Abstract
Supersymmetric Standard Model (MSSM) has two sources of rapid proton decay: (i) R-parity breaking terms and (ii) higher dimensional Planck induced B-violating terms; its extensions to include neutrino masses via the type I seesaw mechanism need not have the first of these problems due to the existence of B−L as a gauge symmetry but for sure always have the second one. If instead, neutrino masses are explained in a type III seesaw extension of standard model, an anomaly free gauge symmetry different from B−L is known to exist. In this note, it is shown that a realistic supersymmetric versions of this model can be constructed (MSSM as well as SUSY left–right with type III seesaw) which eliminate R-parity violating couplings and suppress Planck scale contributions to proton decay. The degree of suppression of the latter depends on the weak gauge group. For the left–right case, the suppression to the desired level is easily achieved.
Highlights
Supersymmetry provides a very attractive way to solve the gauge hierarchy problem of the standard model
There are two new sources of rapid proton decay in made supersymmetric extensions of the standard model (MSSM), which arise from the fact that the theory has supersymmetry: (i) renormalizable R-parity breaking interactions, a combination of two of which, QLdc and ucdcdc, lead to extremely rapid p-decay and secondly (ii) Planck scale induced higher dimensional operators of the form QQQL/MP l and ucucdcec/MP l, which do the same
In this brief note, we have analysed and pointed out a novel feature of the extra gauged U(1)X symmetry which is present in type III seesaw extensions of standard model for explaining small neutrino masses
Summary
Supersymmetry provides a very attractive way to solve the gauge hierarchy problem of the standard model. These are extremely stringent bounds and before supersymmetric models can be accepted as good descriptions of nature, one must find a satisfactory way to either eliminate or suppress these interactions in a natural manner It was pointed out many years ago that extending MSSM to incorporate neutrino masses via type I seesaw mechanism (i.e. include three right handed neutrinos into MSSM) automatically extends the local symmetry to SU (2)L × U (1)I3R × U (1)B−L which when broken by B − L = 2 Higgs fields automatically eliminates the undesirable R-parity breaking terms[2]. This paper is organized as follows: in sec. 2, we discuss the extension of MSSM with type III seesaw (called MSSMIII ); in sec. 3, we discuss the left-right extension and in sec. 4, we conclude with some comments and a summary
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