New Higgs Combinations Released

The LHC Higgs combination group is presenting their ATLAS+CMS Higgs combination plot at the Hadron Collider Physics conference in Paris today at noon and the slides of the talk (Gigi Rolandi) are already online. It includes some nice individual channel combinations as well as the full one we have been expecting. Before I look at those here is my approximate version of the full combination that I showed here two months ago. This version of it is taken from a slide shown by “Bill and Vivek” for the Higgs Combination Group themselves at a kickoff meeting in September for the plots finally shown today.

So how did I do? Here is a version of the new combination that conveniently shows some of the variations you can get just by using different methodologies.

The viXra version of the plot was produced using the minimal data available in the individual ATLAS and CMS Higgs Combination plots shown at Lepton Photon 2011 and approximates the probability distribution function by flat normal error curves. the calculation takes a few milliseconds. The full combination from the HCG goes back to the original data using the real log likelihood numbers and takes into account all known correlations between the data and background calculations. The calculation takes hundreds of thousands of hours of CPU time, yet the difference between the viXra plot and the official HCG one is no bigger than the differences of using alternative methodologies such as Bayesian. This is a nice demonstration of the power of the central limit theorem which says that and error distribution becomes normal given enough data and a finite variance. It also confirms that the effect of correlations on the plot cannot be very big.

To be clear, I think it is important that the full official combinations are worked out carefully because if you want to claim a discovery you have to make sure you have covered all the sources of error correctly. The Higgs Combination Group have done a good job. But if you just want to see the signal in the data we now know that an approximate combination is good enough.

If you want to compare more closely here is the official version with the viXra combination overlaid in red. The areas where it deviates are regions at high mass where there is low background and few events have been recorded. The approximation is not so good there because the normal distribution approximation is less accurate.

Here is the zoom onto the lower mass region

I Like that the combination group have also produced combinations for all the individual channels. My own verisons of these are a little less reliable because there is less data in each case so the normal distribution is not such a good approximation. Even so my plots were not far out which means that with the next batch of data using two to three times the statistics I can expect to get good results.

Here is the crucial combination for the golden channel. This is one of the best hopes for a signal  because its high resolution and good branching ratio at low mass. If you want to compare with my earlier combination it is here.

The other channel that has the potential to find a low mass Higgs is the direct diphoton decay and there is a new combination for that too

I think it is striking that both these plots have healthy excesses at around 140 GeV and perhaps again at lower mass. To see this better we need to combine them both together.

But this data is by now very old and it is no longer worth speculating on the basis of what the plots might show. The story has already been superceded by rumours over at Résonaances that the 5/fb plots show no more than a 2-sigma excess at 120 GeV. If all goes well we may get first results via the CERN Council Meeting during the week starting 12th December.

33 Responses to New Higgs Combinations Released

  1. Dilaton says:

    So I hope that Phil will keep doing some more such nice “nonsense” in the future … ;-)
    I like this and the accompanying possible interpretations of it and comments too :-)

    Cheers

  2. Luboš Motl says:

    Of course, your graph was shown to be basically accurate. Congrats.

    Nothing conclusive coming from this graph, though.

  3. PSTJ Editor says:

    Hi Phil,

    Thanks for a job well done!

  4. carla says:

    Let’s be fair to Bill; he didn’t say the plots here were nonsense but that on the web there was a lot of nonsense, including that published by Cern. Anyway, nice to see that your plots were not far off and looking forward to you combining the Atlas and Cms 5/fb in December to show there is a near 3-sigma excess at 120Gev. I can’t see an official combination being published until the LHC restarts in March to keep the public interested.

    • Philip Gibbs says:

      Carla, he was talking about my plots and only my plots. The bit about some on the CERN website was referring to the fact that someone at CERN showed my plots there. The slide I have included above confirms this in case there was any doubt.

      • carla says:

        Bill mentioned nonsense in the July conference talk, Higgs searches at the LHC. He didn’t show any plots he was referring to.

    • artikcat says:

      Carla how can the CERN plot be nonsense?

  5. [...] This picture has been waitd for a long time since the excellent work of Phil Gibbs at his blog (see here for an account of this). So far, this combination accounted just for a luminosity and what is [...]

  6. Guybrush says:

    Hi, nice results. But I still dont like the fact that the ATLAS and CMS guys are not letting us participate at having a look at the (not) growing of the signal peak. They of course have already made at least a first quick analysis after the complete datasets were available. (It wouldnt make any sense to not look at the data, but to wait half a year to do so !?)

