Charm dynamics from transport models

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Charm dynamics from transport models
Elena Bratkovskaya 28.05.2009 , Workshop Heavy
Quarkonium Production in Heavy-Ion Collisions,
Trento, May 25-29, 2009
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Introduction

• Heavy ion collisions are well suited to study
  dense and hot nuclear matter
• a phase transition to QGP ,
• chiral symmetry restoration,
• in-medium effects

• Observables
• Excitation function of particle yields and ratios
• Transverse mass spectra
• Collective flow
• Dileptons
• Open and hidden charm
• Fluctuations and correlations
• ...

• The way to study
• Experimental energy scan of different observables
  in order to find an anomalous behaviour in
  comparison with theory

Microscopic transport models provide a unique
dynamical description of nonequilibrium effects
in heavy-ion collisions
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Basic concept of HSD

• HSD Hadron-String-Dynamics transport
  approach
• for each particle species i (i N, R, Y, p, r,
  K, ) the phase-space density fi follows the
  transport equations
• with collision terms Icoll describing
• elastic and inelastic hadronic reactions
• baryon-baryon, meson-baryon, meson-meson
• formation and decay of
• baryonic and mesonic resonances
• and strings - excited color singlet states
  (qq - q) or (q qbar) -
• (for inclusive particle production BB -gt X
  , mB -gtX, X many particles)
• implementation of detailed balance on the level
  of 1lt-gt2
• and 2lt-gt2 reactions ( 2lt-gtn multi-particle
  reactions in HSD !)
• off-shell dynamics for short-lived states

BB lt-gt BB, BB lt-gt BBm mB lt-gt mB, mB lt-gt B
Baryons B(p, n, D(1232), N(1440), N(1535),
...) Mesons m(p, h, r, w, f, ...)
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HSD a microscopic model for heavy-ion reactions

• very good description of particle production in
  pp, pA reactions
• unique description of nuclear dynamics from low
  (100 MeV) to ultrarelativistic (20 TeV) energies

HSD
1999 predictions
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Open and hidden charm
Heavy flavor sector reflects the early dynamics
since heavy hadrons can only be formed in the
very early phase of heavy-ion collisions !

• Hidden charm J/Y , Y Anomalous J/Y suppression
  in AA (NA38/NA50/NA60)

J/Y normal absorption by nucleons (Glauber
model) Experimental observation extra
suppression in AA collisions increasing with
centrality
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I.-II. Scenarios for charmonium suppression in AA

• I. QGP threshold melting
• Satz et al03

• II. Comover absorption
• Gavin Vogt, Capella et al.97
• charmonium absorption by low energy inelastic
  scattering with comoving mesons (mp,h,r,...)
• J/Ym lt-gt DDbar
• Ym lt-gt DDbar
• cCm lt-gt DDbar

Quarkonium dissociation temperatures
Dissociation energy density ed 2(Td/Tc)4

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Charm and Charmonium production and absorption in
HSD

• Charmonium hard probe
• gt binary scaling!
• Production s(J/Y) and s(Y ) in NN and pN
  collsions parametrization of the available exp.
  data

Coupled channel problem sJ/Yexp sJ/Y
B(cc?J/Y) scc B(Y?J/Y) sY

• Charmonia-baryon dissociation cross
• sections can be fixed from pA data
• scc B sJ/Y Bsc B 4.18 mb, sY B 7.6 mb
• (adopting a
  Glauber fit from NA50)

J/Y (cc,Y) B ? DDbar X

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II. Modelling of the comover scenario in HSD
1. Charmonia dissociation cross sections with
formed p, r,K and K mesons J/Y (cc,Y) meson
(p, r, K , K) lt-gt DDbar

