J production in Au Au and Cu Cu Collisions at RHIC by MikeJenny



J/y production in
Au+Au and Cu+Cu
Collisions at RHIC

      Taku Gunji
CNS, University of Tokyo

     Heavy Ion Café 2007/2/10


 Physics Motivation
 J/y in the medium

 J/y measurement at SPS

 J/y measurement at RHIC
     d+Au collisions and cold matter effects
     Au+Au and Cu+Cu collisions

 Comparison to the theoretical models
 Summary & Outlook

            Physics Motivation
 J/y suppression in QGP
due to the Debye Color Screening
T.Matsui & H. Satz PLB178 416 (1986)
       Signature of de-confinement
       Debye Color Screening
         • Debye Radius < Rcc
            No formation of c-cbar bound states
       Suppression depends on temperature (density)
         • Recent quenched lattice QCD calculations
            • Melting temp. for J/y ~1.5-2.5Tc
            • Melting temp. for cc,y’ ~1.1Tc
                              T. Hatsuda, M. Asakawa, PRL. 92 (2004) 012001
                              S. Datta, et al., PRD69 (2004) 094507

            J/y = Thermometer of QGP
   2 Key points
      Feed down contribution from y’ and cc
         • All J/y = ~0.6 J/y (direct) + ~0.3cc + ~ 0.1y’
         • Fraction is not well-understood experimentally
       TJ/y ~ 2Tc and Tc, Ty’ ~ 1.1Tc
        Expected J/y (All)
        Suppression Pattern
        “Sequential Melting”

        Temperature can be
        deduced from magnitude
        of suppression.

            J/y in the Medium
   J/y production and evolution of the medium
      All stage of collisions modify the J/y yield.

Initial stage       Nuclear         Hot and dense        Mixed Phase
                    medium          medium               Freeze out

    • Gluon       • Nuclear         • Color screening   • cc coalescence
    Shadowing     Absorption        (Dissociation by    • Dissociation by
    • CGC         • Cronin effect   thermal gluons)     comovers

      Cold Matter Effect                    Final state Effect

          J/y measurement at SPS
   NA38(S+U@19.4 GeV)、NA50(p+A@19.4 GeV, Pb+Pb@17.3GeV)

                              Nuclear Absorption
                              of J/y
                              L: effective path length of J/y
                              in nuclear target

                              Anomalous suppression
                              relative to nuclear Absorption

                               • Very promising to study J/y
                  Pb+Pb        production in A+A collisions at higher
                               collision energy.
      B                             • 10x √sNN at RHIC
                                    • 2-3x gluon density at RHIC

          PHENIX Experiment
   PHENIX can measure J/y in wide rapidity range
Central Arms:
Hadrons, photons, electrons
  J/y  e+e-
  Pe > 0.2 GeV/c
  Df = p (2 arms x p/2)

 Muon Arms:
 Muons at forward rapidity
  J/y  m+m-
  1.2< |h| < 2.4
  Pm > 2 GeV/c
  Df = 2p

RHIC cold nuclear
matter effects (CNM)

             J/y in d+Au collisions
   Understand the cold matter effects                                       rapidity y
        Gluon Shadowing                                       Xd     XAu

        Nuclear absorption                        J/y in
        Cronin effect (pT broadening)             y<0          Xd     XAu

    Coverage of XAu in d+Au at PHENIX
                                                                               J/y in
                                                                              North
South muon arm (y < -1.2) :                 gluons in Pb / gluons in p

        large XAu  0.090
Central arm (y  0) :
        intermediate XAu  0.020                  Shadowing            Anti
North muon arm (y > 1.2) :                                           Shadowing
        small XAu  0.003
                                     Eskola, et al., Nucl. Phys. A696 (2001) 729-746.

        Results of RdAu vs. y
   d+Au experiments at RHIC
     RdAu vs. Rapidity

                      Low x2 ~ 0.003
             0 mb
                    (shadowing region)
                                         •Tendency is consistent with
            3 mb
                                         the shadowing effects.
                                         •Nuclear absorption cross
                                         section : 0~3 mb.
                                            • need more data to
                                            quantify CNM effects.

J/y production in Au+Au and
  Cu+Cu collisions at RHIC

          RAA vs. Npart


                                 Au+Au PHENIX Final
                                 Cu+Cu PHENIX Preliminary


• Final results for Au+Au : nucl-ex/0611020 (submitted to PRL)
• Analysis for Cu+Cu will be finalized soon!

