Wednesday, 4 July 2012

H-day Live


10:58 The party's over now. It was a beautiful day, a historical day, the great triumph of science. Now I'm going to sleep the night off, and tonight we're all gonna celebrate, drink, and make out. Thank you.
10:57 Funny that nobody asks about the loose cable ;-) 
10:56 Higgs says: "I'm glad it happened in my lifetime".  
10:47 I got carried away, no underwear and bras on the stage, sadly. But the atmosphere in the auditorium is such that they might have been.  
10:46 Standing ovations, screams and shouts, the audience throwing bras and underwear at the stage. 
10:44 "I think we have it", concludes the DG. "We have a discovery of a Higgs boson, but which one"?
10:42 In summary, both ATLAS and CMS clearly see a Higgs boson in 2 channels: the diphoton and ZZ 4-lepton. Combining those two, the significance of the Higgs signal is  5.0 sigma in both experiments.


10:40 "This is just the beginning"
10:38 The CMS and ATLAS preferred Higgs mass differ by more than 1 GeV, there will surely be questions about that. 
10:35 5.0 sigma combined excess with the maximum significance mh=126.5 GeV.

Higgs discovered by both experiments!    

 

10:33 Going to the combination (ATLAS won't show any more channels today). 
10:30 Excess near m4l=125 GeV, although by eye less beautiful peak than in CMS. 3.4 sigma excess vs 2.6 expected in the SM.

10:26 Press release is out. The discovery officially blessed.
10:22 Now the ZZ 4-lepton channel. 
10:21 The measured rate in the diphoton channel is almost twice that predicted in the SM, with the SM rate about 1.5 sigma away. Interesting! So both experiments continue to see to much signal in the Higgs diphoton channel.   
10:20 4.5 sigma excess in the Higgs diphoton channel! (who cares about the look elsewhere effect anymore).  
10:11 Diphoton channel, finally. 
10:11 Boooring.... yet another particle being discovered....

10:05 Both speakers today felt compelled to devote the first 15min to irrelevant bla-bla. Probably because the main subject doesn't appear that exciting.
9:53 Fabiola Gianotti on the stage. Time for ATLAS. 
9:50 In summary, CMS observes a Higgs boson with mass 125.3±0.6 GeV at 4.9 sigma significance. Some funny glitches in the data (a slightly too large diphoton signal,  no excess in the di-tau channel) but overall good consistency with the Standard Model predictions.

9:47 All channels combined, 4.9 sigma significance, vs 5.9 expected.
9:41 Some excess, but not signifcant, also observed in the WW dilepton channel, and b-bbar associated with W/Z. No excess at all in the tau-tau channel, although there should be. 
9:38 Combining diphoton and 4-lepton channels the significance of the Higgs signal is 5.0 sigma

Higgs discovered!!!


9:34 Beautiful peak in the 4-lepton channel. Higgs observed with 3.2 sigma significance in this channel, vs 3.5 sigma expected in the SM.
9:32 Now the ZZ 4-lepton channel
9:31 CMS sees a Higgs in the diphoton channel with the rate about 50% larger than predicted by the Standard Model (but barely one sigma above the SM).
9:30 Over 4 sigma signal in the diphoton channel

9:29 "That's pretty significant"

9:22 Finally, Higgs to diphotons.
9:18 It's not that I stopped blogging, it's that Joe is boring. We want the meat!  
9:11 5.2 inverse femtobarn  of 2012 data, 5.6 in the muon channel. 
9:06 "One page for theorists, that's all they deserve" :-)  
9:04 Joe Incandela on the stage, the CMS talk start.
9:02 C'est parti! "Today is a special day" says DG.   
8:56 Yes! Higgs is here!!! Everything ready for the discovery.
 
8:50 10 minutes to the seminar. Still no Higgs. But the other Nobel prize winner this year is already inside.
8:43 By the way, if you come across  a press article today about the god particle that's a perfect gauge the author is an idiot and has no idea what he's talking about. 

8:38 The audience is a funny mix. One half are 60+ big shots who could get themselves a sit reservation, the other half are 20-something Higgs groupies who had a strength to queue all night.  
8:25  The title of the seminar is Higgs Search Update. Reminds me of  A Model of Leptons.

8:15 The first accurate prediction of the Higgs mass was formulated in this video.  It has gone unnoticed, however, because Jim Morrison  was stoned and reading it backwards.
8:05 There's a still a wild crowd in front of the auditorium, looks like Walmart on Black Friday... hope there will be no riot today.  
7:45 While waiting for the announcement it may worth checking this page. There is a theory that Higgs influences our present from the future, so as to avoid being discovered. At this point, destroying the whole universe might be his only chance...  
7:35 The door are open, people flowing in, but miraculously no stampede. 
7:25 People have been have been camping all night in front of the auditorium door  to get inside and see the discovery live. These are pictures from 3am last night.



