1. Azimuthal correlation of hadrons in a partonic/hadronic transport model
Guo-Liang Ma
Background introduction
Model introduction
Analysis method
Results and discussions
Conclusion

2. hydrodynamic expansion
High Energy Nucleus-Nucleus Collisions
initial state
pre-equilibrium
QGP and
hydrodynamic expansion
hadronization
hadronic phase
and freeze-out
4 physics points are included.
Physics:
1) Parton distributions in nuclei
2) Initial conditions of the collision
3) a new state of matter – Quark-Gluon Plasma and its properties
4) hadronization

3. Di-hadron correlations
pT(assoc) > 2 GeV/c
pT(assoc) > 0.15 GeV/c
4 < pT(trig) < 6 GeV/c
Associated
particles
On away side:
Hard associated particles → suppression
One of them is di-hadron correlation, the azimuthal correlation between a high pT triger paticle and associated particles. For associated particles on away side, these hard associted particle are suppressed ,even disappear in central AuAu collisions. But Soft associted particles are enhanced in central collisions .
Soft associated particles → enhancement

4. Soft Associated particles on Away side (thermalization)
near side
away side
What happens to a hard probe that traverses a colored medium?
soften + broaden =?= thermalization
<pT> from away jets
<pT> from medium decay
SOFTENED
thermalization???
BROADENED
These results can be explained by jet quenching. On near side, one jet come out of reaction system, on away side the opposite jet will pass through the densence matter.Its energy is lost and redistributed in medium. The lost energy will be carried by soft asso particles. So the question is if the asso particles can be thermalized. The experimental data show their mean pT is close to that of inclusive particle. At the same time, the corresponding DeltaPhi and Deltapesoradity correlation are broadened. Is soften + broaden equal to themarlization?

5. Mach-like cone Structure
In addition, a strange struacture (double peaks) was observed on away side in azmuthal Deltaphi correlation in Au+Au collisons. The half of distance between double peaks are called as spliting parametter.

6. Θemission= arccos (cs/c) Θemission= arccos (1/n(p))
Possible interpretations of mach-like cone structure
Wake Effect or “sonic boom”
Θemission= arccos (cs/c)
hep-ph/ Casalderrey-Solana,Shuryak,Teaney
nucl-th/ Stöecker
Hep-ph/ Muller,Ruppert
nucl-th/ A. K. Chaudhuri
Cherenkov gluon radiation
Θemission= arccos (1/n(p))
PRL 96, (2006)
Koch, Majumder, X.-N. Wang
Some theriost give some ideas to explain the strange structure. Some
Correlation of Jet with flowing medium
hep-ph/ Armesto,Salgado,Wiedemann

7. AMPT model a multi-phase transport model (2) Melt AMPT
(1) Default AMPT

8. Mix-event Technique (1) Get raw  correlation signal in same event
(2)Get respective background by mixing events in same centrality
(3)Get  correlation by removing background with ZYAM method
Background
Subtracted signal

9.  correlations from AMPT
(3<pTtrigger<6GeV/c ,0.15<pTassoc<3GeV/c)
(1) ▲melt after hadron cascade
(2) ● melt before hadron cascade
(3)◆ default after hadron cascade
(4)★ default before hadron cascade
(5) ■ Star Data
0-5% (4-6)*(0.15-4)GeV/c factor=1.58
Au+Au 200GeV (0-10%)

10. Jet remnants character from AMPT
Au+Au 200GeV

11. Mach-like cone Structure in AMPT model
0-10%
40-90%
20-40%
10-20%
Mach-like cone Structure in AMPT model
 correlations in Au+Au 200GeV (2.5<pTtrigger<4GeV/c ,1<pTassoc<2.5GeV/c)

12. Three-particle correlations in AMPT
mix-event technique
background subtracted
3-particle correlation signal

13. Three-particle correlation density
3-particle correlation density definition:

14. Parton cascade effect on 2- and 3- particle correlation
(1)hadron cascade mechanism also can produce 2- and 3-particle correlation, but it can not give big enough splitting parameters.
(2) the parton cascade mechanism is essential for describing the amplitude of
experimental mach-like structure

15. Conclusion
Di-hadron correlations can be produced by a multi-phase transport model(AMPT).
Mach-like structure is born in the partonic process and further developed in hadronic rescattering process.
hadron cascade mechanism can produce di-hadron correlation, but it can not give big enough splitting parameters.
Cone , deflected and center 3-particle correlations all exist in the central Au+Au collisions, however center 3-particle correlation become more dominant with the decreasing of Npart .

16. Thank you