Constraining Light Gravitino Mass from Cosmic Microwave Background

TL;DR

This paper explores how future cosmic microwave background (CMB) surveys can constrain the mass of light gravitinos, which are relevant for cosmology and particle physics, using lensing measurements.

Contribution

It demonstrates that CMB lensing can effectively constrain light gravitino masses, providing expected bounds for upcoming surveys like PolarBeaR and CMBpol.

Findings

Planck+PolarBeaR can constrain m_{3/2} < 3.2 eV (95% C.L.)

CMBpol can measure m_{3/2} around 1.04 eV with uncertainties

Future CMB lensing data can distinguish light gravitino models from others.

Abstract

We investigate the possibilities of constraining the light gravitino mass m_{3/2} from future cosmic microwave background (CMB) surveys. A model with light gravitino with the mass m_{3/2}<O(10) eV is of great interest since it is free from the cosmological gravitino problem and, in addition, can be compatible with many baryogenesis/leptogenesis scenarios such as the thermal leptogenesis. We show that the lensing of CMB anisotropies can be a good probe for m_{3/2} and obtain an expected constraint on m_{3/2} from precise measurements of lensing potential in the future CMB surveys, such as the PolarBeaR and CMBpol experiments. If the gravitino mass is m_{3/2}=1 eV, we will obtain the constraint for the gravitino mass as m_{3/2} < 3.2 eV (95% C.L.) for the case with Planck+PolarBeaR combined and m_{3/2}=1.04^{+0.22}_{-0.26} eV (68% C.L.) for CMBpol. The issue of Bayesian model selection is also discussed.