC : tracking, momentum RICH & EMC : electron ID TOF, EMC : hadron ID MuID : muon ID ⇒ The PHENIX spectrometers are versatile devices to measure electrons, photons as well as hadrons at the same time. RHIC accelerator  Species : Au+Au, d+Au, proton+proton, Cu+Cu  Energy : √ ｓ _NN = 22.5, 62.5, 200, 500 GeV ⇒ The RHIC accelerator provides various collision systems at a broad range of c.m.s energy. (200Gev is the maximum energy for ion.)

6 What has been measured in PHENIX? φ mesons φ→e + e - BR ~ φ→K + K - BR ~ 50 % ω mesons ω→e + e - BR ~ ω→π 0 γ BR ~ 9 % ω→π 0 π + π - BR ~ 90 % Line shape analysis (Mass peak and width) ⇒ Line shape modification (Mass peaks and width) may be small due to small fraction of φ&ω decay inside a deconfined matter. (τ QGP = 10 fm/c, τ φ = 46 fm/c, τ ω = 23 fm/c ) Yield analysis (Branching ratio) ⇒ The yield of mesons in case of each decay mode can induce significant change (Yiels trough e+e- compared to K+K- channels could be changed because m φ ~m k ). PHENIX has unique capability to measure various decay mode of mesons.

New analysis : no PID methods ( I’m thinking now )

New analysis : new background subtraction methods new background subtraction methods ( I’m thinking now !! )

9 Result : φ meson

pT spectra of φ mesons Npart Scaling Discussion : 1) Can we merge several prerim. Plots ? 2) Can we change to make physics cleat by using their data points ? (i.e. Npart scaling like above ) 3) I will add phi->KK results (with PID)

pT spectra of omega mesons Npart Scaling

12 The yield and temperature for φ mesons I will make a new plot to add points (phi->KK at pp PPG085 etc). So this page will be updated.

13 The yield of ω mesons ω→e+e- Au+Au 200 GeV PHENIX Preliminary I will make a new plot to add points (new prelimin. Etc ). So this page will be updated.

14 Line shape for φ →K + K - PRC (2007) Mass centroid Mass centroid at all centralities are consistent with the PDG value within errors. Mass width There is no convincing evidence of φ width variation as a function of the number of participant nucleons. ⇒ Now analysis for φ→e + e - in Au+Au collision √s_NN = 200 GeV is going on !

15 Line shape for ω mesons PRC (2007) ω mass measured in the π 0 π + π - decay as a function of pT in d+Au and p+p are consistent with the PDG value within errors. ⇒ Now ω analysis in Au+Au collision √s_NN = 200 GeV are going on !

16 Summary Measurement of mass state for light vector mesons (φ,ω) are powerful to study the property of partonic matter.  The PHENIX detector is versatile device to measure electron, photon as well as hadron at the same time.  Analysis of light vector mesons via various decay channel in various collision systems at a broad range of collision energy make progress in PHENIX.  Line shape analysis φ mesons : There are no mass modification of φ → K + K - in Au+Au √s_NN = 200 GeV. φ→e + e - analysis is in progress. ω mesons ： The mass is consistent with the PDG value in d+Au and p+p in √s_NN=200GeV. Analysis in Au+Au is in progress.  Yield analysis …()

17 Thank you for inviting me to Quark Matter 2008 ! I return thanks to all pariticipants and Collaborators!!

Back up

19 Photon & Hadron measurement K+K+ K-K- φ→K + K - MomentumHadron ID π-π- π+π+ ω γ γ π0π0 γγ γ γ π0π0 ω→π 0 π + π - ω→π 0 γγ Energy Momentum Hadron ID Photon ID  Photon and hadron is separated by shower shape in EMC.  Electron is rejected RICH veto. Hadron ID  Hadron identification is mainly done by Time of flight. Time of flight for hadrons

20 Electron measurement e+e+ e-e- MomentumElectron ID Why electrons ?  Electrons carry the original information inside a deconfined matter due to no strong interaction in medium. Electron ID  Electron identification is mainly done by RICH and Energy-Momentum Matching. Energy-Momentum matching in Au+Au φ→e + e - ω→e + e -