259 research outputs found
Heavy Flavor Enhancement as a Signal of Color Deconfinement
We argue that the color deconfinement in heavy ion collisions may lead to
enhanced production of hadrons with open heavy flavor (charm or bottom). We
estimate the upper bound of this enhancement.Comment: 7 pages, LaTeX, 3 PS-figure
Development Strategies for Pythia version 7
This document describes the strategies for the development of the Pythia7
program. Both the internal and external structure of the program is discussed.
Some comments on relationship to other software is given as well as some
comments on coding conventions and other technical details.Comment: 27 pages, 3 eps figure
Bloom-Gilman duality of the nucleon structure function and the elastic peak contribution
The occurrence of the Bloom-Gilman duality in the nucleon structure function
is investigated by analyzing the Q**2-behavior of low-order moments, both
including and excluding the contribution arising from the nucleon elastic peak.
The Natchmann definition of the moments has been adopted in order to cancel out
target-mass effects. It is shown that the onset of the Bloom-Gilman duality
occurs around Q**2 ~ 2 (GeV/c)**2 if only the inelastic part of the nucleon
structure function is considered, whereas the inclusion of the nucleon elastic
peak contribution leads to remarkable violations of the Bloom-Gilman duality.Comment: in Proc. of the XVI European Conference on Few-body Problems in
Physics, Autrans (France), July 199
ExHuME: A Monte Carlo Event Generator for Exclusive Diffraction
We have written the Exclusive Hadronic Monte Carlo Event (ExHuME) generator.
ExHuME implements the perturbative QCD calculation of Khoze, Martin and Ryskin
of the process pp-> p+X+p, where X is a centrally produced colour singlet
system.Comment: 11 pages, 3 figure
Projet: Jet Cross Sections in Deeply Inelastic Electron Proton Scattering (VERSION 4.1)
PROJET is a parton level Monte Carlo program for the calculation of jet cross
sections in deeply inelastic electron proton scattering. In its present version
it contains the Born level diagrams for the production of (1+1), (2+1) and
(3+1) jets and the next-to-leading order corrections for the production cross
sections of (1+1) and (2+1) jets for all polarisations of the exchanged virtual
photon. In particular, the full angular correlations between the lepton and jet
momenta are implemented. The program permits the application of acceptance cuts
on all external momenta. For this purpose, the program creates an event record
accessible to the user program with all momenta in the laboratory frame and in
the center of momentum frame of the proton and the virtual photon. This option
is indispensable for phenomenological studies because of the strong dependence
of cross sections on phase space restrictions and the large uncertainty of
fragmentation corrections in the proton direction. Since PROJET uses the Monte
Carlo integration method for the evaluation of phase space integrals, the
weights of the generated events can be used to produce distributions of
observables related to jet momenta.Comment: 28 pages (LaTeX), CERN-TH.7420/9
Obtaining the nuclear gluon distribution from heavy quark decays to lepton pairs in p collisions
We have studied how lepton pairs from decays of heavy-flavoured mesons
produced in p collisions can be used to determine the modifications of the
gluon distribution in the nucleus. Since heavy quark production is dominated by
the channel, the ratio of correlated lepton pair cross sections from
and decays in p and pp collisions directly reflects the
ratio . We have numerically calculated the lepton
pair cross sections from these decays in pp and p collisions at SPS, RHIC
and LHC energies. We find that ratio of the p to pp cross sections agrees
quite well with the input Thus, sufficiently accurate measurements
could be used to determine the nuclear modification of the gluon distribution
over a greater range of and than presently available, putting strong
constraints on models.Comment: 19 pages, 6 figure
Nonlinear corrections to the DGLAP equations in view of the HERA data
The effects of the first nonlinear corrections to the DGLAP evolution
equations are studied by using the recent HERA data for the structure function
of the free proton and the parton distributions from CTEQ5L and
CTEQ6L as a baseline. By requiring a good fit to the H1 data, we determine
initial parton distributions at GeV for the nonlinear scale
evolution. We show that the nonlinear corrections improve the agreement with
the data in the region of and
GeV without paying the price of obtaining a worse agreement at larger
values of and . For the gluon distribution the nonlinear effects are
found to play an increasingly important role at x\lsim 10^{-3} and
Q^2\lsim10 GeV, but rapidly vanish at larger values of and .
Consequently, contrary to CTEQ6L, the obtained gluon distribution at
GeV shows a power-like growth at small . Relative to the CTEQ6L gluons,
an enhancement up to a factor at , GeV
reduces to a negligible difference at Q^2\gsim 10 GeV.Comment: 13 pages, 5 eps-figures; revision: references added, Fig. 3 revise
Effect of neutral current interactions on high energy muon and electron neutrino propagation through the Earth
High energy electron and muon neutrino propagation through the Earth has been
performed using the Monte Carlo technique. We focused our attention on the
effect of neutral current deep inelastic interactions compared to that of
charged current ones. We have found that NCs do not produce any significant
effect with respect to the case in which only CCs are considered. Therefore we
conclude that NC interactions can be neglected without considerable loss of
accuracy. When computing upward-going neutrino fluxes a simple formula
describing the transmission probability, that depends on the neutrino direction
and energy and the CC cross section, can be used to account for the Earth
shadowing effect.Comment: 9 pages, 4 figures, uses elsart.cls, elsart.sty, elsart12.sty,
submitted to Astroparticle Physycs. The version 3 has been significantly
changed in the frame of preparation for publication in Astroparticle Physics:
new plot and references added, several misprinting have been fixe
J/psi Production at the LHC
We firstly examine hadroproduction of prompt J/psi's at the Fermilab Tevatron
in a Monte Carlo Framework by means of the event generator PYTHIA 5.7 in which
those colour-octet matrix elements processes relevant for charmonium production
have been implemented accordingly. We find that colour-octet matrix elements
presented in literature from p-pbar collider data are systematically
overestimated due to overlooking of the effective primordial transverse
momentum of partons (i.e. including higher-order QCD effects). We estimate the
size of these effects using different parton distribution functions. Finally,
after normalization to Tevatron data, we extrapolate up to LHC energies making
a prediction on the expected pt differential cross-section for charmonium.Comment: 4 pages, LaTex, 3 Figures included in the text, Contribution to the
2nd Int. Conference on Hyperons, charm and beauty hadrons (Montreal, Aug
27-30, 1996
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