719 research outputs found
Strategies to link tiny neutrino masses with huge missing mass of the Universe
With the start of the LHC, interest in electroweak scale models for the
neutrino mass has grown. In this letter, we review two specific models that
simultaneously explain neutrino masses and provide a suitable DM candidate. We
discuss the implications of these models for various observations and
experiments including the LHC, Lepton Flavor Violating (LFV) rare decays,
direct and indirect dark matter searches and Kaon decay.Comment: 17 pages, one diagram, talk given at International Conference on
Flavor Physics in the LHC era in Singapor
On the Sources of CP-violation Contributing to the Electric Dipole Moments
In the framework of seesaw mechanism embedded in the constrained Minimal
Supersymmetric Standard Model (cMSSM), phases of neutrino Yukawa coupling,
-term and -terms can all contribute to the Electric Dipole Moment (EDM)
of the electron. We discuss and classify the situations for which by combined
analysis of the upcoming results on , and
discriminating between these sources will be possible.Comment: 6 pages, 4 figures, talk presented at IPM-LHP06, Tehran, Ira
R-parity violation assisted thermal leptogenesis in the seesaw mechanism
Successful leptogenesis within the simplest type I supersymmetric seesaw
mechanism requires the lightest of the three right-handed neutrino
supermultiplets to be heavier than GeV. Thermal production of such
(s)neutrinos requires very high reheating temperatures which result in an
overproduction of gravitinos with catastrophic consequences for the evolution
of the universe. In this letter, we let R-parity be violated through a
term in the superpotential, where
are right-handed neutrino supermultiplets. We show that in the
presence of this term, the produced lepton-antilepton asymmetry can be
enhanced. As a result, even for masses as low as GeV or
less, we can obtain the observed baryon asymmetry of the universe without
gravitino overproduction.Comment: 4 pages, 1 figure; v2: minor changes, references adde
SLIM at LHC: LHC search power for a model linking dark matter and neutrino mass
Recently a model has been proposed that links dark matter and neutrino
masses. The dark matter candidate which is dubbed as SLIM has a mass of MeV
scale and can show up at low energy experiments. The model also has a high
energy sector which consists of a scalar doublet, . We
discuss the potential of the LHC for discovering the new scalars. We focus on
the and production and the subsequent decay
of the charged scalar to a charged lepton and the SLIM which appears as missing
energy. Identifying the background, we estimate the signal significance and
find that it can exceed at 30 for the 14 TeV run at
the LHC. We comment on the possibility of extracting the flavor structure of
the Yukawa couplings which also determine the neutrino mass matrix. Finally, we
discuss the prospects of this search at the current 7 TeV run of the LHC.Comment: 26 pages, 21 figure
Are small neutrino masses unveiling the missing mass problem of the Universe?
We present a scenario in which a remarkably simple relation linking dark
matter properties and neutrino masses naturally emerges. This framework points
towards a low energy theory where the neutrino mass originates from the
existence of a light scalar dark matter particle in the MeV mass range. A very
surprising aspect of this scenario is that the required MeV dark matter is one
of the favoured candidates to explain the mysterious emission of 511 keV
photons in the centre of our galaxy. A possible interpretation of these
findings is that dark matter is the stepping stone of a theory beyond the
standard model instead of being an embarrassing relic whose energy density must
be accounted for in any successful model building.Comment: 4pages, 2 figures. Two paragraphs have been added. One for the
complex case; the other one for the UV completio
On the Effective Mass of the Electron Neutrino in Beta Decay
In the presence of mixing between massive neutrino states, the distortion of
the electron spectrum in beta decay is, in general, a function of several
masses and mixing angles. For -schemes which describe the solar and
atmospheric neutrino data, this distortion can be described by a single
effective mass, under certain conditions. In the literature, two different
definitions for the effective mass have been suggested. We show that for
quasi-degenerate mass schemes (with an overall mass scale and splitting
) the two definitions coincide up to
corrections. We consider the impact of different effective masses on the
integral energy spectrum. We show that the spectrum with a single mass can be
used also to fit the data in the case of -schemes motivated, in
particular, by the LSND results. In this case the accuracy of the mass
determination turns out to be better than .Comment: 15 pages, Version to appear in Phys. Lett.
Leptonic CP violation: zero, maximal or between the two extremes
Discovery of the CP-violation in the lepton sector is one of the challenges
of the particle physics. We search for possible principles, symmetries and
phenomenological relations that can lead to particular values of the
CP-violating Dirac phase, . In this connection we discuss two extreme
cases: the zero phase, , and the maximal CP-violation, , and relate them to the peculiar pattern of the neutrino mixing. The
maximal CP-violation can be related to the reflection
symmetry. We study various aspects of this symmetry and introduce a generalized
reflection symmetry that can lead to an arbitrary phase that depends on the
parameter of the symmetry transformation. The generalized reflection symmetry
predicts a simple relation between the Dirac and Majorana phases. We also
consider the possibility of certain relations between the CP-violating phases
in the quark and lepton sectors.Comment: 34 pages, no figures; v3: version appeared in JHE
Learning cover context-free grammars from structural data
We consider the problem of learning an unknown context-free grammar when the
only knowledge available and of interest to the learner is about its structural
descriptions with depth at most The goal is to learn a cover
context-free grammar (CCFG) with respect to , that is, a CFG whose
structural descriptions with depth at most agree with those of the
unknown CFG. We propose an algorithm, called , that efficiently learns
a CCFG using two types of queries: structural equivalence and structural
membership. We show that runs in time polynomial in the number of
states of a minimal deterministic finite cover tree automaton (DCTA) with
respect to . This number is often much smaller than the number of states
of a minimum deterministic finite tree automaton for the structural
descriptions of the unknown grammar
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