Critical review of QGP signals

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Critical review of QGP signals

• Marcus Bleicher
• Institut für Theoretische Physik
• Goethe Universität Frankfurt
• Germany

bleicher_at_th.physik.uni-frankfurt.de
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Thanks to the UrQMD group_at_ 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

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Contents

• Introduction
• No kinks, no horns, no steps
• J/y enhancement/suppression
• Jet quenching
• NCQ scaling elliptic flow
• Conclusion

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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

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The J/y story

• In the beginning there was Matsui and Satz
• ccbar can not be bound to J/ys above Tc

Compare J/y in AA with J/y in ppNbinary was/is
done by NA50 and NA60
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Hadron transport

• Different calculations, same results
• Inputs time dependent cross sections,
  j/psiXcross section

Calculations Spieles et al, 1999Cassing et al,
2000
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RHIC energies

• Same cross section is fine at RHIC

Taken from E. Bratkovskaya
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What do we learn from J/Y?

• Is it still a QGP signal?
• yes! Enhancement Suppression
  and no change at all
• signal the QGP

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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(shouldnt there
  be some quarks?)Quarks will induce less
  quenching because they have smaller color charge

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How does a dynamical hadronic - model do?

• AQM cross sections for the leading (di-)quarks
• Interactions only when elt1 GeV/fm3

HSD, Gallmeister et al, 2004
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What about the correlations?

• Half of the jet suppression, is due to
  hadrons!Trigger4-6 GeV

HSD, Gallmeister et al, 2004
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Parton Number Scaling of v2

• in leading order of v2, recombination predicts

P. Soerensen, UCLA STAR _at_ SQM2003
Taken from S.A. Bass
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Elliptic flow scaling

• All hadron v2s should scale with constituent
  quark number

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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.C72064911,200
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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
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Compare apples to apples

• Differential flow

• v22 is heavily affected by the non-flow effects
  especially at large pT.
• The non-flow effects have been eliminated in
  v24 and v26.
• But v24 is still a little larger than the
  exact v2.? Use Lee-Yang zero method

X. Zhu, M.B., H. Stoecker, Phys.Rev.C72064911,200
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LYZ-method in UrQMD nucl-th/0601049
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Do multi-strange hadrons flow?

• Data indicates approximate 32 scaling with
  constituent quarks
• Baryons are generally below mesons
• Decrease of v2 at high pTIs this rough
  scaling a signal for recombination?

P. Sorensen, SQM 2006
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V2(pT) for various hadrons
min. bias
Maybe its just the additive Quark model?
UrQMD
Y. Lu, M.B., et al., nucl-th/0602009
Open MesonsFull -- Baryons
1) Clear separation of meson and baryon v2 2) Low
pT, v2(meson)gtv2(baryon) 3) High pT,
v2(m)ltv2(b) 4) v2s of multi-strange hadrons
comparable to light hadrons
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NCQ-scaling

• there should be an ordering of v2/n if it is due
  to cross sectionsWltXltLltN

UrQMD
Y. Lu, M.B., et al., nucl-th/0602009
AQM cross sections Np 26 mbLp 23 mbXp 20
mbWp 16 mb pp 18 mbKp 14 mb
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NCQ-scaling of v2 is roughly reproduced in UrQMD!
Note that the AQM cross sections are only used as
a guideline above the resonance region in UrQMD
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Known problems in the coalescence approach

• Entropy decreases!
• Pions have 600 MeV mass!

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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!