21 research outputs found
Unintegrated gluon distributions from the color dipole cross section in the BGK saturation model
We evaluate the unintegrated gluon distribution of the proton starting from a
parametrization of the color dipole cross section including DGLAP evolution and
saturation effects. To this end, we perform the Fourier-Bessel transform of
. At large transverse momentum of gluons we match the
so-obtained distribution to the logarithmic derivative of the collinear gluon
distribution. We check our approach by calculating the proton structure
function finding good agreement with HERA data.Comment: 4 pages, 3 fig
Production of heavy particle pairs via photon-photon processes at the LHC
We discuss production of pairs and quark-antiquark pairs
in proton-proton collisions induced by two-photon fusion including transverse
momenta of incoming photons. The unintegrated inelastic fluxes (related to
proton dissociation) of photons are calculated based on modern parametrizations
of deep inelastic structure functions in a broad range of and . We
focus on processes with single and double proton dissociation. Highly excited
remnant systems hadronise producing particles that can be vetoed in the
calorimeter. We calculate associated gap survival factors. The gap survival
factors depend on the process, mass of the remnant system and collision energy.
The rapidity gap survival factor due to remnant fragmentation for double
dissociative (DD) collisions is smaller than that for single dissociative (SD)
process. We observe approximate factorisation:
when imposing rapidity veto. For the final state, the remnant
fragmentation leads to a taming of the cross section when the rapidity gap
requirement is imposed. Also for quark-antiquark pairs such a
condition reverses the hierarchy observed for the case when such condition is
taken into account. Our results imply that for the production of such heavy
objects as quark and antiquark the virtuality of the photons
attached to the dissociative system are very large ( 10 GeV).
A similar effect is observed for the system.Comment: 11 pages, 9 figures, a talk presented by Marta {\L}uszczak at XXVI
Cracow EPIPHANY Conference, LHC Physics: Standard Model and Beyond, 7-10
January 202
Probing proton structure with correlations in ultraperipheral collisions
We study the exclusive diffractive photoproduction in
ultraperipheral collisions. The formalism makes use of off-diagonal
generalizations of the unintegrated gluon distribution, the so-called
generalized transverse momentum dependent distributions (GTMDs). We present two
different formulations. The first one is based directly on gluon GTMD
parametrizations in momentum space. Another option is the calculation of the
GTMD as a Fourier transform of the dipole-nucleon scattering amplitude
. The latter approach requires some extra
regularization discussed in the paper. Different dipole amplitudes from the
literature are used. Compared to previous calculations in the literature, we
integrate over the full phase space and therefore cross sections for realistic
conditions are obtained. We present distributions in rapidity of or , transverse momentum of the pair, four-momentum transfer squared
as well as the azimuthal correlation between a sum and a difference of the
and transverse momenta. The azimuthal correlations are partially due
to the so-called elliptic gluon Wigner distribution. Different models lead to
different modulations in the azimuthal angle. The modulations are generally
smaller than 5%. They depend on the range of transverse momentum selected for
the calculation.Comment: 22 pages, 14 figures, 1 tabl
Charmed Meson Production in Proton - (ANTI)PROTON Collisions
We discuss and compare different approaches to include gluon transverse
momenta for heavy quark-antiquark pair and meson production. The results are
illustrated with the help of different unintegrated gluon distributions (UGDF)
from the literature. We compare results obtained with on-shell and off-shell
matrix elements and kinematics. The results are compared with recent
experimental results of the CDF collaboration.Comment: presented by M. Luszczak at the international conference MESON2006,
June 2006, Cracow, 6 pages, 5 figure
Production of tt/mml:mover> pairs via fusion with photon transverse momenta and proton dissociation
12 pages, 11 figuresWe discuss the production of t t quark- antiquark pairs in proton- proton collisions via the fusion mechanism. We include topologies in which both protons stay intact or one or even both of them undergo dissociation. The calculations are performed within the k T - factorisation approach, including transverse momenta of intermediate photons. Photon uxes associated with inelastic ( dissociative) processes are calculated based on modern parameterisations of proton structure functions. We fi nd an integrated cross section of about 2.36 fb at p s = 13 TeV for all contributions ( without requirement of rapidity gap). The cross section for the fully elastic process is the smallest. Inelastic contributions are signi fi cantly reduced when a veto on outgoing jets is imposed. We present several di ff erential distributions in rapidity and transverse momenta of single t or t quarks/ antiquarks as well as distributions in invariant mass of both the t t and masses of dissociated systems. A few two- dimensional distributions are presented in addition.Peer reviewe
Production of two pairs in double-parton scattering
We discuss production of two pairs of within a simple formalism of
double-parton scattering (DPS). Surprisingly very large cross sections,
comparable to single-parton scattering (SPS) contribution, are predicted for
LHC energies. Both total inclusive cross section as a function of energy and
differential distributions for are shown. We discuss a perspective
how to identify the double scattering contribution.Comment: 8 pages, 6 figure
Diffractive production of heavy mesons at the LHC
We discuss diffractive production of heavy mesons at the LHC. In addition to standard collinear approach, for a first time we propose a kt-factorization approach to the diffractive processes. The unintegrated (transverse momentum dependent) diffractive parton distributions in proton are calculated with the help of the Kimber-Martin-Ryskin prescription where collinear diffractive PDFs are used as input. Some correlation observables, like azimuthal angle correlation between c and c̄, and cc̄ pair transverse momentum distribution were obtained for the first time. The results of the new approach are compared with those of the standard collinear one. Significantly larger cross sections are obtained in the kt-factorization approach where some part of higher-order effects is effectively included
Probing proton structure with c c ¯ correlations in ultraperipheral pA collisions
Abstract We study the exclusive diffractive c c ¯ photoproduction in ultraperipheral pA collisions. The formalism makes use of off-diagonal generalizations of the unintegrated gluon distribution, the so-called generalized transverse momentum dependent distributions (GTMDs). We present two different formulations. The first one is based directly on gluon GTMD parametrizations in momentum space. Another option is the calculation of the GTMD as a Fourier transform of the dipole-nucleon scattering amplitude N(Y, r → ⊥, b → ⊥). The latter approach requires some extra regularization discussed in the paper. Different dipole amplitudes from the literature are used. Compared to previous calculations in the literature, we integrate over the full phase space and therefore cross sections for realistic conditions are obtained. We present distributions in rapidity of c or c ¯ , transverse momentum of the c c ¯ pair, four-momentum transfer squared as well as the azimuthal correlation between a sum and a difference of the c and c ¯ transverse momenta. The azimuthal correlations are partially due to the so-called elliptic gluon Wigner distribution. Different models lead to different modulations in the azimuthal angle. The modulations are generally smaller than 5%. They depend on the range of transverse momentum selected for the calculation