Neutron EDM constrains direct dark matter detection prospects

Manuel Drees,Rahul Mehra

doi:10.1016/j.physletb.2019.135039

Abstract

A non-relativistic effective field theory (NREFT) offers a bottom-up framework to classify Dark Matter (DM) – nucleon interactions relevant for scattering at direct detection experiments by organizing the interactions in powers of the momentum transfer q→ and DM velocity v→. This approach generates a number of operators including P-odd and T-odd operators; these can only be generated from a relativistic theory with CP violating interactions. We consider the leading order P-odd, T-odd operators viz. O10, O11 and O12 and compare the constraints on these operators from leading direct detection searches and from the bound on the neutron EDM (nEDM). We perform our analysis using simplified models with charged mediators and compute the loop diagrams contributing to the nEDM. We find that constraints on the DM scattering cross section from the bound on the nEDM are several orders of magnitude stronger than the limits from direct searches, and even well below the neutrino floor for such NREFT operators, for the entire sub-GeV to TeV DM mass range. We conclude that one may not need to consider these operators when analyzing data from present or future direct dark matter detection experiments.

Highlights

The particle identity of Dark Matter (DM) has not yet been understood despite overwhelming evidence for its gravitational interactions
We find that the constraints from the neutron EDM (nEDM) on the scattering cross section are many orders of magnitude stronger for both CP violation (CPV) non-relativistic effective field theory (NREFT) operators than the current XENON1T bound and even lie below the irreducible background from coherent neutrino scattering (“neutrino floor”) [37,38,39,40]
We had seen in the previous Section that the same combination of Yukawa couplings appears in the expression of the nEDM and in the coefficients of the P- and T-odd operators contributing to Weakly Interacting Massive Particles (WIMPs)-nucleon interactions

Summary

INTRODUCTION

The particle identity of Dark Matter (DM) has not yet been understood despite overwhelming evidence for its gravitational interactions. We find that the constraints from the nEDM on the scattering cross section are many orders of magnitude stronger for both CPV NREFT operators than the current XENON1T bound and even lie below the irreducible background from coherent neutrino scattering (“neutrino floor”) [37,38,39,40]. This casts doubt on the importance of these operators for the analysis of future experiments [41] and for the formalism of NREFT itself.

NREFT FORMALISM

DM SIMPLIFIED MODELS

Model I

Model II

RESULTS AND DISCUSSION

CONCLUSIONS