   Observation 1
Different suppression
   pattern between
   mid-rapidity and

               RAA vs. Npart in Au+Au
  1                                              RAA vs. Npart.
                                                     |y|<0.35
                                                     1.2<|y|<2.2

      Bar: uncorrelated error                 • Different behavior in RAA
      Bracket : correlated error
  0                                           between mid-rapidity and

                                              • J/y suppression is larger
                                              at forward-rapidity than
                                              at mid-rapidity
      S = RAA (1.2<|y|<2.2) /RAA (|y|<0.35)       • S ~ 0.6 for Npart>100

           RAA and CNM effects
                                          CNM effects
RAA                                         Gluon shadowing +
                                           nuclear absorption
                                            J/y measurement in
                                             d+Au collisions.

                                        RHIC CNM effects
                                        (sabs = 0, 1, 2mb at y=0, y=2)
                                        R. Vogt et al., nucl-th/0507027

      • Significant suppression relative to CNM effects.
      • CNM effects predict larger suppression at mid-rapidity,
      while data shows larger suppression at forward-rapidity.

              Larger suppression by
  Heavy quark production is expected to be
suppressed due to “Color Glass Condensate”
at forward-rapidity. K. L. Tuchin hep-ph/0402298
     Open charm yield
     in Au+Au @ 200 GeV


    • Larger suppression of J/y at forward-rapidity (Npart>100)
    could be ascribed to Color Glass Condensate?

             Larger suppression by
             larger feed down?
   Pythia calculation (done by S. X. Oda)
         Red : 88 gg  c1cg  J/y
         Green : 89 gg  c2cg  J/y
         Blue : 105 gg  c2c  J/y
         Magenta : MSEL 5 bbbar  J/y   Larger suppression
                                        of J/y yield
                                        at forward rapidity
                                        might be partly
                                        (~15%) due to the
                                        broad distribution
                                        of J/psi from chi_c.

   Observation 2
   J/y suppression
from final state effect
 is stronger at RHIC
  compared to SPS

           Comparison of RAA to NA50
NA50 at SPS (0<y<1)
PHENIX at RHIC (|y|<0.35)            RAA vs. Npart
PHENIX at RHIC (1.2<|y|<2.2)
                                         NA50 at SPS
                                          • 0<y<1
                                       PHENIX at RHIC
                                          • |y|<0.35
                                          • 1.2<|y|<2.2
                                      • J/y Suppression (CNM
Bar: uncorrelated error
Bracket : correlated error            effects included) is similar
Global error = 12% and
Global error = 7% are not shown       at RHIC (y=0) compared
                                      to at SPS (0<y<1).

          RAA and CNM
NA50 at SPS (0<y<1)
PHENIX at RHIC (|y|<0.35)
                                     RAA at RHIC and SPS
PHENIX at RHIC (1.2<|y|<2.2)

                                  RHIC CNM effects
                                  (sabs = 0, 1, 2mb at y=0, y=2)
                                  R. Vogt et al., nucl-th/0507027

                                  SPS CNM effects (sabs = 4.18 mb)
                                  NA50, Eur. Phys. J. C39 (2005):355

Bar: uncorrelated error
Bracket : correlated error
Global error = 12% and
Global error = 7% are not shown

          RAA/CNM vs. Npart
 NA50 at SPS (0<y<1)
 PHENIX at RHIC (|y|<0.35)                      RAA/CNM at RHIC and SPS.
 PHENIX at RHIC (1.2<|y|<2.2)
                       Here, SPS data will          sabs = 4.18 mb for SPS
                       have sys. errors.
                                                    sabs = 1 mb for RHIC
                                                     • Additional sys. error due to the
                                                       uncertainty of CNM (0-2mb) is
                                                       shown as box.

                                                 • J/y suppression relative
Bar: uncorrelated error                          to CNM effects is larger at
Bracket : correlated error
Global errors (12% and 7%)                       RHIC for the similar Npart.
are not shown here.
Box : uncertainty from CNM effect                (much larger
                                                 at forward rapidity)

RAA vs. pT

                Suppression
                 trend is similar
                 for forward and
                 mid rapidity.

                Suppression
                 consistent with

    Exercise :
  Comparison to
theoretical models

        Dissociation by thermal
Dissociation by thermal gluons
  • Successfully describe J/y suppression at SPS.
  • Gluon density extrapolated to RHIC energy

                                       R. Rapp et al., nucl-th/0608033
                                       Nu Xu et al., nucl-th/0608010
                                       Calculation for only y=0

                                          • At mid-rapidity,
                                          suppression is
                                          weaker compared
                                          to the dissociation
                                          scenario in QGP.

             Recombination of J/y                                      c-bar         c

   Coalescence of c-cbar
       Abundant ccbar pairs at RHIC [10-30@central Au+Au]
       Dissociation + Recombination of J/y
         R.Rapp et al, EPJC43 (2005) 91               N. Xu at al, nucl-th/0608010

                Kinetic formation model                     Transport model

                                  total                                    total

                                      dissociation           recombination

        Magnitude of suppression matches better.
        However, tendency can not be reproduced well.

