Glimpses of Higgs

Finally, after some frantic waiting filled with rumors, we heard the truth from people at CERN. And we discovered that rumors were just right. Evidence is mounting for a Higgs particle at around 120-130 GeV, after new data were accounted for. All these evidences point toward a Standard Model Higgs. But some caution words are needed (see Matt Strassler’s post) as a discovery cannot be claimed yet. ATLAS sees a 3.6 sigma overall evidence but, accounting for look elsewhere effect, this go down to 2.5 sigma while CMS has a similar 2.6 sigma going down to 1.9 with look elsewhere effect. This is not enough to rule out a fluctuations but, anyhow, a strong indication where to point researchers attention for the near future. All the matter will be pinned down later next year. From my side, I just note a possible contradiction between the two experiments as ATLAS keeps on claiming an excess around 500-600 GeV, also with increasing number of data and indeed evidence now goes beyond 2 sigma, while, as for today, CMS claims this range ruled out. It is possible that this is another glimpse for a Higgs multiplet as required by supersymmetry. I think that also this matter will be fixed soon next year.

The conference raised a lot of enthusiasm (see here) to some caution (see here) or skepticism (see here).

Fabiola Gianotti, Rolf Heuer and Guido Tonelli

What makes these hints striking is the fact that both experiments see the excess in the same region where the particle was expected and with the proper rates. It should also be said that, with these data and energy, people at CERN have done an excellent work with the analysis of them. But, of course, it is still possible that we are coping with a fluctuation and the particle is hiding elsewhere or is something else. For sure, next year the puzzle will be completed and also this part of the Standard Model will be part of our textbooks in the right way. What we have here is a completely new situation holding the premises for a clear understanding of one of the greatest question of mankind ever. So, when a child will ask to you: “Mom, what are we made of?” this question will have an answer, an answer arising from the work of a lot of smart people running one of the greatest technological achievement of our history: LHC.

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4 Responses to Glimpses of Higgs

  1. [...] Glimpses of Higgs | Marco Frasca | The Gauge Connection [...]

  2. ohwilleke says:

    * The observation that the presence or absence of additional Higgs bosons could be a key test of supersymmetry (or at the very least a power means to rule out particular supersymmetry vacua) is a good one, although I wonder if a narrow extension of the SM with 8-3=5 Higgs bosons rather than 4-3=1 of them, without the remainder of the supersymmetry, would be a workable possibility even then. Higgs proposed 1 rather than 5 Higgs bosons on the basis of parsimony, if I recall correctly, but while supersymmetry seems to require more than one Higgs boson, it isn’t obvious that the converse, that more than one Higgs boson necessarily implies supersymmetry, is true.

    * As far as the 500 GeV-600 GeV range goes, it looks to me like this is an energy scale where there simply isn’t enough data to have much statistical power one way or the other yet, something that should creep up gradually in the years to come at LHC. This is roughly the same scale where the current lighest supersymmetric particle exclusions from LHC are hovering.

    * Does a firm data point on a SM Higgs boson mass do anything to change the accuracy with which QCD backgrounds can be calculated?

    My intuition is that it wouldn’t make much difference, because the Higgs boson seems to be an electroweak thing that only indirectly impacts QCD calculations via its role in establishing fundamental particle masses, but I don’t know the equations well enough to say that with confidence.

    • mfrasca says:

      Dear Andrew,

      No, QCD is not involved here at all. The only interesting question to be asked is if the way particles get their masses is the same a mass gap forms in QCD as is going to be realized in these years. This question gets its motivation by the simple fact that often nature repeats itself at different levels but this can be also said of the Higgs mechanism as it arises from condensed matter physics as firstly understood by Anderson.

      If it would be true that the mechanism to get mass is the same as for a Yang-Mills theory then I proved a theorem about (see http://arxiv.org/abs/1007.5275). In this case the potential of the scalar field would be somewhat different from that of a Higgs field but the Yukawa couplings would be the same. The only essential difference is that now the self-coupling of the scalar field would be not so small and a mass gap would form. This would be immediately a proof of existence of supersymmetry.

      Finally, a peculiar characteristic of this approach is that this particle would have an internal set of states with a mass formula m_n=(2n+1)\frac{\pi}{2K(i)}\sqrt{\sigma} being K(i) an elliptic integral and \sigma an experimental number having the dimension of the square of energy. So, people at CERN would see a fundamental state and all its excited levels.

      Marco

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