High Mass Dark Matter Searches With the High Speed Flux From the Large Magellanic Cloud

TL;DR

This work shows that the local dark matter velocity distribution is significantly shaped by the Large Magellanic Cloud, especially boosting the high-velocity tail relevant for heavy dark matter. By leveraging a MW-LMC analogue from Auriga simulations, the authors extract a realistic velocity distribution and compute detector fluxes for Ohya and Skylab, moving beyond the standard halo model. They derive improved exclusion bounds by comparing predicted event counts to Poisson expectations while accounting for energy loss through overburden, finding that LMC effects extend the reachable parameter space, particularly at low masses and with latitude-dependent flux. The methodology provides a general approach to incorporate external perturbers into heavy dark matter searches, with potential applications to future orbital detectors and mineral-slab analyses.

Abstract

As the hunt for dark matter progresses, recently there have been advances in the search for heavy dark matter with a mass well above a TeV. We show the importance of properly modeling the local dark matter velocity distribution, beyond the standard Maxwellian halo model, and in particular how the dynamics of the Large Magellanic Cloud and Milky Way may impact heavy dark matter searches. We introduce some new computational techniques for accurately computing the dark matter flux and the associated detector response. As a specific example, we examine the effect of the Large Magellanic Cloud on heavy dark matter bounds obtained from experiments searching for cosmic rays and magnetic monopoles using plastic etch detectors at the Ohya Mine and aboard the Skylab Space Station.

Figures (7)

• Figure 1: A comparison of dark matter's local speed distribution in the Earth reference frame for the SHM (blue) and the simulated MW analogue including the effect of the LMC (red).
• Figure 1: The experimental parameters from the Skylab and Ohya experiments relevant to this work. These are taken from Bhoonah2021.
• Figure 2: Comparison of the speed and direction of origin for incoming dark matter particles assuming the results of the MW-LMC simulation (top) and the SHM (bottom). The samples are normalized to have approximately the same number of particles. The axes are the declination and right ascension of the incoming particle. The color bars specify the speed of the incoming dark matter particles in the Earth reference frame.
• Figure 3: Comparisons of the integrated dark matter mass flux intercepting the Skylab (left) and Ohya (right) detectors above a cutoff speed $v_{\mathrm{min}}$, between the SHM and the simulated MW analogue including the LMC. Note the significantly increased higher flux at high speeds for the simulated system compared to the SHM.
• Figure 4: A closeup of the right panel of Figure \ref{['fig:massFlux']}, demonstrating the procedure for interpolating the flux. The solid blue line is the naive discrete counts for the flux, given by Equation \ref{['eq:fluxAboveSpeed']}. The red dotted line is the conservatively interpolated value which was used to compute the bounds.