Speaker
Joakim Nystrand
(University of Bergen (NO))
Description
The strong electromagnetic fields surrounding the Pb-ions accelerated
at the CERN Large Hadron Collider (LHC) allow two-photon and
photonuclear interactions to be studied in a new kinematic regime.
These interactions can be studied in ultra-peripheral collisions,
where the impact parameters are larger than the sum of the nuclear
radii and hadronic interactions are suppressed.
During the heavy-ion runs at the LHC in 2010 and 2011, and during the
proton- lead run in 2013, the ALICE experiment implemented dedicated
triggers to select ultra-peripheral collisions. These triggers were
based on the Muon spectrometer, the Time-of-Flight detector, the
Silicon Pixel detector, and the VZERO scintillator array. Information
from other detectors was also used in the analysis. The cross section
for photoproduction of J/Psi meson at mid and forward rapidities in
Pb-Pb collisions will be presented. The results will be compared to
model calculations and their implications for nuclear gluon shadowing
will be discussed. First results on J/Psi photoproduction in p-Pb
collisions will also be discussed.
Author
Joakim Nystrand
(University of Bergen (NO))
