Still looking for dark matter

Once more, physicists have not found particles of dark matter, this strange stuff that makes up about 83% of the matter in the Universe.

A few days ago, the XENON100 collaboration announced at a seminar in Gran Sasso National Laboratory, in Italy, that they have not detected any dark matter particles. One of the most popular hypothesis suggests dark matter is made of weakly interacting massive particles (WIMPs), that interact only through the weak force and gravity. XENON100 is looking for this particular kind of particles as they pass through the central portion of 161 kilograms of liquid xenon beneath 1.4 kilometres of rock at Gran Sasso. When colliding with the xenon nuclei, the particles should produce electric charge and light signals.

The XENON100 researchers reported here that 100 days’ worth of data taking turned up three events that could be due to dark matter particles. However, the scientists expected roughly two false positives due to interactions caused by a radioactive contaminant in the xenon: the three events are probably background events, and the result is statistically negative. This no-show rules out the existence of many of the heavier WIMPs, and also has important implications regarding supersymmetry: this theory, proposed to solve the hierarchy problem of the standard model, predicts the existence of a few particles that may be WIMPs.

Other large-scale experiments are planned in the near future, such as the Large Underground Xenon (LUX) detector. These new experiments should be able to detect lighter WIMPs, or to discard them too…

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