dilepton production in hic at rhic energy haojie xu( 徐浩洁 ) in collaboration with h. chen, x....
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Dilepton production in HIC at RHIC Energy
Haojie Xu(徐浩洁 )In collaboration with H. Chen, X. Dong, Q. Wang
2011-8-9 Hadron2011, WeiHai
Haojie Xu(徐浩洁 ) University of Science and Technology of China
I. Introduction
II. Dileptons emission in Heavy Ion
Collisions
III. Semileptonic decays of charmed hadrons
IV. Summary
Electromagnetic Probes
Haojie Xu(徐浩洁 ) University of Science and Technology of China
Hadron2011, WeiHaiIntroduction
Suffer less interaction after their production
Emitted in the whole volume of the fireball
Provide crucial of the medium properties created by HIC
Why Dileptons?
α = 1/137
Dileptons signal in HIC
Haojie Xu(徐浩洁 ) University of Science and Technology of China
Hadron2011, WeiHaiIntroduction
SPS NA60, PRL96, 162302 (2006) van Hees and Rapp , PRL97,102301(2006) Broadening spectral VS Dropping mass Baryon density VS Meson gasA strong broadening but essentially no shift in mass of rho meson spectrum is needed to explain this result
STAR
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2011
, Jie
Zha
o
PHEN
IX P
RC 8
1 (2
010)
03
4911
Hydrodynamic
Haojie Xu(徐浩洁 ) University of Science and Technology of China
Hadron2011, WeiHai
2+1 dimensional ideal hydrodynamic model
Equation of states
Bjorken assumption
[J. D. Bjorken, Phys. Rev. D 27, 140 (1983)]
5 equations, 6 unknown functions
[https://wiki.bnl.gov/hhic/index.php/Lattice_calculatons_of_Equation_of_State]
Dileptons emission in Heavy Ion Collisions
Equation of states(EOS)
Haojie Xu(徐浩洁 ) University of Science and Technology of China
Hadron2011, WeiHai
[S. S. Adler et al. (PHENIX), Phys. Rev. C69, 034910 (2004)]Chemical equilbrium EOS Partial Chemical equilbrium EOS
Dileptons emission in Heavy Ion Collisions
30
0
40 /
0.4
128
0dec
i
e GeV fm
fm
T MeV
30
0
60 /
0.4
140
( )dec
i i
e GeV fm
fm
T MeV
T
For the hadronic phase(Vector Dominance Model)
Thermal Dilepton production
Haojie Xu(徐浩洁 ) University of Science and Technology of China
Hadron2011, WeiHaiDileptons emission in Heavy Ion Collisions
In the thermalized medium HG or QGP, the rate for the dilepton production per unit volume is given by
For the partonic phase(Leading order)
q
q
e+
e-
e+
e-
p -
p +
γ*
ρ,ω,φ γ*
Hadronic Many Body Theory
Haojie Xu(徐浩洁 ) University of Science and Technology of China
Hadron2011, WeiHaiDileptons emission in Heavy Ion Collisions
The in-medium vector meson self-energy is related to the forward two-body scattering amplitude of the surrounding thermal mesons(.ie.ρπ->a1)[R. Rapp, Phys. Rev. C63, 054907 (2001)]
and hR
Thermal dilepton spectra
Haojie Xu(徐浩洁 ) University of Science and Technology of China
Hadron2011, WeiHai
• Including the in-meidum ρ, ω and φ sources
•Thermal dilepton are dominated by the in- medium
ρ meson in LMR.
•the ω compontent is submerged under the
broadening ρ spectra.
•The partonic phase dominated the dilepton yields
for their invariant mass M>1.1GeV.
•w/(w/o) chemical freezeout process(EOS
difference)
Non-zero chemical potential below Tchem
No chemical freeze out process
Dileptons emission in Heavy Ion Collisions
Effective parameter and elliptic flow
Haojie Xu(徐浩洁 ) University of Science and Technology of China
Hadron2011, WeiHaiDileptons emission in Heavy Ion Collisions
Effective temperature Elliptic flowJ Deng, Q Wang, N Xu, P ZhuangPhys.Lett.,B701,581.
Teff(slope parameter) in the intermediate mass region shows the collectivity developed in the partonic stage.
The decline near rho mass reveals a phase transition from partonic phase to hadronic phase.
Dilepton at thermal freeze out
Haojie Xu(徐浩洁 ) University of Science and Technology of China
Hadron2011, WeiHaiDileptons emission in Heavy Ion Collisions
The vector meson momentum spectra at thermal freezeout can be expressed by the extended Cooper-Frye formular[van Hees and R. Rapp, Nucl. Phys. A806, 339 (2008)]
The dilepton emission rate from the freezeout vector meson is given by
The imaginary parts of the and propagators can be given by the Breit-Wigner formula
Most of the ρ decay in the medium due to its short lifetime.
Dilepton at thermal freeze out
Haojie Xu(徐浩洁 ) University of Science and Technology of China
Hadron2011, WeiHaiDileptons emission in Heavy Ion Collisions
• The medium effects have been included in the
freeze out contribution, the broadening of ρ is
even more obvious
•Only a much lower peak from the in-medium φ
meson is invisible, indicating clear medium effects
•Substracting these sharp peaks from ω and φ the
broadened spectrum of the in-medium ρ meson
can be seen.
•The partonic contribution dominates over the
hadronic one when M>1.1GeV
PYTHIA generator
Haojie Xu(徐浩洁 ) University of Science and Technology of China
Hadron2011, WeiHaiSemileptonic decays of charmed hadrons
PYTHIA 6.416 MSEL=4PARP(91)=1 PARP(31)=3.5MSTP(33)=1 MSTP(32)=4
PHENIX p +p collisions: The dilepton yield in the mass range from 1.1-2.5
PHENIX geometrical acceptance correction
[A. Adare et al. (PHENIX), Phys. Lett. B670, 313 (2009)]
Extrapolated to zero dielectrons mass
Converted to Charmed cross section using known branching ratios of semileptonic decays
4.21e-8
Cross Section: 0.5mb
Nuclear Modification Factor
Haojie Xu(徐浩洁 ) University of Science and Technology of China
Hadron2011, WeiHaiSemileptonic decays of charmed hadrons
B. I. Abelev et al. (STAR), Phys. Rev. Lett. 98, 192301 (2007)
ɑ =1.22871,b = -1.51186
Significant impact in accessingmedium physics in both IMR and LMR
Summary
Haojie Xu(徐浩洁 ) University of Science and Technology of China
Hadron2011, WeiHaiSummary
•Dilepton signals serve as clean probes to the hot and dense medium
created in HIC
•Dileptons production from partonic phase, hadronic phase and
freeze out vector hadrons in heavy ion collision at RHIC energy are
investigated.
•The medium modification of vector mesons are employ in our
calculations.
•Charmed background is a significant impact in accessing medium
physics in both IMR and LMR.
Thank you for your attention
Haojie Xu(徐浩洁 ) University of Science and Technology of China
Hadron2011, WeiHai
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