5,642 research outputs found
Effective theory of a doubly charged singlet scalar: complementarity of neutrino physics and the LHC
We consider a rather minimal extension of the Standard Model involving just
one extra particle, namely a single singlet scalar and its
antiparticle . We propose a model independent effective operator, which
yields an effective coupling of to pairs of same sign weak gauge
bosons, . We also allow tree-level couplings of
to pairs of same sign right-handed charged leptons of the
same or different flavour. We calculate explicitly the resulting two-loop
diagrams in the effective theory responsible for neutrino mass and mixing. We
propose sets of benchmark points for various masses and couplings
which can yield successful neutrino masses and mixing, consistent with limits
on charged lepton flavour violation (LFV) and neutrinoless double beta decay.
We discuss the prospects for discovery at the LHC, for these
benchmark points, including single and pair production and decay into same sign
leptons plus jets and missing energy. The model represents a minimal example of
the complementarity between neutrino physics (including LFV) and the LHC,
involving just one new particle, the .Comment: 57 pages, 14 figures, 10 tables, version accepted for publication in
JHE
Dark Radiation or Warm Dark Matter from long lived particle decays in the light of Planck
Although Planck data supports the standard \Lambda CDM model, it still allows
for the presence of Dark Radiation corresponding up to about half an extra
standard neutrino species. We propose a scenario for obtaining a fractional
"effective neutrino species" from a thermally produced particle which decays
into a much lighter stable relic plus standard fermions. At lifetimes much
longer than 1 sec, both the relic particles and the non-thermal neutrino
component contribute to Dark Radiation. By increasing the stable-to-unstable
particle mass ratio, the relic particle no longer acts as Dark Radiation but
instead becomes a candidate for Warm Dark Matter with mass O(1keV - 100GeV). In
both cases it is possible to address the lithium problem.Comment: 18 pages, 2 figures; v3 matches version to be published in PL
The Decline and Fall of the Wall of Separation between Church and State and Its Consequences for the Funding of Public and Private Institutions of Higher Education
Generalised CP and Family Symmetry
We perform a comprehensive study of family symmetry models based on
combined with the generalised CP symmetry . We investigate the
lepton mixing parameters which can be obtained from the original symmetry
breaking to different remnant symmetries in the
neutrino and charged lepton sectors. We find that only one case is
phenomenologically viable, namely in the neutrino sector and in the charged lepton sector, leading to the
prediction of no CP violation, namely and the Majorana phases
and are all equal to either zero or . We then
propose an effective supersymmetric model based on the symmetry in which trimaximal lepton mixing is predicted together with
either zero CP violation or with non-trivial
Majorana phases. An ultraviolet completion of the effective model yields a
neutrino mass matrix which depends on only three real parameters. As a result
of this, all three CP phases and the absolute neutrino mass scale are
determined, the atmospheric mixing angle is maximal, and the Dirac CP can
either be preserved with or maximally broken with
and sharp predictions for the Majorana phases and
neutrinoless double beta decay.Comment: 38 pages, 3 figure
E6SSM vs MSSM gluino phenomenology
The E6SSM is a promising model based on the group E6, assumed to be broken at
the GUT scale, leading to the group SU(3)\times SU(2)\times U(1)\times U(1)' at
the TeV scale. It gives a solution to the MSSM {\mu}-problem without
introducing massless axions, gauge anomalies or cosmological domain walls. The
model contains three families of complete 27s of E6, giving a richer
phenomenology than the MSSM. The E6SSM generically predicts gluino cascade
decay chains which are about 2 steps longer than the MSSM's due to the presence
of several light neutralino states. This implies less missing (and more
visible) transverse momentum in collider experiments and kinematical
distributions such as M_eff are different. Scans of parameter space and MC
analysis suggest that current SUSY search strategies and exclusion limits have
to be reconsidered.Comment: Presented at the 2011 Hadron Collider Physics symposium (HCP-2011),
Paris, France, November 14-18 2011, 3 pages, 7 figure
Neutrino Mass and Mixing: from Theory to Experiment
The origin of fermion mass hierarchies and mixings is one of the unresolved
and most difficult problem in high-energy physics. One possibility to address
the flavour problem is by extending the Standard Model to include a family
symmetry. In the recent years it has become very popular to use non-Abelian
discrete flavour symmetries because of their power in the prediction of the
large leptonic mixing angles relevant for neutrino oscillation experiments.
Here we give an introduction to the flavour problem and to discrete groups
which have been used to attempt a solution for it. We review the current status
of models in the light of the recent measurement of the reactor angle and we
consider different model building directions taken. The use of the flavons or
multi Higgs scalars in model building is discussed as well as the direct vs.
indirect approaches. We also focus on the possibility to distinguish
experimentally flavour symmetry models by means of mixing sum rules and mass
sum rules. In fact, we illustrate in this review the complete path from
mathematics, via model building, to experiments, so that any reader interested
to start working in the field could use this text as a starting point in order
to get a broad overview of the different subject areas.Comment: Accepted for publication in NJP, 62 pages, 9 tables, 7 figure
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