677 research outputs found
Pythia version 7-0.0 - a proof-of-concept version
This document describes the first proof-of-concept version of the Pythia7
program.
Pythia7 is a complete re-write of the Pythia program in C++. It is mainly
intended to be a replacement for the `Lund' family of event generators, but is
also a toolkit with a structure suitable for implementing any event generator
model.
In this document, the structure of the program is presented both from the
user and the developer point of view. It is not intended to be a complete
manual, but together with the documentation provided in the distribution, it
should be sufficient to start working with the program.Comment: 39 pages, 3 figure
Hadronic final state interactions at ALEPH and OPAL
The studies of Fermi-Dirac correlations of and
pairs in hadronic decays,
Bose-Einstein correlations and colour reconnection in -pairs decays
performed by the ALEPH collaboration in annihilation at LEP
are presented. The OPAL analysis of Bose-Einstein correlations in
-pair decays is also discussed.Comment: 5 pages, 5 figures; LaTeX (espcrc2.sty). Talk presented at QCD'99,
Montpellier, 7-13 July 1999. To appear in Nucl. Phys. B (Proc. Suppl.
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
RunMC - an object-oriented analysis framework for Monte Carlo simulation of high-energy particle collisions
RunMC is an object-oriented framework aimed to generate and to analyse
high-energy collisions of elementary particles using Monte Carlo simulations.
This package, being based on C++ adopted by CERN as the main programming
language for the LHC experiments, provides a common interface to different
Monte Carlo models using modern physics libraries. Physics calculations
(projects) can easily be loaded and saved as external modules. This simplifies
the development of complicated calculations for high energy physics in large
collaborations.This desktop program is open-source licensed and is available on
the LINUX and Windows/Cygwin platforms.Comment: 15 pages, 1 eps figure, accepted by Comp. Phys. Commu
Modelling Bose-Einstein correlations at LEP 2
We present new algorithms for simulating Bose-Einstein correlations among
final-state bosons in an event generator. The algorithms are all based on
introducing Bose-Einstein correlations as a shift of final-state momenta among
identical bosons, and differ only in the way energy and momentum conservation
is ensured. The benefits and shortcomings of this approach, that may be viewed
as a local reweighting strategy, is compared to the ones of recently proposed
algorithms involving global event reweighting.
We use the new algorithms to improve on our previous study of the effects of
Bose-Einstein correlations on the W mass measurement at LEP 2. The intrinsic
uncertainty could be as high as 100 MeV but is probably reduced to the order of
30 MeV with realistic experimental reconstruction procedures.Comment: 1+34 pages, LaTeX2e, 10 eps figures attache
Diffractive and non-diffractive wounded nucleons and final states in pA collisions
We review the state-of-the-art of Glauber-inspired models for estimating the
distribution of the number of participating nucleons in pA and AA collisions.
We argue that there is room for improvement in these models when it comes to
the treatment of diffractive excitation processes, and present a new simple
Glauber-like model where these processes are better taken into account. We also
suggest a new way of using the number of participating, or wounded, nucleons to
extrapolate event characteristics from pp collisions, and hence get an estimate
of basic hadronic final-state properties in pA collisions, which may be used to
extract possible nuclear effects. The new method is inspired by the Fritiof
model, but based on the full, semi-hard multiparton interaction model of Pythia
8.Comment: 50 pages, 13 figure
Estimating the Parameters of Bose-Einstein Correlations from the Two-Particle Correlation Function in Multihadronic Final States
To estimate the strength of the Bose-Einstein correlations and the radius of
the hadronization region in multiparticle production, the two-particle
correlation functions for identical pairs is adjusted to a parametric
function describing the enhancement at small momentum differences. This is
usually done by means of a binned uncorrelated least squares fit. This article
demonstrates that this procedure underestimates the statistical errors. A
recipe is given to construct from the data the covariance matrix To estimate
the strength of the Bose-Einstein correlations and the radius of the
hadronization region in multiparticle production, the two-particle correlation
functions for identical pairs is adjusted to a parametric function
describing the enhancement at small momentum differences. This is usually done
by means of a binned uncorrelated least squares fit. This article demonstrates
that this procedure underestimates the statistical errors. A recipe is given to
construct from the data the covariance matrix between the bins of the histogram
of the two-particle correlation function.Comment: 9 pages, 4 figure
Correcting the Colour-Dipole Cascade Model with Fixed Order Matrix Elements
An algorithm is presented in which the Colour-Dipole Cascade Model as
implemented in the Ariadne program is corrected to match the fixed order
tree-level matrix elements for e+e- -> n jets. The result is a full parton
level generator for e+e- annihilation where the generated states are correct on
tree-level to fixed order in alpha_S and to all orders with modified leading
logarithmic (MLLA) accuracy. In this paper, matrix elements are used up to
second order in alpha_S, but the scheme is applicable also for higher orders.
An improvement to also include exact virtual corrections to fixed order is
suggested and the possibility to extend the scheme to hadronic collisions is
discussed
Reconnecting coloured dipoles
Reconnections among the produced colour dipoles in the Dipole Cascade Model are discussed, and an implementation in theAriadne program is presented. The reconnections are shown to have only small effects on event shapes at LEP 1, on theW mass determination at LEP 2 and on rapidity gaps in deep inelastic scattering at HERA
JET ANALYSIS BY NEURAL NETWORKS IN HIGH ENERGY HADRON-HADRON COLLISIONS
We study the possibility to employ neural networks to simulate jet clustering
procedures in high energy hadron-hadron collisions. We concentrate our analysis
on the Fermilab Tevatron energy and on the algorithm. We consider both
supervised multilayer feed-forward network trained by the backpropagation
algorithm and unsupervised learning, where the neural network autonomously
organizes the events in clusters.Comment: 9 pages, latex, 2 figures not included
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