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Register a new userStability of R parity in supersymmetric models extended by U(1)_{B-L}
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Jos\\'e Eliel Camargo Molina
Publication date
2012
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English
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We perform a study of the stability of R-parity-conserving vacua of a constrained version of the minimal supersymmetric model with a gauged U(1)_{B-L} which can conserve R-parity, using homotopy continuation to find all the extrema of the tree-level potential, for which we also calculated the one-loop corrections. While we find that a majority of the points in the parameter space preserve R-parity, we find that a significant portion of points which naively have phenomenologically acceptable vacua which conserve R-parity actually have deeper vacua which break R-parity through sneutrino VEVs. We investigate under what conditions the deeper R-parity-violating vacua appear. We find that while previous exploratory work was broadly correct in some of its qualitative conclusions, we disagree in detail.
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We study the origin of electroweak symmetry under the assumption that $SU(4)_{rm C} times SU(2)_{rm L} times SU(2)_{rm R}$ is realized on a five-dimensional space-time. The Pati-Salam type gauge symmetry is reduced to $SU(3)_{rm C} times SU(2)_{rm L} times U(1)_{rm R} times U(1)_{rm B-L}$ by orbifold breaking mechanism on the orbifold $S^1/Z_2$. The breakdown of residual gauge symmetries occurs radiatively via the Coleman-Weinberg mechanism, such that the $U(1)_{rm R} times U(1)_{rm B-L}$ symmetry is broken down to $U(1)_{rm Y}$ by the vacuum expectation value of an $SU(2)_{rm L}$ singlet scalar field and the $SU(2)_{rm L} times U(1)_{rm Y}$ symmetry is broken down to the electric one $U(1)_{rm EM}$ by the vacuum expectation value of an $SU(2)_{rm L}$ doublet scalar field regarded as the Higgs doublet. The negative Higgs squared mass term is originated from an interaction between the Higgs doublet and an $SU(2)_{rm L}$ singlet scalar field as a Higgs portal. The vacuum stability is recovered due to the contributions from Kaluza-Klein modes of gauge bosons.
The $B-L$ MSSM is the MSSM with three right-handed neutrino chiral multiplets and gauged $B-L$ symmetry. The $B-L$ symmetry is broken by the third family right-handed sneutrino acquiring a VEV, thus spontaneously breaking $R$-parity. Within a natural range of soft supersymmetry breaking parameters, it is shown that a large and uncorrelated number of initial values satisfy all present phenomenological constraints; including the correct masses for the $W^{pm}$, $Z^0$ bosons, having all sparticles exceeding their present lower bounds and giving the experimentally measured value for the Higgs boson. For this valid set of initial values, there are a number of different LSPs, each occurring a calculable number of times. We plot this statistically and determine that among the most prevalent LSPs are chargino and neutralino mass eigenstates. In this paper, the $R$-parity violating decay channels of charginos and neutralinos to standard model particles are determined, and the interaction vertices and decay rates computed analytically. These results are valid for any chargino and neutralino, regardless of whether or not they are the LSP. For chargino and neutralino LSPs, we will-- in a subsequent series of papers --present a numerical study of their RPV decays evaluated statistically over the range of associated valid initial points.
We analyze the dark matter problem in the context of supersymmetric U(1)_{B-L} model. In this model, the lightest neutalino can be the B-L gaugino widetilde {Z}_{B-L} or the extra Higgsinos widetilde{chi}_{1,2} dominated. We compute the thermal relic abundance of these particles and show that, unlike the LSP in MSSM, they can account for the observed relic abundance with no conflict with other phenomenological constraints. The prospects for their direct detection, if they are part of our galactic halo, are also discussed.
The neutralino sector in E_6 inspired supersymmetric models with extra neutral gauge bosons and singlet Higgs fields contains additional gaugino and singlino states compared to the MSSM. We discuss the neutralino mixing in rank 5 and rank 6 models and analyze the supersymmetric parameter space where the light neutralinos have mainly singlino or MSSM character. The neutralino character, resonance effects of the new gauge bosons and, assuming mSUGRA-type RGEs, different selectron masses lead to significant differences between the MSSM and the extended models in neutralino production at an e^+e^- linear collider. Beam polarization may improve the signatures to distinguish between the models. In an appendix, we present the mass terms of the gauge bosons, charginos and sfermions which show a significant different mass spectrum than in the MSSM and give all relevant neutralino couplings.
Standard Model with right handed neutrinos charged under additional $U(1)_{B-L}$ gauge symmetry offer solutions to both dark matter (DM) problem and neutrino mass generation, although constrained severely from relic density, direct search and Higgs vacuum stability. We therefore investigate a multicomponent DM scenario augmented by an extra inert scalar doublet, that is neutral under $U(1)_{B-L}$, which aids to enlarge parameter space allowed by DM constraints and Higgs vacuum stability. The lightest right-handed neutrino and the $CP$-even inert scalar are taken as the dark matter candidates and constitute a two component dark matter framework as they are rendered stable by an unbroken $mathbb{Z}_2 times mathbb{Z}_2^prime$ symmetry. DM-DM conversion processes turn out crucial to render requisite relic abundance in mass regions of the RH neutrino that do not appear in the stand-alone $U(1)_{B-L}$ scenario. In addition, the one-loop renormalisation group (RG) equations in this model demonstrate that the electroweak (EW) vacuum can be stabilised till $sim 10^{9}$ GeV in a parameter region compatible with the observed relic, the direct detection bound and other relevant constraints.
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