Monthly Modulation in Dark Matter Direct-Detection Experiments

TL;DR

This paper investigates monthly modulation effects in dark matter detection signals, analyzing their potential to distinguish signals from background noise, with a focus on WIMP and WISP searches and the influence of lunar motion and gravitational focusing.

Contribution

It provides a detailed analysis of monthly modulation signatures in dark matter experiments, highlighting their detectability in WISP searches and the negligible effects in WIMP experiments.

Findings

Monthly modulation in WIMP signals is too small to detect.

WISP photon frequencies exhibit detectable monthly shifts.

Lunar gravitational focusing affects WISP signal frequencies.

Abstract

The signals in dark matter direct-detection experiments should exhibit modulation signatures due to the Earth's motion with respect to the Galactic dark matter halo. The annual and daily modulations, due to the Earth's revolution about the Sun and rotation about its own axis, have been explored previously. Monthly modulation is another such feature present in direct detection signals, and provides a nearly model-independent method of distinguishing dark matter signal events from background. We study here monthly modulations in detail for both WIMP and WISP dark matter searches, examining both the effect of the motion of the Earth about the Earth-Moon barycenter and the gravitational focusing due to the Moon. For WIMP searches, we calculate the monthly modulation of the count rate and show the effects are too small to be observed in the foreseeable future. For WISP dark matter experiments, we show that the photons generated by WISP to photon conversion have frequencies which undergo a monthly modulating shift which is detectable with current technology and which cannot in general be neglected in high resolution WISP searches.