121 research outputs found
Lepton flavor violation in the Simplest Little Higgs model
The flavor sector of Little Higgs models based on product groups, notably the
Littlest Higgs with T parity (LHT), has been extensively studied and some
amount of fine tuning was found to be required to meet the experimental
constraints. However, no such attention has been paid to other classes of
models. Here we analyze the phenomenology of flavor mixing in the lepton sector
of a simple group model, the Simplest Little Higgs (SLH). We obtain the Feynman
rules of the SLH in the 't Hooft-Feynman gauge up to the necessary order and
calculate the leading contributions to the rare processes mu -> e gamma, mu ->
eee and mu-e conversion in nuclei. We find results comparable to those of the
LHT model, because in both cases they arise at the one-loop level. These
require the flavor alignment of the Yukawa couplings of light and heavy leptons
at the per cent level or an effective scale of around 10 TeV.Comment: 41 pages, 8 figures; minor changes and one reference added, version
to appear in JHE
Chiral Anomaly and CPT invariance in an implicit momentum space regularization framework
This is the second in a series of two contributions in which we set out to
establish a novel momentum space framework to treat field theoretical
infinities in perturbative calculations when parity-violating objects occur.
Since no analytic continuation on the space-time dimension is effected, this
framework can be particularly useful to treat dimension-specific theories.
Moreover arbitrary local terms stemming from the underlying infinities of the
model can be properly parametrized. We (re)analyse the undeterminacy of the
radiatively generated CPT violating Chern-Simons term within an extended
version of and calculate the Adler-Bardeen-Bell-Jackiw triangle anomaly
to show that our framework is consistent and general to handle the subtleties
involved when a radiative corretion is finite.Comment: 16 pages, LaTeX, version to appear in PR
Comparing Implicit, Differential, Dimensional and BPHZ Renormalisation
We compare a momentum space implicit regularisation (IR) framework with other
renormalisation methods which may be applied to dimension specific theories,
namely Differential Renormalisation (DfR) and the BPHZ formalism. In
particular, we define what is meant by minimal subtraction in IR in connection
with DfR and dimensional renormalisation (DR) .We illustrate with the
calculation of the gluon self energy a procedure by which a constrained version
of IR automatically ensures gauge invariance at one loop level and handles
infrared divergences in a straightforward fashion. Moreover, using the
theory setting sun diagram as an example and comparing explicitly
with the BPHZ framework, we show that IR directly displays the finite part of
the amplitudes. We then construct a parametrization for the ambiguity in
separating the infinite and finite parts whose parameter serves as
renormalisation group scale for the Callan-Symanzik equation. Finally we argue
that constrained IR, constrained DfR and dimensional reduction are equivalent
within one loop order.Comment: 21 pages, 2 figures, late
A Little Higgs model of neutrino masses
Little Higgs models are formulated as effective theories with a cut-off of up
to 100 times the electroweak scale. Neutrino masses are then a puzzle, since
the usual see-saw mechanism involves a much higher scale that would introduce
quadratic corrections to the Higgs mass parameter. We propose a model that can
naturally accommodate the observed neutrino masses and mixings in Little Higgs
scenarios. Our framework does not involve any large scale or suppressed Yukawa
couplings, and it implies the presence of three extra (Dirac) neutrinos at the
TeV scale. The masses of the light neutrinos are induced radiatively, they are
proportional to small (\approx keV) mass parameters that break lepton number
and are suppressed by the Little Higgs cut-off.Comment: 10 pages, 3 figure
Implicit Regularization and Renormalization of QCD
We apply the Implicit Regularization Technique (IR) in a non-abelian gauge
theory. We show that IR preserves gauge symmetry as encoded in relations
between the renormalizations constants required by the Slavnov-Taylor
identities at the one loop level of QCD. Moreover, we show that the technique
handles divergencies in massive and massless QFT on equal footing.Comment: (11 pages, 2 figures
Neutrino physics at large colliders
Large colliders are not sensitive to light neutrino masses and character, but
they can produce new heavy neutrinos, allowing also for the determination of
their Dirac or Majorana nature. We review the discovery limits at the next
generation of large colliders.Comment: LaTeX 32 pages. This review summarises and extends work presented at
several conferences. To appear in the proceedings of CORFU2005. References
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