Moriond Higgs Update

The latest Higgs updates are now being presented at Moriond. CMS have kicked off this morning with a presentation of bosonic decays including WW and ZZ but still not including the important diphoton channel. The full LHC run 1 dataset is now being used including 19.6/fb at 8 TeV

In ZZ they get a very clear signal on the event plot


Higgs Mass from ZZ is 125.8 +- 0.5(stat) +- 0.2(Syst)

The cross section relative to standard model is 0.91 +- 0.27

ATLAS also updated ZZ with 20.7/fb at 8 TeV to produce a similarly impressive plot

MZZATLAS1Higgs mass for ZZ from ATLAS is 124.3 +- 0.6(stat) +- 0.4(syst)

cross-section 1.7 +- 0.5

Unlike CMS, ATLAS have presented their diphoton results giving a mass estimate of 126.8 +- 0.2(stat) +- 0.7(stat)


diphoton cross-section is 1.65 +- 0.24(stat) +- 0.21(syst)

Rumour puts the CMS diphoton excess at 1.0 +- 0.2, to be shown at Moriond QCD next week perhaps (via Jester on twitter)

The excess over the standard model remains high but its significance has not increased because the value has gone down as more data has been added. When we first saw this excess a year ago we were excited that it may be real physics and we hoped that by this time we would have a truely significant effect. This has not happened. We still need to wait for CMS to show their diphoton results before we can draw any conclusion but rumours are that their overexcess has fallen even more dramatically. This means that expectations of significant BSM effects from run 1 are now lower.

CMS also gave us a plot of excesses in the WW channel over the standard model with Higgs at 125 GeV. In other words this plot should only show any excesses attributed to any other Higgs like particles. They said they are now doing this analysis for all the high mass searches which is a good move.

The WW cross-section from CMS is 0.76 +- 0.21


This shows that there are not yet any signs of higher mass Higgs particles as would be expected in Higgs multiplet models. If they exist then they must be quite well decoupled from the observed Higgs boson. The usual combined ZZ channel plot tells a similar story with no significant excesses beyond the known Higgs.


By the way, we are still waiting for the AMS-02 results due out soon. They had hoped to reveal them yesterday at Moriond but approval was not ready in time. Next oportunity could be the Moriond Cosmology conference next week

27 Responses to Moriond Higgs Update

  1. Marc says:

    The uncertainty in the cross section relative to the Standard Model has two sources: the uncertainty in their measurement and the uncertainty in the Standard Model cross section. Does anyone know if both of these included? I recall that the SM cross section is uncertain by 10-20%…

    • Philip Gibbs says:

      Someone asked a related question at the talk but not details were given. Hopefully the analysis reports will say more.

  2. mfrasca says:

    While I keep on saying some peaks above background where they say there is nothing?

    • Philip Gibbs says:

      It’s normal for the line to fluctuate anywhere inside the brazil bands and occasionally outside. If any excesses were real they would grow with more data and appear for both CMS and ATLAS in the same place. Always happy to hear a little speculation though. Are there any particular points you see that you think are interesting?

      • mfrasca says:

        If you look at the ZZ plot, the interesting one for higher masses, there is a clear peak above background at around 200 GeV. A similar peak is also seen on ATLAS graph. But there are more as energy increases even if not so clear. What I can realize is that they have more sophisticated tools than my eyes to check for this.

      • Philip Gibbs says:

        I don’t think you need sophisticated tools beyond what these plots show. All these fluctuations are sadly normal statistics until they fall well outside the yellow bands.

      • mfrasca says:

        Fine. I see.

  3. Marc says:

    Just to clarify. When you say “Rumour puts the CMS diphoton excess at 1.0 +- 0.2, to be shown at Moriond QCD next week perhaps”, you don’t really mean “excess”, do you (if so, then it would be 2.0 +- 0.2 times the SM value).

    • Philip Gibbs says:

      I mean excess over standard model with no Higgs boson at this mass. When I talk about excess over standard model with Higgs boson I usually say over-excess 🙂 Yeah I should be more explicit.

      Anyway, this is just what Jester is saying on twitter.

  4. […] the gamma-gamma channel are not ready yet. Philip Gibbs has very good coverage of the latest news here, including this about […]

  5. Robert L. Oldershaw says:

    It looks ever more likely that Weinberg’s “Nightmare Scenario” will be nature’s verdict on 45 years of “beyond the standard model” speculations.

