Long-lived heavy neutrinos from Higgs decays Deppisch, Frank F.; Liu, Wei; Mitra, Manimala
The journal of high energy physics,
08/2018, Letnik:
2018, Številka:
8
Journal Article
Recenzirano
Odprti dostop
A
bstract
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
μN
≈ 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.
A
bstract
We make a comparative study of the neutrinoless double beta decay constraints on heavy sterile neutrinos versus other direct and indirect constraints from both lepton number conserving and ...violating processes, as a sensitive probe of the extent of lepton number violation and possible interference effects in the sterile sector. We introduce a phenomenological parametrisation of the simplified one-generation seesaw model with one active and two sterile neutrino states in terms of experimentally measurable quantities, such as active-sterile neutrino mixing angles, CP phases, masses and mass splittings. This simple parametrisation enables us to analytically derive a spectrum of possible scenarios between the canonical seesaw with purely Majorana heavy neutrinos and inverse seesaw with pseudo-Dirac ones. We then go on to constrain the simplified parameters of this model from various experiments at the energy, intensity and cosmic frontiers. We emphasise that the constraints from lepton number violating processes strongly depend on the mass splitting between the two sterile states and the relative CP phase between them. This is particularly relevant for neutrinoless double beta decay, which is weakened for small mass splitting and opposite CP parities between the sterile states. On the other hand, neutrinoless double beta decay is especially sensitive for Majorana sterile neutrinos with masses around 0
.
1
−
10 GeV.
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.
Motivated by nonzero neutrino masses and the possibility of new physics discovery, a number of experiments search for neutrinoless double beta decay. While hunting for this hypothetical nuclear ...process, a significant amount of two-neutrino double beta decay data have become available. Although these events are regarded and studied mostly as the background of neutrinoless double beta decay, they can also be used to probe physics beyond the standard model. In this Letter, we show how the presence of right-handed leptonic currents would affect the energy distribution and angular correlation of the outgoing electrons in two-neutrino double beta decay. Consequently, we estimate constraints imposed by currently available data on the existence of right-handed neutrino interactions without having to assume their nature. In this way, our results complement the bounds coming from the nonobservation of neutrinoless double beta decay as they limit also the exotic interactions of Dirac neutrinos. We perform a detailed calculation of two-neutrino double beta decay under the presence of exotic (axial-) vector currents, and we demonstrate that current experimental searches can be competitive to existing limits.
Vector leptoquarks provide an elegant solution to a series of anomalies and at the same time generate naturally light neutrino masses through their mixing with the standard model Higgs boson. We ...present a simple Froggatt-Nielsen model to accommodate the B physics anomalies R sub()Kand R sub()D neutrino masses, and the 750 GeV diphoton excess in one cohesive framework adding only two vector leptoquarks and two singlet scalar fields to the standard model field content.
A
bstract
The large and growing library of measurements from the Large Hadron Collider has significant power to constrain extensions of the Standard Model. We consider such constraints on a ...well-motivated model involving a gauged and spontaneously-broken
B
−
L
symmetry, within the C
ontur
framework. The model contains an extra Higgs boson, a gauge boson, and right-handed neutrinos with Majorana masses. This new particle content implies a varied phenomenology highly dependent on the parameters of the model, very well-suited to a general study of this kind. We find that existing LHC measurements significantly constrain the model in interesting regions of parameter space. Other regions remain open, some of which are within reach of future LHC data.
A
bstract
A large experimental program is being mounted to search for neutrinoless double-beta decay over the next decade. Multiple experiments using different target isotopes are being prepared to ...explore the whole parameter space allowed for inverted-ordered light neutrinos, and have the potential to make discoveries in several other scenarios, including normal-ordered light neutrinos and other exotic mechanisms. We investigate to what extent long-range and exotic short-range contributions may be distinguished by combining measurements of the decay half-life across isotopes in the framework of a global Bayesian analysis. We demonstrate how measurements in two isotopes will constrain the parameter space up to a two-fold degeneracy, and how a further measurement in a third isotope removes such a degeneracy. We also discuss the impact of uncertainties and correlations in nuclear matrix element calculations. Our work motivates an experimental program measuring neutrinoless double-beta decay in more than one isotope, as this would break parameter degeneracies and advance our understanding of particle physics beyond the Standard Model.
Measuring a nonzero value for the cross section of any lepton number violating (LNV) process would put a strong lower limit on the washout factor for the effective lepton number density in the early ...Universe at times close to the electroweak phase transition and thus would lead to important constraints on any high-scale model for the generation of the observed baryon asymmetry based on LNV. In particular, for leptogenesis (LG) models with masses of the right-handed neutrinos heavier than the mass scale observed at the LHC, the implied large washout factors would lead to a violation of the out-of-equilibrium condition and exponentially suppress the net lepton number produced in such LG models. We thus demonstrate that the observation of LNV processes at the LHC results in the falsification of high-scale LG models. However, no conclusions about the viability of LG models can be drawn from the nonobservation of LNV processes.
A
bstract
We investigate the possibility to probe lepton number violating (LNV) operators in the rare kaon decay
K → πνν
. Performing the analysis in the Standard Model effective field theory with ...only light active Majorana neutrinos, we determine the current limits on the corresponding LNV physics scale from the past E949 experiment at BNL as well as the currently operating experiments NA62 at CERN and KOTO at J-PARC. We focus on the specific signature of scalar currents in
K → πνν
arising from the LNV nature of the operators and study the effect on the experimental sensitivity, stressing the need for dedicated searches for beyond the SM currents. We find that the rare kaon decays probe high operator scales Λ
LNV
≈
15 to 20 TeV in different quark and neutrino flavours compared to neutrinoless double beta decay. Furthermore, we comment that the observation of LNV in kaon decays can put high-scale leptogenesis under tension. Finally, we discuss the connection with small radiatively generated neutrino masses and show how the severe constraints therefrom can be evaded in a minimal ultraviolet-complete scenario featuring leptoquarks.
A
bstract
We investigate forces induced by the exchange of two light neutrinos be- tween Standard Model (SM) fermions in the presence of effective operators parametrising physics beyond the SM. We ...first set up a general framework in which we derive the long-range potential mediated by weakly interacting neutrinos in the SM, retaining both spin-independent and spin-dependent terms. We then derive neutrino-mediated potentials when there are vector, scalar and tensor non-standard interactions present as well as an exotic neutrino magnetic moment. Examining the phenomenology of such long-range potentials in atomic scale laboratory experiments, we derive upper bounds on the Wilson coefficients of the effective operators and compare these to those from processes such as charged lepton flavour violation.
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