74 research outputs found
D* Production in Deep Inelastic Scattering at HERA
This paper presents measurements of D^{*\pm} production in deep inelastic
scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The
data have been taken with the ZEUS detector at HERA. The decay channel
(+ c.c.) has been used in the study. The
cross section for inclusive D^{*\pm} production with
and is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region
{ GeV and }. Differential cross
sections as functions of p_T(D^{*\pm}), and are
compared with next-to-leading order QCD calculations based on the photon-gluon
fusion production mechanism. After an extrapolation of the cross section to the
full kinematic region in p_T(D^{*\pm}) and (D^{*\pm}), the charm
contribution to the proton structure function is
determined for Bjorken between 2 10 and 5 10.Comment: 17 pages including 4 figure
Observation of Scaling Violations in Scaled Momentum Distributions at HERA
Charged particle production has been measured in deep inelastic scattering
(DIS) events over a large range of and using the ZEUS detector. The
evolution of the scaled momentum, , with in the range 10 to 1280
, has been investigated in the current fragmentation region of the Breit
frame. The results show clear evidence, in a single experiment, for scaling
violations in scaled momenta as a function of .Comment: 21 pages including 4 figures, to be published in Physics Letters B.
Two references adde
Observation of hard scattering in photoproduction events with a large rapidity gap at HERA
Events with a large rapidity gap and total transverse energy greater than 5
GeV have been observed in quasi-real photoproduction at HERA with the ZEUS
detector. The distribution of these events as a function of the
centre of mass energy is consistent with diffractive scattering. For total
transverse energies above 12 GeV, the hadronic final states show predominantly
a two-jet structure with each jet having a transverse energy greater than 4
GeV. For the two-jet events, little energy flow is found outside the jets. This
observation is consistent with the hard scattering of a quasi-real photon with
a colourless object in the proton.Comment: 19 pages, latex, 4 figures appended as uuencoded fil
Fusion and Binary-Decay Mechanisms in the Cl+Mg System at E/A 8 MeV/Nucleon
Compound-nucleus fusion and binary-reaction mechanisms have been investigated
for the Cl+Mg system at an incident beam energy of E= 282
MeV. Charge distributions, inclusive energy spectra, and angular distributions
have been obtained for the evaporation residues and the binary fragments.
Angle-integrated cross sections have been determined for evaporation residues
from both the complete and incomplete fusion mechanisms. Energy spectra for
binary fragment channels near to the entrance-channel mass partition are
characterized by an inelastic contribution that is in addition to a fully
energy damped component. The fully damped component which is observed in all
the binary mass channels can be associated with decay times that are comparable
to, or longer than the rotation period. The observed mass-dependent cross
sections for the fully damped component are well reproduced by the fission
transition-state model, suggesting a fusion followed by fission origin. The
present data cannot, however, rule out the possibility that a long-lived
orbiting mechanism accounts for part or all of this yield.Comment: 41 pages standard REVTeX file, 14 Figures available upon request -
Observation of Events with an Energetic Forward Neutron in Deep Inelastic Scattering at HERA
In deep inelastic neutral current scattering of positrons and protons at the center of mass energy of 300 GeV, we observe, with the ZEUS detector, events with a high energy neutron produced at very small scattering angles with respect to the proton direction. The events constitute a fixed fraction of the deep inelastic, neutral current event sample independent of Bjorken x and Q2 in the range 3 · 10-4 \u3c xBJ \u3c 6 · 10-3 and 10 \u3c Q2 \u3c 100 GeV2
Charged-particle nuclear modification factors in PbPb and pPb collisions at â=sNN=5.02 TeV
The spectra of charged particles produced within the pseudorapidity window
|η| < 1 at â
sNN = 5.02 TeV are measured using 404 ”b
â1 of PbPb and 27.4 pbâ1 of pp data
collected by the CMS detector at the LHC in 2015. The spectra are presented over the
transverse momentum ranges spanning 0.5 < pT < 400 GeV in pp and 0.7 < pT < 400 GeV
in PbPb collisions. The corresponding nuclear modification factor, RAA, is measured in
bins of collision centrality. The RAA in the 5% most central collisions shows a maximal
suppression by a factor of 7â8 in the pT region of 6â9 GeV. This dip is followed by an increase,
which continues up to the highest pT measured, and approaches unity in the vicinity
of pT = 200 GeV. The RAA is compared to theoretical predictions and earlier experimental
results at lower collision energies. The newly measured pp spectrum is combined with the
pPb spectrum previously published by the CMS collaboration to construct the pPb nuclear
modification factor, RpA, up to 120 GeV. For pT > 20 GeV, RpA exhibits weak momentum
dependence and shows a moderate enhancement above unity
Helicobacter pylori induces MAPK phosphorylation and AP-1 activation via a NOD1-dependent mechanism.
Helicobacter pylori rapidly activates MAPKs and transcription factors, NF-kappaB and AP-1, in gastric epithelial cells following host attachment. Activation of these signal transducers is largely dependent on the cag pathogenicity island (cagPAI)-encoded Type IV Secretion System. H. pylori was shown to translocate peptidoglycan through the Type IV Secretion System, which is recognized by the pathogen recognition molecule, NOD1, thus resulting in NF-kappaB activation. The mechanisms of H. pylori-induced MAPK and AP-1 activation, however, are less well defined and therefore, we assessed the contribution of NOD1 to their activation. For this, we used gastric epithelial cell lines, stably expressing siRNA to either NOD1 or a control gene. In siNOD1-expressing cells stimulated with cagPAI(+) H. pylori, we observed significant reductions in p38 and ERK phosphorylation (p < 0.05), whereas the levels of Jnk phosphorylation remained unchanged. Consistent with a previous report, however, we were able to demonstrate NOD1-dependent Jnk phosphorylation by the invasive pathogen Shigella flexneri, highlighting pathogen-specific host responses to infection. We also show that NOD1 was essential for H. pylori induction of not only NF-kappaB, but also AP-1 activation, implying that NOD1 induces robust proinflammatory responses, in an attempt to rapidly control infection. Pharmacological inhibition of p38 and ERK activity significantly reduced IL-8 production in response to H. pylori, further emphasizing the importance of MAPKs in innate immune responses to the pathogen. Thus, for the first time we have shown the important role for NOD1 in MAPK and AP-1 activation in response to cagPAI(+) H. pylori
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