Pure gravitational dark matter, its mass and signatures

Yong Tang,Yue-Liang Wu

doi:10.1016/j.physletb.2016.05.045

Abstract

In this study, we investigate a scenario that dark matter (DM) has only gravitational interaction. In the framework of effective field theory of gravity, we find that DM is still stable at tree level even if there is no symmetry to protect its longevity, but could decay into standard model particles due to gravitational loop corrections. The radiative corrections can lead to both higher- and lower-dimensional effective operators. We also first explore how DM can be produced in the early universe. Through gravitational interaction at high temperature, DM is then found to have mass around TeV $\lesssim m_X \lesssim 10^{11}$GeV to get the right relic abundance. When DM decays, it mostly decays into gravitons, which could be tested by current and future CMB experiments. We also estimate the resulting fluxes for cosmic rays, gamma-ray and neutrino.

Highlights

Evidence for the existence of dark matter (DM) is compelling, supported from astrophysical length to cosmological scale
From the current experimental searches for DM, we have already known that the interaction between DM and the standard model particle should be weak
As we shall show in this paper, if perturbative gravitational loop corrections are taken into account, effective operators are induced and can make DM decay

Summary

INTRODUCTION

Evidence for the existence of dark matter (DM) is compelling, supported from astrophysical length to cosmological scale. We consider the weak gravity case and express the metric field around the flat Minkowski background spacetime as follows, gμν = ημν + κ hμν , ημν = ημν ≡ (1, −1, −1, −1),. √ where κ = 16πG ≡ 1/MP and hμν is identified as quantum field for spin-2 massless graviton, propagating in flat background spacetime This expression is useful and justified when we are only interested in environment without strong gravity and in low-energy physics if the energy is smaller than Planck scale [1, 2]. We have already seen that there are infinite operators in the expansion series, which partially shows the non-renormalizability of gravity This is not a problem in effective field theory where one can only keep terms up to κn and n is determined by the concerned precision.

PRODUCTION MECHANISM FOR GDM

EFFECTIVE OPERATORS OUT OF GRAVITY

SIGNATURES OF GDM

SUMMARY