    Given that the standard model can only be viewed as a provisional heuristic model, …

  6. Tony Smith says:

    mfrasca said “… the [CMS] ZZ plot … there is a clear peak above background at around 200 GeV.
    A similar peak is also seen on ATLAS graph …”.

    Philip Gibbs said “… All these fluctuations are sadly normal statistics until they fall well outside the yellow bands. …”.

    The ZZ to 4l + 2l2tau plot shown does show a peak around 200 GeV (and you can see corresponding high event plots in the basic event histograms for full ZZ to 4l at CMS and ATLAS)
    that peak is inside the yellow band so is not distinguishable from statistical fluctuation at the present level of 25/fb of data.

    That 200 GeV peak is clearly not a simple SM Higgs because its height is only about 20 per cent of SM cross-section.
    it MIGHT be a second Higgs state with lower-than-SM cross section
    determination of that would require a lot more than 25/fb in order to push the green/yellow bands well below the 20 per cent cross-section line.
    When (if) that data becomes available (2016?) you will either see the 200 GeV peak sink well below 20 per cent and go away
    you will see the 200 GeV peak stay around 20 per cent cross-section and the green/yellow bands sinking well below it.

    The apparent possible peaks around 270 GeV and 320 GeV are in the same situation.

    My personal favorite model would be consistent with the 200 GeV and 270 GeV possible peaks being real,
    but it will be at the earliest 2016 before the truth will be known.


    • Philip Gibbs says:

      Can your model predict the actual cross-section? If not you will always be hoping for confirmation at the next update.

      • Tony Smith says:

        My model roughly indicates the cross-section for the 200 and 270 GeV peaks should be about 25 per cent of the full SM cross-section
        it may be that it could be ruled out fairly soon after 2016
        even allowing “rough estimate” to be +/- 10 per cent
        thus allowing something as low as 15 per cent to be observed.

        One reason that I mention this is that Europe is in a period of financial problems and it would be nice to show the politicians a specific thing that could be seen by spending the money to upgrade and do a 2016+ run.
        Without regrard to my model (there are surely others in which the 126 GeV SM Higgs has Little Brothers (little with respect to cross-section, not mass) and other models might go as low as 10 per cent or so for cross-section
        anybody (including politicians) can see the three peaks around 20 per cent (200 GeV, 270 GeV, 320 GeV)
        can therefore be impressed with the importance of finding out which (if any) of them are real down to the level of, say, 10 per cent of the SM Higgs cross-section.


    • 200 Gev=18 Gev x11.11
      270 Gev=18 Gev x 15
      320 Gev=18 Gev x17.77

      126 Gev=18 Gev x 7

  7. Orwin O'Dowd says:

    Meanwhile the muttering about detector issues comes to light with mass-detector interaction at 3-4 sigma, depending on which sigma you use. That’s just what this murky data yields, and no more, which reinforces the impression that there’s something missing, in the line of a Kaluza-Klein phase, or something more contemporary:

    Quantum particle on a Mobius strip:

    Quantum Hamilton-Jacobi with intrinsic curvature:

    The latter article relates quite strongly to Matti Pitkanen’s recent work – the relation is quadratic and could be taken to a Kahler metric – but I broached the possibility of microcurvature with him, and hit a blank. For the record, Epicurus introduced a ‘swerve’ in the path of atoms…

  8. Tienzen (Jeh-Tween) Gong says:

    Combination or contradiction

    The reason for two labs is not for a ball game, a competition. They should be checking up each other. That is, in principle, their data cannot be combined as a proof.

    When two sets of data (from the mutual-checking labs) are comparable, they can be combined as a hint, never as a proof. When two sets of data are contradicting to each other, they must not combine. For example, in the tau-tau channel, “if” Atlas = 0 while CMS = 2, it shows that one is disproving the other while the combination is a prefect “1”.

  9. ohwilleke says:

    It is worth noting that the ratio of the combined experiment cross sections relative to the Standard Model, which controls for uncertainty in Higgs boson production rates, is even closer to the Standard Model expectation than are the individual cross sections.

  10. […] L’incubo continua: Peter Woit e Philip Gibbs. […]

  11. […] dat vervalt in twee Z-bosonen, waargenomen met de CMS-detector. Bron: New Scientist + Vixra + Cosmic […]

  12. Orwin O'Dowd says:

    Hi ohwilleke! Like I said, “if this is a Higgs, we’re seeing double.”

    Just remember this: Tommaso Dorigo and Lubos Motl once got together and agreed that this signal is odd and has just five chi-squared degrees of freedom. Just five. That was historic and that is what we can see of this phenomenon.

