Search for Light Dark Matter in XENON10 Data

We report results of a search for light ($\lesssim 10\mathrm{GeV}$) particle dark matter with the XENON10 detector. The event trigger was sensitive to a single electron, with the analysis threshold of 5 electrons corresponding to 1.4 keV nuclear recoil energy. Considering spin-independent dark matter-nucleon scattering, we exclude cross sections ${\sigma }_n>7\times {10}^{-42}{\mathrm{cm}}^2$, for a dark matter particle mass $m_{\chi }=7\mathrm{GeV}$. We find that our data strongly constrain recent elastic dark matter interpretations of excess low-energy events observed by CoGeNT and CRESST-II, as well as the DAMA annual modulation signal.

Figure 1

The electron yield ${\mathcal{Q}}_y$ of liquid xenon for nuclear recoils. Theoretical curves (solid and dashed) were calculated from Eq. (1), as described in the text. Also shown are measurements from [17] (★), [22] (dash-dot curve, with $\pm 1\sigma$ contours), and [29] (○ and ▪, uncertainty omitted for clarity).

Figure 2

(left) All candidate dark matter events remaining (× and ○) after the cuts listed in Table 1. Events in which an $S1$ was found are shown as ○. The number of electrons in the $S2$ signal is indicated by the inset scale. (top) Distribution of candidate events with $\le 4$ electrons (+), and distribution of background single electrons (▵) as described in the text. (right) $S2$ pulse width distributions for single scatter nuclear recoils in the top, middle and bottom third of the detector.

Figure 3

Curves indicate 90% C.L. exclusion limits on spin-independent ${\sigma }_n$ for elastic dark matter scattering, obtained by CDMS (dotted [11], and dashed [12]) and XENON100 (dash-dot [23]). The region consistent with assumption of a positive detection by CoGeNT is shown (hatched) [2], and (shaded) [4]; the latter assumes a 30% exponential background. Also shown is the $3\sigma$ allowed region for the DAMA annual modulation signal (solid contour) [43].