7:20 This is the day. The most important day for particle physics in this century, and probably  ever.

42 comments:

Luboš Motl said...

Nice pictures, Jester!

For everyone who has more time etc.: you may open a HIGGS CHAT BOX where dozens of people are already debating and will be debating everything they see in the CERN press conference.

Now the topic is Veltman and his rho-parameter argument against the Higgs.

Anonymous said...

"The most important day for particle physics in this century, and probably ever." jejeje. Then comes from the future a Marty McFly with a cure for cancer, a solution for world's starvation, a teleportation machine and finally the final volume of Martin's heptalogie!

Anonymous said...

So, which is it? Heaven or Hell?

Jester said...

Not clear yet, might be either.

Anonymous said...

It's "Gianotti" (one "n").

Jester said...

now it is

Anonymous said...

You should keep that top plot a secret.

Anonymous said...

The director of this webcast seems obsessed with the speaker rather than showing us the slides.

Anonymous said...

Yes, I now know much more about the top of Joe's head than I do about the CMS data.

Thomas Larsson said...

If I understand correctly, the SM is internally consistent down to m_H = 126 GeV. How sharp is this border, an in particular would 125.3 GeV mean that the SM is inconsistent?

Jester said...

If you assume the SM is valid up to the Planck scale, then it's inconsistent below 127 GeV. But there's no reason to assume there is no new physics all the way up the Planck scale, so this sort of arguments have little weight.

Trisha Roberson said...

Thank you for this live blog! I don't have sound and couldn't listen to the webcast, and like another poster mentioned, they showed the speaker half the time rather than the slides. Kudos to you!

wolfgang said...

>> then it's inconsistent below 127 GeV

Shaposhnikov and Wetterich have mH at 126GeV with SM only and asymptotic safety of gravitation: arxiv.org/abs/0912.0208

Mitchell said...

I have some interest in models where only the top couples directly to the Higgs and all other masses arise through loop effects. In this regard the slide at 9.47 is interesting: WW and ZZ as expected, digamma excess, bb and tautau deficit.

Cyril Hugonie said...

Yeahh !!!! That was good !
Thx for the funny live comments (which I just read as I was looking at the live webcast) and the not less funny final countdown. I don't know if we're entering a new era (AH vs. BH) but at least we were not walking in the wrong direction. And it feels so good !

Anonymous said...

Wow, great stuff! Well deserved congrats to everybody involved on both sides of this tough equation!

Anonymous said...

Comic Sans? Really? You don't discover the Higgs and use Comic Sans.

Jester said...

Can someone explain me what is the issue with comic sans? Everyone on facebook talking about it, smf my feeling is I'm missing out on an important part of internet culture....

Anonymous said...

Hi Jester,

Great blog. You had written in aq previous posting: "Which of the last 2 scenarios [Heaven or Hell] is true will not be decided on the 4th of July, but the odds may be affected."

So what do you feel are the odds now? Did they change from what they were before?

Marco said...

One of many sites on the subject:
http://www.comicsanscriminal.com/

But personally I think comic sans was just one of the many problems of those slides (walls of text, colors, tiny plots).

Anonymous said...

Jester, look up "comic sans" in Wikipedia. The talk by Fabiola Gianotti today is already mentioned there. Apparently she was using that font originating in comics books for her talk.

Anonymous said...

I admit I gave talks in chalkboard back in the day, but I got better. It's ugly and looks kind of immature. You're announcing the biggest science discovery in the last 40 years or so. This is for the world; you should use a grown-up font.

Unknown said...

Maybe now Comic Sans will get some respect. It's the official font of the Higg's particle. Don't let the typographical esthetes bother you. They're just following the fashion, not verifying the standard model.

Anonymous said...

Is something in that new data that is not fully-consistent/expected under predictions from SM ? Is there any hint for new physics here ?

Jester said...

There is some excess in the LHC Higgs-to-gamma-gamma rate, and some excess in the Tevatron Higgs-to-b-bbar rate. But it's not very significant for the moment. The ZZ and WW rates seem to be right on the SM stop. Overall, the odds for just the SM Higgs have grown up a bit with the new data, but there's still some room for hope.

Ulla said...

If those too big bumps are corrected suiting SM, is there then any longer any 'discovery'? Doesn't they depend on too much gammas resp b-particles?

Jester said...

Well, by the time the bump may come into a better agreement with SM there will be twice as much data, so unlikely the significance of the bump will ever go down.

