Size of the neutralino--nucleon cross--section in the light of a new determination of the pion--nucleon sigma term
A. Bottino, F. Donato, N. Fornengo, S. Scopel
TL;DR
The paper addresses uncertainties in the neutralino-nucleon cross-section arising from hadronic matrix elements, foregrounding a new determination of the pion-nucleon sigma term $\sigma_{\pi N}$. It recomputes the cross-section within the effMSSM framework, incorporating the updated $\sigma_{\pi N}$ range, radiative corrections to Higgs-quark couplings, and recent LEP2/CDF bounds. The main finding is that the new $\sigma_{\pi N}$ range can enhance the predicted cross-section by factors of about $1.5$–$6$, broadening the SUSY parameter space where relic neutralinos have cosmological relevance ($0.05 \lesssim \Omega_m h^2 \lesssim 0.3$). While this strengthens direct-detection prospects and associated neutrino fluxes, the implication of a large strange-quark content prompts caution and calls for further hadron-physics study.
Abstract
We discuss the implications of a new determination of the pion-nucleon sigma term for the evaluation of the neutralino-nucleon cross-section, and, in turn, for detection rates for relic neutralinos in WIMP direct experiments and in some of the indirect searches. It is shown that the new range for the pion-nucleon sigma term, taken at its face value, favours values of the neutralino-nucleon cross-sections which are sizeably larger than some of the current estimates. Implications for neutralino cosmological properties are derived.