# Very long-lived Stop NLSP in MSSM scenarios with Gravitino LSP

## TL;DR

This paper calculates the extremely long lifetimes of stop squarks decaying into gravitinos in MSSM scenarios, showing they are cosmologically safe and decay outside detectors at colliders.

## Contribution

It provides a comprehensive calculation of stop lifetimes for various decay modes using full gravitino Feynman rules and compares with the goldstino approximation.

## Key findings

- Stop lifetimes range from 10^8 to 10^20 seconds.
- All decay modes are safe from big bang nucleosynthesis constraints.
- Stops decay outside detectors at colliders, even for shortest lifetimes.

## Abstract

We present the calculation of the stop ($\tilde{t}$) lifetime that results from its decay into gravitinos ($\tilde{\Psi}^{\mu}$) in the final state, namely $\tilde{t}\to \tilde{\Psi}^{\mu} + X$, where $X=t, bW, b l\nu_l$ for the two-, three- and four-body decay modes. The full calculation is obtained using the Feynman rules for massive gravitino, which is compared with the results obtained employing the equivalence theorem, where the longitudinal component of the gravitino is replaced by the goldstino. The stop turns out to be very long-lived in these scenarios, with lifetimes of $\mathcal{O}$($10^8$s, $10^{14}$s, $10^{20}$s) for the corresponding 2-,3- and 4-body modes under consideration, and therefore all of them are safe from the big bang nucleosynthesis problem. However, the lifetime for the four body decay mode occurs during the epoch of galaxy formation. When the stop is produce at colliders, in these scenarios, it will hadronize and decay outside of the detector, even for the lowest values of stop lifetime.