Speaker
Akihisa Takahara
(University of Tokyo)
Description
The idea to use the strong electromagnetic fields present in high-energy nucleus
nucleus collisions to study photoproduction at hadron colliders has attracted
growing interest in recent years.
PHENIX measured J/\psi photo-production in ultra-peripheal (UPC) Au+Au collisions
at \sqrt{sNN} =200 GeV.
We define central UPC trigger as events with no activity in the Beam-Beam Counters,
but activity in ZDC and EMCal.
This trigger selects the collisions with the impact parameter larger than twice the nuclear
radius with a small background contribution from strong interactions. It provides a unique
opportunity to study photo-production of hadrons by a strong electromagnetic field.
The purpose of the measurement of J/\psi photo-production cross section in ultra-peripheral collisions
is to probe the gluon distribution at low-x.
We will report J/\psi cross section and its pT dependence measured using the high luminosity 2007 data.
Author
Akihisa Takahara
(University of Tokyo)
