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.
119411437
Comparison between variable flavor number schemes for charm quark electroproduction
A comparison is made between two variable flavor number schemes which describe charm quark production in deep inelastic electron-proton scattering. In these schemes the coefficient functions are derived from mass factorization of the heavy quark coefficient functions presented in a fixed flavor number scheme. Since the coefficient functions in the variable flavornumber schemes have to be finite in the limit m → 0 we have defined a prescription for those processes where the virtual photon is attached to a light quark. Furthermore one has to construct a parton density set with four active flavors (u,d,s,c) out of a set which only contains three light flavors (u,d,s). In order � 2 the two sets are discontinuous at µ = mc which follows from mass factorization of the heavy quark coefficient functions. The charm component ofthe structure function F2,c is insensitive to the different variable flavor number schemes. In particular in the threshold region they both agree with the description in fixed order perturbation theory presented in a three flavor scheme. However one version does not lead to a correct description of the threshold behavior of the longitudinal structure function FL,c. This happens when one requires a non-vanishing zeroth order longitudinal coefficient function.
123056572
Polarized electroproduction of charm
Abstract We discuss the NLO corrections to polarized electroproduction of charmed quarks.
121531502
QCD corrections to heavy flavour photoproduction and electroproduction
We investigate the QCD corrections to the total cross sections and single-particle inclusive differential distributions for γ + p → Q(Q) + X and e + p → e + Q(Q) + X. In the latter reaction we assume that the exchanged photon is almost real (Weizsacker-Williams approximation). This requires the calculation of the O(αs) corrections to the photon-parton reaction γ + g → Q + Q including the virtual gluon contributions and the soft and hard gluon radiation in the reaction γ + g → Q + Q + g. The contributions from γ + q(q) → Q + Q + q(q) are also calculated. We give exact results for the O(α2αS2) total cross sections and single particle inclusive differential distribution for b-quark production at HERA. Results for b- and t- production at future ep colliders (the LEP∗LHC option at CERN) are also presented.
123858028
Radiative corrections to the invariant-mass spectrum of a dalitz pair
16322936
Charm and bottom quark production cross sections near threshold
The cross sections for charm and bottom quark production in the threshold region are discussed. We consider the effects of an all order resummation of initial state soft-plus-virtual gluon radiation on the total cross sections compared to the order $←pha_{s}^{3}$ results.
209999698
Inclusive gamma-Ray Spectra from psi (3095) and psi-prime (3684)
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.
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.
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.
16140569
Determination of the phase of V(ub) from charmless hadronic B decay rates
We perform a model dependent fit to recent data on charmless hadronic B decays and determine $\gamma$, the phase of $V^*_{ub}$. We find $\gamma = 114^{+25}_{-21}$ degrees, which disfavors the often quoted $\gamma \sim 60^\circ$ at the two standard deviation level. We also fit for the form factors $F_0^{B\pi}$ and $A_0^{B\rho}$, and the strange-quark mass. They are consistent with theoretical expectations, although $m_s$ is somewhat low. Such agreement and the good $\chi^2$ for the fit may be interpreted as a confirmation of the adequacy of our model assumptions.