1. QGP at RHIC: Seen through Modified Jet Fragmentation
The discovery of Jet Quenching by STAR experiment at RHIC points to the formation of extremely dense and hot matter produced at RHIC. This lays down the foundation of future studies of properties of the dense matter using Jet Tomography Theory developed at LBNL.
Xin-Nian Wang
王新年
LBNL
CCAST Workshop
August 10, 2004

2. My Collaborators China: US: Enke Wang, Benwei Zhang, Hanzhong Zhang
X.F. Guo, J. Osborne, J. Owens, A. Majumder

3. Medium Response Function
Dynamic System: Photon or dilepton emission (space-like photon)
J/Y suppression
QCD Response:
Parton scattering & dE/dx

4. Jet Quenching & Modified Jet Fragmentation
hadrons ph
parton E
Dh/a(z)=dN/dz (z=ph/E)
Fragmentation Function
are measured, and its QCD evolution
tested in e+e-, ep and pp collisions
How to measure dE/dx ?
Modification of fragmentation function
Suppression of leading particles (Huang, XNW’96)

5. DIS off Nuclei e-
Frag. Func.

6. Parton Fragmentation Function
e+e- annihilation q S

7. DGLAP Evolution
Splitting function

8. DGLAP Evolution Binnewies, Kniehl, Kramer 1995 0.075 0.15 0.25 0.35
0.5
0.75
z=0.9

9. Multiple Parton Scattering
Formation time

10. Modified Fragmentation
Guo & XNW’00
Modified splitting functions
Two-parton correlation:
LPM
Virtual correction important, rediscovered by BDMS

11. Parton Energy Loss
Quark energy loss = energy carried by radiated gluon
Asymptotic form of parton energy loss
BDPM
Gyulassy Vitev Levai
Wang & Wang
Wiedemann; Zakharov

12. HERMES data
E. Wang & XNW
PRL 2000
in Au nuclei

13. High pT spectra in A+A collisions
pQCD Parton Model

14. High pt spectra in pp collisions
H. Zhang
J. Owens
E. Wang
XNW
2004

15. High pt spectra in Au+Au
H. Zhang
E. Wang
J. Owens
XNW
2004, in preparation

16. Single hadron suppression

17. Suppression of away-side jetDf

18. Azimuthal anisotropy I
Single hadron

19. Di-hadron fragmentation function
jet

20. DGLAP for Dihadron Fragmentation

21. Comparison with Monte Carlo

22. Medium Modification
Triggering h1
D(z1,z2)/D(z1)

23. Modification due to recombinationh h
work in progress h
Hwa & Yang ?

24. Flavor of Jet Quenching
Parton recombination

25. Criteria for Discovery of QGP
Open system, expanding, short-lived, small volume
Criteria:
High density: e>>ec
Large volume: V>>l (mean-free-path)
Long life-time: t>>l
Local thermal equilibration (interaction): approximately
parton degrees of freedom
Debye screening of strong interaction: deconfinement

26. High density at RHIC GeV
From RHIC high pT data: single & di-hadron, v2
GeV
for E=10 GeV
Initial (energy) density 30 (100) times of that in a Cold Au Nucleus
Energy density is about 100 times that of that in cold nuclear matter
Consistent with estimate of initial condition
also consistent with hydrodynamic analysis of radial flow from

27. Good agreement with ideal fluid hydro Hadron chemical composition
Thermalization
Jet quenching
Single and dihadron suppression
Thermalization of hadrons in away-side jet
Elliptic flow
Requires early thermalization
tth<1 fm/c (U. Heinz)
Good agreement with ideal fluid hydro
Hadron chemical composition

28. Partonic d.o.f. and Deconfinement
Parton recombination effect
Reverse ordering of RAA and v2
Qualitatively model independent
Deconfinement
J/y suppression (sufficient?)

29. Summary
Discovery of Jet Quenching at RHIC proves that a interacting dense matter is formed: Opaque to jets
Jet quenching is caused by partonic energy loss
Dense matter at RHIC is 30 times higher than cold nuclei, energy density is 100 times higher
Collective behavior: Hydrodyamic limit strongly interactive QGP
Jet tomography become useful and power tool for studying properties of dense matter

30. Beginning of jet tomography study
Future Perspective
Beginning of jet tomography study
Details of modified fragmentation
Heavy quark fragmentation
Dihadron fragmentation
Jet-gamma events
Measurements of rare events
J/y suppression
Dilepton and direct photon production

32. A Perfect Fluid ? Hydrodynamic model with zero viscosity
Weakly colored
Bound states
String theory
AdS5/CFT
Policastro,Son,Starinets

33. Bulk Elliptic Flow Pressure gradient anisotropy Hydro-dynamics calc.
Self quenching

35. Parton Energy Loss Same-side jet profile Same-side jet cone
remains the same as
in pp collision
Hadron rescattering will change the correlation
Between leading and sub-leading hadrons

36. Effect of Hadron Absorption
Hadron formation time:
Uncertainty principle:
For protons

37. Geometry of Heavy Ion Collisionsx z y
EZDC ET ET
Centrality of the collisions
Impact Parameter (b)
EZDC
In heavy ion collisions, you are colliding two extended objects.

38. No jet quenching in d+Au
Initial state effect: Shadowing & pt broadening:
XNW, PRC61(00)064910

39. Azimuthal Anisotropy II
Azimuthal Mapping of jet quenching
20-60%
STAR preliminary
out-plane
In-plane