1,110 research outputs found
QED Radiative Corrections to the Pionium Life Time
The lowest order QED radiative corrections to the cross-section of the
recharged process of transition of two charged pions to two neutral ones and to
the pionium life time are calculated in frames of scalar QED. It is argued that
the ultraviolet cut--off of the loop momentum is to be chosen of order of
meson mass. This fact permits to perform the calculation in frames of
Effective Chiral Lagrangian theory with vector-meson dominance. The Coulomb
factor corresponding to interaction in the initial state, shown, is to be
removed to avoid the double counting. Resulting value of the radiative
correction to the pionium life time is -0.25%.Comment: 4 pages, LaTeX (considerable improvements
QED radiative corrections to impact factors
We consider the radiative corrections to the impact factors of electron and
photon. According to a generalized eikonal representation the e\bar e
scattering amplitude at high energies and fixed momentum transfers is
proportional to the electron form factor. But we show that this representation
is violated due to the presence of non-planar diagrams. One loop correction to
the photon impact factor for small virtualities of the exchanged photon is
obtained using the known results for the cross section of the e\bar e
production at photon-nuclei interactions.Comment: 8 pp, plain LaTe
Radiative Tail in Decay and Some Comments on Universality
The result of lowest-order perturbation theory calculations of the photon and
positron spectra in radiative pion(e2) decay are generalized to all orders of
perturbation theory using the structure-function method. An additional source
of radiative corrections to the ratio of the positron and muon channels of pion
decay, due to emission of virtual and real photons and pairs, is considered. It
depends on details of the detection of the final particles and is large enough
to be taken into account in theoretical estimates with a level of accuracy of
0.1%.Comment: 5 pages, LaTeX, some misprints are corrected, submitted to Pisma Zh.
Eksp. Teor. Fi
Tensor Meson Production in Proton-Proton Collisions from the Color Glass Condensate
We compute the inclusive cross-section of tensor mesons production in
proton-proton collisions at high-energy. We use an effective theory inspired
from the tensor meson dominance hypothesis that couples gluons to
mesons. We compute the differential cross-section in the
-factorization and in the Color Glass Condensate formalism in the
low density regime. We show that the two formalisms are equivalent for this
specific observable. Finally, we study the phenomenology of mesons by
comparing theoretical predictions of different parameterizations of the
unintegrated gluon distribution function. We find that -meson production
is another observable that can be used to put constraints on these
distributions.Comment: 26 pages, 3 figures, to be submitted in Phys. Rev.
Radiative corrections to muon decay in leading and next to leading approximation for electron spectrum
We have noted that the electron spectrum of muon decay in the leading
logarithmic approximation calculated in two lowest orders of the perturbation
theory in the paper of Berman (1958), can be reproduced by the parton language.
This fact permits one to generalize the result to all orders of the
perturbation theory using the structure function method.Comment: 4 pages, 1 figur
Probing doubly charged Higgs in Colliders in 3-3-1 Model
The SU(3)_L\otimesU(1)_N electroweak model predicts new Higgs bosons beyond
the one of the standard model. In this work we investigate the signature and
production of doubly charged Higgs bosons in the International Linear
Collider and in the CERN Linear Collider. We compute the branching ratios for
the doubly charged gauge bosons of the model.Comment: 17 pages, 12 figure
All Two-Loop MHV Amplitudes in Multi-Regge Kinematics From Applied Symbology
Recent progress on scattering amplitudes has benefited from the mathematical
technology of symbols for efficiently handling the types of polylogarithm
functions which frequently appear in multi-loop computations. The symbol for
all two-loop MHV amplitudes in planar SYM theory is known, but explicit
analytic formulas for the amplitudes are hard to come by except in special
limits where things simplify, such as multi-Regge kinematics. By applying
symbology we obtain a formula for the leading behavior of the imaginary part
(the Mandelstam cut contribution) of this amplitude in multi-Regge kinematics
for any number of gluons. Our result predicts a simple recursive structure
which agrees with a direct BFKL computation carried out in a parallel
publication.Comment: 20 pages, 2 figures. v2: minor correction
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