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Register a new userExperimentally Verifiable $U(1)_{rm B-L}$ Symmetric Model with Type-II Seesaw and Dark Matter
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Added by
Satyabrata Mahapatra
Publication date
2021
fields
Physics
and research's language is
English
Authors
Purusottam Ghosh
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In an endeavor to explain the light neutrino masses and dark matter (DM) simultaneously, we study a gauged $U(1)_{rm B-L}$ extension of the standard model (SM). The neutrino masses are generated through a variant of type-II seesaw mechanism in which one of the scalar triplets has a mass in a scale that is accessible at the present generation colliders. Three right chiral fermions $chi_{iR}$($i=e,mu,tau$) with $rm B-L$ charges -4, -4, +5 are invoked to cancel the $rm B-L$ gauge anomalies and the lightest one among these three fermions becomes a viable DM candidate as their stability is guaranteed by a remnant $mathcal Z_2$ symmetry to which $U(1)_{rm B-L}$ gauge symmetry gets spontaneously broken. Interestingly in this scenario, the neutrino mass and the co-annihilation of DM are interlinked through the breaking of $U(1)_{rm B-L}$ symmetry. Apart from giving rise to the observed neutrino mass and dark matter abundance, the model also predicts exciting signals at the colliders especially regarding the discovery of the triplet scalar in presence of the $rm B-L$ gauge boson. We see a $(34-54)%$ enhancement in the production of the TeV scale doubly charged scalar in presence of the $Z_{rm BL}$ gauge boson in a mass range $2.5$ TeV to $4.4$ TeV. We discuss all the relevant constraints on model parameters from observed DM abundance and null detection of DM at direct and indirect search experiments as well as the constraints on the $rm B-L$ gauge boson from recent colliders.
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The Standard Model (SM) is inadequate to explain the origin of tiny neutrino masses, the dark matter (DM) relic abundance and also the baryon asymmetry of the Universe. In this work to address all the three puzzles, we extend the SM by a local U$(1)_{rm B-L}$ gauge symmetry, three right-handed (RH) neutrinos for the cancellation of gauge anomalies and two complex scalars having nonzero U$(1)_{rm B-L}$ charges. All the newly added particles become massive after the breaking of U$(1)_{rm B-L}$ symmetry by the vacuum expectation value (VEV) of one of the scalar fields $phi_H$. The other scalar field $phi_{DM}$, which does not have any VEV, becomes automatically stable and can be a viable DM candidate. Neutrino masses are generated using Type-I seesaw mechanism while the required lepton asymmetry to reproduce the observed baryon asymmetry, can be attained from the CP violating out of equilibrium decays of RH neutrinos in TeV scale. More importantly within this framework, we have studied in detail the production of DM via freeze-in mechanism considering all possible annihilation and decay processes. Finally, we find a situation when DM is dominantly produced from the annihilation of RH neutrinos, which are at the same time also responsible for neutrino mass generation and leptogenesis.
We investigate a $U(1)_{B-L}$ gauge extension of the Standard Model (SM) where the gauge boson mass is generated by the Stueckelberg mechanism. Three right-handed neutrinos are added to cancel the gauge anomaly and hence the neutrino masses can be explained. A new Dirac fermion could be a WIMP dark matter whose interaction with the SM sector is mediated by the new gauge boson. Assuming the perturbativity of the gauge coupling up to the Planck scale, we find that only the resonance region is feasible for the dark matter abundance. After applying the $Delta N_{eff}$ constraints from the current Planck experiment, the collider search constraints as well as the dark matter direct detection limits, we observe that the $B-L$ charge of dark matter satisfies $|Q_{chi}|>0.11$. Such a scenario might be probed conclusively by the projected CMB-S4 experiment, assuming the right-handed neutrinos are thermalized with the SM sector in the early universe.
In this work, we have considered a gauged $U(1)_{rm B-L}$ extension of the Standard Model (SM) with three right handed neutrinos for anomaly cancellation and two additional SM singlet complex scalars with non-trivial B-L charges. One of these is used to spontaneously break the $U(1)_{rm B-L}$ gauge symmetry, leading to Majorana masses for the neutrinos through the standard Type I seesaw mechanism, while the other becomes the dark matter (DM) candidate in the model. We test the viability of the model to simultaneously explain the DM relic density observed in the CMB data as well as the Galactic Centre (GC) $gamma$-ray excess seen by Fermi-LAT. We show that for DM masses in the range 40-55 GeV and for a wide range of $U(1)_{rm B-L}$ gauge boson masses, one can satisfy both these constraints if the additional neutral Higgs scalar has a mass around the resonance region. In studying the dark matter phenomenology and GC excess, we have taken into account theoretical as well as experimental constraints coming from vacuum stability condition, PLANCK bound on DM relic density, LHC and LUX and present allowed areas in the model parameter space consistent with all relevant data, calculate the predicted gamma ray flux from the GC and discuss the related phenomenology.
We propose a model based on an alternative $U(1)_{B-L}$ gauge symmetry with 5 dimensional operators in the Lagrangian, and we construct the neutrino masses at one-loop level, and discuss lepton flavor violations, dark matter, and the effective number of neutrino species due to two massless particles in our model. Then we search allowed region to satisfy the current experimental data of neutrino oscillation and lepton flavor violations without conflict of several constraints such as stability of dark matter and the effective number of neutrino species, depending on normal hierarchy and inverted one.
We calculate the relic density of the lightest neutralino in a supersymmetric seesaw type-II (``triplet seesaw) model with minimal supergravity boundary conditions at the GUT scale. The presence of a triplet below the GUT scale, required to explain measured neutrino data in this setup, leads to a characteristic deformation of the sparticle spectrum with respect to the pure mSugra expectations, affecting the calculated relic dark matter (DM) density. We discuss how the DM allowed regions in the (m_0,M_{1/2}) plane change as a function of the (type-II) seesaw scale. We also compare the constraints imposed on the models parameter space form upper limits on lepton flavour violating (LFV) decays to those imposed by DM. Finally, we briefly comment on uncertainties in the calculation of the relic neutralino density due to uncertainties in the measured top and bottom masses.
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