Wednesday 16 December 2009

A little update on CDMS

I guess I owe you a short summary to straighten out what I messed up. This Thursday CDMS is going to announce their new results on dark matter detection based on the 2008 and 2009 runs. The collaboration has scheduled two simultaneous talks, one in Fermilab and one in SLAC, for 5pm Eastern time (23:00 in Europe). The SLAC talk will be webcasted here. An ArXiv paper is also promised, and it will probably get posted Thursday evening. These facts are based on the news from the official CDMS page, so they may turn out to be facts after all, unlike the previous facts I called facts even though they were unfacts :-)

Having rendered unto Caesar, I can go on indulging in completely unfounded speculations. It is pretty clear that no discovery will be announced this week, in the formal scientific sense of the word "discovery". Earlier expectations of a discovery that I was reporting on were based on the rumors of a CDMS paper accepted in Nature, which turned out to be completely false.
Moreover, some CDMS members seem to play down the hopes. But the secrecy surrounding the announcement of the new results may suggest that CDMS has seen at least a hint of a signal:
not enough for a 3 sigma evidence, but enough to send us all into an excited state.

So I see two possible scenarios:
  • Scenario #1
    CDMS has detected 2-3 events with the expected background of order 0.5. All eyes will turn to XENON100 - a more sensitive direct detection experiment that is kicking off as we speak - who should provide the definitive answer by the next summer. In the meantime, theorists will produce a zillion of papers fitting their favorite recoil spectrum to the 3 events.
  • Scenario #2
    All this secrecy was just smoke and mirrors. CDMS has found 0 or 1 events, thus setting the best bounds so far on the dark matter-nucleon cross section. Given the expectations they raised in the physics community, the Thursday speakers will be torn to pieces by an angry mob, and their bones will be thrown to undergrads.
It's fifty-fifty: either they have seen dark matter or they have not ;-) We'll see in 2 days, stay tuned.


José Manuel said...


Two conferences in sync is a little weird right? Something kept up its sleeve.


Anonymous said...

Independent of the rumors, I have it from a very well-known physicist that CDMS will in fact announce that they have discovered dark matter tomorrow.

Anonymous said...

"I have it from a very well-known physicist that CDMS will in fact announce that they have discovered dark matter tomorrow."

"Discovered" is a strong word, you know. Stronger than CDMS's statistics can plausibly allow them to claim.

Anonymous said...

Just curious, what if the dark matter distribution in the solar system is fairly clumpy? Could this be consistent with having observed no events last time, but a number of events now (assuming this is the case)? Maybe for the recent run, we went through a 'cloud' while during the previous run we went through 'clear skies'.

Anonymous said...

let's be scientific. The right thing to do is preparing 5 papers describing how SUSY can beautifully fit 0 or 1 or 2 or 3 or 4 events at CDMS and submit the right paper as soon as possible.

Anonymous said...

They've seen 3 events above their expected background of 0.5. The cross-sections roughly correspond with a neutralino mass of around 100 GeV.

Anonymous said...

"let's be scientific...." F* LOL!

Anonymous said...

Results from the CDMS II Experiment

[ abstract ]
A blind analysis of data taken by 30 detectors between October 2006 and July 2007 found zero events consistent with WIMPs elastically scattering in our Ge detectors.

"found zero events"

Jester said...

Man, that abstract is from an old talk describing the previous analysis...