413 research outputs found
Pion and Kaon Production in Nucleon - Nucleon Collisions
Inclusive cross section for pion production in proton - proton collisions are
calculated based on unintegrated parton distribution functions (uPDFs). In
addition to purely gluonic terms the present approach includes also quark
degrees of freedom. Phenomenological fragmentation functions from the
literature are used. The new mechanisms are responsible for -
asymmetry. In contrast to standard collinear approach, application of 2 1
- factorization approach can be extended towards much lower transverse
momenta, both at mid and forward rapidity region. The results of the
calculation are compared with SPS and RHIC data.Comment: a talk presented by Marta Tichoruk at the international conference
MESON2006, Cracow, June 2006, 5 pages, 3 figure
Reggeons in diffractive interactions in deep inelastic scattering at HERA
The "triple-Regge" analysis of subleading Reggeon contributions to the
diffractive structure function in DIS at HERA is presented. The recently
published data allow to estimate the only free parameter of the analysis
related to the ratio of the RRP and PPP couplings. The large value of this
ratio is prefered which is in agreement with analyses of soft hadronic
interactions. The role of the subleading Reggeons as well as pions for the fast
forward neutron production in diffractive processes is estimated. The forward
piN state production is also discussed.Comment: 6 pages, 2 figures, uses sprocl.sty and epsfig. To be published in
Proceedings of the Madrid low-x Workshop, Miraflores de la Sierra, June
18-21,199
Photon-jet correlations in and collisions
We compare results of the -factorization approach and the
next-to-leading order collinear-factorization approach for photon-jet
correlations in and collisions at RHIC and Tevatron energies.
We discuss correlations in the azimuthal angle as well as in the
two-dimensional space of transverse momentum of photon and jet. Different
unintegrated parton distributions (UPDF) are included in the
-factorization approach. The results depend on UPDFs used. The standard
collinear approach gives cross section comparable to the -factorization
approach. For correlations of the photon and any jet the NLO contributions
dominate at relatively small azimuthal angles as well as for asymmetric
transverse momenta. For correlations of the photon with the leading jet (the
one having the biggest transverse momentum) the NLO approach gives zero
contribution at which opens a possibility to study
higher-order terms and/or UPDFs in this region.Comment: 14 pages, 17 figure
Unintegrated CCFM parton distributions and transverse momentum of gauge bosons
Transverse momentum distribution of gauge bosons and is
calculated using unintegrated parton distributions obtained by solving leading
order CCFM equation(s) in the impact parameter space. For illustration we
compare the results of the fixed-order collinear, soft-gluon resummation and
CCFM approaches. A parameter of a nonperturbative form factor is adjusted to
the D0 data. In contrast to the collinear approach, the leading order
calculation based on the unintegrated CCFM parton distributions generates
transverse momentum distributions of gauge bosons, which are almost consistent
with experimental data provided the parameter of the nonperturbative form
factor is appropriately adjusted. The - asymmetry is calculated as a
function of the boson rapidity and transverse momentum. Predictions are given
for RHIC and LHC.Comment: 19 pages, 8 figure
Dijet correlations at RHIC, leading-order -factorization approach versus next-to-leading order collinear approach
We compare results of -factorization approach and next-to-leading order
collinear-factorization approach for dijet correlations in proton-proton
collisions at RHIC energies. We discuss correlations in azimuthal angle as well
as correlations in two-dimensional space of transverse momenta of two jets.
Some -factorization subprocesses are included for the first time in the
literature. Different unintegrated gluon/parton distributions are used in the
-factorization approach. The results depend on UGDF/UPDF used. For
collinear NLO case the situation depends significantly on whether we consider
correlations of any two jets or correlations of leading jets only. In the first
case the contributions associated with soft radiations summed up in
the -factorization approach dominate at and at equal
moduli of jet transverse momenta. The collinear NLO contributions
dominate over -factorization cross section at small relative azimuthal
angles as well as for asymmetric transverse momentum configurations. In the
second case the NLO contributions vanish at small relative azimuthal angles
and/or large jet transverse-momentum disbalance due to simple kinematical
constraints. There are no such limitations for the -factorization
approach. All this makes the two approaches rather complementary. The role of
several cuts is discussed and quantified.Comment: 26 pages, 17 figure
Exclusive Production at the LHC with Forward Proton Tagging
A process of Central Exclusive production in proton-proton
collisions and its theoretical description is presented. A possibility of its
measurement, during the special low luminosity LHC runs, with the help of the
ATLAS central detector for measuring pions and the ALFA stations for tagging
the scattered protons is studied. A visible cross section is estimated to be 21
b for TeV, which gives over 2000 events for 100 b
of integrated luminosity. Differential distributions in pion pseudorapidities,
pion and proton transverse momenta as well as invariant mass are
shown and discussed.Comment: 9 pages, 7 figure
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