577 research outputs found
Higher-order Abel equations: Lagrangian formalism, first integrals and Darboux polynomials
A geometric approach is used to study a family of higher-order nonlinear Abel
equations. The inverse problem of the Lagrangian dynamics is studied in the
particular case of the second-order Abel equation and the existence of two
alternative Lagrangian formulations is proved, both Lagrangians being of a
non-natural class (neither potential nor kinetic term). These higher-order Abel
equations are studied by means of their Darboux polynomials and Jacobi
multipliers. In all the cases a family of constants of the motion is explicitly
obtained. The general n-dimensional case is also studied
Hepatic Endothelial CCL25 Mediates the Recruitment of CCR9+ Gut-homing Lymphocytes to the Liver in Primary Sclerosing Cholangitis
Primary sclerosing cholangitis (PSC), a chronic inflammatory liver disease characterized by progressive bile duct destruction, develops as an extra-intestinal complication of inflammatory bowel disease (IBD) (Chapman, R.W. 1991. Gut. 32:1433–1435). However, the liver and bowel inflammation are rarely concomitant, and PSC can develop in patients whose colons have been removed previously. We hypothesized that PSC is mediated by long-lived memory T cells originally activated in the gut, but able to mediate extra-intestinal inflammation in the absence of active IBD (Grant, A.J., P.F. Lalor, M. Salmi, S. Jalkanen, and D.H. Adams. 2002. Lancet. 359:150–157). In support of this, we show that liver-infiltrating lymphocytes in PSC include mucosal T cells recruited to the liver by aberrant expression of the gut-specific chemokine CCL25 that activates α4β7 binding to mucosal addressin cell adhesion molecule 1 on the hepatic endothelium. This is the first demonstration in humans that T cells activated in the gut can be recruited to an extra-intestinal site of disease and provides a paradigm to explain the pathogenesis of extra-intestinal complications of IBD
Study of vector mesons in dimuon production in a large kinematic region in p-W and S-W interactions at 200 GeV/c/nucleon
Results are presented on , and production in p--W and S--W interactions at 200~GeV/c/nucleon measured via the dimuon decay in a large kinematic region. The data are normalized to the charged particle multiplicity in the same rapidity interval. They have been %CORR 1 obtained collected using the HELIOS/3 muon spectrometer at the CERN SPS. %CORR 2 and The ratio increases between proton and sulphur projectiles, and is further enhanced going from peripheral to central nucleus-nucleus interactions. This results from an increase in the number of produced 's per charged particle. The increase in the ratio is not clearly dependent on p, but appears larger at higher rapidities, due to kinematic effects %CORR 3 and in conjunction with varying acceptance. production, likewise normalized to charged multiplicity, is significantly lower in S--W compared to p--W interactions
Measurement of the diffractive structure function in deep inelastic scattering at HERA
This paper presents an analysis of the inclusive properties of diffractive
deep inelastic scattering events produced in interactions at HERA. The
events are characterised by a rapidity gap between the outgoing proton system
and the remaining hadronic system. Inclusive distributions are presented and
compared with Monte Carlo models for diffractive processes. The data are
consistent with models where the pomeron structure function has a hard and a
soft contribution. The diffractive structure function is measured as a function
of \xpom, the momentum fraction lost by the proton, of , the momentum
fraction of the struck quark with respect to \xpom, and of . The \xpom
dependence is consistent with the form \xpoma where
in all bins of and
. In the measured range, the diffractive structure function
approximately scales with at fixed . In an Ingelman-Schlein type
model, where commonly used pomeron flux factor normalisations are assumed, it
is found that the quarks within the pomeron do not saturate the momentum sum
rule.Comment: 36 pages, latex, 11 figures appended as uuencoded fil
Measurement of inclusive D*+- and associated dijet cross sections in photoproduction at HERA
Inclusive photoproduction of D*+- mesons has been measured for photon-proton
centre-of-mass energies in the range 130 < W < 280 GeV and a photon virtuality
Q^2 < 1 GeV^2. The data sample used corresponds to an integrated luminosity of
37 pb^-1. Total and differential cross sections as functions of the D*
transverse momentum and pseudorapidity are presented in restricted kinematical
regions and the data are compared with next-to-leading order (NLO) perturbative
QCD calculations using the "massive charm" and "massless charm" schemes. The
measured cross sections are generally above the NLO calculations, in particular
in the forward (proton) direction. The large data sample also allows the study
of dijet production associated with charm. A significant resolved as well as a
direct photon component contribute to the cross section. Leading order QCD
Monte Carlo calculations indicate that the resolved contribution arises from a
significant charm component in the photon. A massive charm NLO parton level
calculation yields lower cross sections compared to the measured results in a
kinematic region where the resolved photon contribution is significant.Comment: 32 pages including 6 figure
Search for R-parity Violating Supersymmetry in Dimuon and Four-Jets Channel
We present results of a search for R-parity-violating decay of the neutralino
chi_1^0, taken to be the Lightest Supersymmetric Particle. It is assumed that
this decay proceeds through one of the lepton-number violating couplings
lambda-prime_2jk (j=1,2; k=1,2,3). This search is based on 77.5 pb-1 of data,
collected by the D0 experiment at the Fermilab Tevatron in ppbar collisions at
a center of mass energy of 1.8 TeV in 1992-1995.Comment: 10 pages, 3 figure
Measurement of Jet Shapes in Photoproduction at HERA
The shape of jets produced in quasi-real photon-proton collisions at
centre-of-mass energies in the range GeV has been measured using the
hadronic energy flow. The measurement was done with the ZEUS detector at HERA.
Jets are identified using a cone algorithm in the plane with a
cone radius of one unit. Measured jet shapes both in inclusive jet and dijet
production with transverse energies GeV are presented. The jet
shape broadens as the jet pseudorapidity () increases and narrows
as increases. In dijet photoproduction, the jet shapes have been
measured separately for samples dominated by resolved and by direct processes.
Leading-logarithm parton-shower Monte Carlo calculations of resolved and direct
processes describe well the measured jet shapes except for the inclusive
production of jets with high and low . The observed
broadening of the jet shape as increases is consistent with the
predicted increase in the fraction of final state gluon jets.Comment: 29 pages including 9 figure
Search for New Physics Using Quaero: A General Interface to D0 Event Data
We describe Quaero, a method that i) enables the automatic optimization of
searches for physics beyond the standard model, and ii) provides a mechanism
for making high energy collider data generally available. We apply Quaero to
searches for standard model WW, ZZ, and ttbar production, and to searches for
these objects produced through a new heavy resonance. Through this interface,
we make three data sets collected by the D0 experiment at sqrt(s)=1.8 TeV
publicly available.Comment: 7 pages, submitted to Physical Review Letter
Search for Electroweak Production of Single Top Quarks in ppbar Collisions
We present a search for electroweak production of single top quarks in the
electron+jets and muon+jets decay channels. The measurements use ~90 pb^-1 of
data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with
the DZero detector between 1992 and 1995. We use events that include a tagging
muon, implying the presence of a b jet, to set an upper limit at the 95%
confidence level on the cross section for the s-channel process ppbar->tb+X of
39 pb. The upper limit for the t-channel process ppbar->tqb+X is 58 pb.Comment: 11 pages, 2 figures. This is the published versio
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