• Phase-space model for charmonium meson
  dissociation

constant matrix element
2. J/Y recombination cross sections by DDbar
annihilation DDbar ? J/Y (cc,Y) meson (p,
r, K , K) are determined by detailed balance!
Note comover dissociation as well as DDbar
recombination can occure only if the local energy
density at the collision point e lt 1GeV/fm3
PRC 67 (2003) 054903
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Charmonium recombination by D-Dbar annihilation
At SPS recreation of J/Y by DDbar annihilation
is negligible
NDD16
but at RHIC recreation of J/Y by DDbar
annihilation is strong!
PRC 67 (2003) 054903
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Suppression in dA at RHIC
Charmonium is absorbed by scattering on baryons
Effect of shadowing at forward y
O. Linnyk et al., arXiv0808.1504 Int J Mod
Phys E17 (2008) 1367
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I. Modelling of the QGP melting scenario in HSD
Energy density e (x0,y0,zt) from HSD for
PbPb collisions at 160 A GeV
Energy density e (x0,y0,zt) from HSD for
AuAu collisions at 21300 A GeV
Dissociation threshold energy densities J/Y
melting e(J/Y )16 GeV/fm3 cc melting
e(cc ) 2 GeV/fm3 Y melting e(Y ) 2
GeV/fm3
Melting temperature T(J/Y) lt 1.6-2 TC T(cc)
lt 1-1.2 TC T(Y ) lt 1-1.2 TC
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(I.) Local energy density e versus Bjorken
energy density eBj

• transient time for central AuAu at 200 GeV
• tr 2RA/gcm 0.13 fm/c
• c-cbar formation time
• tC 1/MT 1/4GeV 0.05 fm/c
  lt tr
• c-cbar pairs are produced in the initial hard NN
• collisions in time period tr

Y
J/Y
cc

• Bjorken energy density

AT is the nuclei transverse overlap area t is
the formation time of the medium

• at RHIC eBj t 5 GeV/fm2/c

Local energy density e during transient time tr
e 5GeV/fm2/c / 0.13 fm/c 30
GeV/fm3 accounting tC e 28 GeV/fm3

• HSD reproduces PHENIX data for Bjorken energy
  density very well
• HSD results are consistent with simple estimates
  for the energy density

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J/Y and Y suppression in InIn and PbPb at
SPS (II.) Comover absorption ( recombination
by D-Dbar annihilation)

• Exp. data (NA50/NA60) for J/Y and Y suppression
  for PbPb and InIn at 160 A GeV are consistent
  with the comover absorption model for the same
  set of parameters!

Olena Linnyk et al., nucl-th/0612049, NPA 786
(2007) 183
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J/Y and Y suppression in InIn and PbPb at
SPS (I.) QGP threshold melting scenario
Dissociation energy density e(J/Y )16 GeV/fm3,
e(cc ) 2 GeV/fm3, e(Y ) 2 GeV/fm3

• J/Y suppression is qualitatively described, but
  QGP threshold melting scenario shows a too strong
  Y absorption, which contradicts the NA50 data!

Olena Linnyk et al., nucl-th/0612049, NPA 786
(2007) 183
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J/Y and Y suppression in AuAu at RHIC (II.)
Comover absorption ( recombination by D-Dbar
annihilation)
Olena Linnyk et al., nucl-th/0612049, NPA 786
(2007) 183 arXiv0801.4282, NPA 807 (2008) 79
In the comover scenario the J/Y suppression at
mid-rapidity is stronger than at forward
rapidity, unlike the data!
Pure comover scenario is ruled out by PHENIX data!
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J/Y and Y suppression in AuAu at RHIC (I.)
QGP threshold melting scenario
Olena Linnyk et al., arXiv0705.4443, PRC 76
(2007) 041901
Melting model complete dissociation of initial
J/Y and Y due to the huge local energy
densities !
Charmonia recombination by D-Dbar annihilation is
important, however, it can not generate enough
charmonia, especially for peripheral collisions!
QGP threshold melting scenario is ruled out by
PHENIX data!
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Summary (I.-II. )
I. QGP threshold melting versus
experimental data
SPS RHIC J/Y survival -
Y / J/Y ratio - ?

• II. Hadronic comover absorption
• ( recombination by D-Dbar annihilation)
• versus experimental data
• SPS RHIC
• J/Y survival -
• Y / J/Y ratio ?

Comover absorption and threshold melting
scenarios are ruled out by experimental data
evidence for non-hadronic interaction ?!

