WIMP-nucleon scattering is analyzed at order 1/M in Heavy WIMP Effective Theory. The 1/M power corrections, where M ≫ mW is the WIMP mass, distinguish between different underlying UV models with the same universal limit and their impact on direct detection rates can be enhanced relative to naive expectations due to generic amplitude-level cancellations at leading order. The necessary one- and two-loop matching calculations onto the low-energy effective theory for WIMP interactions with Standard Model quarks and gluons are performed for the case of an electroweak SU(2) triplet WIMP, considering both the cases of elementary fermions and composite scalars. The low-velocity WIMP-nucleon scattering cross section is evaluated and compared with current experimental limits and projected future sensitivities. Our results provide the most robust prediction for electroweak triplet Majorana fermion dark matter direct detection rates; for this case, a cancellation between two sources of power corrections yields a small total 1/M correction, and a total cross section close to the universal limit for M ≳ few x 100 GeV. For the SU(2) composite scalar, the 1/M corrections introduce dependence on underlying strong dynamics. Using a leading chiral logarithm evaluation, the total 1/M correction has a larger magnitude and uncertainty than in the fermionic case, with a sign that further suppresses the total cross section. These examples provide definite targets for future direct detection experiments and motivate large scale detectors capable of probing to the neutrino floor in the TeV mass regime.

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Published in Physics Letters B, v. 781, p. 473-479.

© 2018 The Authors. Published by Elsevier B.V.

This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

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Funded by SCOAP3.

Work of MPS was supported by the Office of High Energy Physics of the U.S. DOE under Contract Numbers DE-AC02-05CH11231 and DE-SC0011632. Research at the Perimeter Institute is supported in part by the Government of Canada through NSERC and by the Province of Ontario through MEDT. TRIUMF receives federal funding via a contribution agreement with the National Research Council of Canada. Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.