100 research outputs found
Semi-inclusive photon-hadron production in pp and pA collisions at RHIC and LHC
We investigate semi-inclusive photon-hadron production in the color glass
condensate (CGC) framework at RHIC and the LHC energies in proton-proton (pp)
and proton-nucleus (pA) collisions. We calculate the coincidence probability
for azimuthal correlation of pairs of photon-hadron and show that the away-side
correlations have a double-peak or a single-peak structure depending on trigger
particle selection and kinematics. This novel feature is unique for
semi-inclusive photon-hadron production compared to a similar measurement for
double inclusive dihadron production in pA collisions. We obtain necessary
conditions between kinematics variables for the appearance of a double-peak or
a single peak structure for the away-side photon-hadron correlations in pp and
pA collisions at forward rapidities and show that this feature is mainly
controlled by the ratio p_T^hadron/p_T^photon. Decorrelation of away-side
photon-hadron production by increasing the energy, rapidity and density, and
appearance of double-peak structure can be understood by QCD saturation
physics. We also provide predictions for the ratio of single inclusive prompt
photon to hadron production, and two-dimensional nuclear modification factor
for the semi-inclusive photon-hadron pair production at RHIC and the LHC at
forward rapidities.Comment: 16 pages, 20 figures; v2: latex Compilation problem in Figs. 3,4
correcte
Gluon saturation effects at forward rapidities at LHC in pp collisions
We investigate hadrons and direct photon production in pp collisions at the
LHC energy within the color-dipole approach. We show that greatest sensitivity
to gluon saturation effects is reached at very forward rapidities in pp
collisions at LHC (\sqrt{s}=14 TeV). The discrepancies among various saturation
models (fitted to HERA data) results can be about a factor of 2-3 at forward
rapidities. We found that the ratio of direct-photon to pion production can be
about 20-10 at forward rapidities \eta=7-8. Therefore, direct photon production
at forward rapidities should provide a rather clean probe as the background
from radiative hadronic decays is significantly suppressed.Comment: 4 pages, 6 figures, Contributed to "Lepton-Photon 2009 (LP09)",
Hamburg, German
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