More dark chatter

While Mars and exoplanets stole most of the science headlines in 2008, papers reporting results from a number of cosmic ray detectors gathered a lot of attention in the (astro-)physics community. Excesses in the number of particles detected at high energies (~50 GeV) that could not be explained by theoretical predictions sparked speculations that cosmic ray satellite PAMELA may be picking up the signature of dark matter in the Galaxy. A commonly accepted scenario for the nature of dark matter are the so-called WIMPs, or weakly interacting massive particles, which don’t interact in “regular” processes but may annihilate each other to produce high energy cosmic radiation. A number of cosmic ray and gamma ray detectors have produced intriguing results, leaving scientists with an intricate puzzle of information to assemble into a coherent picture.

I’ve written about the cosmic ray-dark matter connection before, and the story recently resurfaced when one of the papers describing the anomalous PAMELA data was published in Physics Review Letters (PRL). This particular paper describes the anti-proton versus proton cosmic ray detections, which in fact do follow quite nicely the theoretical predictions based on expected sources of cosmic rays in the Galaxy. Physicist Simon Swordy wrote a commentary on the paper over at Physics. While on the surface this aspect of the PAMELA results seems to contradict the dark matter signature theory, all it means is that the WIMP annihilation scenario has to accommodate this phenomenon – Sean over at Cosmic Variance explains in more detail. Or the data could just be evidence of something completely different. In any case, data we don’t understand always present us with an exciting opportunity to discover new phenomena, new processes. With the resurrection of the LHC (fingers crossed) later this year, the search for dark matter will remain likely headline material in 2009, as it was in 2008.

Read Swordy’s article here. You can read more physicists’ views on Resonaances and Symmetry breaking.

Update, 10/02/09: Another great post on dark matter by Mark on Cosmic Variance with a welcome nod to the instrumentation community for making possible these exciting new findings.