Large-scale nuclear structure calculations for spin-dependent WIMP scattering with chiral effective field theory currents

Abstract

We perform state-of-the-art large-scale shell-model calculations of the structure factors for elastic spin-dependent WIMP scattering off Si. This comprehensive survey covers the nonzero-spin nuclei relevant to direct dark matter detection. We include a pedagogical presentation of the formalism necessary to describe elastic and inelastic WIMP-nucleus scattering. The valence spaces and nuclear interactions employed have been previously used in nuclear structure calculations for these mass regions and yield a good spectroscopic description of these isotopes. We use spin-dependent WIMP-nucleus currents based on chiral effective field theory (EFT) at the one-body level and including the leading long-range two-body currents due to pion exchange, which are predicted in chiral EFT. Results for all structure factors are provided with theoretical error bands due to the nuclear uncertainties of WIMP currents in nuclei.

Nuclear structure aspects of spin-independent WIMP scattering off xenon

“…For a given coupling between WIMPs and nucleons, these encode the nuclear structure aspects relevant for WIMP-nucleus scattering. In this work, we calculate the structure factors for spin-independent (SI) WIMP scattering, complementing our previous work on elastic [11,12] and inelastic [13] spin-dependent (SD) interactions. We focus on scattering off xenon, which is used as target of major direct detection experimental efforts such as XENON and LUX [8,9].…”

“…For the remaining nucleons we consider a valence space consisting of the 0g 7/2 , 1d 5/2 , 1d 3/2 , 2s 1/2 , and 0h 11/2 orbitals, both for neutrons and protons, and the effective nuclear interaction GCN5082 [20,21]. The same valence space and nuclear interaction have been used for the study of SD WIMP scattering off the odd-mass isotopes 129 Xe and 131 Xe [11][12][13] and for the neutrinoless doublebeta decay of 136 Xe [20,21]. Throughout all calculations we use the shell-model code ANTOINE [22,23].…”

“…The even-mass xenon isotopes are practically insensitive to SD scattering due to their J = 0 ground state, so that only the odd-mass xenon isotopes 129 Xe and 131 Xe are relevant. In previous work [11,12], we have calculated SD structure factors for xenon, also including two-body currents in chiral effective field theory. To complete the study of WIMP scattering off xenon, we also compare these calculations to the results obtained by Fitzpatrick et al in Ref.…”

Isospin violating dark matter in Stückelberg portal scenarios

“…Notice that in this case one can also define the Xephobic scenario for a n /a p . However, it depends on the ratio between the zero momentum expectation values of the spin for protons and neutrons in xenon which are of the order of O(10 −2 ) (using the latest calculations [62]), and for simplicity it is not included in figure 2.…”

“…In this work we use the Helm factor for the SI component and the SD structure functions given in ref. [62] for the SD component.…”