911 research outputs found
Contact terms in charged current processes at HERA
We obtain bounds on the mass scales characterizing four-fermion contact interactions in charged current processes. The bounds arise from the Q^2 and x distributions in the processes e p -> \nu X measured by the two HERA experiments, H1 and ZEUS
Nuclear effects in photoproduction of heavy quarks and vector mesons in ultraperipheral PbPb and pPb collisions at the LHC
The comparison of photoproduction cross sections for and b-b(bar)
in PbPb and pPb collisions can give sensitivity to nuclear shadowing effects.
The photoproduction of vector mesons is even more sensitive to the underlying
gluon distributions. In this study we present the cross sections and rapidity
dependence of the photoproduction of heavy quarks and exclusive production of
vector mesons in ultraperipheral pPb and PbPb collisions at the Large Hadron
Collider at sqrt(s_NN)=5 TeV and sqrt(s_NN)=2.76J/\psi\Upsilon$ in
PbPb collisions in particular exhibit very good sensitivity to gluon shadowing.Comment: 4 pages, 4 figure
Constraining Gluon Shadowing Using Photoproduction in Ultraperipheral pA and AA Collisions
Photoproduction of heavy quarks and exclusive production of vector mesons in
ultraperipheral proton-nucleus and nucleus-nucleus collisions depend
significantly on nuclear gluon distributions. In the present study we
investigate quantitatively the extent of the applicability of these processes
at the Large Hadron Collider (LHC) in constraining the shadowing component of
nuclear gluon modifications.Comment: 15 pages, 10 figures. arXiv admin note: substantial text overlap with
arXiv:1104.428
Pion wave functions from holographic QCD and the role of infrared renormalons in photon-photon collisions
In this article, we calculate the contribution of the higher-twist Feynman
diagrams to the large- inclusive single pion production cross section in
photon-photon collisions in case of the running coupling and frozen coupling
approaches within holographic QCD. We compare the resummed higher-twist cross
sections with the ones obtained in the framework of the frozen coupling
approach and leading-twist cross section. Also, we show that in the context of
frozen coupling approach a higher-twist contribution to the photon-photon
collisions cross section is normalized in terms of the pion electromagnetic
form factor.Comment: 21 pages, 15 figures. arXiv admin note: text overlap with
arXiv:0709.2072 by other author
On QCD analysis of stucture function in alternative approach
The alternative approach to QCD analysis of the photon structure function
is presented. It differs from the conventional one by the
presence of the terms which in conventional approach appear in higher orders.
We show that this difference concerns also the photonic parton distribution
functions. In the alternative approach, the complete LO analysis of
can be performed as all required quantities are known. At the
NLO, however, one of the coefficient function is so far not available and thus
only the photonic parton distribution function can be computed and compared to
those of standard approach. We discuss the numerical difference of these
approaches at the LO and the NLO approximation and show that in case of
this difference is non-negligible and may play an important role
in the analysis on photon data of the future experiments.Comment: 25 page
Recherches micrographiques sur la nature et l'origine des roches phosphatées: notice préliminaire
Semileptonic and Decays and the Chiral Anomaly at One-loop
We calculate the corrections to the anomalous form factors appearing
in , and decays in
Chiral Perturbation Theory. The relevant dimension terms of the lagrangian
are evaluated assuming their saturation by the vector meson contribution.Comment: 10 pages of LaTeX (+3 figures available on request
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