Jet quenching and direct photon production. F.M. Liu 刘复明 Central China Normal University, China T. Hirano 平野哲文 University of Tokyo, Japan K.Werner University of Nantes, France Y. Zhu 朱燕 Central China Normal University, China Mainly based on arXiv: hep-ph/0807.4771v2.
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F.M. Liu 刘复明Central China Normal University, China
T. Hirano平野哲文University of Tokyo, Japan
K.Werner University of Nantes, France
Y. Zhu 朱燕Central China Normal University, China
Mainly based on arXiv: hep-ph/0807.4771v2
ATHIC2008 Tsukuba Oct 13-15
2. Direct photons (thermal, jet-photon conversion) are penetrating probes for the interaction of partons inside the bulk and the interaction between jet and bulk. We can make cross check of the properties of the medium.
( interaction between jet + plasma)
A precise calculation requires careful treatments on
Described with ideal hydrodynamics in full 3D space
Constrained with PHOBOS data
Tested with hadrons’ yields, spectra, v2 and particles correlation
For more details, read T. Hirano
MRST 2001 LO pDIS and EKS98 nuclear modification are employed
Jet phase space distribution at τ=0:
fQGP: fraction of QGP at a given point
via modified fragmentation function
Factorization scale and renormalization scale to be
A common D
Interactions of thermal partons
are inside the rate!
Coupling depends on temperature
Ignored contributions: Medium induced radiation (mainly at low pt )
radiation from pre-equilibrium phase (short time)
PHENIX data: PRL 98, 012002 (2007) & arXiv:0801.4020
Our predictions coincide with the precise measurement!
PRL 98, 012002 (2007)
A good test for contributions
from leading order +
fragmentation without Eloss
in AA collisions.
The PHENIX fit of pp spectrum is used for Raa of thermal photons.
Thermal and LO dominate low and high pt region respectively.
Raa is not sensitive to E loss, because of the centrality dependence of them.
When collisions move to perpherial, JPC becomes less important
while fragmentation becomes more important .
Raa due to thermal source
Energy density at plasma center
Contrary to hadronic v2 (ideal hydro predicted increase monotonically),
the elliptic flow of thermal photons decrease at high pt!
( Information for the earlier evolution of the plasma?)
1) the dominance of leading order contribution
2) strong suppression to JPC and frag. contributions due to E-loss
The dominant contribution at high pt is the LO contribution from NN collisions:
Isosping mixture and nuclear shadowing:
The isospin mixture
and nuclear shadowing
reduce Raa at high pt.
This is the initial effect, not
related to QGP formation.