120632854
Evaluation of a test for the tau neutrino in the zero-muon channel
Abstract Extending previous work, we assess the feasibility of using the visible energy distribution for zero-muon events in a beam dump experiment as a possible means of observing the tau neutrino. The method would require an extremely precise knowledge of various neutrino fluxes and corresponding background reactions, and hence is not as reliable as the muon-trigger test proposed earlier.
115908540
Radiative corrections to the decay pi0 ---> gamma e+ e-
122854560
Modified minimal subtraction scheme parton densities with NNLO heavy flavor matching conditions
A study is made of charm and bottom flavor matching conditions on parton densities. Starting from an $\overline{\mathrm{MS}}$ three-flavor density set, where the scale $\ensuremath{\mu}l{m}_{c},$ and using the recently derived two-loop matching conditions, we provide a new set of four-flavor parton densities where ${m}_{c}l~\ensuremath{\mu}l{m}_{b}$ and five-flavor densities where $\ensuremath{\mu}g~{m}_{b}.$ The effect of the next-to-next-to-leading order matching conditions on the evolution equations is important for scales just above the transition regions. This includes the small x and small ${Q}^{2}$ domain studied by the H1 and ZEUS experiments at DESY HERA. At small x the effects of the matching conditions never die away even for large ${\ensuremath{\mu}}^{2}.$
123858028
Radiative corrections to the invariant-mass spectrum of a dalitz pair
123015361
Electromagnetic production of trimuons in muon scattering: Bethe-Heitler reactions with muon and heavy-lepton pairs
We analyze the Bethe-Heitler production of muon and heavy-lepton pairs using high-energy muon beams on a variety of targets. We give results for coherent production from a nucleus, for incoherent production from individual protons and neutrons, and for deep-inelastic production. Differential distributions are presented for the final leptons and the effects of experimental cuts are considered. This work complements our previous study of trimuon production via muon radiation, Compton radiation, and hadronic final-state interactions.
14067577
NLO corrections to differential cross sections for pseudo-scalar Higgs boson production
Abstract We have computed the full next-to-leading (NLO) QCD corrections to the differential distributions d 2 σ/(dp T dy) for pseudo-scalar Higgs (A) production at large hadron colliders. This calculation has been carried out using the effective Lagrangian approach which is valid as long as the mass of the pseudo-scalar Higgs boson m A and its transverse momentum p T do not exceed the top-quark mass  m t . The shape of the distributions hardly differ from those obtained for scalar Higgs (H) production because, apart from the overall coupling constant and mass, there are only small differences between the partonic differential distributions for scalar and pseudo-scalar production. Therefore, there are only differences in the magnitudes of the hadronic differential distributions which can be mainly attributed to the unknown mixing angle β describing the pseudo-scalar Higgs coupling to the top quarks.
121273996
A study of double tagged two-photon reactions at spear☆
Abstract We have identified 262 doubly tagged two-photon events. A subset of the data shows an enhancement of 21 events in the inclusive two-photon mass squared distribution between 0.8 and 2.2 GeV 2 . If these events result from spin 2 resonance production then Γ γγ = 9.5 ± 3.9 ± 2.4 keV (statistical and systematic). From another subset of 58 events in which the final state could be classified we determine the two-photon hadron to muon cross section ratio R γγ = 1.1 ± 0.3 ± 0.3.
118343286
Charmless Hadronic B-Meson Decays
We give an overview of the experimental measurements and the theoretical understanding of the branching fractions and CP-violating asymmetries of charmless B meson decays. Most experimental results are from the BaBar and Belle Collaborations’ data, accumulated during the past decade. The global features of these experimental results are typically well described by quantum chromodynamics (QCD)-motivated theories such as QCD factorization, perturbative QCD, and soft-collinear effective theory. The agreement between theory and experiment is generally satisfactory, although there remain some unsolved puzzles that pose a great challenge to both theorists and experimentalists.
118854850
Polarized quark distributions in nuclear matter
We compute the polarized quark distribution function of a bound nucleon. The chiral quark-soliton model provides the quark and antiquark substructure of the nucleon embedded in nuclear matter. Nuclear effects cause significant modifications to the polarized distributions, including an enhancement of the axial coupling constant.
94362727
Studies of radiation damage to CAMEX64 preamplifiers exposed to gamma -rays at the Cornell High Energy Synchrotron Source
CAMEX64 preamplifiers, developed for use in the readout of silicon strip detectors, have been exposed to well-measured doses of monochromatic gamma -rays from the Cornell High Energy Synchrotron Source (CHESS), and measurements of the resulting radiation damage have been made. Silicon strip detectors with their associated CAMEXes will be installed close to the interaction region in the CLEO experiment at Cornell University, where they will be exposed to both charged particle and photon fluences. Powered and unpowered CAMEXes were irradiated and after each exposure measurements of pedestals, gains, and coherent and incoherent noise were made until the devices could no longer be read out. Results are presented for noise and gain degradation as a function of dose. Using well-controlled and calibrated 20 keV synchrotron radiation, failure begins at 20 krad in powered CAMEXes and between 60 and 120 krad in unpowered CAMEXes. These failure levels are considerably larger than the projected radiation dose.<<ETX>>
121485718
Return of the EMC effect
The relationship between the properties of nuclear matter and structure functions measured in lepton-nucleus deep inelastic scattering is investigated using light front dynamics. We find that relativistic mean field models such as the Walecka, Zimanyi-Moszkowski (and point-coupling versions of the same), and Rusnak-Furnstahl models contain essentially no binding effect, in accord with an earlier calculation by Birse. These models are found to obey the Hugenholtz\char21{}van Hove theorem, which is applicable if nucleons are the only degrees of freedom. Any model in which the entire Fock space wave function can be represented in terms of free nucleons must obey this theorem, which implies that all of the plus momentum is carried by nucleons, and therefore that there will be essentially no binding effect. The explicit presence of nuclear mesons allows one to obtain a modified form of the Hugenholtz\char21{}van Hove theorem, which is equivalent to the often-used momentum sum rule. These results argue in favor of a conclusion that the depletion of the deep inelastic structure function observed in the valence quark regime is due to some interesting effect involving dynamics beyond the conventional nucleon-meson treatment of nuclear physics.