Measuring the Running of the Electromagnetic Coupling Alpha in Small Angle Bhabha Scattering

We propose a method to determine the running of $\alpha_{QED}$ from the measurement of small-angle Bhabha scattering. The method is suited to high statistics experiments at $e^{+} e^{-}$ colliders, which are equipped with luminometers in the appropriate angular region. We present a new simulation code predicting small-angle Bhabha scattering. A detailed description of this idea can be found in A.B. Arbuzov, D. Haidt, C. Matteuzzi, M. Paganoni and L. Trentadue, The running of the electromagnetic coupling alpha in small-angle Bhabha scattering, Eur. Phys. J. C34, 267 (2004).Comment: 4 pages, talk given at the International Conference on Linear Colliders - LCWS 2004, Paris, Carre' des Sciences, April 19-23, 200

On the QCD Evolution of Transverse Momentum Dependent Distributions

We reconsider the evolution equations for transverse momentum dependent distributions recently proposed by us and recast them in a form which allows the comparison with results recently appeared in the literature. We show under which conditions the obtained results might be consistent with each other.Comment: 13 pages, no figures, minor changes to text, one reference adde

One loop Standard Model corrections to flavor diagonal fermion-graviton vertices

We extend a previous analysis of flavor-changing fermion-graviton vertices, by adding the one-loop SM corrections to the flavor diagonal fermion-graviton interactions. Explicit analytical expressions taking into account fermion masses for the on-shell form factors are computed and presented. The infrared safety of the fermion-graviton vertices against radiative corrections of soft photons and gluons is proved, by extending the ordinary infrared cancellation mechanism between real and virtual emissions to the gravity case. These results can be easily generalized to fermion couplings with massive gravitons, graviscalar, and dilaton fields, with potential phenomenological implications to new physics scenarios with low gravity scale.Comment: 30 pages, 11 figures, revised final version, to appear on Phys. Rev.

Axial Anomaly and Polarized Radiative Decays

We extend the approach of Dolgov and Zakharov to the axial anomaly to study polarized radiative decays. We analyse the pattern of mass singularity cancellation in the corresponding decay rates. We compare polarized and unpolarized cases. The cancellation of the infrared and collinear singularities is verified to all powers of the lepton mass for the $\pi^+$ and $Z^0$ polarized radiative decays.Comment: 18 pages, LaTeX, 4 PostScript figure

An inclusive and exclusive algorithm for QED evolution

A novel algorithm to calculate radiative corrections to e+e- annihilation which is both inclusive and exclusive is proposed. The method uses the structure functions formalism and is based on the factorization of mass singularities in the QED perturbation expansion. The general approach is presented together with its ability to reproduce the infrared and collinear singularity structure of QED as well as the all-order multiple photon radiation. Some numerical results are given.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27762/1/0000155.pd

Fracture Functions and Jet Calculus

By using Jet Calculus as a consistent framework to describe multiparton dynamics we explain the peculiar evolution equation of fracture functions by means of the recently introduced extended fracture functions.Comment: 12 pages, 1 postscript figure, version to appear on Phys. Lett.

Axial Anomaly Effects in Pion and Z0Z^0 Radiative Decays

We discuss a connection between axial anomaly and polarized radiative processes. By comparison with the corresponding unpolarized cases, we consider some physical outputs for the $\pi^+$ and $Z^0$ polarized radiative decays. We analyse in detail the pattern of mass singularity cancellation.Comment: 30 pages, 7 figure

Mass Corrections to Flavor-Changing Fermion-Graviton Vertices in the Standard Model

In a previous study, the flavor-changing fermion-graviton interactions have been analyzed in the framework of the standard model, where analytical results for the relevant form factors were obtained at the leading order in the external fermion masses. These interactions arise at one-loop level by the charged electroweak corrections to the fermion-graviton vertex, when the off-diagonal flavor transitions in the corresponding charged weak currents are taken into account. Due to the conservation of the energy-momentum tensor, the corresponding form factors turn out to be finite and gauge invariant when external fermions are on-shell. Here we extend this previous analysis by including the exact dependence on the external fermion masses. Complete analytical results are provided for all the relevant form factors to the flavor-changing fermion-graviton transitions.Comment: 19 pages, 9 figure

A New Fracture Function Approach to QCD Initial State Radiation

Ordinary fracture functions, describing hadrons production in the deep inelastic scattering target fragmentation region, are generalized to account for the production of hadrons in arbitrary number, thus offering a renewed framework for dealing with QCD initial state radiation. We also propose a new jet-like observable which measures beam remnants and low-$p_{\perp}$ scattering fragments and derive its QCD evolution equations by using Jet Calculus. Possible implications for semi-inclusive deep inelastic scattering and hadron-hadron reactions are shortly discussed.Comment: 10 pages, 5 figures, revtex