# ‘Exotic vector-like pair’ of color-triplet scalars

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## Abstract

We propose a minimal extension of Standard Model, generating a Majorana mass for neutron, connected with a mechanism of Post-Sphaleron Baryogenesis. We consider an ‘exotic vector-like pair’ of color-triplet scalars, an extra Majorana fermion *ψ*, and a scalar field *ϕ*, giving mass to *ψ*. The vector-like pair is defined ‘exotic’ because of a peculiar mass term of the color-triplet scalars, violating Baryon number as Δ*B* = 1. Such a mass term could be generated by exotic instantons in a class of string-inspired completions of the Standard Model: open (un-)oriented strings attached between D-brane stacks and Euclidean D-branes. A Post-Sphaleron Baryogenesis is realized through *ϕ*-decays into six quarks (antiquarks), or through *ψ*-decays into three quarks (antiquarks). This model suggests some intriguing B-violating signatures, testable in the next future, in Neutron-Antineutron physics and LHC. We also discuss limits from FCNC. Sterile fermion can also be light as 1 − 100GeV. In this case, the sterile fermion could be (meta)-stable and *n* − \( \overline{n} \) oscillation can be indirectly generated by two *n* − *ψ*, *ψ* − \( \overline{n} \) oscillations, without needing of an effective Majorana mass for neutron. Majorana fermion *ψ* can be a good candidate for WIMP-like dark matter.

## Keywords

Supersymmetry Phenomenology Strings and branes phenomenology## Notes

### **Open Access**

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