8,597 research outputs found
Two-Photon Processes at Intermediate Energies
Exclusive hadron production processes in photon-photon collisions provide
important tests of QCD at the amplitude level, particularly as measures of
hadron distribution amplitudes and skewed parton distributions. The
determination of the shape and normalization of the distribution amplitudes has
become particularly important in view of their importance in the analysis of
exclusive semi-leptonic and two-body hadronic B-decays. Interesting two-photon
physics, including doubly-tagged reactions, will be
accessible at low energy, high luminosity colliders, including
measurements of channels important in the light-by-light contribution to the
muon --2 and the study of the transition between threshold production
controlled by low-energy effective chiral theories and the domain where
leading-twist perturbative QCD becomes applicable. The threshold regime of
hadron production in photon-photon and annihilation, where hadrons
are formed at small relative velocity, is particularly interesting as a test of
low energy theorems, soliton models, and new types of resonance production.
Such studies will be particularly valuable in double-tagged reactions where
polarization correlations, as well as the photon virtuality dependence, can be
studied.Comment: Paper PEP-N W01 presented at the e+ e- Physics at Intermdiate
Energies Workshop, SLAC, April 30-May 2, 2001. References adde
The Newtonian limit at intermediate energies
We study the metric solutions for the gravitational equations in Modified
Gravity Models (MGMs). In models with negative powers of the scalar curvature,
we show that the Newtonian Limit (NL) is well defined as a limit at
intermediate energies, in contrast with the usual low energy interpretation.
Indeed, we show that the gravitational interaction is modified at low densities
or low curvatures.Comment: 4 pages, REVTeX 4; minor typos corrected, one reference adde
Extracting the Weinberg angle at intermediate energies
A recent experiment by the NuTeV collaboration resulted in a surprisingly
high value for the weak mixing angle . The Paschos-Wolfenstein
relation, relating neutrino cross sections to the Weinberg angle, is of pivotal
importance in the NuTeV analysis. In this work, we investigate the sensitivity
of the Paschos-Wolfenstein relation to nuclear structure aspects at neutrino
energies in the few GeV range. Neutrino-nucleus cross sections are calculated
for O and Fe target nuclei within a relativistic quasi-elastic
nucleon-knockout model.Comment: To appear in the proceedings of International School of Nuclear
Physics: 27th Course: "Neutrinos in Cosmology, in Astro, Particle and Nuclear
Physics", Erice, Sicily, Italy, 16-24 Sep 200
Fission induced by nucleons at intermediate energies
Monte Carlo calculations of fission of actinides and pre-actinides induced by
protons and neutrons in the energy range from 100 MeV to 1 GeV are carried out
by means of a recent version of the Li\`ege Intranuclear Cascade Model, INCL++,
coupled with two different evaporation-fission codes, GEMINI++ and ABLA07. In
order to reproduce experimental fission cross sections, model parameters are
usually adjusted on available (p,f) cross sections and used to predict (n,f)
cross sections for the same isotopes.Comment: 36 pages, 18 figures, to appear in Nuclear Physics
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