Wednesday, June 27, 2012

CMS leak: Higgs cross section will be announced with a 30% error

The pirate at the top, next to the flags, opens the mobile format of this blog entry: try it.

A member of the CMS collaboration has leaked the information that on July 4th (see the counter in the sidebar), the discovery of the Higgs boson will be accompanied by the information that the cross section for its production will have been measured with the 30% error margin.



While this error may look large, it doesn't mean that the significance of the discovery is only 3 sigma. In reality, the large uncertainty of the cross section may be partly if not mostly explained by the nonzero background events' cross section, its uncertainty, and the uncertainty of the overall luminosity of the LHC. One may roughly estimate that 30% of the Higgs cross section (which is comparable to 20 picobarns) is less than 20% of the total cross section for the Higgs and (i.e. plus) the background events which is why one is more than 5-sigma certain that the Higgs contribution is nonzero.




I won't tell you the last name of the person who leaked this information, in a pretty obvious way, because this could cause some trouble to Tommaso. :-) I think that he should get a confirmation from his psychiatrist that he just can't resist to leak these things – and then he should defend himself at the CMS by the claim that they shouldn't discriminate against psychopaths.

BTW, after some time, he changed the number with the leak to another number, 50%. When you're masking your footprints, you shouldn't make the masking more visible than the footprints themselves...

12 comments:

  1. Lubos,

    In case you are interested, this is a good analysis on various theoretical uncertainties related to Higgs searches at LHC:

    http://arxiv.org/pdf/1012.0530v5.pdf



    Cheers,


    Ervin

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  2. Ah, this CMS leak seems to be a stable one :-P



    Now Lumo got me because my mouse slipped on the "trouble" link in the text but I usually dont click the leak any more LOL

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  3. What is the impact of this uncertainty, if any, on your $500 bet with John Ramsden?

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  4. Ervin, are you still a member of the E-infinity group?

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  5. It is disconcerting to me that the paper you link fails to cite Mohamed El Naschie, who surely has a finer grasp on Higgs search uncertainties than any other mortal.

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  6. Lubos, if the Higgs is confirmed and the last piece of the SM is put in place, will the "Standard Model of Particle Physics" be renamed the "Standard Theory of Particle Physics"? Or can you elaborate a bit on the usage of the words "Model" and "Theory" in physics/science? Thanks.

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  7. Why do you write so false and nasty things about Tommaso?

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  8. There is of course no impact. Every measured quantity has an error margin. But the 30% error margin doesn't mean that there is anything uncertain about the existence of the Higgs itself which will be discovered at 5+ sigma. Please read the fucking sentences of mine, or the whole Dorigo text


    http://www.science20.com/quantum_diaries_survivor/basic_education_particle_hunters_significance_and_rate_error-91535



    or at least its last sentence where the number "50%" was originally correctly "30%".

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  9. No, Steven Weinberg gave it the name, "Standard Model", and its renaming is less likely than the renaming of the Higgs boson.


    In the case of the Standard Model, the word "theory" would indeed be more appropriate. But that's not because "model" sounds like a "hypothesis" and suggests that it's not yet proven. Both "model" and "theory" are used for systems of ideas, equations, concepts, and hypotheses that may have been established but more likely, they have not.


    Instead, the word "model" differs from "theory" because it means that the given model/theory is just one detailed realization of some concept – like different models are just different realizations of the general concept of a car or different supermodels are just different realizations of the concept of a woman – while "theory" is meant to be more unique.


    However, one should still not say that "theory" refers to the concepts and general principles and methodologies only. If we only want to separate the set of principles and methodologies etc., we would prefer to pick an even more general word than a "theory", namely a "framework".


    The Standard Model would better be called a theory but SM has become an inseparable part of the jargon regardless of the possible "inaccuracies" in the structure of this term.

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  10. Dear Lubos, I think you are a bit harsh on Tommaso Dorigo. His post is not really a leak, it is a hypothetical exposition. For all we know the accuracy of the cross section measurement might be 15% ( and I am not leaking anything since I have not seen or discussed any unpublished data from CMS ).

    There is little doubt that the Higgs is there anyway. What would be great is if on the 4th of July we could see a real honest to god old fashioned resonance plot, width and all, in a specific channel.

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  11. Dear Anna,


    do you want to make a bet that at least one paper or talk on July 4th will contain a statement about a Higgs-related cross section measured with the error margin 30-35 percent? I think this was clearly implied by Dorigo's original article, by the very fact that he wrote about this otherwise off-topic issue with these particular numbers.
    Otherwise I think that the plots on July 4th will be similar to some of the plots we have already seen in the "negative" papers on the Higgs, they will just be given a more prominent position.

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  12. So we'll be opening the box on 4th July but since there is no collapse we already kinda know the outcome ;-) Still I can't wait to have it tattooed on my... shoulder ? :-)

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