LSP baryogenesis and neutron-antineutron oscillations from R-parity violation

Lorenzo Calibbi,Eung Jin Chun,Chang Sub Shin

doi:10.1007/jhep10(2017)177

Abstract

R-parity and baryon number violating operators can be allowed in the Super-symmetric Standard Model and thus lead to interesting baryon number violating processes such as n-overline{n} oscillations and baryogenesis of the Universe via the decay of the lightest supersymmetric particle (LSP). Adopting the LSP baryogenesis mechanism realized by the late decay of the axino, we identify a single coupling λ313′ ′ as a common origin for the matter-antimatter asymmetry of the Universe as well as potentially observable n-overline{n} oscillation rates. From this, rather strong constraints on the supersymmetry breaking masses and the axion decay constant are obtained. The favoured parameter space of λ313′ ′ ∼ 0.1 and sub-TeV masses for the relevant sparticles is readily accessible by the current and future LHC searches.

Highlights

JHEP10(2017)177 at the usual second order of λ [13]
We have presented a scenario that consistently accounts for some formidable shortcomings of the Standard Model: the baryon asymmetry of the Universe, the observed amount of Dark Matter, the strong CP problem, as well as the hierarchy problem
The baryon asymmetry can be successfully produced by the decay of the axino lightest supersymmetric particle (LSP) to SM quarks through RPV interactions, while DM and the strong CP problem are accounted for by the axion

Summary

Observable neutron-antineutron oscillations

From the analysis of [10], one can see that the λ113 contribution to Cnn is much larger than the λ313 contribution (involving a suppression from smaller CKM entries) for the same set of parameters, and observable n–n rates from λ113 requires smaller values of the BNV coupling or a rather heavier supersymmetric spectrum. Such values make the axino decay much later than the Bing-Bang Nucleosynthesis (BBN) epoch and can not lead to a viable baryogenesis as will be shown . While this was obtained directly employing free neutrons, the indirect limit from bounded neutrons in Super-Kamiokande is τnn > 2.7 × 108 sec [2]

DFSZ axino baryogenesis

KSVZ axino baryogenesis

Findings

Conclusions