Bino Variations: Effective Field Theory Methods for Dark Matter Direct Detection
PHYSICAL REVIEW D 93, 095008 (2016) Bino variations: Effective field theory methods for dark matter direct detection Asher Berlin,1 Denis S. Robertson,2,3,4 Mikhail P. Solon,2,3 and Kathryn M. Zurek2,3 1Department of Physics, Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637, USA 2Theoretical Physics Group, Lawrence Berkeley National Laboratory, Berkeley, California 94709, USA 3Berkeley Center for Theoretical Physics, University of California, Berkeley, California 94709, USA 4Instituto de Física, Universidade de São, Paulo R. do Matão, 187, São Paulo, São 05508-900, Brazil (Received 7 December 2015; published 10 May 2016) 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 2 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.
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