Determining the mass for an ultralight gravitino at LHC

TL;DR

This paper proposes a new method to determine the ultralight gravitino mass at the LHC by measuring slepton decay branching ratios, achieving about 10% accuracy with realistic data.

Contribution

It introduces a novel approach to measure the gravitino mass for ultralight scenarios using slepton decay modes, applicable at the LHC.

Findings

Gravitino mass can be estimated with ~10% accuracy.

Method works for integrated luminosities of 10-100 fb^{-1}.

Applicable to gauge-mediation models.

Abstract

In supersymmetric (SUSY) models with the gravitino being the lightest SUSY particle (LSP), the SUSY breaking scale (i.e., the gravitino mass) could be determined by measuring the lifetime of the next-to-lightest SUSY particle (NLSP). However, for an ultralight gravitino of mass of O(1) eV, which is favored cosmologically, the determination of the SUSY breaking scale, or the gravitino mass, is difficult because the NLSP decay length is too short to be measured directly. Recently we proposed a new determination of the gravitino mass by measuring a branching fraction of two decay modes of sleptons. In this paper, we investigate the prospects for determining the gravitino mass at LHC. For demonstration we take some explicit gauge-mediation models and show that the gravitino mass can be determined with an accuracy of a few 10% for an integrated luminosity 10-100 fb^{-1}.