114 research outputs found
Probing Leptonic Models at the LHC
Models of neutrino mass generation provide well motivated scenarios of
Beyond-the-Standard-Model physics. The synergy between low energy and high
energy LHC searches facilitates an effective approach to rule out, constrain or
ideally pinpoint such models. In this proceedings report, we provide a brief
overview of scenarios where searches at the LHC can help determine the
mechanism of light neutrino masses and potentially falsify baryogenesis
mechanisms.Comment: Talk presented at CIPANP2015. 9 pages, 3 figure
Thermal Right-Handed Sneutrino Dark Matter in the F_D-Term Model of Hybrid Inflation
We compute the relic abundance of the right-handed sneutrinos in the
supersymmetric F_D-term model of hybrid inflation. As well as providing a
natural solution to the mu- and gravitino overabundance problems, the F_D-term
model offers a new viable candidate to account for the cold dark matter in the
Universe: the lightest right-handed sneutrino. In particular, the F_D-term
model predicts a new quartic coupling of purely right-handed sneutrinos to the
Higgs doublets that thermalizes the sneutrinos and makes them annihilate
sufficiently fast to a level compatible with the current cosmic microwave
background data. We analyze this scenario in detail and identify favourable
regions of the parameter space within the framework of minimal supergravity,
for which the lightest right-handed sneutrino becomes the thermal dark matter,
in agreement with WMAP observations of cosmological inflation. Constraints
derived from direct dark matter searches experiments are presented.Comment: 26 pages, 4 eps figures, version published in JHE
Lepton Flavour Violation and theta(13) in Minimal Resonant Leptogenesis
We study the impact of minimal non-supersymmetric models of resonant
leptogenesis on charged lepton flavour violation and the neutrino mixing angle
theta(13). Possible low-scale flavour realisations of resonant tau-, mu- and
e-leptogenesis provide very distinct and predictive frameworks to explain the
observed baryon asymmetry in the Universe by sphaleron conversion of an
individual tau-, mu- and e-lepton-number asymmetry which gets resonantly
enhanced via out-of-equilibrium decays of nearly degenerate heavy Majorana
neutrinos. Based on approximate flavour symmetries, we construct viable
scenarios of resonant tau-, mu- and e-leptogenesis compatible with universal
right-handed neutrino masses at the GUT scale, where the required
heavy-neutrino mass splittings are generated radiatively. The heavy Majorana
neutrinos in such scenarios can be as light as 100 GeV and their couplings to
two of the charged leptons may be large. In particular, we explicitly
demonstrate the compelling role that the three heavy Majorana neutrinos play,
in order to obtain successful leptogenesis and experimentally testable rates
for lepton flavour violating processes, such as mu --> e gamma and mu --> e
conversion in nuclei.Comment: 40 pages, 9 figures, PRD versio
Minimal Resonant Leptogenesis and Lepton Flavour Violation
We discuss minimal non-supersymmetric models of resonant leptogenesis, based
on an approximate flavour symmetries. As an illustrative example, we consider a
resonant tau-leptogenesis model, compatible with universal right-handed
neutrino masses at the GUT scale, where the required heavy-neutrino mass
splittings are generated radiatively. In particular, we explicitly demonstrate,
how a minimum number of three heavy Majorana neutrinos is needed, in order to
obtain successful leptogenesis and experimentally testable rates for processes
of lepton flavour violation, such as mu --> e gamma and mu --> e conversion in
nuclei.Comment: 7 pages, invited talk given by AP at the international conference
GUT2012, Kyoto, Japan, 15-17 March 201
Dark Matter and Lepton Flavour Violation in a Hybrid Neutrino Mass Model
We describe a hybrid model in which the light neutrino mass matrix receives
both tree-level seesaw and loop-induced contributions. An additional U(1) gauge
symmetry is used to stabilize the lightest right-handed neutrino as the Dark
Matter candidate. After fitting the experimental neutrino data, we analyze and
correlate the phenomenological consequences of the model, namely its impact on
electroweak precision measurements, the Dark Matter relic abundance, lepton
flavour violating rare decays and neutrinoless double beta decay. We find that
natural realizations of the model characterized by large Yukawa couplings are
compatible with and close to the current experimental limits.Comment: 25 pages, 9 figures. V2: references added, typos corrected, version
accepted by JHE
Heavy neutrino production via at the lifetime frontier
We investigate the pair production of right-handed neutrinos from the decay
of an additional neutral boson in the gauged model. Taking
into account current constraints on the mass and the associated
gauge coupling , we analyse the sensitivity of proposed
experiments at the lifetime frontier, FASER 2, CODEX-b, MATHUSLA as well as a
hypothetical version of the MAPP detector to a long lived heavy neutrino
originating in the decays of the . We further complement this study
with determining the reach of LHCb and a CMS-type detector for the
high-luminosity LHC run. We demonstrate that in a background free scenario with
near the current limit, FASER 2 is sensitive to the
active-sterile neutrino mixing down to , while a
reach of can be obtained for CODEX-b and LHCb, in a
mass regime of GeV and GeV.
Finally, MATHUSLA can probe and cover the mixing
regime expected in a canonical seesaw scenario of light neutrino mass
generation.Comment: 20 pages, 6 figures, matches published versio
Long-lived Heavy Neutrinos from Higgs Decays
We investigate the pair-production of right-handed neutrinos via the Standard
Model (SM) Higgs boson in a gauged model. The right-handed neutrinos with
a mass of few tens of GeV generating viable light neutrino masses via the
seesaw mechanism naturally exhibit displaced vertices and distinctive
signatures at the LHC and proposed lepton colliders. The production rate of the
right-handed neutrinos depends on the mixing between the SM Higgs and the
exotic Higgs associated with the breaking, whereas their decay length
depends on the active-sterile neutrino mixing. We focus on the displaced
leptonic final states arising from such a process, and analyze the sensitivity
reach of the LHC and proposed lepton colliders in probing the active-sterile
neutrino mixing. We show that mixing to muons as small as can be probed at the LHC with 100 fb and at proposed lepton
colliders with 5000 fb. The future high luminosity run at LHC and the
proposed MATHUSLA detector may further improve this reach by an order of
magnitude.Comment: 23 pages, 9 figures, matches published versio
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