Direct Photons Direct photons come from initial hot dense matter Compton scattering of quarks and gluons: q(q)gægq(q) Annihilation of quarks: qqægg In

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ああすむらかわ
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1 Direct Photons and Electrons

2 Direct Photons Direct photons come from initial hot dense matter Compton scattering of quarks and gluons: q(q)gægq(q) Annihilation of quarks: qqægg Information on Thermo-dynamical state of medium Initial temperature, Degree of freedom, etc. Other sources of photons? Decayed photons from hadronic sources Invariant Yield Pb+Pb s NN =17.3GeV WA98 Collaboration at CERN p T [GeV/c] Phys. Rev. Lett. 85, 3595 (2000)

Analysis ( s NN =130GeV Au+Au) Calculated gamma Count Count p T [GeV/c] Generate gammas from hadron sources Take observed p 0 p T spectra h, h, r: m T scaling of power-law fit to p 0 is applied and

3 Analysis ( s NN =130GeV Au+Au) Calculated gamma Count Count p T [GeV/c] Generate gammas from hadron sources Take observed p 0 p T spectra h, h, r: m T scaling of power-law fit to p 0 is applied and estimated Generate Flat rapidity of 0.5<y<0.5 Generate p T measured or estimated Decay hadrons into gammas Inclusive photon spectra Efficiency and contamination estimated by comparing real data and simulation Systematic Error: Showing 1s level p 0 fitting error of 25-35% + table listed Measured gamma Energy[GeV]

4 Comparison of Cluster Energy Distributions (I) s NN =130GeV Au+Au 60-80% Central Events Comparison between measured and calculated energy spectra Systematic error bans(cyan) Measured inclusive photons are consistent with contributions from known hadronic sources! Counts/100MeV Comparison of measured and calculated p T [GeV/c] Ratio of measured and calculated Ratio p T [GeV/c]

5 Comparison of Cluster Energy Distributions (II) s NN =130GeV Au+Au 0-10% Central Events Systematic error bands (Cyan) Counts/100MeV Comparison of measured and calculated Measured inclusive photons are yet not inconsistent with contributions from known hadronic sources within current systematic errors Ratio of measured and calculated Ratio p T [GeV/c] p T [GeV/c]

sources Numerator: Inclusive photons measured Measured

6 Photon Result - s NN =200GeV Au+Au- Plotted are ratios of photons to p 0 Denominator: Photons calculated from hadronic sources Numerator: Inclusive photons measured Measured inclusive photons are yet not inconsistent within current systematic errors..

7 time Single electron and Charm Two Au nuclei collide Formation of Hot & Dense matter Initial gluon density gluon shadowing? Thermal production of charm Energy loss of charm Charm cross section Charm suppression? Charm enhancement? Charm pt distribution Hadronization Hadron gas Charm is a very good probe of initial stage of heavy ion collisions. Open charm measurement is important to understand J/Y production Freeze Out Charm production at RHIC can be studied from its decay to single electrons

8 Charm measurement Direct method: Reconstruction of D-meson(e.g. D 0 Kp). Very challenging without measurement of displaced vertex c c 0D K+ -l nl K- p + 0D Indirect method: Measure leptons from semileptonic decay of charm. This method is used by PHENIX at RHIC

9 Single electron in RUN-1(130GeV) Inclusive electron spectra are measured at y=0 The background from p 0 Dalitz, photon conversions, etc are estimated and subtracted. Observe excess over background in pt>0.8 GeV/c PRL 88,

10 Background-subtracted single electron spectra Background subtracted electron spectra are compared with the charm decay contribution. Charm decay contribution is calculated as EdN e /dp 3 = T AA Eds/dp 3 T AA : nuclear overlap integral Eds/dp 3 : electron spectrum from charm decay calculated using PYTHIA From the single electron yield in pt>0.8 GeV/c, charm cross section per binary collision is obtained as s cc = 380±60±200 mb PRL 88,

11 Comparison with other experiments PHENIX single electron cross section is compared with the ISR data Charm cross section derived from the electron data is compared with fixed target charm data Solid curves: PYTHIA Shaded band: NLO pqcd PRL 88,

12 RUN2 single electron result The yield of non-photonic electron at 200 GeV is higher than 130 GeV The increase is consistent with PYTHIA charm calculation (s cc (130GeV)=330 mb s cc (200GeV)=650 mb) PRL nucl-ex/ ,

13 Centrality Dependence In all 4 centralities, the data are consistent with N coll scaled charm decay contribution calculated by PYTHIA. nucl-ex/