         <pT2> vs. centrality
   Another test for recombination

                                No recombination

                                  (pQCD charm )

                                     (thermal charm)

         Kinetic formation model.
Dissociation + recombination model (R. Rapp and so on)

                               Charm cross section (binary scaling)
                                   • NLO pQCD calc, PHENIX, STAR
                                gc ~ 10 at RHIC, ~30 at LHC

                                    ¼ sc+g     X.N.Wang PLB540 (2002) 62

                                                    Gluon thermal dist.
                                                    (T=0.35 GeV)

         Transport model
Dissociation + recombination model (Nu Xu et al.)

                                                  ccbar  J/y +g

                                                       J/y +g ccbar

                                  R. L. Thews Eur. Phys. J C43, 97 (2005)

          Sequential Melting
                                              RAA/CNM vs. Bjorken
                                               energy density

                     Here, SPS data will
                     have sys. errors .           t0 = 1 fm/c. Be careful!
                                                   • Not clear t0 at SPS
                                                   • Crossing time ~ 1.6 fm/c

                                                • J/y suppression at SPS
                                                can be understood
F. Karsch et al., PLB, 637 (2006) 75            from the melting of y’
                                                and cc.

         Sequential Melting
                                             RAA/CNM vs. Bjorken
                                              energy density

                        Here, SPS data will
                        have sys. errors.
                                                 t0 = 1 fm/c. Be careful!
                                                  • Not clear t0 at SPS
                                                  and RHIC.
                                                  • t0 < 1 fm/c at RHIC
Bar: uncorrelated error
Bracket : correlated error                        • Nucl. Phys. A757, 2005
Global error = 12% is not shown here.
Box : uncertainty from CNM effects
F. Karsch et al., PLB, 637 (2006) 75
dET/dy : PHENIX, PRC 71, 034908 (2005)

         Sequential Melting
                                                RAA/CNM vs. Bjorken
                                                 energy density

                       Here, SPS data will
                       have sys. errors.
                                                    t0 = 1 fm/c Be careful!
                                                     • t0 < 1 fm/c at RHIC

                                             • Direct J/y melting at RHIC?
Bar: uncorrelated error
Bracket : correlated error
                                                 • Error is large and need better
Global error = 12% and 7%                        CNM measurements at RHIC.
are not shown here.                              • Need to measure feed-down
Box : uncertainty from CNM effects
                                                 contribution at RHIC energy.

            Threshold Model
   All J/y is suppressed above a threshold density.
                                            • Fate of J/y depends on the
     A. K. Chaudhuri, nucl-th/0610031       local energy density
     Calculation for only y=0.              ( participants density, n)
                                             Similar model to the sequential

                                            melting and associated to “onset
                                            of J/y suppression”.
                                             nc = 4.0 fm-2 matches to our

                                            mid-rapidity data.
                                            (cf. n~4.32 fm-2 in most central
                                            Au+Au collisions)

                                               • Describes well mid-
                                               rapidity data.
       nc = threshold participant density      • How about forward-


  First high statistic data of J/y in Au+Au and Cu+Cu collisions
at mid-rapidity and forward-rapidity are available.
 Suppression is larger at forward-rapidity than at
mid-rapidity for Npart>100.
     Suggesting initial state effect such as Color Glass Condensate?
     More feed down contribution at forward-rapidity?
 RAA/CNM seems to be lower at RHIC compared to at SPS
     However, suppression at mid-rapidity isn’t so strong as
       expected by the models (destruction by thermal gluons)
       extrapolated from SPS to RHIC.
     Suppression + Recombination models match better.
     Not consistent with the picture of only y’ and cc melting at
       RHIC. Suppression of directly produced J/y?
Backup slides
             Regeneration should cause narrowing of pT – does it?
Mean pT2 pretty flat
• as expected in regeneration picture of Thews
• Yan picture almost flat to start with, gives
slight fall-off with centrality
Caution - <pT2> from fits often unreliable for AA
(stable when restricted to pT<5 GeV/c here)
Better for theoretical comparisons to look at RAA(pT)?

          First cc observation
   From run5 p+p central arms
   Further analysis is on going.

