4,830 research outputs found
Displaced vertex signatures of doubly charged scalars in the type-II seesaw and its left-right extensions
The type-II seesaw mechanism with an isospin-triplet scalar
provides one of the most compelling explanations for the observed smallness of
neutrino masses. The triplet contains a doubly-charged component
, which dominantly decays to either same-sign dileptons or to a
pair of bosons, depending on the size of the triplet vacuum expectation
value. However, there exists a range of Yukawa couplings of the triplet
to the charged leptons, wherein a relatively light tends to be
long-lived, giving rise to distinct displaced-vertex signatures at the
high-energy colliders. We find that the displaced vertex signals from the
leptonic decays could probe a
broad parameter space with and 45.6
GeV GeV at the high-luminosity LHC. Similar
sensitivity can also be achieved at a future 1 TeV collider. The mass
reach can be extended to about 500 GeV at a future 100 TeV proton-proton
collider. Similar conclusions apply for the right-handed triplet
in the TeV-scale left-right symmetric models, which provide a natural embedding
of the type-II seesaw. We show that the displaced vertex signals are largely
complementary to the prompt same-sign dilepton pair searches at the LHC and the
low-energy, high-intensity/precision measurements, such as neutrinoless double
beta decay, charged lepton flavor violation, electron and muon anomalous
magnetic moments, muonium oscillation and M{\o}ller scattering.Comment: 49 pages, 25 figures and 2 tables, minor changes, version to appear
in JHE
Asymmetric Dark Matter in the Sun and the Diphoton Excess at the LHC
It has been recently pointed out that a momentum-dependent coupling of the
asymmetric Dark Matter (ADM) with nucleons can explain the broad disagreement
between helioseismological observables and the predictions of standard solar
models. In this paper, we propose a minimal simplified ADM model consisting of
a scalar and a pseudoscalar mediator, in addition to a Dirac fermionic DM, for
generating such momentum-dependent interactions. Remarkably, the pseudoscalar
with mass around 750 GeV can simultaneously explain the solar anomaly and the
recent diphoton excess observed by both ATLAS and CMS experiments in the early
TeV LHC data. In this framework, the total width of the resonance
is naturally large, as suggested by the ATLAS experiment, since the resonance
mostly decays to the ADM pair. The model predicts the existence of a new light
scalar in the GeV range, interacting with quarks, and observable dijet, monojet
and signatures for the 750 GeV resonance at the LHC.Comment: 7 pages, 4 figures. Version to appear in PR
Natural Standard Model Alignment in the Two Higgs Doublet Model
The current LHC Higgs data provide strong constraints on possible deviations
of the couplings of the observed 125 GeV Higgs boson from the Standard Model
(SM) expectations. Therefore, it now becomes compelling that any extended Higgs
sector must comply with the so-called SM alignment limit. In the context of the
Two Higgs Doublet Model (2HDM), this alignment is often associated with either
decoupling of the heavy Higgs sector or accidental cancellations in the 2HDM
potential. Here we present a new solution realizing natural alignment based on
symmetries, without decoupling or fine-tuning. In particular, we show that in
2HDMs where both Higgs doublets acquire vacuum expectation values, there exist
only three different symmetry realizations leading to natural alignment. We
discuss some phenomenological implications of the Maximally-Symmetric 2HDM
based on SO(5) symmetry group and analyze new collider signals for the heavy
Higgs sector, involving third-generation quarks, which can be a useful
observational tool during the Run-II phase of the LHC.Comment: 15 pages, 1 table, 8 figures; Contribution to the Proceedings of
DISCRETE 2014, Londo
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