Metastable Charged Sparticles and the Cosmological Li7 Problem

TL;DR

This paper investigates how metastable charged supersymmetric particles could influence Big-Bang Nucleosynthesis, potentially resolving the longstanding cosmological lithium-7 problem by analyzing bound states and decay effects within the CMSSM framework.

Contribution

It introduces a new analysis of bound states of charged sparticles with nuclei and a code to track their abundances, exploring solutions to the Li7 problem in the context of CMSSM.

Findings

Bound states of charged sparticles can alter BBN element abundances.

Certain CMSSM parameter regions can fit observed light-element abundances.

Metastable charged sparticles may solve the cosmological Li7 problem.

Abstract

We consider the effects of metastable charged sparticles on Big-Bang Nucleosynthesis (BBN), including bound-state reaction rates and chemical effects. We make a new analysis of the bound states of negatively-charged massive particles with the light nuclei most prominent in BBN, and present a new code to track their abundances, paying particular attention to that of Li7. Assuming, as an example, that the gravitino is the lightest supersymmetric particle (LSP), and that the lighter stau slepton, stau_1, is the metastable next-to-lightest sparticle within the constrained minimal supersymmetric extension of the Standard Model (CMSSM), we analyze the possible effects on the standard BBN abundances of stau_1 bound states and decays for representative values of the gravitino mass. Taking into account the constraint on the CMSSM parameter space imposed by the discovery of the Higgs boson at the LHC, we delineate regions in which the fit to the measured light-element abundances is as good as in standard BBN. We also identify regions of the CMSSM parameter space in which the bound state properties, chemistry and decays of metastable charged sparticles can solve the cosmological Li7 problem.