    Seems like they really have seen something and are preparing a clean and crosschecked analysis for a publication…

    By the way, I would like to ask you if you have a link for me where I can see what such a brazil band plot would look like at, lets say 10/fb or more, with a given SM Higgs existence at a certain mass. I am just interested in the peak shapes for diffrent m_H. Thanks a lot for that!

  7. Tony Smith says:

    As to “rumours over at Résonaances that the 5/fb plots show no more than a 2-sigma excess at 120 GeV”
    and
    “both these plots have healthy excesses at around 140 GeV”

    coupled with the statements at HCP11 by Gigi Rolandi
    “ZZ channel alone exclude 108 < MH < 480 GeV" (slide 19)
    "Observed exclusion 95% CL 141-476 GeV" (slide 25)
    "LEE CORRECTED MAX SIGNIFICANCE 1.6 SIGMA" (slide 29)
    "Conclusions: LIttle room left for the SM Higgs !
    114 < mH < 141 GeV at 95% CL" (slide 38)

    does that indicate an emerging CERN consensus for a single SM Higgs at 140 GeV
    interpreted as a simple Standard Model good up to the Planck scale ?

    I have some questions about such a situation:

    1 – Is the Look Elsewhere Effect being used properly with respect to possible Higgs around 200 GeV and 240 GeV ?

    2 – Alexander Rivero over on Resonaances asked:
    "The point of having all the line off by two sigma up to the top quark, can not be a hint of … some special new role for the top."
    Could such a "new role" be Tquarjk condensate as Higgs
    with a 3-state mass system for the Tquark and Higgs ?

    3 – Will such issues be considered carefully at CERN,
    and would any such consideration and discussion be made public ?

    Tony

    • Kea says:

      Yes, Tony, I agree that if anything the data seem to favour your scenario. What if your condensate states were ‘spread out’ over the range? Then we would need a better handle on the non perturbative techniques to fix this ‘background’.

  8. Van says:

    So, it seems to me that there is actually a 2-sigma Higgs signal at ~120 GeV in the current combined plots with 2/fb rather than in the 5/fb plots. If it’s there, there should be a 3-4 sigma excess in the 5/fb plots when they are released.

  9. Philip Gibbs says:

    Tony,

    1 – I don’t think they actually add any LEE to these plots. When they show p-value plots you can take LEE into account, but LEE does not really apply to exclusions anyway since it is expected almost everywhere. There is still a possibility of something at 240 GeV because the exclusion is not strong and there are small excesses. Perhaps there is a scalar boson with smaller cross sections than Higgs, but more likely there are just statistical fluctuations.

    2 – The breadth of the excess is understood in terms of the low energy resolution in the WW channel. I have mentioned it several times here and it was even mentioned in the combo talk today. Of course there could still be some kind of real broad feature but I dont think the present data positively supports it.

    3 – I am sure they will make their conclusions known but less so for internal discussions. Some possibilities will be considered by the theorists but until there is some indication of what the result looks like they can’t say much new.

  10. [...] it agrees closely with what Philip Gibbs put together back in September. For more about this, see here, especially this plot. In the past, many have speculated that the first observation of the Higgs [...]

  11. ohwilleke says:

    IIRC, one reason to have less than great enthusiasm for the 140 GeV signal is that if there was really a SM Higgs at 140 GeV we would expect the signal to be much stronger than the one observed given the quality of the data we have at that mass.

    Hence, the greater focus on a possible excess at ca 120 GeV where the signal, if there is a SM Higgs at that mass, would not be expected to be so great, since the data resolution is lower, and also because the precision electro-weak data are tugging towards a lower end value for the Higgs boson mass.

    But, the golden channel and diphoton data really don’t look like much to write home about in the 120 GeV range right now, and the 140 GeV signal looks awfully wide.

    What kind of theoretical bounds are there on a SM Higgs boson decay width? Generally, higher mass translates to shorter decay widths (e.g. the top quark with 173 GeV is 2.1 GeV; W boson with 81 GeV is 2.3 GeV). Eyeballing the charts, the 140 GeV signals seem to have a width on the order of 5-10 GeV or more.

    In other words, wouldn’t we expect a signal that would become a Higgs boson signal with more data to be pointier?

    • Philip Gibbs says:

      The width of the Higgs is predicted by the standard model for a given mass and increases with mass. I think the width at 140GeV is about 3 GeV. To that you need to add the energy resolution of the detector for leptons which is about 5 GeV I think. The events can therefore easily be spread over 10 GeV.

