DAMA/LIBRA is an Italian dark matter experiment that most colleagues apparently don't take too seriously. In recent years, it has claimed to detect some clear signatures of dark matter, especially through the dark matter seasonal modulation. Some effects are different in the summer and in the winter, and so on. This is what you would expect from a dark matter counterpart of the "aether wind", if I dare to borrow to a debunked concept. ;-)
The most recent DAMA/LIBRA paper is this 2013 update which says that the statistical significance of their observed – nominally discovered – dark matter modulation signal is 9.3 sigma. If true, it's a discovery on steroids.
When the pro-dark matter side seemed to be winning in the dark matter wars, there were other reasons to think that this modulation exists. CoGeNT has confirmed some modulation in 2011, too.
The atmosphere is different now and the anti-dark matter side seems to be on an offensive. It's particularly clear from the today's new preprint by the XENON collaboration:
Search for Electronic Recoil Event Rate Modulation with 4 Years of XENON100 DataXENON, one of the most formidable dark matter detectors in the world (I think that LUX and XENON are upgrading and fighting for the leadership), investigated the annual modulation as well. Using the 2010-2014 data, they have evaluated the theory with dark matter modulation and parameters suggested by the claimed DAMA/LIBRA signal. And they have excluded this theory. Experimenters normally tend to disprove theories with newly proposed effects at 2 sigma or 95% confidence level – because the "null hypothesis" to which they return to isn't extraordinary and doesn't need extraordinary evidence.
But in this case, they could take the DAMA/LIBRA claim to be a "natural hypothesis" and XENON excluded it at 5.7 sigma – because it's more than five, you may say that XENON has made a discovery that DAMA/LIBRA is wrong.