Ulla said...

By the time, only, not now. So this is not actually in so good agreement with SM?

The loop you describe, can it actually belong to string theory with 1D strings? Not even 2D. Someone said it has to be a 3 body system. Or...?

Walter Rowntree said...

Thank you, Thank you, thank you!

Doddy said...

Can you explain where the inconsistency of the SM comes from if the Higgs is heavy (>127GeV)? Is there a sub-Planckian Landau pole or something?

Jester said...

It's actually opposite: if the Higgs is too light the self-coupling turns negative before reaching the Planck scale. According to 1205.6497, the Higgs mass below which there's an instability is given by 129.4±1.8 GeV, the error being dominated by the uncertainty of the top mass measurement.

Ervin Goldfain said...

Jester,

In 1205.6497, vacuum instability is judged exclusively by the change in sign of the Higg self-coupling. Leaving aside the validity of main assumptions made there (on boundary conditions and the behavior of all perturbative contributions up to the Planck scale), is this the only way to define stability of the Higgs vacuum? What if a different stability criterion pushes up the lower limit on the Higgs mass, say, above 150 GeV instead of 129.4 GeV?

Anonymous said...

Le Roi est decouverte, ....Jester, would you like to write a post on life after (discovery of) Higgs? (still a bit unbelievable as it sounds). Obviuosly, other than Higgs programme, what else can/will LHC work on? Susy, dark matter, more mundane matters?

Stephen Paul King said...

Exactly how many events where registered?

Jester said...

Stephen, in the diphoton channel a few hundred of Higgs events were registered, although on top of a larger background. In the ZZ* 4-lepton channel we've got a handful of events, but with almost no background.
Anon, LHC will go on with all these programs, but if it keeps confirming the SM at some point serious depression will set in.
Ervin, I'm not aware of anything else than the stability bound (excluding too light Higgs) and the triviality bound (excluding too heavy Higgses). But, again, don't take these bounds seriously because it's highly unlikely the SM is a valid theory all the way up to the Planck scale.

Ervin Goldfain said...

Thanks Jester.

I agree that stability bounds cannot be entirely trusted at this point. The whole question of whether or not there is physics beyond SM hinges on a number of yet unproven assumptions. For example, if the anomalous Higgs dimension runs with the RG scale in some unknown fashion, or there are deviations from asymptotic freedom in QCD, or RGE become non-perturbative above few TeV's, SM may be destabilized much sooner than we naively expect.

Anonymous said...

the stability argument is just qualitative: if you take a fundamental scalar with a quartic self-coupling seriously, then non-perturbative effects are all over the place (triviality and so on). drawing conclusions from \sim 1 GeV shifts in m_H is simply a veeery long shot...

Anonymous said...

Jester, but susy does not (or does not have to) exist in the SM, does it? So is there any deliberate effort/ prospects for LHC to discover it? I guess that it may not be obvious that some new "resonance" happens to be a superpartner of a known particle?
From an aesthetics point of view, isn't susy more of a fundamental idea (a natural symmetry between bosons and fermions), while Higgls field considered on its own, more of a superficial gymmick to fix some questions not answered by SM? Wouldn't it be ironic if mother nature showed us real frivolity by choosing Higgs over susy?

Anonymous said...

Some background on the Higgs boson in a lecture at the Stanford Linear Accelerator Center:
http://www.youtube.com/watch?v=sqrwtQcrNBI&list=UUKzqyRUej9BI5dhdjwF09vQ&index=1&feature=plcp
It seems to assume some background in calculus and electromagnetism.

Anonymous said...

Concerning stability bounds, Jester got it right. Ervin, "vacuum instability is judged exclusively by the change in sign of the Higg self-coupling." It's actually the effective potential one looks at, although just checking the sign of the quartic is a good approximation. What else you need to check to convince yourself the EW vacuum is metastable? Moreover, all couplings remain nicely perturbative up to Mp, so we should trust this calculation, within the framework of the SM, of course. Anon, you must be confusing the triviality limit with the stability bound, in the calculation of which there
are no nonperturbative effects whatsoever.

Ervin Goldfain said...

"Moreover, all couplings remain nicely perturbative up to Mp, so we should trust this calculation, within the framework of the SM, of course."

This is precisely my point. Stability estimates are only valid if RGE's remain strictly perturbative all the way up to the Planck scale. But nobody knows if this ansatz is right or wrong. In fact, there are reasons to suspect that EW metastability may break down at much lower scales, see my reply above.

Thomas Larsson said...

Hi Jester, would you like to comment on http://arxiv.org/abs/1207.1718? It would be nice to see an executive summary for us who are too busy/lazy to read the paper in detail.