Abstract
We present first results on the scalar coupling of weakly interacting massive particles (WIMPs) to pions from 1 t yr of exposure with the XENON1T experiment. This interaction is generated when the WIMP couples to a virtual pion exchanged between the nucleons in a nucleus. In contrast to most nonrelativistic operators, these pion-exchange currents can be coherently enhanced by the total number of nucleons and therefore may dominate in scenarios where spin-independent WIMP-nucleon interactions are suppressed. Moreover, for natural values of the couplings, they dominate over the spin-dependent channel due to their coherence in the nucleus. Using the signal model of this new WIMP-pion channel, no significant excess is found, leading to an upper limit cross section of 6.4×10^{-46} cm^{2} (90%confidence level) at 30 GeV/c^{2} WIMP mass.
Highlights
We present first results on the scalar coupling of weakly interacting massive particles (WIMPs) to pions from 1 t yr of exposure with the XENON1T experiment
A systematic expansion in the effective theory of QCD, chiral effective field theory (EFT) [28,29,30,31], valid at the relevant nuclear structure energies and momentum transfers of the order of the pion mass, reveals a new class of contributions referred to as two-body currents. These interactions proceed by the coupling of the WIMP to a virtual pion exchanged between nucleons within the nucleus
Drawing on the analogy to both SI and SD WIMP-nucleon interactions, we demonstrate in this Letter that these new couplings can be interpreted as cross sections for a WIMP scattering off a pion, a channel that has previously not been considered in dark matter searches
Summary
A systematic expansion in the effective theory of QCD, chiral effective field theory (EFT) [28,29,30,31], valid at the relevant nuclear structure energies and momentum transfers of the order of the pion mass, reveals a new class of contributions referred to as two-body currents These interactions proceed by the coupling of the WIMP to a virtual pion exchanged between nucleons within the nucleus. Integrating out the mediator produces effective operators involving the WIMP, quark, and gluon fields, which together with the hadronic matrix elements define the single-nucleon cross section that appears as a coefficient of the WIMP-nucleus rate Corrections to this picture emerge from the fact that a nucleus is a strongly interacting many-body system, e.g., mediated by the exchange of virtual pions between two nucleons. With nuclear structure factors that encode the response of the nucleus to the interaction with
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