119810153
Comparison of trimuon production mechanisms
We compare the predictions of six models for neutrino (and antineutrino) production of trimuon events. In particular, results are given for models based on heavy-charged-lepton decays, heavy-neutral- lepton decays together with heavy-quark decays, diffractive production and decay of heavy-quark pairs, heavy-quark cascade decays, the decays of Higgs mesons, and the radiative production of muon pairs. Our comparison should help to unravel the sources of the trimuon events detected at Fermilab and CERN. We also examine the probability of explaining the so-called superevents in which the muons are extremely energetic.
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.
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.
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 ${\ensuremath{\mu}}^{2}.$
115908540
Radiative corrections to the decay pi0 ---> gamma e+ e-
123858028
Radiative corrections to the invariant-mass spectrum of a dalitz pair
119443667
Return of the EMC effect: Finite nuclei
A light front formalism for deep inelastic lepton scattering from finite nuclei is developed. In particular, the nucleon plus momentum distribution and a finite system analog of the Hugenholtz-van Hove theorem are presented. Using a relativistic mean field model, numerical results for the plus momentum distribution and ratio of bound to free nucleon structure functions for Oxygen, Calcium and Lead are given. We show that we can incorporate light front physics with excellent accuracy while using easily computed equal time wavefunctions. Assuming nucleon structure is not modified in-medium we find that the calculations are not consistent with the binding effect apparent in the data not only in the magnitude of the effect, but in the dependence on the number of nucleons.
120150178
Measurement of anomalous muon pair production in electron-positron annihilations
We have observed 16 events of the type ..mu../sup +/..mu../sup -/ + (missing energy and momentum) from e/sup +/e/sup -/ annihilations at center-of-mass energies between 6.4 and 7.4 GeV. Taking into account QED backgrounds, we find an excess of 11 anomalous dimuon events. If these are attributed to the production and subsequent decay of a pair of heavy leptons L/sup + -/, we obtain the muonic braching ratio B ((L/sup +/ ..-->.. ..mu../sup +/..nu../sub ..mu../nu-bar/sub L/)/ (L/sup +/ ..-->.. all)) = 0.22/sup +0.07//sub -0.08/.
120135663
Studies of tau decay modes with K0 mesons from CLEO
We examine five final states involving K 0 mesons, presenting branching fractions for the decays τ → K 0 πν τ , τ → K 0 ππ 0 ν τ , τ → K 0 Kν τ , τ → K 0 Kπ 0 ν τ , and τ → K s K s hν τ . The mass spectra provide evidence for the dominant role of K * in Kπ decays and K 1 in Kππ modes. We find evidence for a significant K * K contribution to the KKπ decays.
119434142
Role of the nuclear vector potential in deep inelastic scattering
We study the influence of the strong nuclear vector potential, treated using the mean-field approximation, in deep inelastic scattering. A physically consistent treatment of the electromagnetic current operator, combined with the use of the operator product expansion is presented and discussed.
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.