58 research outputs found
Leading electroweak corrections at the TeV scale
The planned next generation of linear colliders (NLCs) will be able to probe
the infrared structure of Standard Model electroweak interactions, that
determines the behavior of electroweak radiative corrections at TeV scale
energies. I present results of a recent calculation at the leading log level,
and discuss my view on open issues and possible future developments of this new
and interesting subject.Comment: LaTeX, 6 pages, 3 figures. Talk presented at the 2nd ECFA/DESY Study
on Physics and Detectors for a Linear Electron-Positron Collider, Obernai
(France) 16-19th October, 199
Enhanced Electroweak Corrections to Inclusive Boson Fusion Processes at the TeV Scale
Electroweak radiative corrections with double-log enhancements occur in
inclusive observables at the TeV scale because of a lack of compensation of
virtual corrections with real emission due to the nonabelian (weak isospin)
charges of the accelerator beams. Here we evaluate such Bloch-Nordsieck
violating corrections in the case of initial longitudinal bosons, which is
experimentally provided by boson fusion processes, and is related to the
Goldstone-Higgs sector. All four states of this sector are involved in the
group structure of the corrections, and cause in particular a novel double log
effect due to hypercharge mixing in the longitudinal states. We study both the
light- and the heavy-Higgs cases, and we analyze the symmetry breaking pattern
of the corrections. The latter turn out to be pretty large, in the 5-10 %
range, and show an interesting Higgs mass dependence, even for processes
without Higgs boson in the final state.Comment: 15 pages, 6 figure
Electroweak double logarithms in inclusive observables for a generic initial state
High energy observables are characterized by large electroweak radiative
corrections of infrared origin; double logarithms are present even for
inclusive cross sections, thus violating the Bloch Nordsieck theorem. This
effect, related to the initial states carrying nonabelian isospin charges, is
here investigated for {\sl any} inclusive cross section in the
SU(2)U(1) symmetric limit, that is appropriate for energies much
higher than the weak scale. We develop a general formalism allowing to
calculate the all order double log resummed cross sections once the hard (tree
level) ones are known. The relevant cases of fermion-fermion, fermion-boson and
boson-boson scattering are discussed.Comment: 6 pages, 2 figure
Electroweak Bloch-Nordsieck violation at the TeV scale: "strong" weak interactions ?
Hard processes at the TeV scale exhibit enhanced (double log) EW corrections
even for inclusive observables, leading to violation of the Bloch-Nordsieck
theorem. This effect, previously related to the non abelian nature of free EW
charges in the initial state (e- e+, e- p, p p ...), is here investigated for
fermion initiated hard processes and to all orders in EW couplings. We find
that the effect is important, especially for lepton initiated processes,
producing weak effects that in some cases compete in magnitude with the strong
ones. We show that this (double log) BN violating effect has a universal energy
dependence, related to the Sudakov form factor in the adjoint representation.
The role of this form factor is to suppress cross section differences within a
weak isospin doublet, so that at very large energy the cross sections for
left-handed electron-positron and neutrino-positron scattering become equal.
Finally, we briefly discuss the phenomenological relevance of our results for
future colliders.Comment: 18 pages, 6 figures, uses epsfig.sty and subequation.st
Initial State Radiation in Majorana Dark Matter Annihilations
The cross section for a Majorana Dark Matter particle annihilating into light
fermions is helicity suppressed. We show that, if the Dark Matter is the
neutral Majorana component of a multiplet which is charged under the
electroweak interactions of the Standard Model, the emission of gauge bosons
from the initial state lifts the suppression and allows an s-wave annihilation.
The resulting energy spectra of stable Standard Model particles are importantly
affected. This has an impact on indirect searches for Dark Matter.Comment: 9 pages, 3 figure
TeV scale Dark Matter and electroweak radiative corrections
Recent anomalies in cosmic rays data, namely from the PAMELA collaboration,
can be interpreted in terms of TeV scale decaying/annihilating Dark Matter. We
analyze the impact of radiative corrections coming from the electroweak sector
of the Standard Model on the spectrum of the final products at the interaction
point. As an example, we consider virtual one loop corrections and real gauge
bosons emission in the case of a very heavy vector boson annihilating into
fermions. We show that the effect of electroweak corrections is relevant, but
not as big as sometimes claimed in the literature. At such high scales, one
loop electroweak effects are so big that eventually higher orders/resummations
have to be considered: we advocate for the inclusion of these effects in parton
shower Montecarlos aiming at the description of TeV scale physics.Comment: Comments added, published versio
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