Abstract
One IGEX 76Ge double-beta decay detector is currently operating in the Canfranc Underground Laboratory in a search for dark matter WIMPs, through the Ge nuclear recoil produced by the WIMP elastic scattering. A new exclusion plot, has been derived for WIMP-nucleon spin-independent interactions. To obtain this result, 40 days of data from the IGEX detector (energy threshold E \~ 4 keV), recently collected, have been analyzed. These data improve the exclusion limits derived from all the other ionization germanium detectors in the mass region from 20 GeV to 200 GeV, where a WIMP supposedly responsible for the annual modulation effect reported by the DAMA experiment would be located. The new IGEX exclusion contour enters, by the first time, the DAMA region by using only raw data, with no background discrimination, and excludes its upper left part. It is also shown that with a moderate improvement of the detector performances, the DAMA region could be fully explored.
Highlights
Experimental observations and robust theoretical arguments have established that our universe is essentially non-visible, the luminous matter scarcely accounting for one per cent of the critical density of a flat universe (Ω = 1)
Germanium detectors have reached one of the lowest background levels of any type of detector and have a reasonable ionization yield ranging from 20% to 30% depending on the nuclear recoil energy
This paper presents new WIMPs constraints in the cross-section WIMP-nucleon versus WIMP mass plot, derived from a germanium detector of the IGEX collaboration, which improve previous limits obtained with Ge ionization detectors, and enter by the first time the so-called DAMA region without using mechanisms of background rejection, but relying only in the ultra-low background achieved
Summary
This paper presents new WIMPs constraints in the cross-section WIMP-nucleon versus WIMP mass plot, derived from a germanium detector (enriched up to 86 % in 76Ge) of the IGEX collaboration, which improve previous limits obtained with Ge ionization detectors, and enter by the first time the so-called DAMA region (corresponding to a WIMP supposedly responsible for the annual modulation effect found in the DAMA experiment [2]) without using mechanisms of background rejection, but relying only in the ultra-low background achieved. The rejected veto-coincident events amount up to about the 5% of the total rate and are distributed in the low energy region as shown by the Figure 2.
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