A stable supermassive charged gravitino?

TL;DR

This paper revisits a rare experimental event to explore the hypothesis that dark matter could include supermassive, fractionally charged gravitinos, proposing an alternative interpretation that could support or refute this novel idea.

Contribution

It re-analyzes a discarded experimental event to consider its implications for the existence of supermassive charged gravitinos as dark matter candidates.

Findings

Possible reinterpretation of the MACRO event supports the gravitino dark matter hypothesis.

Highlights need for dedicated experiments to confirm or refute the hypothesis.

Suggests that such gravitinos would be the only new fermionic particles beyond the Standard Model.

Abstract

Some time ago it was suggested that dark matter may consist in part of an extremely dilute gas of supermassive gravitinos with fractional charge 2$e$/3 \cite{MeissnerNicolai2019}. This scheme makes the definite (and falsifiable) prediction that massive gravitinos are the {\em only} new fermionic degrees of freedom beyond the known three generations of quarks and leptons of the Standard Model of Particle Physics. In this note we re-examine one special outlier event reported and subsequently discarded by the MACRO collaboration \cite{MACRO1} in the light of this proposal and point out the possibility of an alternative interpretation of this event supporting the above hypothesis, whose confirmation (or refutation) would, however, require an independent dedicated experimental effort.