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III. Scenarios for charmonium suppression in AA

• III. Pre-hadronic interaction scenario
• early interactions of charmonium (ccbar) and
  D-mesons with unformed (i.e. under formation time
  t g tF , tF 0.8 fm/c in the hadron rest frame)
  baryons and mesons - pre-hadrons
• comover absorption with recombination by
  D-Dbar annihilation

• Dissociation cross sections of charmonium by
  pre-hadrons
• sdiscc pre-Baryon 5.8 mb,
• sdiscc pre-meson 2/3 sdiscc pre-Baryon
• Elastic cross sections with prehadrons
• Charmonium - prehadrons D-meson - prehadrons
• selcc pre-Baryon 1.9 mb,
  selD pre-Baryon 3.9 mb,
• selcc pre-meson 2/3 selcc pre-Baryon
  selD pre-meson 2/3 selcc
  pre-Baryon
• Pre-hadronic interaction scenario only
  simulates the interactions in the QGP in the
  Hadron-String model without (!) explicit partonic
  interactions and phase transition gt NOT (yet!)
  a consistent description ! gt PHSD

Fitted to PHENIX data

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J/Y and Y suppression in AuAu at RHIC (III.)
Pre-hadronic interaction scenario
Olena Linnyk et al., arXiv0801.4282, NPA 807
(2008) 79
In the prehadronic interaction scenario the J/Y
rapidity distribution has the right shape like
the PHENIX data! gt can describe the RHIC data
at s1/2200 GeV for AuAu at mid- and
forward-rapidities simultaneously.
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J/Y and Y suppression in AuAu at RHIC
Olena Linnyk et al., arXiv0801.4282, NPA 807
(2008) 79
PHENIX data ? evidence for non-hadronic
interactions of charm degrees of freedom !
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HSD v2 of DDbar and J/Y from AuAu versus pT
and y at RHIC

• Pre-hadronic interactions lead to an increase of
  the elliptic flow v2
• The pre-hadronic interaction scenario is
  consistent with the preliminary PHENIX data on
  the D-mesons v2
• gt strong initial flow of
  non-hadronic nature!

Olena Linnyk et al., arXiv0801.4282, NPA 807
(2008) 79
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Quenching of D mesons at RHIC
Evidence of additional high pT suppression in
the most central collisions. Suppression of D
mesons in peripheral collisions is consistent
with a purely hadronic scenario.
O. Linnyk et al., arXiv0808.1504 Int J Mod
Phys E17 (2008) 1367
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Quenching of J/Y at RHIC

• Strong suppression at low pT observed
  experimentally cannot be explained
• by hadronic absorption of initially produced
  J/Ys
• as weel as by DDbar recombination since
  D-mesons follow a similar RAA pattern as J/Y.

Possible indication of J/Y formation by parton
coalescence!
O. Linnyk et al., arXiv0808.1504 Int J Mod
Phys E17 (2008) 1367
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Summary

• J/Y probes early stages of fireball and HSD is
  the tool to model it.
• Comover absorption and threshold melting both
  reproduce J/Y survival in PbPb as well as in
  InIn at SPS, while Y/J/Y data appear to be in
  conflict with the melting scenario.
• Comover absorption and threshold melting fail to
  describe the RHIC data at s1/2200 GeV for AuAu
  at mid- and forward-rapidities simultaneously
• Prehadronic interaction scenario can describe the
  RHIC data at s1/2200 GeV for AuAu at mid- and
  forward-rapidities simultaneously
• STAR data on v2 of high pT charged hadrons and
  charm D mesons are not reproduced in the
  hadron-string picture gt evidence for a plasma
  pressure ?!

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Outlook open problems

• Energy, rapidity, pT - dependent hadronic
  absorption cross sections
• from experiments systematic energy and
  system scan for pA
• Explicit dynamics of c-cbar in the QGP phase !
• Theory modeling of parton-hadron phase
  transition based on lQCD EoS and off-shell parton
  transport ?
• Parton-Hadron-String-Dynamics (PHSD)

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Thanks to
Olena Linnyk Wolfgang Cassing

O. Linnyk, E.L. Bratkovskaya and W. Cassing,
arXiv0808.1504 Int J Mod Phys E17 (2008) 1367