Systematic measurements of light vector mesons in RHIC-PHENIX Yoshihide Nakamiya Hiroshima University, Japan for the PHENIX collaboration Quark Matter 2008, Jaipur, India ~ Contents ~ Topics in this talk PHENIX experiment Results Summary

Topics in this talk <Topic 1> Mass modification of light vector mesons - as a probe of the chiral phase transition - in the low pT region Question 1 : Have we observed changes in line shape and/or yield? Mass Line Shape Possible modification of line shape of the invariant mass distribution for f/w/r is expected to be observed. 　　 ->Effects are small and can’t be detected with current statistics and signal to background ratio. Yield difference between fe+e- and f K+K- Branching ratio between e+e- and K+K- may be sensitive to mass modification, since Mphi is approximately 2  MK. -> Compare yields of fe+e- and f K+K- e+e- in Au+Au √sNN=200 GeV ω f

Topics in this talk (Cont’d) <Topic 2 > Particle yield suppression of light vector mesons in medium - as a probe of medium effects - at relatively high pT Systematic measurements give information about properties of the medium: pT/mT spectra of f and w in several decay channels Nuclear modification factors (RAA and RdA) as functions of pT We are trying to answer the following questions: Question 1 : Does the particle yield suppression depend on mass or on quark number ? -> Nuclear modification factor RAA of the f meson is compared to proton results. Question 2 : Does RAA of mesons have a mass or flavor dependence? ->RAA of several mesons are compared to each other. (p, h, w, f, …) <Baseline> Results of p+p and d+Au are also shown. All data shown in this talk are taken at sNN = 200 GeV.

Electron, hadron and photon in PHENIX f/w  e+e- Momentum Electron ID f,w e+ e- PHENIX acceptance -0.35 < η < 0.35 2 x 90°in azimuthal angle for two arms Event selection BBC Electron ID RICH EMCal photon ID EMCal Hadron ID TOF EMCal-TOF w  p+p-p0, p0g f  K+K- p+ w g g Energy Momentum Hadron ID p- p0 f Momentum Hadron ID K+ K-

Results for p+p and d+Au as baseline measurement

d+Au d+Au p+p p+p Extended f  K+K- analysis Consistency between f  K+K- and f e+e- d+Au 0-20% f p+p 　　No ID 　　Single ID 　　Double ID 　　e+e- M.B. f f candidates Double ID analysis no ID analysis Single ID analysis K+ K+ or K- K- h+ h- h+ or h- d+Au 0-20% 　　No ID 　　Single ID 　　Double ID M.B. p+p In p+p, spectra of e+e- and K+K- show reasonable agreement! fK+K- measurements have been extended to both higher and lower pT using new methods, i.e. no kaon ID and single kaon ID methods. The three independent kaon analyses are consistent with each other.

d+Au p+p Measurements of w in wide pT range w pT spectra of w are measured for several decay modes in d+Au and p+p. wp0g dAu MB (PRC75 151902) wp0p+p- dAu MB(PRC75 151902) w e+e- pp MB (PHENIX preliminary) wp0g pp MB (PRC75 151902) wp0p+p- pp MB(PRC75 151902) wp0g pp ERT (PHENIX preliminary) wp0p+p- pp ERT (PHENIX preliminary) w d+Au p+p Spectra show good agreement among several decay channels.

RdA of f and w mesons in 200 GeV As a baseline check, RdA is calculated for f and w and compared to other mesons. RdA f RdA w 0-20% 0-20% wp0p+p- wp0g hgg p0gg fK+K-hgg p0gg M.B. M.B. RdA does not show suppression in central arm. f and w results are consistent with p0 and h.

f/p, w/p ratios in p+p and d+Au 200 GeV f/p, f/K w/p f/p dAu f/K pp pp f/p pp f/p and w/p ratio have little or no pT dependence at pT >2.0 GeV/c. /0 in p+p Run5 @ √s = 200 GeV = 0.81 ± 0.02(stat) ± 0.07(syst) /0 in d+Au Run3 @ √sNN = 200 GeV = 0.94 ± 0.08(stat) ± 0.12(syst)

Chiral symmetry restoration Topic 1 Chiral symmetry restoration

Yield comparison between fe+e- and f K+K- Question 1’: Have we observed changes of yield between e+e- and K+K- ? Comparison of integrated yield is not enough, because mass modification effects depend on the pT region. Low pT mesons tend to decay inside the hot/dense matter f f Low pT High pT In addition, To determine the integrated yield, an extrapolation to lower pT is needed. There is a large uncertainty in the calculation. Thus, pT-dependent information is essential for comparison. Now, we should ask Have we observed changes of spectra between e+e- and K+K- ?

