40 research outputs found
Double parton effects for jets with large rapidity separation
We discuss production of four jets with at least
two jets with large rapidity separation in proton-proton collisions at the LHC
through the mechanism of double-parton scattering (DPS). The cross section is
calculated in a factorizaed approximation. Each hard subprocess is calculated
in LO collinear approximation. The LO pQCD calculations are shown to give a
reasonably good descritption of CMS and ATLAS data on inclusive jet production.
It is shown that relative contribution of DPS is growing with increasing
rapidity distance between the most remote jets, center-of-mass energy and with
decreasing (mini)jet transverse momenta. We show also result for angular
azimuthal dijet correlations calculated in the framework of -factorization
approaximation.Comment: Invited talks at Diffraction 2014 (Primosten, Croatia, September
10-15, 2014) and MPI@LHC 2014 (Krak\'ow, Poland, November 3-7 2014
Nonphotonic electrons at RHIC within -factorization approach and with experimental semileptonic decay functions
We discuss production of nonphotonic electrons in proton-proton scattering at
RHIC. The distributions in rapidity and transverse momentum of charm and bottom
quarks/antiquarks are calculated in the -factorization approach. We use
different unintegrated gluon distributions from the literature. The
hadronization of heavy quarks is done by means of Peterson and Braaten et al.
fragmentation functions. The semileptonic decay functions are found by fitting
recent semileptonic data obtained by the CLEO and BABAR collaborations. We get
good description of the data at large transverse momenta of electrons and find
a missing strength concentrated at small transverse momenta of electrons.
Plausible missing mechanisms are discussed.Comment: 16 pages, 11 figure
Subdominant terms in the production of pairs in proton-proton collisions
At high-energies the gluon-gluon fusion is the dominant mechanism of production. This process was calculated in the NLO collinear as well as in
the k-factorization approaches in the past. We show that the present
knowledge of gluon distributions does not allow to make a precise predictions
for production at LHC, in particular at forward rapidities. In this
paper we study production of pairs including several subleading
mechanisms. This includes: , , , . In this context we use
MRST-QED parton distributions which include photon as a parton in the proton as
well as elastic photon distributions calculated in the equivalent photon
approximation. We present distributions in the quark ( antiquark)
rapidity and transverse momenta and compare them to the dominant gluon-gluon
fusion contribution. We discuss also inclusive single and central diffractive
processes using diffractive parton distribution found from the analysis of HERA
diffractive data. As in the previous case we present distribution in () rapidity and transverse momentum. Finally we present results for exclusive
central diffractive mechanism discussed recently in the literature. We show
corresponding differential distributions and compare them with corresponding
distributions for single and central diffractive components.Comment: 20 pages, 19 figure
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
Exclusive double-diffractive production of open charm in proton-proton and proton-antiproton collisions
We calculate differential cross sections for exclusive double diffractive
(EDD) production of open charm in proton-proton and proton-antiproton
collisions. Sizeable cross sections are found. The EDD contribution constitutes
about 1 % of the total inclusive cross section for open charm production. A few
differential distributions are shown and discussed. The EDD contribution falls
faster both with transverse momentum of the quark/antiquark and the invariant mass than in the inclusive case.Comment: 11 pages, 7 figure
Beauty production measurements in pp, p–Pb and Pb–Pb collisions with the ALICE detector
Production asymmetry of open charm mesons within unfavoured ragmentation scenario
We consider unfavoured light quark/antiquark to D meson fragmentation. We discuss nonperturbative effects for small transverse momenta. The asymmetry for D+ and D- production measured by the LHCb collaboration provides natural constraints on the parton (quark/antiquark) fragmentation functions. We find that already a fraction of q/q¯→D fragmentation probability is sufficient to account for the measured asymmetry. Large D-meson production asymmetries are found for large xF which is related to dominance of light quark/antiquark q/q¯→D fragmentation over the standard c → D fragmentation. As a consequence, prompt atmospheric neutrino flux at high neutrino energies can be much larger than for the conventional c → D fragmentation. The latter can constitute a sizeable background for the cosmic neutrinos claimed to be observed recently by the IceCube Observatory