               Mixed event BG

     cc1 cc2      Meeg-Mee [GeV]    Meeg-Mee [GeV]
Color Glass Condensate
   At RHIC, coherent charm production in nuclear color
    field at y>0 (Qs > mc) and dominant at y>2. 
    Description by Color-Glass-Condensate
                                   sdAu = spp (2x197)a
XAu, XF dependence of a
 Shadowing is weak.             sdAu = spp (2x197)a
 Not scaling with X2
but scaling with XF.
    Coincidence?
         • Shadowing
         • Gluon energy loss
         • Nuclear Absorption
       Sudakov Suppression?
         • Energy conservation
                                  (in gold)
         • hep-ph/0501260                             = Xd - XAu
                                    E866, PRL 84, (2000) 3256
       Gluon Saturation?           NA3, ZP C20, (1983) 101
         • hep-ph/0510358           PHENIX, PRL96 (2006) 012304
SPS J/y suppression
   Dissociation by gluons

                             NA60 In-In 158 GeV

       Pb-Pb @ 158 GeV
            Dissociation by gluons
   Cross section : g+J/y  c + c-bar
       LO calculation

       Decay width                      k[GeV]

T = 350 MeV, G = 0.8 fm/c
     Dissociation by gluons

Cross sectionはLO計算。正しいのか?
  • Binding Energyの小さいy’やccに適応可能か?

             Successful models (1)
   Dissociation by thermal gluons
       Based on LO pQCD cross section between J/y (cc) and g

        R. Rapp PLB92 (2004) 212301    X.N.Wang PLB540 (2002) 62

        Pb-Pb @ 158 GeV

                                        20 40           100
                                                          ET [GeV]
      PHENIX – p+p J/ψ – new run6 data
• Forward rapidity falloff steeper than 3-
gluon pQCD model - black curve [Khoze et al. , Eur.
Phys. J. C39, 163-171 (2005)]                           PHENIX - hep-ex/0611020
• Slightly favors flatter shape at mid-rapidity
than most models
• BR•stot = 178 ± 3 ± 53 ± 18 nb
                                                                          <pT2> = 3.59±0.06
• Harder pT than lower energy & softer at             <pT2> = 4.14±0.18
forward rapidity                                            +0.30-0.20
Statistical Model (1)
   Statistical Hadronization
       元々のMotivationはSPSで<J/y>/<h>が中心衝突度に
       Hadronの生成量

       もうひとつのパラメター:gu,d,s,c (Fugacity)
        • u,d,s,c quarkがどれほど化学平衡に達しているかという指標
        • 実際のYield = g x ni
     Statistical Model (2)
    RHICではgs ~ 1 (SPSでは、gs<0.7)
        Strange quarkがようやく平衡状態
    Charm quarkは重い。殆どがHiggs Mass
        衝突初期にしか出来ない。
        QGP中での熱的生成量(exp-(2mc/Tc)) ~ 10-7
    なのに、平衡状態を仮定して、J/yのYieldを計算
        gcが平衡状態からのずれを担う。

       cc-bar cross section
       (experiment, FONLL)

Model Input: Nccdir, T, m, Volume

このModelはp+p, Au+AuにおけるCharm Productionに大きく依存する。
  Statistical Model (3)
     Charm Production Cross sectionによる大きな不確定
     NNLO pQCD計算
 ds/dy = 63.7+95.6-42.3 mb

ds/dy = 123 mb (PHENIX)
  •CDFが測定したCharm Cross

 NNLO pQCD計算のCharm Cross
Recombination – In medium Formation
   Medium中でもJ/y生成。
       Kinetic Formation Model

       Transport Model
    Recombination – In medium Formation
   問題点と疑問点
      • Charm Cross Sectionの大きな不確定性
      • p+p, Au+AuにおけるCharm y, pT分布?
        • QGP中ではCharmはDiffusiveに動いているが、理由はまだ分かっていない。
      • J/y+gccbar のCross Sectionが正しいか?
      • Ncの与え方。どのモデルもNcは時間に対して一定。正しい?
        • Charmの熱的生成はない、Charm数は保存。
        • DメソンへのRecombinationも考慮すべき。NcNc(t)、tと共に減少するはず。
            • J/yの方が圧倒的に早く生成されるなら、正しいかも。
        • Naïveには、ccが空間的に近くにないといけない。ccがCoupleするよりも、
                                 Au+AuにおけるCharm, D, J/y生成

             Charm Production at RHIC
Need to understand charm          Yield vs. pT for two
                                  rapidity ranges
production and its modification
                                  in p+p collisions.
in the medium.                    Charm vs. y

 Non-photonic e spectra
 from PHENIX.
 Implication of charm
 Energy loss                  Non-photonic e v2          BW fit of D-meson spectra
                              from PHENIX.               From STAR.
                              Thermalization of          Freeze out and collective
                              Charm.                     Behavior of charm.

                                                             AuAu Central charm
                                                                        AuAu Central p,
                                                                        K, p

To top