Au+Au Spectra comparison between fe+e- and f K+K- f e+e- AuAu MB f e+e- 20-40% x 10-3 f e+e- 40-92% x 10-1 f K+K- AuAu MB (no PID) f K+K- AuAu MB (double PID) f K+K- AuAu MB (PRC72 014903) f K+K- 20-40% x 10-3 (double PID) f K+K- 40-92% x 10-1 (double PID) f K+K- 40-92% x 10-1 (PRC72 014903) M.B. 40-92% 20-40% Errors are too large to make any clear statement about the comparison of spectra for f  e+e- and f  K+K-.

Nuclear modification factors Topic 2 Nuclear modification factors

Au+Au fK+K- in Au+Au is also extended to higher mT 　　No ID 　　Single ID 　　Double ID 0-10% 60-90% p+p M.B. f candidates Double ID analysis no ID analysis K+ K- h+ h- fK+K- measurement has been extended to higher mT using no kaon ID method. mT region is extended to ~ 5 GeV. The two independent hadron decay analyses are consistent with each other in Au+Au.

Is RAA suppression carried by mass or quark number? Question 1 : Is particle yield suppression carried by mass or quark number ? RAA of proton (mp=938 MeV/c2) Comparison between f and p: RAA of f meson (mf=1019 MeV/c2) 60-93% MinBias 0-10% RAA of f in central collisions is lower than in peripheral at high pT. RAA of protons is nearly independent of centrality. f RAA shows a different trend as compared to the proton. Difference of RAA between f and proton suggests that energy loss occurs at the partonic level.

w mesons in Au+Au Background estimate is improved in ωπ０γ analysis pT spectra of w are measured for several centralities and at high pT. [GeV/c2] Magenda = Red + Green + Blue 3 BG sources Invariant mass reconstructed by 3g PHENIX preliminary w  e+e-, AuAu MB x 102 w  p0g, AuAu MB x 102 w  p0g, AuAu 0-20 % x 104  p0g, AuAu 20-60% x 10 w  p0g, AuAu 60-92% 0-20% M.B. Details are in M.Ouchida’s poster 20-60% Background and shape are carefully estimated. 60-92% Measurement of w mesons up to 10 GeV/c is made.

Mass dependence of RAA between mesons Question 2 : Does RAA of mesons have a mass or a flavor dependence? f w f meson has a different RAA for pT < 5 GeV/c.

Summary <Topic 1> Mass modification of light vector mesons - as a probe of chiral phase transition - in low pT region Question 1 : Have we observed changes of line shape, yield, and/or spectra? Answer 1 : We are still trying to quantify the difference. Improvement of statistics and signal to background ratio in the next run will improve existing measurements. <Topic 2 > Particle yield suppression of light vector mesons in medium - as a probe of medium effect - at relatively high pT Question 1 : Is particle yield suppression carried by mass or quark number ? Answer 1 : Difference between RAA of f meson vs proton suggests that energy loss occurs at the partonic level . Question 2 : Does RAA of mesons have a mass or flavor dependence ? Answer 2 : f meson has a different RAA compared to other mesons (p, h).

Thank you for inviting me to Quark Matter 2008 ! I’d like to say thanks to all participants and collaborators

Back up

Yield and temperature for φ mesons After several experimental checking, we found integrated information is not enough to determine the difference between e+e- and K+K-. Need a careful check of mT spectra.

The invariant mass spectra for φ mesons f-> e+e- p+p f-> e+e- d+Au f->e+e- Au+Au φ φ f->K+K- (double PID) d+Au f-> K+K- (double PID) Au+Au

The invariant mass spectra for φ mesons f->K+K- (no PID) pp f->K+K- (single PID) pp f->K+K- (no PID) AuAU f->K+K- (no PID) dAu

The invariant mass spectra for ω mesons w-> e+e- p+p w->e+e- d+Au w->e+e- Au+Au ω ω w->p0p+p- p+p w->p0g p+p w->p0g Au+Au