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Medium modifications on vector meson in 12GeV p+A reactions

Medium modifications on vector meson in 12GeV p+A reactions. Kyoto Univ. a , KEK b , RIKEN c , CNS Univ. of Tokyo d , Megumi Naruki, RIKEN, Japan J. Chiba b , H. En’yo c , Y. Fukao a , H. Funahashi a , H. Hamagaki d , M. Ieiri b ,

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Medium modifications on vector meson in 12GeV p+A reactions

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  1. Medium modifications on vector meson in 12GeV p+A reactions Kyoto Univ.a , KEKb, RIKENc, CNS Univ. of Tokyod, Megumi Naruki, RIKEN, Japan J. Chibab, H. En’yoc, Y. Fukaoa, H. Funahashia, H. Hamagakid, M. Ieirib, M. Ishinoe, H. Kandaf, M. Kitaguchia, S. Miharae, K. Miwaa, T. Miyashitaa, T. Murakamia, R. Mutoc, T. Nakuraa, K. Ozawad, F. Sakumaa, O. Sasakib, M. Sekimotob, T. Tabaruc, K.H. Tanakab, M. Togawaa, S. Yamadaa, S. Yokkaichic, Y. Yoshimuraa (KEK-PSE325 Collaboration) • Introduction • Result of r/we+e- analysis • Result of fe+e- analysis • Result of f K+K-analysis

  2. Mass modification at finite density r w f Hatsuda & Lee PRC46(1992)R34 dropping mass • Brown-Rho scaling (’91) • m*/m = 0.8 atr = r0 • QCD Sum Rule by Hatsuda & Lee (’92) • m*/m = 1 - 0.16 r/r0forr/w • m*/m = 1 - 0.03 r/r0 for f • Lattice Calc. by Muroya, Nakamura & Nonaka(’03) width broadening (at r0) • Klingl, Kaiser, Weise (’97-8) G*/G~10 for r/w/f • Rapp & Wambach(’99): G*r/Gr~2 • Oset & Ramos (’01) : DGf = 22MeV • Cabrera & Vicente (’03) : DGf = 33MeV

  3. E325 experiment Invariant Mass ofe+e-, K+K- in 12GeV p + Ar, w, f + X • History • ’93 proposed • ’96 construction start • NIM, A457, 581 (2001). • NIM, A516, 390 (2004). • ’97 first K+K- data • ’98 first e+e- data • PRL, 86, 5019 (2001). • ’99~’02 • x100 statistics in e+e- • r/w: PRL 96, 092301 (‘06). • f ee: nucl-ex/0511019 • a : PRC, 75, 025201 (‘06) x6 statistics in K+K- • fKK : nucl-ex/0606029 • slowly movingr,w,f (plab~2GeV/c） • larger probability to decay inside nucleus • primary proton beam~109 ppp • thin targets: 0.2%/0.05% (C/Cu) • radiation length: 0.4/0.5%(C/Cu) B beam

  4. Invariant Mass Spectrum of e+e- we+e- we+e- C Cu fe+e- fe+e- we examine how well the data are reproduced with known hadronic sources & combinatorial background

  5. Invariant Mass Spectrum of e+e- we+e- we+e- Cu C c2/dof=163/140 (8%) c2/dof=156/140 (16%) fe+e- fe+e- the excess over the known hadronic sources on the low mass side of w peak has been observed.

  6. Invariant Mass Spectrum of e+e- (background subtracted) C Cu r/w ratio is consistent with zero Nr/Nw=0.0±0.02(stat.)±0.2(sys.) 0.0±0.04(stat.)±0.3(sys.) most of r decay in nucleus due to their short lifetime; t~ 1.3fm

  7. Invariant Mass Spectrum of e+e- we+e- we+e- C Cu fe+e- fe+e- we examine how well the data are reproduced with known hadronic sources & combinatorial background

  8. e+e- Invariant Mass Distributions C Cu f f [GeV/c2] [GeV/c2] • fit with MC shape & quadratic curve • a hint on the spectrum of Cu data. • longer lifetime; t~50fm  kinematical dependence

  9. To see bg dependence Slowly moving f mesons have a larger probability to decay inside the target nucleus. We divided the data into three by bg ( = p/m ); bg<1.25, 1.25<bg<1.75 and 1.75<bg. bg distribution

  10. Invariant spectra of fe+e- 1.75<bg (Fast) bg<1.25 (Slow) 1.25<bg<1.75 Small Nucleus Large Nucleus Rejected at 99% confidence level nucl-ex/0511019

  11. Energy Loss Resonance Shape : Breit-Wigner + internal radiative correction experimental effect estimated by Geant4 simulation – energy loss, mass resolution, mass acceptance etc. detector simulation for f • Blue histogram : Detector Simulation • Red line : Breit-Wigner (gaussian convoluted) fitting result Experimental effects are fully taken into account we fit the data by the simulated shape, which fully includes the experimental effect

  12. Model Calculationw/ medium modification e e r/w f • dropping mass: M(r)/M(0) = 1 – k1 (r/r0) (Hatsuda & Lee) • width broadening: G(r)/G(0) = 1 +k2(r/r0) (k2~10 (Klingl et.al ))

  13. Fit Results of Model Calculation m*/m = 1 - 0.092r/r0 C Cu [GeV/c2] [GeV/c2] the excesses for both C and Cu are well reproduced by the model including the 9% mass decrease at r0.

  14. Invariant spectra of fe+e-fit with modified M.C. ( k1=0.034, k2=2.6 ) 1.75<bg (Fast) bg<1.25 (Slow) 1.25<bg<1.75 Small Nucleus Large Nucleus

  15. Fit Results of model calculationm*/m = 1 – k1r/r0, G*/G = 1 + k2r/r0 Contours for k1 and r/w Contours for k1 and k2 of fe+e- 1 0.9 0.8 0.7 fit result f m(r)/m(0) fit result r/w The data were well reproduced with the model; mr/w decreases by 9%, mf decreases by 3% and Gfincreases by 3.6 at r0 prediction 0 0.5 1 r/r0 syst. error is not included

  16. Fitting Results of f K+K- 2.2<bg (Fast) bg<1.7 (Slow) 1.7<bg<2.2 Small Nucleus Large Nucleus modification is not statistically significant • Our statistics in the K+K- decay mode are very limited in the bg region in which we find the excess in the e+e- mode

  17. nuclear mass number dependence of GfK+K- / Gfe+e- colored contour : MC • kK/e was obtained from the amount of excess. • kK = 2.0±1.1(stat.)±2.2(syst.) • The measured Da provides constraints on kK and ke. F. Sakuma, nucl-ex/0606029 the first experimental limits of the in-medium broadening of the partial decay widths

  18. We have observed the excess over the known hadronic sources at the low-mass side of w. Obtained r / w ratio indicates that the excess is mainly due to the modification of r. We also observed the excess at the low-mass side of f, only at the low bg region of Cu data. The data were well reproduced by the model calculation based on the mass modification. The fit results show that; r/w : the massdecreases by 9% at r0 . f :the mass decreases by 3%, and the width increases by a factor of 3.6 at r0. The mass modification is not statistically significant for the K+K- invariant mass distributions. The observed nuclear mass-number dependences of fe+e- and fK+K- are consistent. We have obtained limits on the in-medium decay width broadenings for both the fe+e- and fK+K- decay channels. Summary

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