14 Observations PHENIX single electron data are consistent with binary scaling within current statistical and systematic errors. Both errors will be much reduced in final RUN-2 result NA50 has inferred a factor of ~3 charm enhancement at lower energy. We do not see this large effect at RHIC. PHENIX observes a factor of ~3-5 suppression in high p T p 0 relative to binary scaling. We do not see this large effect in the single electrons. Initial state high pt suppression is excluded? smaller energy loss for heavy quark? (dead cone effect) Enhancement of Open Charm Yield NA50 - Eur. Phys. Jour. C14, 443 (2000). N part Binary Scaling PHENIX Preliminary

15 J/y Suppression

16 time J/Y measurement Two Au nuclei collide Initial ccbar production Formation of Hot & Dense matter Hadronization J/Y can not form due to Debye Screening in QGP Statistical formation of J/Y from ccbar pair J/Y suppression J/Y enhancement at RHIC?! Hadron gas J/Y suppression, predicted by Matsui and Satz and observed by NA50 at SPS, is considered as one of the strongest evidence of QGP formation. If J/Y suppression is due to QGP formation, much stronger suppression is expected at RHIC. Freeze Out New theory of J/Y formation predicts J/Y enhancement at RHIC energy by statistical formation of J/Y at hadronizatoin Do we observe J/Y suppression or enhancement at RHIC?

17 V V Vector Meson = 1 = C q = Charmonium 4pr a eff = 0.52, k = GeV/fm, m c = 1.84 GeV = kr a eff = 0.30, k = 1.18 GeV/fm, m c = 1.65 GeV linear 2 p aeff H = - + kr 2m r 2 q Ê 4 ˆ aeff = Á= as 4p Ë 3 Confined q 2 4 = g 3 2 vector mesons J/y Y Y composition cc cc bb Mass (GeV) G (kev) G ee (kev) r (fm)

18 ( ) : Debye screening mass m : Debyescreening length 4 1 D / - - = = D r D e r q r V l l p l ( ) D D / r eff / r eff e r r r E r / p e r p H l - l - a - m = = a - m = ( ) ( ) ( ) ( ) at : x. x f e x x x f e r r dr r de max x D eff / r D D D = = + = ml a = ˆ Á Ë Ê l + l Æ = - l - 1/(a eff m l D ) > 0.84 r Bohr = 1 / a eff m (l D = Bohr ) 1.19 r Bohr > l D QGP Charmonium Debye screening

19 l D l ( PQCD) 1 = T Ê Á Ë N 3 C 1 + N = 0.36 fm at T = 200 MeV :g 6 f ˆ g 2 1 a m = 3, N = 0.52 ( Lattice - QCD) ~ 0.5l ( PQCD) ; = ~ 0.4 fm : m 1840 / 2 MeV ( N D D r Bohr = eff = gt 2 = 4pa eff c, a eff f = 3) TX = m a eff 9p = a eff (GeV) charm: a eff = 0.30 Tx = 143 MeV a eff = 0.52 Tx = 209 MeV bottom: Tx = (4.73/1.84) x 143 = 368 MeV J/y MeV Y J/y Y r, w, f QGP

20 J/y CERN-SPS NA38 (NA50) muon 200 AGeV O, S + A J/y vs E T E T J/y Y suppression E T J/y e e = E / V ~ (de T /dy)/ (pr 02 A 2/3 t 0 )

21 p + A A + A Fermi-Lab E772 (A) A a Drell-Yan (DY) a = 1 J/y, Y a = 0.92 U a = 0.96 p+a, A + A p + A QGP

22 J/y suppression J/y + h D + D + X Bs J/y AB /AB = 4.1 exp[-r 0 s abs (L A + L B )] mb r 0 = 0.14 fm -3 s abs = 5.2 mb L A + L B : scaling - J/y suppression? s tot J/y-N = 2.2 (0.7) mb (J.J. Aubert et al., Nucl. Phys. B213 (1983) 1) s quasi-elastic J/y-N = 0.79 (0.12) mb (R.L. Anderson, SLAC-Pub 1741 (1976)) s abs J/y-N = 1.4 mb A B

23 Y Y J/y Y - J/y ratio p + A S + A, Pb + Pb J/y Y suppress

24 Pb + Pb J/y Suppression suppression p+a S+A J/y - Drell-Yan ratio

25 Co-mover S+U Pb+Pb s yco = 3.2 mb if corss section scales with (radius) 2 s y co = 3.8 s yco s cco = 2.4 s yco Solid line: s yn = 4.8 mb, s yco = 3.2 mb, n co =0.8/fm 3 dashed line: s yn = 4.8 mb dot-dashed line: s yn = 7.3 mb Solid line: s yco = 3.2 mb, s y co = 25 mb, n co =0.8/fm 3 dashed line: s y co = 3.8 s yco n co =0.5/fm 3 a parameter set with feeding to J/y from c and y included

