Speaker
Mr
Akihisa Takahara
(CNS, University of Tokyo and JRA RIKEN)
Description
Title:J/psi Photoproduction in ultra-peripheral Au+Au collisions measured by RHIC-PHENIX.
Ultra-peripheral collisions are heavy-ion collisions with impact parameter larger than twice the nuclear radius.
Since there is no nuclear overlap, strong interactions cannot occur and
ions interact through photon-ion (coherent), photon-nucleus (incoherent), and photon photon collisions.
Measurement of vector meson photo production is a sensitive probe of gluon distribution in nuclei.
At RHIC energy, measurement of J$/\psi$ photo production corresponds to x $\cong$ 0.015 and Q$^{2}$ =2.5 $GeV/c^2$.
In the kinematic region, nuclear shadowing plays an important role and that still have large uncertainty.
PHENIX has the capability of measuring J$/\psi$'s via their dielectron
decays at mid-rapidity ($|y|<0.35$) and dimuon decays at forward (1.2$<|y|<$2.2) rapidity.
PHENIX published J$/\psi$ photo production cross section at mid-rapidity in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV in the 2004 dataset [1] (add reference in the end). The measured cross
section was found to be consistent with theoretical calculations
within its statistical error.
PHENIX collected higher statistics Au+Au collisions datasets in 2007 and 2010 that allow a more precise measurement over a wider rapidity range. In this talk I will present present new preliminary results
for the integrated and differential cross section of UPC J$/\psi$ at central and forward rapidity.
Author
Mr
Akihisa Takahara
(CNS, University of Tokyo and JRA RIKEN)
