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Hot Quarks 2006 (PowerPoint)

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					Critical review of QGP signals




Marcus Bleicher
Institut für Theoretische Physik
Goethe Universität Frankfurt
Germany
bleicher@th.physik.uni-frankfurt.de   Marcus Bleicher, Hot Quarks 2006
  Thanks to the UrQMD group
         @ Frankfurt
• Sascha Vogel (Resonances)
• Stephane Haussler (Event-by-Event Fluctuations)
• Hannah Petersen (Flow at FAIR)
• Diana Schumacher (Di-Leptons)
• Qingfeng Li (HBT)
• Xianglei Zhu (Elliptic Flow and Charm)
• Mohamed Abdel-Aziz (Event-by-Event Fluctuations)

• and Horst Stoecker, Yan Lu, Paul Sorensen, Nu Xu
                                   Marcus Bleicher, Hot Quarks 2006
            Contents

•   Introduction
•   No kinks, no horns, no steps
•   J/y enhancement/suppression
•   Jet quenching
•   NCQ scaling & elliptic flow
•   Conclusion
                       Marcus Bleicher, Hot Quarks 2006
The tools: Hadron-string models

• Non-equilibrium transport model
• Hadrons and resonances
• String excitation and fragmentation
• Cross sections are parameterized
  via AQM or calculated by detailed balance
• pQCD hard scattering at high energies

• Generates full space-time dynamics of hadrons
  and strings

                             Marcus Bleicher, Hot Quarks 2006
         The J/y story…

In the beginning there was Matsui and Satz:
“ccbar can not be bound to J/y’s above Tc”




Compare J/y in AA with J/y in pp*Nbinary
was/is done by NA50 and NA60


                           Marcus Bleicher, Hot Quarks 2006
                  Hadron transport

                                     • Different
                                       calculations,
                                       same results
                                     • Inputs: time
                                       dependent cross
                                       sections, j/psi+X
                                       cross section

Calculations: Spieles et al, 1999
Cassing et al, 2000
                                    Marcus Bleicher, Hot Quarks 2006
                 RHIC energies…

                                      • Same
                                        cross
                                        section is
                                        fine at
                                        RHIC




Taken from E. Bratkovskaya   Marcus Bleicher, Hot Quarks 2006
 What do we learn from J/Y?

• Is it still a QGP signal?

• yes! : Enhancement
         Suppression
         and no change at all
         signal the QGP



                              Marcus Bleicher, Hot Quarks 2006
         Jet quenching…
• Jet quenching can only be due to
  interactions of quarks/gluons with other
  quarks and gluons
• Predicts a broadening of the away side jet
  (no modification observed)
• Needs 1000 gluons at midrapidity
  (shouldn’t there be some quarks?)
  Quarks will induce less quenching
  because they have smaller color charge

                           Marcus Bleicher, Hot Quarks 2006
            How does a dynamical
            – hadronic - model do?
                               • AQM cross sections
                                 for the leading (di-
                                 )quarks
                               • Interactions only
                                 when e<1 GeV/fm3



HSD, Gallmeister et al, 2004

                                Marcus Bleicher, Hot Quarks 2006
  What about the correlations?

                               • Half of the jet
                                 suppression, is
                                 due to hadrons!




HSD, Gallmeister et al, 2004    Trigger:4-6 GeV
                                  Marcus Bleicher, Hot Quarks 2006
               Parton Number Scaling of v2

                                              •in leading order of v2,
                                              recombination predicts:




        P. Soerensen, UCLA & STAR @ SQM2003




Taken from S.A. Bass                           Marcus Bleicher, Hot Quarks 2006
    Elliptic flow scaling

All hadron v2’s should scale with
     constituent quark number




                    Marcus Bleicher, Hot Quarks 2006
           Elliptic flow: Magnitude I
   • Integral flow
                                                                 • V2 from UrQMD is
                                                                  about 50% smaller
                                                                  than the data

                                                                 • Space for parton
                                                                   rescattering?




                                                                  STAR data is from
                                                                  nucl-ex/0409033


X. Zhu, M.B., H. Stoecker, Phys.Rev.C72:064911,2005


                                                      Marcus Bleicher, Hot Quarks 2006
      Elliptic flow: Magnitude II
• Integral flow
                                       • V2 from UrQMD is
                                        3.5 % at Apart ~ 100
                                       • HSD gives 4.5 -5 %
                                        at Apart ~ 100

                                             20% systematic
                                       uncertainty in different
                                       implementations (e.g
                                       formation times, cross
                                       sections, particles,…)

HSD by Bratkovskaya and Cassing


                                  Marcus Bleicher, Hot Quarks 2006
                                                             Compare apples to apples
                                 • Differential flow
                                                                                                         •v2{2} is heavily
X. Zhu, M.B., H. Stoecker, Phys.Rev.C72:064911,2005




                                                                                                         affected by the non-
                                                                                                         flow effects especially
                                                                                                         at large pT.

                                                                                                         •The non-flow effects
                                                                                                         have been eliminated
                                                                                                         in v2{4} and v2{6}.

                                                                                                         •But v2{4} is still a
                                                                                                         little larger than the
                                                                                                         exact v2.

                                                                                                           Use Lee-Yang
                                                                                                            zero method

                                                      LYZ-method in UrQMD: nucl-th/0601049   Marcus Bleicher, Hot Quarks 2006
                        Do multi-strange hadrons flow?
                                            • Data indicates
                                             approximate 3:2 scaling
                                             with constituent quarks

                                            • Baryons are generally
                                              below mesons

                                            •Decrease of v2 at high pT
P. Sorensen, SQM 2006




                                            Is this rough scaling a
                                            signal for recombination?

                                           Marcus Bleicher, Hot Quarks 2006
                                       V2(pT) for various hadrons
                                           min. bias
                                                                               Maybe its just the
Y. Lu, M.B., et al., nucl-th/0602009




                                           UrQMD                                additive Quark
                                                                                   model?



                                                                             Open – Mesons
                                                                             Full -- Baryons
                                 1) Clear separation of meson and baryon v2
                                 2) Low pT, v2(meson)>v2(baryon)
                                 3) High pT, v2(m)<v2(b)
                                 4) v2’s of multi-strange hadrons comparable to lightQuarks 2006
                                                                       Marcus Bleicher, Hot hadrons
                                                          NCQ-scaling
                                                                                        •there should be an
Y. Lu, M.B., et al., nucl-th/0602009




                                                   UrQMD                                ordering of v2/n if it is
                                                                                        due to cross sections:
                                                                                        W<X<L<N
                                                                                          AQM cross sections:
                                                                                          Np: 26 mb
                                                                                          Lp: 23 mb
                                                                                          Xp: 20 mb
                                                                                          Wp: 16 mb               ~3:2
                                                                                          pp: 18 mb
                                                                                          Kp: 14 mb


                                 NCQ-scaling of v2 is roughly reproduced in UrQMD!
                                 Note that the AQM cross sections are only used as
                                                                                     Marcus Bleicher, Hot Quarks 2006
                                 a guideline above the resonance region in UrQMD
     Known problems in the
     coalescence approach
• Entropy decreases!

• Pions have 600 MeV mass!




                        Marcus Bleicher, Hot Quarks 2006
                Summary

J/psi suppression might be from hadronic stage

A lot of jet quenching might be from hadronic stage

Constituent quark scaling (w/o ReCo! but AQM)

                     “be critical!”




                                  Marcus Bleicher, Hot Quarks 2006

				
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posted:11/8/2011
language:German
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