Thursday, 17 December 2009

CDMS Live

  • 16:41. Welcome to the live commentary from the CDMS seminar starting today at 2pm Pacific time at SLAC. It might be the event of the year, or the flop of the decade. Though most likely it will be a hint of the century.
  • 16:50 Our seminar room is starting to get packed. The webcast from SLAC will be projected on a big screen.
  • 17:00. The SLAC seminar has started! The speaker is Jodi Cooley.
  • 17:06. Dark matter history. Zwicky, Ruben, rotation curves, bullet clusters. No way around it, we have to suffer through that....
  • 17:09. There is also a webcast of the Fermilab seminar here. They are ahead of SLAC...
  • 17:12. Now talking at length about WIMPs. Does it mean they see a vanilla-flavor WIMP?
  • 17:14. A picture of a cow on one of the slides.
  • 17:15. Fermilab already got to the gamma rejection. We are watching the wrong webcast, booo.
  • 17:18. Jodi starts describing the CDMS experiment.
  • 17:20. Previous CDMS results at Fermilab. They're getting close.
  • 17:30. We switched to the Fermilab talk here in Rutgers. Now the speaker is Lauren Hsu. She seems faster.
  • 17:35. Very technical details about phonon timing and data quality monitoring.
  • 17:38. Expected backgrounds. Finally some important details.
  • 17:39. Estimated cosmogenic neutron background 0.04, and similarly for radiogenic ones.
  • 17:40. Surface event background estimated at 0.6.
  • 17:45. They are talking about expected limits. Scaring. They don't have a signal? If there were no signal they would obtain two times better bounds than the last time.
  • 17:47. Rumors reaching me, of 2 events at 11 and 15 keV.
  • 17:49. It's official: 2 events. One at 12 keV, the other at 15 kev.
  • 17:49. There are additional 2 events very close to the cut window, approximately at 12 keV.
  • 17:58. Now discussing the post-unblinding analysis and the statistical significance.
  • 18:00. Both events were registered on weekends. Grad students having parties?
  • 18:01. The significance of the signal is less than two sigma.
  • 18:04. One of the events has something suspicious with the charge pulse. A long discussion unfolds.
  • 18:12. After post-unblinding analysis the signal significance drops to 1.5sigma (23 percent probability of the background fluctuation).
  • 18:14. The new limits on dark matter $4x10^{-44} cm^2$ for a 70 GeV WIMP. Slightly better (factor 1.5) than the last ones.
  • 18:17. Inelastic dark matter interpretation of the DAMA signal is not excluded by the new CDMS data.
  • 18:18. Nearing the end. The speaker discusses super-CDMS, the possible future upgrade of the experiment.
  • 18:20. Summarizing, no discovery. Just a hint of a signal but with a very low statistical significance. Was fun anyway.
  • 18:20. So much for now. Good night and good luck. The first theory papers should appear on Monday.
A summary by CDMS here, and the paper here (on Arxiv password-protected untill Sunday evening; if you can't wait click here). See also a much better live commentary from eye-witnesses on Cosmic Variance.

40 comments:

Anonymous said...

outline shown in kipac

Anonymous said...

kudos on doing a live blog.

I'm watching via my uber slow wireless in Ferney Voltaire which keeps conking out!

Anonymous said...

bullet cluster at kipac

Anonymous said...

WIMPs detector at kipac

Anonymous said...

THE SPHERICAL CAW slide at kipac

Anonymous said...

"Now talking at length about WIMPs. Does it mean they see a vanilla-flavor WIMP?"

The FNAL stream is all about the detector and backgrounds so far. Sounds like we're hearing completely different talks.

(The KIPAC video stream is completely broken for me.)

Anonymous said...

detection challenges at kipac

Anonymous said...

at kiapc the seminar is too fast !!!!!!
something at the end ???
squid readout at kipac

Anonymous said...

Surface event rejection at kipac

Anonymous said...

Detector, cuts, calibration @ fnal...

Anonymous said...

too much on the method, they want to sell 3 events as a signal !!

Anonymous said...

No, this is not too much on the method, _you_ are impatient :p

Anonymous said...

old upper limt and bck at kipac, she is going to ..

Anonymous said...

the box open at kipac, she is nervous

Anonymous said...

I REALLY hope someone is recording this. I can't see ANY of the live video and if this is historic....well...

Anonymous said...

