XENON100 – Battle of the WIMPS.
The XENON100 detector uses liquid xenon to detect Weakly Interacting Massive Particles (WIMPs). (Courtesy: Zina Deretsky, National Science Foundation)
While it might sound like a futuristic race, the XENON100 is an ultra-sensitive device which measures extremely small light signals and charges at the smallest levels.
These are the ones which might occur when a Weakly Interacting Massive Particle (WIMP) comes into contact with the nuclei of xenon atoms. In this case, it’s a race alright… the race to detect dark matter!
Located deep underground at the Gran Sasso National Laboratory of the INFN, in Italy, the XENON detector hides from the constant influx of cosmic rays. It will only utilize the inner 34 kg of its liquid xenon core to sample events – avoiding false detections from natural radiation sources. It is blanketed by highly engineered layers of copper, poyethylene, lead and water.
This layer further reduces background “noise”. However, after 13 long months, no signal from the WIMPs has been detected, despite a more than three hundred percent increase in sensitivity.
“XENON100 is a two-phase time projection chamber with a 62 kg liquid xenon target. Interaction vertex reconstruction in three dimensions with millimeter precision allows to select only the innermost 48 kg as ultra-low background fiducial target.” says E. Aprile (et al). “In 100.9 live days of data, acquired between January and June 2010, no evidence for dark matter is found.”
Despite this lack of evidence, cosmological observations have uniformly pointed to the fact that about 4% of the Universe consists of “normal matter” – leaving the remainder to consist of mysterious dark matter and dark energy. It’s an assumption that complies with the Standard Model of particle physics – one where these particles must exist and their properties make them dark matter candidates. The WIMPs are there… it’s only a matter of finding them.
The previous XENON10 run set the pace during its 10 day study, but the 100 resulted in double the sensitivity by continually reducing background noise. But, alas… No signal.
When it comes to WIMPs, it’s apparent that even more sensitive and more sophisticated equipment will be necessary and the XENON100 detector will continue on its hunt. The new XENON1T is currently under construction and perhaps its results will one day bring evidence of dark matter to light.
Original Story Source: Particle Physics News and Resources.
