Type III seesaw for neutrino masses in U(1)B−L model with multi-component dark matter

Abstract

We propose a B − L gauged extension of the Standard Model where light neutrino masses arise from type III seesaw mechanism. Unlike the minimal B −L model with three right handed neutrinos having unit lepton number each, the model with three fermion triplets is however not anomaly free. We show that the leftover triangle anomalies can be cancelled by two neutral Dirac fermions having fractional B − L charges, both of which are naturally stable by virtue of a remnant Z 2 × Z 2 symmetry, naturally leading to a two component dark matter scenario without any ad-hoc symmetries. We constrain the model from all relevant phenomenological constraints including dark matter properties. Light neutrino mass and collider prospects are also discussed briefly. Due to additional neutral gauge bosons, the fermion triplets in type III seesaw can have enhanced production cross section in collider experiment.

Connecting light dirac neutrinos to a multi-component dark matter scenario in gauged $$B-L$$ model

“…It should be noted that the anomaly cancellation conditions we are solving here are same as the ones adopted in our earlier work [93] leading to type III seesaw for Majorana neutrinos. However, we are using a different solution to the anomaly conditions here from the earlier work.…”

“…The two right handed neutrinos with B − L charge -1 take part in generating light neutrino masses via type I seesaw mechanism resulting in massless lightest neutrino. In another recent work [93], while implementing type III seesaw in a gauged U (1) B−L , it was found the triangle anomalies can be canceled by two component fermion dark matter.…”

“…Let n 2 = n ξ 2 + nξ 2 and n 1 = n ξ 1 + nξ 1 are the total number densities of two dark matter candidates respectively. Assuming there is no asymmetry in number densities of ξ i andξ i , the two coupled Boltzmann equations in terms of n 2 and n 1 are given below [93],…”

“…where, n eq i is the equilibrium number density of dark matter species i and H denotes the Hubble parameter, defined earlier. For further details of these Boltzmann equations for two component Dirac fermion DM and their annihilation channels (ξ iξi → XX , X being all particles where DM can annihilate into) contributing to σ v , please refer to [93] where a similar scenario was discussed recently. We have solved these two coupled Boltzmann equations using micrOMEGAs [127] where the model information has been supplied to micrOMEGAs using FeynRules [128].…”

“…Such null results have not only motivated the studies of beyond thermal WIMP paradigm but also a richer DM sector consisting of multiple DM components. Some recent proposals for multi-component DM can be found in [60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94] and references therein. As several of these works pointed out, apart from having larger allowed region of parameter space due to freedom of tuning relative DM abundances, such multi-component DM scenarios often offer complementary probes at experiments spanning out to different frontiers.…”