127 research outputs found
Measuring the Running of the Electromagnetic Coupling Alpha in Small Angle Bhabha Scattering
We propose a method to determine the running of from the
measurement of small-angle Bhabha scattering. The method is suited to high
statistics experiments at 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 and
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 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 and 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- 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
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