3,234 research outputs found
Physical (ir)relevance of ambiguities to Lorentz and CPT violation in QED
We discuss the regularization and renormalization of QED with Lorentz and CPT
violation, and argue that the coefficient of the Chern-Simons term is an
independent parameter not determined by gauge invariance. We also study these
issues in a model with spontaneous breaking of Lorentz and CPT symmetries and
find an explicit relation with the ABJ anomaly. This explains the observed
convergence of the induced Chern-Simons term.Comment: 16 pages, references adde
Differential Renormalization of Gauge Theories
The scope of constrained differential renormalization is to provide
renormalized expressions for Feynman graphs, preserving at the same time the
Ward identities of the theory. It has been shown recently that this can be done
consistently at least to one loop for abelian and non-abelian gauge theories.
We briefly review these results, evaluate as an example the gluon selfenergy in
both coordinate and momentum space, and comment on anomalies.Comment: LaTex, 8 pages with 1 ps figures, talk given at the Zeuthen Workshop
on Elementary Particle Physics "Loops and Legs in Gauge Theories",
Rheinsberg, Germany, April 19-24, 1998, to appear in Acta Physica Polonica
Vector triplets at the LHC
Several popular extensions of the Standard Model predict extra vector fields
that transform as triplets under the gauge group SU(2)_L. These multiplets
contain Z' and W' bosons, with masses and couplings related by gauge
invariance. We review some model-independent results about these new vector
bosons, with emphasis on di-lepton and lepton-plus-missing-energy signals at
the LHC.Comment: LaTex 5 pages. Talk by M. Perez-Victoria at LHCP 2013, Barcelona,
Spain, May 13-18, 2013. New reference adde
Asymmetries in t tbar production: LHC versus Tevatron
The measurement of a charge asymmetry in t tbar production at LHC constitutes
more than an independent confirmation of the forward-backward asymmetry found
at Tevatron. Indeed, both measurements together can be used to identify the
source of the asymmetry. This is demonstrated for the case of new Z', W' vector
bosons and colour-sextet and triplet scalars, exchanged in t, u channels
respectively, and a very heavy axigluon in the s channel.Comment: LaTeX 5 pages. Updated with discussion on implications of summer
results. Final version to appear in PR
Physics of Brane Kinetic Terms
Models with extra dimensions may give new effects visible at future
experiments. In these models, bulk fields can develop localized corrections to
their kinetic terms which can modify the phenomenological predictions in a
sizeable way. We review the case in which both gauge bosons and fermions
propagate in the bulk, and discuss the limits on the parameter space arising
from electroweak precision data.Comment: Presented at Matter To The Deepest: Recent Developments In Physics of
Fundamental Interactions, XXVII International Conference of Theoretical
Physics, Ustron 15-21 September 2003, Polan
Observable contributions of new exotic quarks to quark mixing
Models with new vector-like quarks can produce observable quark mixing
effects which are forbidden in the Standard Model. We classify all such models
and write down the effective Lagrangian that results from integrating out the
new quarks. We study the relations between neutral and charged currents and
discuss how to distinguish among the different possibilities.Comment: 15 pages, 1 figure, typos corrected, version to appear in JHE
Bulk fields with brane terms
In theories with branes, bulk fields get in general divergent corrections
localized on these defects. Hence, the corresponding brane terms are
renormalized and should be included in the effective theory from the very
beginning. We review the phenomenology associated to brane kinetic terms for
different spins and backgrounds, and point out that renormalization is required
already at the classical level.Comment: Presented at HEP2003, International Europhysics Conference on High
Energy Physics (July 17-23, 2003) Aachen, German
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