156 research outputs found
Semi-inclusive Diffractive Deep Inelastic Scattering at Small-
Inspired by a recent study of Iancu, Mueller and Triantafyllopoulos [1] and
earlier papers by Golec-Biernat and Wusthoff [2,3], we propose semi-inclusive
diffractive deep inelastic scattering (SIDDIS) to investigate the gluon
tomography in the nucleon and nuclei at small-. The relevant diffractive
quark and gluon parton distribution functions (DPDF) can be computed in terms
of the color dipole S-matrices in the fundamental and adjoint representations,
respectively. Novel correlations from the gluon tomography in the dipole
S-matrix can be experimentally studied through the DPDFs in these processes at
the future electron-ion collider (EIC).Comment: Added appendices, 10 pages, 5 figure
The Quark Beam Function at Two Loops
In differential measurements at a hadron collider, collinear initial-state
radiation is described by process-independent beam functions. They are the
field-theoretic analog of initial-state parton showers. Depending on the
measured observable they are differential in the virtuality and/or transverse
momentum of the colliding partons in addition to the usual longitudinal
momentum fraction. Perturbatively, the beam functions can be calculated by
matching them onto standard quark and gluon parton distribution functions. We
calculate the inclusive virtuality-dependent quark beam function at NNLO, which
is relevant for any observables probing the virtuality of the incoming partons,
including N-jettiness and beam thrust. For such observables, our results are an
important ingredient in the resummation of large logarithms at N3LL order, and
provide all contributions enhanced by collinear t-channel singularities at NNLO
for quark-initiated processes in analytic form. We perform the calculation in
both Feynman and axial gauge and use two different methods to evaluate the
discontinuity of the two-loop Feynman diagrams, providing nontrivial checks of
the calculation. As part of our results we reproduce the known two-loop QCD
splitting functions and confirm at two loops that the virtuality-dependent beam
and final-state jet functions have the same anomalous dimension.Comment: 27 pages, 3 figures; v2: journal versio
Excited charmonium suppression in proton-nucleus collisions as a consequence of comovers
Recent results from proton(deuteron)-nucleus collisions at RHIC and LHC
energies have shown an unexpected suppression of excited quarkonium states as
compared to their ground states. In particular, stronger suppression of the
relative to the has been detected. Similar observations
were made at lower energies and were easily explained by nuclear absorption. At
higher energies, a similar explanation would violate the Heisenberg principle,
since the calculations based on the uncertainty principle lead to a charmonium
formation time expected to be larger than the nuclear radius, which results in
identical nuclear break-up probability for the and . On the
contrary, this behavior is naturally explained by the interactions of the
quarkonium states with a comoving medium. We present our results on
and production for d+Au collisions at GeV and for
p+Pb collisions at TeV.Comment: 7 pages, 5 figures. Extended version, figures unchanged. Accepted for
publication in Physics Letters
Gluon shadowing and unitarity effects
New data from HERA experiment on deep inelastic scattering have been used to
parametrize nucleon and Pomeron structure functions. Within the Gribov theory,
the parameterizations were employed to calculate gluon shadowing for various
heavy ions. The latter was compared with predictions from other models.
Calculations of multiplicity reduction due to gluon shadowing for d+Au
collisions at forward rapidities at =200 GeV are in good agreement
with BRAHMS data on the nuclear modification factor.Comment: 5 pages, 4 figures, submitted to Acta Physica Hungarica A, Quark
Matter 2005 poster session proceedings; minor changes in the text adde
Heavy-flavour production in pp collisions and correlations in pp and p-Pb collisions measured with ALICE at the LHC
Thanks to its excellent tracking and particle identification performance, the
ALICE detector is capable of measuring D mesons at central rapidity via their
hadronic decay channels down to very low transverse momentum. We show an
extension of the prompt -differential cross section
measurement down to zero transverse momentum, which allows us to determine the
-integrated charm production cross section at central rapidity in pp
collisions at = 7 TeV. We also present measurements of azimuthal
correlations of prompt , and mesons with
charged hadrons in pp collisions at = 7 TeV and p-Pb collisions at
= 5.02 TeV and compare the results with
expectations from models.Comment: Proceedings for Strangeness in Quark Matter 2016 conference - 4
pages, 3 figure
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