    Opt for the system sigmas (that’s excluding beam variance, I take it) and the two profiles are very significantly different. Move to analysis of variance in sigma squared (variance accounted for or strength of correlation) and the system measure can distinguish some eight moments of the beam phase.

    For my money, that’s the Eighfold Way in there, following the analysis of Sir RA Fisher, interaction factors have a group structure, here the symmetry group of quarks. How those protons swerve and collide is going to depend on what the quarks are doing.

    As for the phase involved, you need to place potential energy and the Lande g factor and in the absence of Dirac’s blessed magnetic monopoles, the chiral switch in magnetism as it tunnels through the fermion. So I opt for a complementary mash-up of Mobius, dark matter/longitudional Higgs wave, and Kaluza-Klein phase, which is just not simple, and not going to get credence anytime soon.

    Discovery is typically accidental and i’m just interested in the idea of a biopotential, following Schrodinger in What is Life? Matti Pitkanen opened that trail, and still has the best wish-list in the game, just very poor decidability.

  13. Christian Skyler McClelland says:

    Mr Gibbs,

    I am not quite sure on the data/statistical methods that would be needed/appropriate to properly combine this updated data from the various decay modalities in regards to determining the Higgs mass more exactly. Given the various branching ratios, or other factors, would we expect any specific decay channel to yield a better mass estimate than another? And I am reading these charts correctly, that the Higgs mass is now likely to be closer to 126-127 GeV than the ~125 GeV that was the initial value announced? I ask mostly due to the predicted stability of the Electroweak Vacuum, and the critical threshold between stable and meta-stable up to plank energies for a Higgs mass closer to 127 GeV.

    Thank you for any insight you may provide.

    • Philip Gibbs says:

      Christian, yes some channels give better estimates for the Higgs mass than others. You can crudely combine them by taking an average weighted by the inverse square of the errors, but there is no need here because CMS and ATLAS have already provided more careful combinations. CMS says 125.8 +- 0.6 GeV and ATLAS says 125.5 +- 0.6 , Combining these we are looking at something like 125.6 +- 0.4 GeV.

      When considering the stability of the vacuum you will find that errors in the top mass are now more important than errors in the Higgs mass. There were some talks yesterday at Moriond so have a look at the slides there. We seem to be most likely in the metastable region but this assumes no knew physics up to Plank scale, quite an extrapolation given that we at least expect something new to account for dark matter,

  14. […] κάτι ακόμη πιο ενδιαφέρον»…. Διαβάστε περισσότερα ΕΔΩ και […]

  15. […] ATLAS team has two different computations of the Higgs mass, 124.3 GeV versus 126.8 GeV, which lie outside each other’s error bars (while CMS says 125.8 GeV), and the data has not yet pinned down that […]

  16. It seems fair to say that situation remains the same as before. The two-photon discrepancy is still there although the production rate is now about 1.6 times higher than predicted. The error bars are however getting narrower so that there are excellent reasons to hope/fear that unexpected kind of new physics is trying to tell about itself. Also the masses deduced from gamma pair and Z pair decay widths are slightly different.

    The TGD-based explanation would be in terms of M89 hadron physics, a fractal copy of ordinary hadron physics with 512 times higher overall mass scale. If the pion of this new physics has mass not too far from 125 GeV its decays to gamma and Z pairs would affect the observed decay rates of Higgs to gamma and Z pairs if one assumes just standard model. Fermi anomaly suggests mass of about 135 GeV for the pion of M89 hadron physics. The observations of RHIC and those from proton-heavy nucleus collisions – correlated pairs of charged particles moving in same or opposite directions- could be understood in terms of decays of M89 mesons behaving like hadronic strings in low energies in the relevant energy scale.

    Lubos tells in his recent posting about 3 sigma excess for new charged and neutral particles with mass around 420 GeV. They would be produced as pairs of charged and neutral particle. M89 physics based explanation would be in terms of kaons of M89 hadron physics. The naive scaling by the ratio r=m(π+107)/m(K+107) of masses of ordinary pion and kaon predicts that the M89 pion should have mass m(π+89)= r× 420 GeV. This would give m(π+89)=119 GeV not too far from 125 GeV to affect the apparent decay rates of Higgs to gamma and Z pairs since its width as strongly interacting particle decaying to ordinary quarks and gluons is expected to be large. This mass however deviates from the 135 GeV mass suggested by Fermi data by 18 per cent.

    See my blog posting.

  17. […] the most important plots of the data, see the viXra log, or the slides from the relevant talk at Moriond. For analysis of the agreement with the Standard […]

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