259 research outputs found
Soft Color Interactions and Diffractive Hard Scattering at the Fermilab Tevatron
An improved understanding of nonperturbative QCD can be obtained by the
recently developed soft color interaction models. Their essence is the
variation of color string-field topologies, giving a unified description of
final states in high energy interactions, e.g., diffractive and nondiffractive
events in ep and ppbar. Here we present a detailed study of such models (the
soft color interaction model and the generalized area law model) applied to
ppbar, considering also the general problem of the underlying event including
beam particle remnants. With models tuned to HERA ep data, we find a good
description also of Tevatron data on production of W, beauty and jets in
diffractive events defined either by leading antiprotons or by one or two
rapidity gaps in the forward or backward regions. We also give predictions for
diffractive J/psi production where the soft exchange mechanism produces both a
gap and a color singlet ccbar state in the same event. This soft color
interaction approach is also compared with Pomeron-based models for
diffraction, and some possibilities to experimentally discriminate between
these different approaches are discussed.Comment: 35 pages, 15 figures, uses REVTeX. Minor changes, version to appear
in Phys. Rev.
Heavy Flavour Physics at HERA - a Survey
At the HERA collider at DESY, high energy electron and positron beams
interact with proton beams. A review is presented of the variety of ways in
which these collisions produce final states containing charm and beauty quarks.Comment: 45 pages including 30 figures. Submitted to International Journal of
Modern Physics
Soft Color Enhancement of the Production of J/psi's by Neutrinos
We calculate the production of J/psi mesons by neutrino-nucleon collisions in
fixed target experiments. Soft color, often referred to as color evaporation
effects, enhance production cross sections due to the contribution of color
octet states. Though still small, J/\psi production may be observable in
present and future experiments like NuTeV and muon colliders.Comment: 7 pages, Revtex, 4 postscript figures, uses epsfig.st
A Cell of One’s Own? Incarceration and Other Turning Points in Women’s Journeys to Desistance
Research has shown the importance of turning points in desistance from criminal behavior. Using qualitative data from a sample of 100 formerly incarcerated mothers interviewed about their criminal behavior, this article explores their descriptions of transition moments and whether and how those moments affected their criminal behavior. The findings indicate that whereas parenting emerges as a turning point, the practical difficulties of reentry may reduce the impact of mothering on women’s desistance. More self-focused turning points, such as those due to incarceration, arrest, and sobriety appeared to be particularly important to the women’s desistance. This article emphasizes the need for research into the subjective and environmental factors that affect women’s desistance behaviors
Diffractive Dissociation In The Interacting Gluon Model
We have extended the Interacting Gluon Model (IGM) to calculate diffractive
mass spectra generated in hadronic collisions. We show that it is possible to
treat both diffractive and non-diffractive events on the same footing, in terms
of gluon-gluon collisions. A systematic analysis of available data is
performed. The energy dependence of diffractive mass spectra is addressed. They
show a moderate narrowing at increasing energies. Predictions for LHC energies
are presented.Comment: 12 pages, latex, 14 figures (PostScript Files included); accepted for
publication in Phys. Rev. D (Feb.97
Hadron Production in Diffractive Deep-Inelastic Scattering
Characteristics of hadron production in diffractive deep-inelastic
positron-proton scattering are studied using data collected in 1994 by the H1
experiment at HERA. The following distributions are measured in the
centre-of-mass frame of the photon dissociation system: the hadronic energy
flow, the Feynman-x (x_F) variable for charged particles, the squared
transverse momentum of charged particles (p_T^{*2}), and the mean p_T^{*2} as a
function of x_F. These distributions are compared with results in the gamma^* p
centre-of-mass frame from inclusive deep-inelastic scattering in the
fixed-target experiment EMC, and also with the predictions of several Monte
Carlo calculations. The data are consistent with a picture in which the
partonic structure of the diffractive exchange is dominated at low Q^2 by hard
gluons.Comment: 16 pages, 6 figures, submitted to Phys. Lett.
Structure Functions of the Nucleon and their Interpretation
The current status of measurements of the nucleon structure functions and
their understanding is reviewed. The fixed target experiments E665, CCFR and
NMC and the HERA experiments H1 and ZEUS are discussed in some detail. The
extraction of parton momentum distribution functions from global fits is
described, with particular attention paid to much improved information on the
gluon momentum distribution. The status of alpha_s measurements from deep
inelastic data is reviewed. Models and non-perturbative approaches for the
parton input distributions are outlined. The impact on the phenomenology of QCD
of the data at very low values of the Bjorken x variable is discussed in
detail. Recent advances in the understanding of the transition from deep
inelastic scattering to photoproduction are summarised. Some brief comments are
made on the recent HERA measurements of the ep NC and CC cross-sections at very
high Q2.Comment: 196 pages, 79 figures, uses ijmpa.sty and psfig.tex (included
On the phenomenological analyses of - asymmetry in the nucleon sea
Two phenomenological models which give opposite predictions for the
- asymmetry in the nucleon sea are re-analyzed carefully. It is
pointed out that although the quantitative results in both models depend
dramatically on the parameters, the predictions for the shape of in the two models are parameter independent and opposite. Thereby the
coming experiments are likely to be able to distinguish the two models. We find
that the reason for the two models giving opposite predictions is that the
fluctuation functions and parametrizations for the strange (anti-strange) quark
distribution in the baryon (meson) in the two models are quite different. To
further investigate these models, we use the same parametrizations for the
strange (anti-strange) distributions of the baryon (meson) in the two models.
We find that one of the models depends strongly on the parameter which controls
the behavior of the meson-baryon fluctuation function. Also the two models
agree on the shape and size of - for some values of the model
parameters, but can disagree strongly for others.Comment: RevTex, 11 pages, 7 Postscript figure
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