Overcoming velocity suppression in dark-matter direct-detection experiments

Keith R. Dienes, Jason Kumar, Brooks Thomas, David Yaylali

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


Pseudoscalar couplings between Standard-Model quarks and dark matter are normally not considered relevant for dark-matter direct-detection experiments because they lead to velocity-suppressed scattering cross sections in the nonrelativistic limit. However, at the nucleon level, such couplings are effectively enhanced by factors of order O(mN/mq)∼103, where mN and mq are appropriate nucleon and quark masses, respectively. This enhancement can thus be sufficient to overcome the corresponding velocity suppression, implying - contrary to common lore - that direct-detection experiments can indeed be sensitive to pseudoscalar couplings. In this work, we explain how this enhancement arises, and present a model-independent analysis of pseudoscalar interactions at direct-detection experiments. We also identify those portions of the corresponding dark-matter parameter space which can be probed at current and future experiments of this type, and discuss the role of isospin violation in enhancing the corresponding experimental reach.

Original languageEnglish (US)
Article number015012
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Issue number1
StatePublished - Jul 11 2014

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Physics and Astronomy (miscellaneous)


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