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WIMP Velocity Impact on Direct Dark Matter Searches

Michal Brhlik, Leszek Roszkowski

TL;DR

The paper investigates how uncertainties in the Galactic halo WIMP velocity distribution, notably the peak velocity $v_0$, affect direct dark matter searches and the DAMA Collaboration's annual modulation signal. It presents the Majorana WIMP detection rate in NaI detectors, including scalar and axial contributions, and shows that the scalar channel dominates the NaI response; the rate depends on $\xi\sigma_p$ and a velocity-averaged factor $\widetilde{T}(E_R)$ derived from a Maxwellian halo with Earth's motion. The key finding is that reasonable variations in $v_0$ can substantially widen DAMA-compatible regions in the $(m_ ext{ extcolor{white}{ ext}}_ ext{χ}, \xi \sigma_p)$ plane, increasing the upper mass bound by up to ~60%, which broadens the viable SUSY parameter space. The work emphasizes that astrophysical and nuclear uncertainties must be accounted for when deriving exclusion limits and interpreting direct-detection results for WIMP models.

Abstract

We examine the effect of some uncertainties in the input astrophysical parameters on direct detection searches for WIMPs in the Galactic halo. We concentrate on the possible WIMP annual modulation signal recently reported by the DAMA Collaboration. We find that allowing for a reasonable uncertainty in a WIMP Maxwellian velocity distribution leads to significantly relaxed constraints on the WIMP mass as compared to the original DAMA analysis.

WIMP Velocity Impact on Direct Dark Matter Searches

TL;DR

The paper investigates how uncertainties in the Galactic halo WIMP velocity distribution, notably the peak velocity , affect direct dark matter searches and the DAMA Collaboration's annual modulation signal. It presents the Majorana WIMP detection rate in NaI detectors, including scalar and axial contributions, and shows that the scalar channel dominates the NaI response; the rate depends on and a velocity-averaged factor derived from a Maxwellian halo with Earth's motion. The key finding is that reasonable variations in can substantially widen DAMA-compatible regions in the plane, increasing the upper mass bound by up to ~60%, which broadens the viable SUSY parameter space. The work emphasizes that astrophysical and nuclear uncertainties must be accounted for when deriving exclusion limits and interpreting direct-detection results for WIMP models.

Abstract

We examine the effect of some uncertainties in the input astrophysical parameters on direct detection searches for WIMPs in the Galactic halo. We concentrate on the possible WIMP annual modulation signal recently reported by the DAMA Collaboration. We find that allowing for a reasonable uncertainty in a WIMP Maxwellian velocity distribution leads to significantly relaxed constraints on the WIMP mass as compared to the original DAMA analysis.

Paper Structure

This paper contains 4 sections, 16 equations, 3 figures.

Table of Contents

  1. Introduction
  2. DAMA Analysis
  3. Majorana WIMP Detection Rate in NaI Detectors
  4. Results and Conclusions

Figures (3)

  • Figure 1: The expected differential event rate spectrum versus the detected energy $E$ for $m_{\chi}=60\,\hbox{GeV}$, $\sigma_p=7\times10^{-6}\,\hbox{pb}$ and several choices of $v_0$.
  • Figure 2: Contours of the function $\kappa=10$ (Eq. \ref{['kappa:eq']}) for different values of the peak of the halo WIMP Maxwellian velocity distribution. Denoted by dots is the $2\sigma$ region selected by DAMA assuming $v_0=220\,\hbox{km/s}$.
  • Figure 3: Several contours of (a) the time-independent and (b) time-dependent parts of $\kappa$ for $v_0=220\,\hbox{km/s}$. Denoted by dots is the contour of 10 of total $\kappa$.