Higgs what?

ResearchBlogging.org

In these days it has been announced the new version of Review of Particle Physics by the Particle Data Group (PDG). This is the bread and butter of any particle physicist and contains all the relevant data about this area of research. It is quite common for us to search the on-line version or using the booklet to know a mass or a decay rate. After the first run of LHC data gathering about Higgs particle, this edition contains a bunch of fundamental informations about it and I post a part of them.

Higgs on PDG

It is Standard Model Higgs! No, not so fast. Take a look at the WW final state. It is somewhat low but yes, it is perfectly consistent with the Standard Model. Also, error bars are somewhat large to conclude something definitive. So, let us take a look nearer at these strengths.

Higgs decay to WWWe discover that the strengths measured by CMS are really low and takes down this value. Indeed, this is consistent with my proposal here. I get 0.68 for both channels WW and ZZ. On the other side, ATLAS moves all upward consistently and there is this strange behaviour compensating each other. So, let us also take a look at the ZZ strength. PDG yields

Higgs decay to ZZagain CMS agrees with my conclusions and ATLAS moves all upward to compensate. But both these results, due to the large error bars, agree rather well with the Standard Model. So, I looked for the publication by CMS  that were produced till today if one or both these analyses were improved. The result was that CMS improved the measure of the strength in the WW channel to leptons (see here). What they measure is

\frac{\sigma}{\sigma_{SM}}=0.72^{+0.20}_{-0.18}.

The error is significantly smaller and the result striking. It is bending in the “wrong” turn loosing higgsness. It would be interesting to understand why CMS appear to get results downward for these strengths and ATLAS more upward compensating each other toward the Standard Model. On the other side, I should admire the more aggressive approach by CMS with their results more and more similar to my expectations. I am just curious to see with the restart of LHC what will happen to these data that CMS sharpened to such a point.

Marco Frasca (2013). Scalar field theory in the strong self-interaction limit Eur. Phys. J. C (2014) 74:2929 arXiv: 1306.6530v5

CMS Collaboration (2013). Measurement of Higgs boson production and properties in the WW decay
channel with leptonic final states JHEP 01 (2014) 096 arXiv: 1312.1129v2

7 Responses to Higgs what?

  1. ohwilleke says:

    Those PDG numbers for the Higgs are already old news. The best fit mass is now about 125.35+/- 0.4 (per the latest preprint conference papers).

    The diphoton excess is now CMS μ= 1.14 ± 0.26 and ATLAS μ = 1.17 ± 0.27 (per Resonances) as of the end of LHC Run 1, for a combined value of far less than the 1.58 of PDG and with a significantly lower MOE. So a two sigma deviation has dropped to half a sigma.

    IIRC, the WW and ZZ numbers are also a bit closer to μ= 1 than in PDG, although with less dramatic changes.

    The reduction in the diphoton excess, which was the biggest deviation from the SM, also greatly reduces the combined decay rate deviation from the SM to well under μ= 1.17 and less than one sigma.

    It may take a year or two for the new numbers to make their way into the PDG since it relies, IRRC, only on published data and not on preprints or conference papers.

    Also the Higgs decay width limits have been tightened dramatically to about 4.3x of the SM prediction or less at 95% CI (with the best fit being even closer); and the spin alternatives other than spin-0 even have been pretty definitively ruled out.

  2. mfrasca says:

    Dear ohwilleke,

    Thank you for posting these data. I avoid to do that because this information is already widespread in the web through channels better informed than me. For the aim of my post, the diphoton rate is not relevant at all. My aim was to point out that the current rates for WW and ZZ have room for an interesting discussion and, surely, are open doors for different solutions to the scalar field theory as those I have found and published.

    Of course, if you have up to date strengths for WW and ZZ this would be better information and more at the point. I have obtained my value from the last paper published by CMS on this matter and PDG was just a stimulating starting point.

    This holds for everyone knows these data better, why CMS and ATLAS differ in this way and so on. I think it would be helpful for me and my other twelve readers.

    Marco

  3. ohwilleke says:

    The WW and ZZ data from ATLAS as of Spring 2014 is here: https://indico.cern.ch/event/279518/session/9/contribution/10/material/slides/0.pdf at page 62.

    The most recent CMS report that I can find (Dec 2013) is here: http://arxiv.org/abs/1312.5353

    The latest spin exclusions based upon complete data reports from Tevatron show a 125 GeV Higgs bosons signal at 3 sigma with branching fractions consistent with the Standard Model prediction. A Standard Model 0+ spin-parity combination (i.e. a scalar Higgs boson) is favored over a pseudoscalar O- hypothesis at 99.9% significance, and over a tensor 2+ hypothesis at 99.5% significance.

    • mfrasca says:

      Fine. This is the same data I gave for WW strength from CMS and so it is an intriguing clue for a different Higgs field. Thanks for the rest.

  4. ohwilleke says:

    New CMS data showing mu=0.93.

    The old CMS value that went into the PDG meeting was mu=0.60 CMS v. 0.99 for ATLAS v. 0.94 for Tevatron.

    • mfrasca says:

      Dear ohwilleke,

      Thank you very much to keep on posting useless information. 0.93 is the overall value for the compliance of the Higgs sector with the Standard Model that I have never questioned. You are also messing up with the rates being 0.6 just for WW and 0.93 the overall value. Note that my point was on the strengths of WW and ZZ decay only and about this there is nothing more to say than what CMS and ATLAS have already published and I have cited in my post. So, please, before further commenting read again my post carefully.

      Please, take also into account that error bars are meaningfully large at this stage and further refinement will be necessary. This will be work for the upgraded LHC.

      Cheers.

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