Direct generation of a Majorana mass for the Neutron from Exotic Instantons

Abstract

We discuss a new mechanism in which non-perturbative quantum gravity effects directly generate a Majorana mass for the neutron. In particular, in string theory, exotic instantons can generate an effective six quark operator by calculable mixed disk amplitudes. In a low string scale scenario, with $M_S\simeq 10÷10^5\mathrm{TeV}$, a neutron-antineutron oscillation can be reached in the next generation of experiments. we argue that protons and neutralinos are not destabilized and that dangerous FCNCs are not generated. We show an example of quiver theories, locally free by tadpoles and anomalies, reproducing MSSM plus a Majorana neutron and a Majorana neutrino. These models naturally provide a viable baryogenesis mechanism by resonant RH neutrino decays, as well as a stable WIMP-like dark matter. We also discuss how LHC data will provide useful inputs for our model, in the immediate future, testing several different regions of the parameter space. Such a mechanism represents a simple and calculable counter-example to the Wilsonian UV completion of effective non-renormalizable operators.

Version accepted by Physics Letter B

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• Unitarization and Causalization of Non-local quantum field theories by Classicalization
• Dark Matter from Starobinsky Supergravity
• Neutron-antineutron oscillations beyond the quasi-free limit
• More about Neutron Majorana mass from Exotic Instantons: an alternative mechanism in Low-Scale String theory
• More about the Instanton/Soliton/Kink correspondence
• Super-light baryphotons, Weak Gravity Conjecture and Exotic instantons in Neutron-Antineutron transitions
• Weak Gravity Conjecture as a Razor Criterium for Exotic D-brane instantons
• Testing B-violating signatures from Exotic Instantons in future colliders
• Chaotic instantons in scalar field theory
• Evaporation and Antievaporation instabilities