We show that if the new physics beyond the standard model is associated with a first-order phase transition around 10 super(7)-10 super(8)GeV, the energy density stored in the resulting stochastic ...gravitational waves and the corresponding peak frequency are within the projected final sensitivity of the advanced LIGO/VIRGO detectors. We discuss some possible new physics scenarios that could arise at such energies, and in particular, the consequences for Peccei-Quinn and supersymmetry breaking scales.
A
bstract
The type-II seesaw mechanism with an isospin-triplet scalar Δ
L
provides one of the most compelling explanations for the observed smallness of neutrino masses. The triplet contains a ...doubly-charged component
H
L
±
±
, which dominantly decays to either same-sign dileptons or to a pair of
W
bosons, depending on the size of the triplet vacuum expectation value. However, there exists a range of Yukawa couplings
f
L
of the triplet to the charged leptons, wherein a relatively light
H
L
±
±
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
H
L
±
±
→
ℓ
α
±
ℓ
β
±
could probe a broad parameter space with 10
−10
≲ |
f
L
| ≲ 10
−6
and
45.6
GeV
<
M
H
L
±
±
≲
200
GeV
at the high-luminosity LHC. Similar sensitivity can also be achieved at a future 1 TeV
e
+
e
−
collider. The mass reach can be extended to about 500GeV at a future 100TeV proton-proton collider. Similar conclusions apply for the right-handed triplet
H
R
±
±
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-antimuonium oscillation and Møller scattering.
Many new physics scenarios beyond standard model often necessitate the existence of a (light) neutral scalar H, which might couple to the charged leptons in a flavor violating way, while evading all ...existing constraints. We show that such scalars could be effectively produced at future lepton colliders, either on shell or off shell depending on their mass, and induce lepton flavor violating (LFV) signals, i.e., e^{+}e^{-}→ℓ_{α}^{±}ℓ_{β}^{∓}(+H) with α≠β. We find that a large parameter space of the scalar mass and the LFV couplings can be probed well beyond the current low-energy constraints in the lepton sector. In particular, a scalar-loop induced explanation of the long-standing muon g-2 anomaly can be directly tested in the on-shell mode.
Neutrinos and collider physics Deppisch, Frank F; Bhupal Dev, P S; Pilaftsis, Apostolos
New journal of physics,
08/2015, Letnik:
17, Številka:
7
Journal Article
Recenzirano
Odprti dostop
We review the collider phenomenology of neutrino physics and the synergetic aspects at energy, intensity and cosmic frontiers to test the new physics behind the neutrino mass mechanism. In ...particular, we focus on seesaw models within the minimal setup as well as with extended gauge and/or Higgs sectors, and on supersymmetric neutrino mass models with seesaw mechanism and with R-parity violation. In the simplest type-I seesaw scenario with sterile neutrinos, we summarize and update the current experimental constraints on the sterile neutrino mass and its mixing with the active neutrinos. We also discuss the future experimental prospects of testing the seesaw mechanism at colliders and in related low-energy searches for rare processes, such as lepton flavor violation and neutrinoless double beta decay. The implications of the discovery of lepton number violation at the Large Hadron Collider for leptogenesis are also studied.
We consider the scotogenic model, where the standard model (SM) is extended by a scalar doublet and three Z2 odd SM-singlet fermions (Ni, i=1, 2, 3), all odd under an additional Z2 symmetry, as a ...unifying framework for simultaneous explanation of inflation, dark matter, baryogenesis and neutrino mass. The inert doublet is coupled nonminimally to gravity and forms the inflaton. The lightest neutral particle of this doublet later becomes the dark matter candidate. Baryogenesis is achieved via leptogenesis by the decay of N1 to SM leptons and the inert doublet particles. Neutrino masses are generated at the one-loop level. Explaining all these phenomena together in one model is very economic and gives us a new set of constraints on the model parameters. We calculate the inflationary parameters like spectral index, tensor-to-scalar ratio and scalar power spectrum, and find them to be consistent with the Planck 2018 constraints. We also do the reheating analysis for the inert doublet decays/annihilations to relativistic, SM particles. We find that the observed baryon asymmetry of the Universe can be obtained and the sum of light neutrino mass bound can be satisfied for the lightest Z2 odd singlet fermion of mass around 10 TeV, dark matter in the mass range 1.25–1.60 TeV, and the lepton number violating quartic coupling between the SM Higgs and the inert doublet in the range of 6.5×10−5 to 7.2×10−5.
We study the radio signals generated when an axion star enters the magnetosphere of a neutron star. As the axion star moves through the resonant region where the plasma-induced photon mass becomes ...equal to the axion mass, the axions can efficiently convert into photons, giving rise to an intense, transient radio signal. We show that a dense axion star with a mass ∼10−13 M⊙ composed of ∼10 μeV axions can account for most of the mysterious fast radio bursts.
A
bstract
We study the Higgs mass spectrum as predicted by a Maximally Symmetric Two Higgs Doublet Model (MS-2HDM) potential based on the SO(5) group, softly broken by bilinear Higgs mass terms. We ...show that the lightest Higgs sector resulting from this MS-2HDM becomes naturally aligned with that of the Standard Model (SM), independently of the charged Higgs boson mass and tan
β
. In the context of Type-II 2HDM, SO(5) is the simplest of the
three
possible symmetry realizations of the scalar potential that can naturally lead to the SM alignment. Nevertheless, renormalization group effects due to the hypercharge gauge coupling
g
′ and third-generation Yukawa couplings may break sizeably this alignment in the MS-2HDM, along with the custodial symmetry inherited by the SO(5) group. Using the current Higgs signal strength data from the LHC, which disfavour large deviations from the SM alignment limit, we derive lower mass bounds on the heavy Higgs sector as a function of tan
β
, which can be stronger than the existing limits for a wide range of parameters. In particular, we propose a new collider signal based on the observation of four top quarks to directly probe the heavy Higgs sector of the MS-2HDM during the run-II phase of the LHC.
We analyze the sensitivity of low-energy fundamental symmetry tests to interactions mediated by doubly-charged scalars that arise in type II seesaw models of neutrino mass and their left-right ...symmetric extensions. We focus on the next generation measurement of the parity-violating asymmetry in Møller scattering planned by the MOLLER collaboration at Jefferson Laboratory. We compare the MOLLER sensitivity to that of searches for charged lepton flavor violation (CLFV) and neutrinoless double beta-decay (0νββ-decay) as well as present and possible future high-energy collider probes. We show that for the simplest type-II seesaw scenario, CLFV searches have the greatest sensitivity. However, in a left-right symmetric extension where the scale of parity-breaking is decoupled from the SU(2)R-breaking scale, the MOLLER experiment will provide a unique probe of scalar triplet interactions in the right-handed sector for a doubly-charged scalar mass up to ∼10 TeV and help elucidate the mechanism of 0νββ-decay.
We study a new production mechanism for heavy neutrinos at the LHC, which dominates over the usually considered s-channel W-exchange diagram for heavy-neutrino masses larger than 100-200 GeV. The new ...mechanism is infrared enhanced by t-channel W gamma -fusion processes. This has important implications for experimental tests of the seesaw mechanism of neutrino masses and, in particular, for the ongoing heavy neutrino searches at the LHC. We find that the direct collider limits on the light-to-heavy neutrino mixing can be significantly improved when this new production channel is properly taken into account. The scope of this new mechanism can be equally well extended to other exotic searches at the LHC.
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