TWO EVETNS OF SIGNAL AT KIPAC

José Manuel said...

Yo quiero unirme a los comentarios en Español. Si esto es histórico...


Saludos desde España.

Anonymous said...

no evidence for wimp at kipac

Anonymous said...

Fermilab stream completely disappeared for me just as the discussion of surface event backgrounds was starting...

Anonymous said...

they want to sell the new detector
as necessary

Anonymous said...

Well, that was the definition of anticlimactic.
(zzzzzzz)

Anonymous said...

Clearly background spillage into signal region, and consistent with previous results. Bah-humbug.

Anonymous said...

TWO events is completely insignificant to anyone outside of the experiment itself. They're just selling superCDMS as an earlier post said. They're justified in doing so, but this is an uninteresting result to the rest of us.

Anonymous said...

Selling SuperCDMS? Sounds like they just presented what they saw. Other people spread rumors which gave this result more hype than the others. Looks to me like solid, careful analysis with a possible hint of a signal.

Anonymous said...

I wonder why do the comments get so increasingly stupid. In case you missed this, nobody promised anybody anything. You probably noticed only because of the dramatic post. It'd be amazing if we could either just sit back and get real and watch the presentation or find smth that we're interested in to do...

Anonymous said...

If it is a signal, the detection is there for the taking for either XE100 or LUX; only another 1-2 years.

Anonymous said...

I don't think this sells their next detector too well... rather to the contrary.

Anonymous said...

Less than 2 sigmas. And one of the events is not even in the bulk of the band. Much ado about (absolutely) nothing.

Anonymous said...

My own interpretation is what we (in the field) already knew: CDMS in its present form is reaching the point of diminishing returns where the technology needs to be improved, if the experiment is to progress in sensitivity. Backgrounds are starting to spill into the signal box, as expected from the limitations in these detectors. This only starts to show after sufficient exposure is acquired. To the trained eye, there are forms of analysis that would point to an even larger than 22% probability that these two events are background spillage. CDMS needs to demonstrate a dramatic technology upgrade (last transparency in FNAL's stream) to justify continued funding at the very high level required.

Anonymous said...

Theory papers about a 1.5 sigma fluke?? common....

Anonymous said...

"Common"? The best jokes are the unintended ones...

Beijixiong said...

The 23% claim ignores the previous CDMSb result: 0 events seen with 0.6 background events expected. Combining the results gives 2 events seen with 1.4 bkgnd events expected, somewhere around 50%.

Anonymous said...

What a circus.

Anonymous said...

Wow, they must *really* be desperate for money if they are willing to make themselves look so foolish. "WE HAVE A MAJOR RESULT TO ANNOUNCE....NAMELY.....WAIT FOR IT...THAT WE HAVE NOT FOUND ANYTHING INTERESTING WHATEVER!!!!! COOL EH?????"

As for the people claiming that they didn't promise anything: can you really be that naive? Simultaneous talks. Arxiv papers announced in advance. A *very* easily predictable rumour explosion. Then they announce bugger-all and say, "Well we didn't promise that we would announce anything important!"

What bullshit.

Anonymous said...

isnt supercdms already funded? how would they be desperate for funding? i never saw any hype coming from cdms other than a response to the rumors posted (started?) by this blog...

Anonymous said...

The great sadness of all is that, as usual, folks with zero to no familiarity with treatment of data are forgetting about something called the "null hypothesis": it is clear in several of the plots shown today that no WIMP model can provide a better fit to these signals than background spillage into the "box". Not like this will stop many theoreticians from foaming at the mouth. Physics is fast becoming two tribes, and one is the proverbial ship-o-fools. You know which one you belong to.

Physicsphile said...

WTF, 1.5 sigma is not a hint! Its nothing.

Anonymous said...

"Physics is fast becoming two tribes, and one is the proverbial ship-o-fools."

You mean the experimentalists right? Because I don't see any theorists getting excited about this non-event. Even Nima Arkani-Hamed can't be bothered.

Laura Zaillian said...

Thanks for this live post. :)) Supercdms is already funded, i think so, isn't it? I am a college sophomore with a dual major in Physics and Mathematics @ University of California, Santa Barbara. By the way, i came across these excellent geography flash cards. Its also a great initiative by the FunnelBrain team. Amazing!!!

Jester said...

Who said "common" :-) I know my fellow men...10 papers about 2 events and still counting...