    • Quark decays are weak, thus quintic in the mass and become cubic after electroweak unification. Neutral bosons are usually cubic, there is not a general rule, but even the Z0 boson seems to match. I think to remember that strong particles go linear. Hmm I did an empirical plot some years ago… Ok, page 3 here http://dftuz.unizar.es/~rivero/research/emdecay.pdf Well, it does not include the Higgs. But the moral is, look at the dimensions of the interaction, and you get a hint of the scaling.

    • Philip Gibbs says:

      According to figure 3b in this paper http://www-library.desy.de/preparch/desy/proc/proc02-02/Proceedings/pl.1a/haber_pr.pdf the width at 140 GeV is much smaller than I thought, so it has to be just the resolution of the detector for these channels that contributes to the width on the plot (and perhaps the binning process)

  12. Ervin Goldfain says:

    Congratulations Phil and keep up the good work!

    Maybe CERN ought to consider bringing you on their staff…

    Cheers,

    Ervin

  13. Tony H says:

    Yes congrats. BTW its been known for some weeks, at least in the circles I inhabit, that your unoffical plot was pretty damn close to the official one

    • Philip Gibbs says:

      Thanks, Tony. I expected it to be OK because I was able to test it on the EPS combination that was never officially released. It can only get better as the amount of data increases.

  14. The large decay width for the state around 140 GeV state suggests that the interactions leading to its decay could be strong interactions. The identification as M_89 neutral pion with mass 139 GeV (different from 144 GeV mass for the charged M_89 pion: a fact that I failed to notice for long!) could make sense. As I proposed earlier, 120 GeV state could correspond to what I would call M_89 spion consisting dominantly(?) of M_89 squark pair.

    Too large mixing in mass squared matrix would make second mass squared eigenvalue negative and one can argue that the state cannot belong to spectrum. This would happen for ordinary light hadrons: the mysterious X and Y bosons would be in the first approximation scharmonium states due to the smaller mixing caused by the small values of alpha_s.

    The really dramatic signature of M_89 physics would be production of jets as multiplet of three from decays of M_89 quarks to ordinary quark and quark pair. M_89 proton would produce nine jets: as Lubos informs nona-jets have been indeed observed and Nanopoulos et al wrote a paper suggesting an explanation in terms of decays if gluino pair: now however 8 would be the minimum jet number, not 9. Two M_89 protons would product 18 jets so that this event would probably revive speculations about mini black-holes at LHC!

    See my blog posting.

  15. [...] porque es similar al que ya obtuvo Philip Gibbs en su blog, como nos comenta en detalle en “New Higgs Combinations Released,” viXra log, Nov. 18, 2011; Philip también se atrevió a combinar LHC+Tevatrón, es decir, [...]

  16. [...] porque es similar al que ya obtuvo Philip Gibbs en su blog, como nos comenta en detalle en “New Higgs Combinations Released,” viXra log, Nov. 18, 2011; Philip también se atrevió a combinar LHC+Tevatrón, es decir, [...]

  17. [...] porque es similar al que ya obtuvo Philip Gibbs en su blog, como nos comenta en detalle en “New Higgs Combinations Released,” viXra log, Nov. 18, 2011; Philip también se atrevió a combinar LHC+Tevatrón, es decir, [...]

  18. Paul Hoiland says:

    Basically, Lattice gauge theory calculations put a top bound of <640 GeV while no new physics below 10^16 GeV limits it to less than 160GeV. So in general, if the event around 140 does turn out to be the Higgs then we could have new physics at less than 10^16 GeV. To me looking at some of the evidence I would say an extension to the SM may be upcoming.

  19. Paul Hoiland says:

    That should read doesn’t instead of does.

  20. anonymous says:

    I have just heard from two CMS physicists that ATLAS and CMS will each give 30 minute talks on the 5/fb Higgs results in two weeks, just after the CERN Council meeting.

  21. [...] that will allow us to anticipate what the eventual result will look like. In fact the method has been shown to be reasonably accurate in the past. I will be doing more combinations right here today. Let me [...]

  22. שטרות says:

    שטרות…

    [...]New Higgs Combinations Released « viXra log[...]…

  23. David says:

    Not sure if this is the right place to say it, but I found Philip Gibb’s 13.12.11 blog extremely lucid, even though I’m essentially an arts person. However, I do remember from grammar school maths how probability curves build up gradually from continually added data, so was able to see how the evidence is accumulating.

    I was directed to the blog by graham d, as he calls himself on the Galaxy Zoo forum, and I can honestly say I followed the argument form start to finish, albeit in three sittings. (like Peter Higgs, I’m an octogenarian). Thank you, Philip Gibbs.

    djj

Follow

Get every new post delivered to your Inbox.

Join 268 other followers

%d bloggers like this: