http://arxiv.org/abs/1312.7772
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 non-relativistic limit. However, at the nucleon level, such couplings are effectively enhanced by factors of order ${\cal O}(m_N/m_q)\sim 10^3$, where $m_N$ and $m_q$ 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.
Tue, 31 Dec 13
21/49
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