A commenter points to the long-awaited release of a preprint from the XENON100 experiment giving results from a 100-day run last year. This is the most sensitive dark matter experiment that has released data. The result: with an expected background of 1.8 +/- .6 events, they see 3 events (i.e. about what you’d expect if there’s nothing there). For a WIMP mass of 50 GeV, this allows them to exclude certain WIMP cross-sections at the level of 7.0 x 10-45cm2. This pretty conclusively kills off some other claims by dark matter experiments to have seen something, especially the CDMS result from late 2009 (see here).
One motivation for supersymmetry has always been that it can provide a WIMP with the right properties to explain astrophysical dark matter observations. This new data rules out some (if you use the SUSY expectations plotted in the new paper), or most (if you use the expectations plotted in the CDMS paper, see here and here) of the possible parameter space where such a particle is expected, providing yet another nail in the SUSY coffin.
Update: More details available at Resonaances and Tommaso Dorigo’s blog.
Update: For a detailed analysis of the implications of the XENON100 result for supersymmetry models, see here.
Regarding SUSY parameter priors, there are generally two categories:
1. Priors based off of theoretical or philosophical motivation
2. Priors chosen by/for experimentalists so that they have sensitivity
Okay, so #2 is not a prior, but it could be easily misinterpreted as such. Experimentalists choose to study theories that their experiment might have sensitivity to (not theories that they consider to be likely). If one were to misinterpret their choice of parameters as some sort of bayesian preference one would come to the misguided conclusion that the preferred versions of SUSY have been excluded. But that’s nonsense.
If, however, the motivation for SUSY requires a certain choice of parameters and those parameters have been excluded that would be a strong case to abandon it at as plausible theory. But is that really the case? (I’m not a theorist so I don’t have much to say about this)
Personally I have a completely flat prior for SUSY parameters (or its existence in the first place), so the whole argument that SUSY should be considered a fringe theory simply because a small set of parameter space has been excluded seems a bit ludicrous to me.
Check out the title of this post-Xenon100 talk by Dan Hooper: http://www.phys.psu.edu/seminars/index.html?event_id=2232;event_type_ids=0;span=
That said, I won’t be terribly surprised if someone like Weiner, Hooper or Zurek will put out another paper in a few weeks, where they tweak a few parameters in one of their pet models and produce another “consistent” scenario 🙂
Peter, what do you think of this paper by ‘Hooft?
My bold prediction: even if LHC finds new physics that is something other than susy, the new physics will cause new naturalness problems, which will be curable by susy. At that point, susy will regain momentum.
I’m also curious about this paper by Hooft. Peter, will you write something?
Well, first I have to find time to read and understand it. Too busy with other things right now, we’ll see. From a very quick glance all I can tell is it’s quite far from anything I’ve ever though much about.