The Bino Variations: Effective Field Theory Methods for Dark Matter Direct Detection

TL;DR

This paper develops effective field theory methods to accurately compute bino-nucleon scattering, revealing that loop corrections can significantly extend the detection reach for heavy bino dark matter in upcoming experiments.

Contribution

It introduces a comprehensive EFT framework for bino dark matter detection, including loop effects, renormalization group evolution, and low-energy matching, improving upon previous fixed-order calculations.

Findings

Loop corrections can double the bino mass reach in some models.

Near-future experiments could detect bino dark matter up to 10 TeV.

Framework includes systematic treatment of uncertainties and low-energy matching.

Abstract

We apply effective field theory methods to compute bino-nucleon scattering, in the case where tree-level interactions are suppressed and the leading contribution is at loop order via heavy flavor squarks or sleptons. We find that leading log corrections to fixed-order calculations can increase the bino mass reach of direct detection experiments by a factor of two in some models. These effects are particularly large for the bino-sbottom coannihilation region, where bino dark matter as heavy as 5-10 TeV may be detected by near future experiments. For the case of stop- and selectron-loop mediated scattering, an experiment reaching the neutrino background will probe thermal binos as heavy as 500 and 300 GeV, respectively. We present three key examples that illustrate in detail the framework for determining weak scale coefficients, and for mapping onto a low energy theory at hadronic scales, through a sequence of effective theories and renormalization group evolution. For the case of a squark degenerate with the bino, we extend the framework to include a squark degree of freedom at low energies using heavy particle effective theory, thus accounting for large logarithms through a "heavy-light current." Benchmark predictions for scattering cross sections are evaluated, including complete leading order matching onto quark and gluon operators, and a systematic treatment of perturbative and hadronic uncertainties.