Enke Wang

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Modification of Fragmentation Function in
Strong Interacting Medium

• Enke Wang
• (Institute of Particle Physics, Huazhong
  Normal University)
• Introduction
• Modification of Frag. Func. in Cold Nucleus
• Modification of Frag. Func. in QGP Medium
• Summary
• Collaborators X.-N. Wang, B.-W.
  Zhang

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I. Introduction

• Rutherford experiment a ? atom discovery of
  nucleus
• SLAC DIS experiment e ? proton discovery
  of quarks

A-A collisions Naturally provides jet and the
QGP

• Jet (hard probe) created by parton scattering
  before QGP is formed
• high transverse momentum
• calculable in pQCD

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Jet quenching and Observation
Jet Quenching
A-A collision
Modification of Fragmentation Function
Particle Production
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Light Quark Energy Loss
PHENIX, Nucl. Phys. A757 (2005) 184
Theoretical results from the light quark energy
loss is consistent with the experimental data
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Heavy quark energy loss Early Expectations
B. Zhang, E. Wang, X.-N. Wang, PRL93 (2004)
072301 Y. Dokshitzer D. Kharzeev PLB
519(2001)199
J. Adams et. al, PRL 91(2003)072304 M.
Djordjevic, et. al. PRL 94(2005)112301
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No Significant Difference Between Heavy
Quark Jet and Light Quark Jet
Charged hadrons from Light quark fragmentation
Non-photonic electrons from heavy quark decays
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Question Heavy Quark Energy Loss?
Theoretical Calculation
Energy loss fraction
How Reasonable?
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II. Modification of Frag. Func. in Cold Nucleus
e-
e-A DIS
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Modified Fragmentation Function
X.-N. Wang, X. Guo, NPA696 (2001) PRL85 (2000)
3591
Fragmentation function in vacuum
Modification term
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Modified Frag. Function in Cold Nuclear Medium
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Rescaling of Modified Fragmentation Function
Solid curve
Dashed curve
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Comparison with HERMES Data
,
,
E. Wang, X.-N. Wang, Phys. Rev. Lett. 89 (2002)
162301
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Heavy Quark Energy Loss in Cold Nucleus
B. Zhang, E. Wang, X.-N. Wang, PRL93 (2004)
072301 NPA757 (2005) 493
Mass effects 1) Formation time of gluon
radiation become shorter
LPM effect is significantly reduced for heavy
quark
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Heavy Quark Energy Loss in Nuclear Medium
The dependence of the ratio between charm
quark and light quark energy loss in a large
nucleus
The dependence of the ratio between charm
quark and light quark energy loss in a large
nucleus
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III. Modification of Frag. Func. in QGP Medium
k
k
Cold Nucleus Medium
QGP Medium
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Same Framework for Light and Heavy Quark
Light quark
Heavy quark
Peterson form
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Generalized Jet Transport Parameter
Unintegrated gluon distribution function
Average tranverse momentum broading
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Jet Energy Loss
LPM effect
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Modified Frag. Function in QGP Medium
Modified splitting functions
Parameters
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Modification of Frag. Func. for light quark in QGP
can be approached by
z
Solid Curve
Dashed curve
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Modified Frag. Func. for heavy quark in QGP
c quark
can be approached by
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b quark
z
z
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Ratio of energy loss between heavy and light
quark in QGP
Solid Curve
Dashed curve
c
b
E

1. In the intermediate jet energy region the ratio
   increase rapidly with increasing energy.
2. In the very high jet energy region the effective
   energy loss of heavy quark is larger than one of
   light quark

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IV. Summary

• The modified fragmentation function in strong
  interacting medium (cold nucleus and QGP) has
  been calculated in pQCD.
• The modified fragmentation function in QGP medium
  can be approached by rescaling fragmentation
  function with effective energy loss fraction
  . For light quark ,
  for heavy quark .
• 3)The different effective energy fraction shift
  of the fragmentation function for light and heavy
  quark will help us to understand the different
  behavior of the light and heavy quark jet.

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Thank You
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