The structure functions of longitudinal virtual photon at low virtualities

The structure functions of longitudinal virtual photon at low virtualities are calculated in the framework of chiral pertubation theory(ChPT) in the zero and first order of ChPT. It is assumed that the virtuality of target longitudinal photon is much less than the virtuality of the hard projectile photon and both are less than the characteristic ChPT scale.Comment: 16 pages, 8 figure

The asymptotic S‐matrix, mass‐shell anomalies and observables

Asymptotic S‐matrix techniques are applied to the identification of a Standard Model background to polarized deep‐inelastic scattering experiments at HERA in search of Right‐handed Charged Currents. It is also pointed out that the Asymptotic S‐matrix produces finite observables free of Mass‐Shell Anomalies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87409/2/297_1.pd

Theoretical aspects of top quark production at hadron collider

We summarize our calculation of the total cross section for top quark production at hadron colliders within the context of perturbative quantum chromodynamics, including resummation of the effects of initial-state soft gluon radiation to all orders in the strong coupling strength

Radiative background to the search for right-handed charged currents

The probability for an electron to emit a collinear, hard photon while undergoing helicity flip is finite in the limit that the electron mass tends to zero. We point out that this provides a background of order [alpha] to tests of the Standard Model, which may affect the search for right-handed, charged currents in deeply inelastic scattering, especially at HERA. It would appear to be exceedingly difficult to discriminate against this background in practice and may make it difficult to improve substantially the mass limits on a right-handed charged vector boson.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29981/1/0000345.pd

Physical consequences of mass singularities

We argue that the perturbation expansion of massless field theories are uniquely and unambiguously defined for properly formed observables. In so doing, we generalize the Kinoshita-Lee-Nauenberg theorem to show that there are no observable "mass-shell anomalies". Paradoxically, in realistic circumstances, massive electrons give rise to non-intuitive, enhanced effects, for example, an unexpected background to the search for right-handed charged currents at HERA.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30154/1/0000531.pd

Threshold Resummation of the Total Cross Section for Heavy Quark Production in Hadronic Collisions

We discuss calculations of the inclusive total cross section for heavy quark production at hadron collider energies within the context of perturbative quantum chromodynamics, including resummation of the effects of initial-state soft gluon radiation to all orders in the strong coupling strength. We resum the universal leading-logarithm contributions, and we restrict our integrations to the region of phase space that is demonstrably perturbative. We include a detailed comparison of the differences between ours and other methods. We provide predictions of the physical cross section as a function of the heavy quark mass in proton-antiproton reactions at center-of-mass energies of 1.8 and 2.0 TeV, and we discuss estimated uncertainties.Comment: 31 pages, RevTeX, 7 figure

Power Corrections in QCD: A Matter of Energy Resolution

We consider power-like corrections in QCD which can be viewed as power surpressed infrared singularities. We argue that the presence of these singularities depends crucially on the energy resolution. In case of poor energy resolution, i.e., inclusive cross sections, there are constraints on infrared singularities expressed by the Kinoshita-Lee-Nauenberg (KLN) theorem. We rewrite the theorem in covariant notations and argue that the KLN theorem implies the extension of the Bloch-Nordsieck cancellation of logarithmic singularities to the case of linear corrections.Comment: 11 pages, Latex file, uses epsf.sty, 5 figures in a uufil

An operator expansion for the elastic limit

A leading twist expansion in terms of bi-local operators is proposed for the structure functions of deeply inelastic scattering near the elastic limit $x \to 1$, which is also applicable to a range of other processes. Operators of increasing dimensions contribute to logarithmically enhanced terms which are supressed by corresponding powers of $1-x$. For the longitudinal structure function, in moment ($N$) space, all the logarithmic contributions of order $\ln^k N/N$ are shown to be resummable in terms of the anomalous dimension of the leading operator in the expansion.Comment: 9 pages, 1 figure, uses REVTEX 3.1 and axodra

Asymptotic Dynamics in Quantum Field Theory

A crucial element of scattering theory and the LSZ reduction formula is the assumption that the coupling vanishes at large times. This is known not to hold for the theories of the Standard Model and in general such asymptotic dynamics is not well understood. We give a description of asymptotic dynamics in field theories which incorporates the important features of weak convergence and physical boundary conditions. Applications to theories with three and four point interactions are presented and the results are shown to be completely consistent with the results of perturbation theory.Comment: 18 pages, 3 figure