26 y S+U J/y Pb + Pb y S+U J/y Pb + Pb Pb+Pb RHIC SPS U

27 pp J/Y at 200 GeV pp e + e - X ( y <0.35) pp m + m - X (1.2<y<2.2) pp J/Y is measured both in ee and in mm nucl-ex/

28 J/Y Bds/dy in p+p(200gev) B s ( pp Æ J / y + X ) = 226 ± 36( stat) ± 79( sys) nb ( pp Æ J / y + X ) = 3.8 ± 0.6( stat) ± 1.3( sys) mb s nucl-ex/

29 Comparison with lower energy PHENIX preliminary s ( pp Æ J / y + X ) = 3.8 ± 0.6( stat) ± 1.3( sys) mb Color evapolation model prediction is consistent with PHENIX data at s 1/2 =200 GeV CEM predictions (Phys.Lett.B390: ,1997)

30 J/y Æ e + e - in Gold-Gold From 26 M min. bias Au+Au 200 GeV (1/2 1/3 of all data) N J/y in 3 centrality bins. 0-20%: 5.9 ± 2.4(stat) ± 0.7(sys) 20-40%: 4.5 ± 2.1(stat) ± 0.5(sys) 40-90%: 3.5 ± 1.9 (stat)± 0.5(sys) nucl-ex/

31 nucl-ex/ J/y B-dN/dy per binary collision

32 Model Comparisons (1) (1) J/y scale with the number of binary collisions (2) J/y follow normal nuclear absorption with s J-N =7.1 mb (3) J/y follow same pattern as NA50 (J/y / DY(mb)) 1 Due to low statistics, our data are compatible all of these models. nucl-ex/ NA50 Phys. Lett. B521, 195 (2001)

33 Model comparion(2) J/Y re-generation models At RHIC, about 10 ccbar pairs produced in central event. They can recombine to form J/Y. Those models that assume formation of J/Y inside of QGP predict enhanced production of J/Y in Au+Au. PHENIX data does not favor a large enhancement. In QGP suppression model, very strong J/Y suppression at RHIC is expected. PHENIX data does not favor a very strong suppression. Models of statistical generation of J/Y at hadronization stage predict that J/Y yield in central Au+Au is about half of that of pp. A much larger statistics is required to test those models. ( RUN4) Theory curve from R. L Thews, PRC63, PHENIX data J/Y regeneration QGP suppression L. Grandchamp and R. Rapp, hep-ph/

35 QCD QCD e( k) ~ 1- ln ~ k m 2 2 L C 2 2 ( k / L ) ( k ( k 2 2 Æ ) Æ 0) rr D = ee E D=0 qq 0 = - a s G p a mn 2 fp m 2m G mn a 2 p q 0 = (-225 ± 25 MeV) = (350 ± 30 MeV) 4 3

36 QCD qq pairing L L L operator = order parameter QCD BCS y Æ e order parameter y Æ e ig q 2ig 5q pair yy yy Æye y order parameter 5 iq QCD H = -gss i s T C Cooper pair <y y > 0 Lagrangian L y pair y y y y y Ø Ø Æy e 2iq y Ø

37 Order Parameter QCD

38 m µ qq low-mass r 0 w f

39 KEK PS f e + e - K + K - INS ES r p + p - Spring-8 f r e + e - GSI r e + e - CERN-SPS CERES r w e + e - RHIC PHENIX f e + e - K + K - r w e + e -

40 KEK- TAGX g g + A -> r + X r -> p + + p - = r

41 p + + p - p + + p -

42 KEK-PS p+a

43 r r 0 e+e- 1.3 fm r N 0 p + p ( r Æ e e ) µ Dt( )

44 ( + - Æ e e ) n V DT freeze-out V = t e+e- = : V ~ = t >> DT Ú DT 0 DT t BN t BN V V dt + + BN n BN V BN t ÚD T t << DT n BN V DT/t V = V BN e V -( t-dt )/ t Ê DT Á1+ Ë t dt ˆ

45 RHIC-PHENIX f e + e - K + K - r w e + e - f

500 6 LHC ALICE ( 25 ) µsec MeV QGP

500 6 LHC ALICE ( 25 ) µsec MeV QGP 5 6 LHC ALICE shigaki@hiroshima-u.ac.jp chujo.tatsuya.fw@u.tsukuba.ac.jp gunji@cns.s.u-tokyo.ac.jp 3 ( 5 ) 5. µsec MeV QGP 98 RHIC QGP CERN LHC. LHC ALICE LHC p+p RHIC QGP ALICE 3 5 36 3, [, ] ALICE [,