Systematic measurements of light vector mesons in RHIC-PHENIX

1. Systematic measurementsof 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

2. f e+e- in Au+Au √sNN=200 GeV ω 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-

3. Topics in this talk (Cont’d) All data shown in this talk are taken at sNN = 200 GeV. • <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.

4. e+ e- f,w Momentum Electron ID gEnergy g p0 g p0 g g K+ p+ w f K- p- g Hadron ID Momentum Momentum Hadron ID Electron, hadron and photon in PHENIX 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-

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

6. Extended f  K+K- analysis Consistency between f  K+K- and f e+e- f Double ID analysis K+ K- f candidates d+Au no ID analysis 0-20% h+ h- f candidates No ID Single ID Double ID No ID Single ID Double ID e+e- Single ID analysis M.B. p+p K+ or K- h+ or h- f candidates f d+Au 0-20% M.B. p+p • 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. In p+p, spectra of e+e- and K+K- show reasonable agreement!

7. 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) Measurements of win wide pT range pT spectra of w are measured for several decay modes in d+Au and p+p. w d+Au p+p Spectra show good agreement among several decay channels.

8. wp0p+p- wp0g hgg p0gg fK+K-hgg p0gg 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. RdAf RdAw 0-20% 0-20% M.B. M.B. • RdA does not show suppression in central arm. • f and w results are consistent with p0 and h.

9. f/p, w/p ratios in p+p and d+Au 200 GeV f/p, f/K w/p dAu 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 inp+p Run5 @ √s = 200 GeV = 0.81 ± 0.02(stat) ± 0.07(syst) /0 ind+AuRun3 @ √sNN = 200 GeV = 0.94 ± 0.08(stat) ± 0.12(syst)

10. Topic 1 Chiral symmetry restoration

11. 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- ?

12. 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) Au+Au 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-.

13. Topic 2 Nuclear modification factors

14. Double ID analysis Au+Au K+ K- f candidates no ID analysis 0-10% h+ h- f candidates M.B. No ID Single ID Double ID p+p 60-90% fK+K- in Au+Au is also extended to higher mT • 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.

15. MinBias 0-10% 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% • 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.

16. 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% Magenda = Red + Green + Blue 3 BG sources [GeV/c2] 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. 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.

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

18. 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).

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

20. Back up

21. 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.

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

23. 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

24. 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