1 / 14

RIKEN, Kyoto Univ. a , KEK b , CNS Univ. of Tokyo c , ICEPP Univ. of Tokyo d , Tohoku Univ. e

RIKEN, Kyoto Univ. a , KEK b , CNS Univ. of Tokyo c , ICEPP Univ. of Tokyo d , Tohoku Univ. e Ryotaro Muto, KEK, Japan J. Chiba b , H. En’yo, Y. Fukao a , H. Funahashi a , H. Hamagaki c , M. Ieiri b , M. Ishino d ,

sari
Download Presentation

RIKEN, Kyoto Univ. a , KEK b , CNS Univ. of Tokyo c , ICEPP Univ. of Tokyo d , Tohoku Univ. e

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. RIKEN, Kyoto Univ.a , KEKb, CNS Univ. of Tokyoc, ICEPP Univ. of Tokyod, Tohoku Univ.e Ryotaro Muto, KEK, Japan J. Chibab, H. En’yo, Y. Fukaoa, H. Funahashia, H. Hamagakic, M. Ieirib, M. Ishinod, H. Kandae, M. Kitaguchia, S. Miharad, K. Miwaa, T. Miyashitaa, T. Murakamia, T. Nakuraa, M. Naruki, K. Ozawac, F. Sakumaa, O. Sasakib, M. Sekimotob, T. Tabaru, K.H. Tanakab, M. Togawaa, S. Yamadaa, S. Yokkaichi, Y. Yoshimuraa (KEK-PSE325 Collaboration) Evidence of r, w and f meson mass modification in nuclear medium measured in 12 GeVp+A reaction at KEK-PS E325 f • Introduction • Result of r/w e+e- analysis • Result of f  e+e- analysis

  2. r w f Vector meson mass at finite density 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/r0for r/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: PRL 98, 042501 (‘07) • a : PRC, 75, 025201 (‘06) x6 statistics in K+K- • fKK: PRL 98, 152302 (‘07) • Slowly movingr,w,f (plab~2GeV/c） Large acceptance • spectrometer • 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 spectra of e+e- we+e- we+e- C Cu Mass resolution 8 MeV/c2 for r/w 11 MeV/c2 for f fe+e- fe+e- We examine how well the data are reproduced with known hadronic sources & combinatorial background

  5. Invariant mass spectra 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 spectra of e+e-(r/w region, 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.)  the excesses are mainly due to modified r mesons Lifetime of r : ct~1.3fm excess can be observed in both C & Cu

  7. Invariant mass spectra of e+e- we+e- we+e- C Cu Mass resolution 8 MeV/c2 for r/w 11 MeV/c2 for f fe+e- fe+e- We examine how well the data are reproduced with known hadronic sources & quadratic background

  8. Invariant mass spectra of f e+e- f f C Cu [GeV/c2] [GeV/c2] Background : Quadratic curve Some hints on the low mass side of the f meson peak in Cu data Slowly moving f has larger probability to decay inside nucleus  We divided the data by bg ( = p/m)

  9. Invariant mass 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

  10. Model calc. including mass modification e+ r/w We attempt to reproduce the observed spectra with model calculation including mass modification e- f

  11. Fit results of model calculation for r/w k1 = 0.092 (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.

  12. Fit result of model calculation for fe+e-k1=0.034, k2=2.6 1.75<bg (Fast) bg<1.25 (Slow) 1.25<bg<1.75 Small Nucleus Large Nucleus

  13. Comparison with the theoretical prediction m*/m = 1 – k1r/r0, G*/G = 1 + k2r/r0 fit result f 1 0.9 0.8 0.7 f m(r)/m(0) fit result r/w r/w prediction (Hatsuda,Lee) The data were well reproduced with the model; mr/w decreases by 9.2%, mf decreases by 3.4%and Gf increases by 3.6 at r0 0 0.5 1 r/r0 syst. error is not included

  14. Summary • We have observed significant excesses over the known hadronic sources both in r/w e+e- and f  e+e- distributions in 12 GeVp+A reactions • The excesses were well reproduced by the model calculation including mass modification, • r/w : 9% mass decrease • f : 3% mass decrease and width broadening by a factor of 3.6 at r0. • From f K+K- analyses we have obtained limits on the in-medium decay width broadenings for both fe+e- and fK+K- decay channels •  See Poster by Fuminori Sakuma (Tomorrow) • We are planning next experiment at J-PARC which will achieve statistics 100 times as large as the present experiment •  See Poster by Satoshi Yokkaichi (Tomorrow)

More Related