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A first hint of Higgs !!? April 1, 2008

Posted by dorigo in news, physics, science.

A plot blessed last Friday at the CDF Higgs meeting made me jump on my chair today. It is the combined result of ZH search channels with Higgs boson decay to b-quark pairs. What you see in the graph below is the distribution of the reconstructed dijet invariant mass for the two jets accompanying the Z-boson signal (either a pair of opposite-signed leptons, or a significant amount of missing Et). The data (2.7/fb collected by CDF in Run 2) are the black points with error bars, and the various contributing physics processes are represented by stacked histograms.

This analysis does much better than the previous ones in selecting b-jets, and an optimized Neural Network was used to improve the dijet mass resolution, for the first time reaching the 10% point; also, the inclusion of multijet data with a Z \to \tau \tau signal improves the acceptance by about 20%. There is a clear excess of events at about 120 GeV, where the expected Higgs signal (purple histogram) provides a better fit to the data than the rest of backgrounds. Pseudoexperiments indicate that the excess represents only a 1.9-sigma significance, but I believe the estimate has been conservative.

I will have more to say about this later today.

UPDATE: since I am already getting in my mailbox messages from reporters and interested outsiders asking for more details, I have better clarify directly here that the above is, indeed, an April’s Fool. The plot comes from the report of the Tevatron Higgs Sensitivity Working Group, and it refers to a pseudo-experiment generated with an equivalent luminosity of 10/fb. The black points are not data! They are randomly fished events from the Monte Carlo generations.



1. Guess Who - April 1, 2008

1.9 sigma? Well, OK… but I can already hear cosmologists snickering…

2. Farsa de 1 Aprilie | Picatura de Fiere - April 1, 2008

[…] Cineva a reusit! Am cazut in plasa ca o musca bauta. Dorigo a reusit cu postul A first hint of the Higgs sa ma faca sa sar din […]

3. carlbrannen - April 1, 2008

This does look pretty good. And regarding popularity, I agree that it is only the science posts, no, only the physics posts, no, only the particle physics posts that count.

From comments on a physics blog where the author writes posts that generate traffic instead of understanding, the commercial motivation is clear. He is paid per view.

4. Anonymous - April 1, 2008

Interesting that there’s another little bump (not very significant, I know) right exactly at the top mass. Coincidence? I would guess your answer to that is probably yes — if so are you sure?

Fodder for your followup note: Could you say something about how the backgrounds are modelled (and how well) and the plot normalization? Is there a public note yet? How well does the data match background simulation when one of the jets is definitely _not_ b-tagged?

5. Tripitaka - April 2, 2008

Amazing! (hopefully the 1 April date is a coincidence)

Is it too late to cancel LHC?!

6. JJD - April 2, 2008

Although Higgs has proven quite elusive, I actually worked with him back in 1982. His first name was Bill, and I am sure that his mass was way more than 120 GeV. Congratulations on your great (re)discovery, anyway. Happy April 1!

7. goffredo - April 2, 2008

a nice plot!

8. piscator - April 2, 2008

this better bloody well not be a particularly cruel april fool!

9. I'm just sayin' is all - April 2, 2008

Don’t CDF public plots typically say ‘CDF’ on them somewhere?

10. Thomas Larsson - April 2, 2008

piscator, it cannot get any worse than this.

11. island - April 2, 2008

Dorigo, you dog, I was on to you three days ago when you weren’t buying your own hype… lol

12. Jon Lester - April 2, 2008

Nice April’s fool, Tommaso.


13. dorigo - April 2, 2008

Hi all,

of course this was an April’s Fool… But I agree that by making the claim not overly improbable I masked it a little.

Carl, I believe you are referring to the other post about blog traffic… In any case, do you think Sean is paid per each click he receives ? I doubt it – I see no ads in his blog.

Anon, in this case I am TOTALLY sure it is a fluctuation at 170 GeV – because events in the “data” are MC as well, and I know exactly their PDF – the same MC distributions plotted in the picture.

Tripitaka, according to the two nutcases who filed a lawsuit against LHC (claiming it would destroy Earth) , it is still possible to stop it…

JJD, who is Bill Higgs ? A physicist ?

Yep I’m just, CDF plots have “CDF Preliminary” somewhere. But I could have cut it by mistake…

Cheers all,

14. Anonymous - April 2, 2008


15. Amara - April 2, 2008

I don’t think you could top this though:

(One of the most elaborate gags I’ve ever seen)


And the perfect response:

16. Kea - April 2, 2008

LOL!!!! Good one!

17. carlbrannen - April 2, 2008

Dorigo, re getting paid for blog traffic. No, it wasn’t Sean, let me see if I can find a good reference. Yes, here it is.

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