94 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

### 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 $Z'$ at the lifetime frontier

We investigate the pair production of right-handed neutrinos from the decay
of an additional neutral $Z^{\prime}$ boson in the gauged $B-L$ model. Taking
into account current constraints on the $Z^{\prime}$ mass and the associated
gauge coupling $g_{1}^{\prime}$, 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 $N$
originating in the decays of the $Z^{\prime}$. 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
$g_1^\prime = 10^{-3}$ near the current limit, FASER 2 is sensitive to the
active-sterile neutrino mixing down to $V_{\mu N} \approx 10^{-4}$, while a
reach of $V_{\mu N} \approx 10^{-5}$ can be obtained for CODEX-b and LHCb, in a
mass regime of $m_N \approx 5-20$ GeV and $m_{Z^{\prime}} \approx 20-70$ GeV.
Finally, MATHUSLA can probe $V_{\mu N} \approx 10^{-7}$ 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 $B-L$ 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 $B-L$ 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 $V_{\mu N} \approx
10^{-7}$ can be probed at the LHC with 100 fb$^{-1}$ and at proposed lepton
colliders with 5000 fb$^{-1}$. 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

### Compressed and Split Spectra in Minimal SUSY SO(10)

The non-observation of supersymmetric signatures in searches at the Large
Hadron Collider strongly constrains minimal supersymmetric models like the
CMSSM. We explore the consequences on the SUSY particle spectrum in a minimal
SO(10) with large D-terms and non-universal gaugino masses at the GUT scale.
This changes the sparticle spectrum in a testable way and for example can
sufficiently split the coloured and non-coloured sectors. The splitting
provided by use of the SO(10) D-terms can be exploited to obtain light first
generation sleptons or third generation squarks, the latter corresponding to a
compressed spectrum scenario.Comment: 35 pages, 10 figures, published versio

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