Nuclear Physics Seminar

This fall, the Large Hadron Collider at CERN will start operations
with p+p collisions at an unprcedented 10 TeV, commensing a new era of
particle physics. But not only particle physicists will be compelled
by the discovery potential of the new machine. With Pb+Pb collisions
at 5.5 TeV, almost 30 times the RHIC energy, the LHC will also
have an extensive heavy-ion program, which will be complementary to
that at RHIC. The greater kinematic reach of the LHC and much
larger cross sections for rare processes will allow for
qualitatively novel tests of our understanding of dense QCD matter
generated from widely different initial conditions.

Of particular interest in understanding heavy-ion collisons is the
production of direct photons. Being free from strong interactions,
they leave the collision region unscathed, providing a reference for
hadron production, a direct measure of medium properties, and, in
direct photon-jet correlations, a handle on jet energy loss.

All three experiments with heavy-ion programs at the LHC--ALICE,
ATLAS, and CMS--plan to measure photons. The different photon
capabilities of the experiments will be assessed and compared to those
of PHENIX and STAR. On this basis, the physics opportunities of
photon measurements at LHC and RHIC will be explored.