First results from the LUX dark matter experiment

Isabel Lopes (Univ. of Coimbra)
Buildg. 2a / Sem. R. 2, 16.45 h

The discovery of the nature of the dark matter is presently one of the greatest challenges in physics, fundamental to our understanding of the Universe. One favored class of dark matter candidates, the Weakly Interacting Massive Particles (WIMPs), is expected to interact with ordinary matter.

LUX is one of the experiments that aim to detect nuclear recoils of energies of several keV resulting from the interaction of galactic WIMPs with nucleons at an expected rate lower than 1 event/kg/year. For that, it employs a double-phase (liquid/gas) xenon time projection chamber with 370 kg of mass, operated in the Davis Cavern of the Sanford Underground Laboratory (SURF), SD, USA.

In this seminar we will present the results from the first WIMP search run of LUX. From a total exposure of 85 live-days, we found no evidence of signal above expected background, constraining scalar WIMP-nucleon interactions above 7.6x10-46 cm2 at 33 GeV/c2 WIMP mass (90% C.L.) - three times more sensitive than any competing experiment. The improvement in the sensitivity is more significant at low energies and seriously challenges the interpretation of hints of signal detected in other experiments as arising for low-mass WIMPs. Although no definitive signal has yet been discovered, the worldwide race towards WIMP direct detection has been accelerated by these results.

Lux is preparing a new dark-matter search run that will last around one year and will improve significantly the current limits. We are also planning a multi-tonne successor to LUX: the LZ experiment. This instrument will have sensitivity ideally matched to explore the bulk of the remaining theoretically favored electroweak phase space for galactic Dark Matter discovery.

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