Higgs 2012

2011 lived up to all expectations and hopes for news about the Higgs Boson, but 2012 promises to be it’s crunch year and the excitement is about to begin

LHC startup

The Large Hadron Collider is getting ready to restart operations after the winter shutdown. The first part of the schedule looks like this

As you can see they should be starting full powering tests today which means the complete circuit of magnets should be cooled down to its working temperature of 1.9 Kelvin. However, as you can see in the picture below one of the RF cavities is still at room temperature. I hope it is something that can be sorted soon and they will be on their way.

A summary of how the LHC will run during 2012 can be found in a presentation by Rogelio Garcia . This slide in particlular says it all.

They expect 15/fb to 19/fb integrated luminosity for the whole year. Last year they expected 1/fb and delivered more than 5/fb, but this year we should not expect such a large overshoot. The machine has been brought close to its present operating capabilities and the peak luminosity cannot be pushed much beyond the numbers they are aiming for. The main uncertainty is in how efficiently it will run. last year there were times when it ran smoothly for two weeks and other times when technical issues held up progress for almost as long. The estimates for 2012 are based on the assumption that an average of the two extremes will be seen, but reality may differ. The decision to stick with 50ns at least means that the running will not be two different, although the higher energy and tighter squeeze than last year will be challenging enough.

ICHEP 2012

This year the International Conference for High Energy Physics will be taking place in July in Melbourne. This is the largest meeting on the HEP calendar and it is only held every two years. The experiments will be keen to have something new to say about the Higgs for the occasion so they have asked for 5/fb by June. With the 5/fb already analysed at 7 TeV and another 5/fb at 8 TeV there is a good chance that very convincing evidence for the Higgs will be found. However, I understand that they will not be combining the results at different energies immediately. I will of course perform my usual party trick of combining the plots unofficially to provide combinations over the different energies, channels, and experiments. I expect to be very busy. However, the approximate combinations do not give a definitive answer to how many sigmas of statistical significant have been observed. That will have to wait for official combinations to provide the pvalue plots.

Moriond 2012

Much sooner than ICHEP we will have the Moriond Meetings. This is split into several parts including the Electro-Weak conference and the QCD conference (there is also Theory and Cosmology).  The Higgs reports should be in the electroweak section but from the preliminary programs you can see that there is more about the Higgs at the QCD meeting with Sunday 11th of March being the crunch day. One talk that is so far noticeable by its absence is the ATLAS+CMS Higgs combination. I am led to believe that this will not now be ready in time due to the recent update by CMS. Producing the combinations is a long process and as the amount of data to analyse increases it can only get longer. It is also possible that the difference in position of the peak excess from the two experiments is giving some cause for delay while they improve their calibration methods to see if they can be brought closer together. I would not be surprised if they abandon the full combination and aim to just get decisive results from both individual experiments instead.

Since the LHC has nothing new to show about the Higgs, the interest will be in what the Tevatron can produce from its complete 10/fb of data. In the last month they have published their final results for the diphoton channel (already reported at AP and TRF) here is the plot

This plot tells us almost nothing because the limits are at ten times the expected Higgs cross-section. Any bumps at this level of sensitivity would be almost certainly statistical fluctuations. The Tevatron is not very sensitive in the diphoton channel because Higgs production is lower at the lower energy and because the mass resolution is not very good compared to the LHC. However, the Tevatron does much better in the bb decay channel and their complete combination should be quite good.

The overall expected sensitivity of the Tevatron to a 125 GeV Higgs is 3-sigma we are told. Previous published results reached 2-sigma sensitivity but only a 1-sigma excess was seen, they were probably unlucky. Due to the inferior energy resolution of the Tevatron any excess at the low mass region should also be expected to be quite wide compared to what we have seen recently at the LHC. Here is my simulation of what we might see as the final result.

Hopefully we will see the real deal on 11th March if they are ready in time. If the excess is any bigger than this fake version we should be happy, any less will be a bit disappointing, but it is all down to chance.

17 Responses to Higgs 2012

  1. Ian Sample says:

    I spoke with Sergio Bertolucci about the prospects for Higgs searches at Moriond and Melbourne while at the AAAS in Vancouver last week. He is keen for both Atlas and CMS to put the combination to one side for now and crack on with gathering data independently ahead of Melbourne. The feeling seems to be that a combination at this stage doesn’t make a great deal of sense, and that it may even be an unhelpful thing to do. I can certainly see the logic in grabbing a further 5/fb each in time for Melbourne and combining afterwards. Until then, good luck to the LHC for a smooth 2012 run, and fingers crossed for the Tevatron.

  2. carla says:

    I don’t think 2011 lived up to all expectations at all when you consider their aim was to collect 1/fb of data, hopefully 2-3/fb at the start of the year. If anything it surpassed expectactations hoped for by the end of 2012!

  3. JollyJoker says:

    5+5/fb @ 8 TeV should in itself be enough for a discovery when combined. This means it will be common knowledge the Higgs has been discovered after Melbourne (both experiments should give us near four sigma using only 2012 data) but we’ll still have to wait for some form of combination to get the official announcement.

    Not so unexpected, I guess, but still a bit odd.

  4. Soap_Bubbles says:

    Which particle decays into two (and only two) particles all the time?

    What is the mean lifetime of a electron neutrino?

  5. BJ says:

    Does anyone here know why they chose 8 TeV rather than 8.1 or 7.9? It can’t only be a coincidence that it was a round number last year and this year? Surely there is an optimum, after weighing up all the competing factors, and rounding to the nearest whole number of TeVs is very unlikely to be it. It seems a pointless waste of efficiency to me.

    • Philip Gibbs says:

      It is just a case of how high they dare put it before the calculated risk seems too big. This is an imprecise requirement.

      There was a suggestion that having the ratio of this years energy to last years energy equal to the ratio of Z to W mass would be optimal for some precision measurements. That would require an energy of 7.94 TeV this year. Other than that there is just no reason to not pick round numbers.

  6. Tony Smith says:

    As to “… the ATLAS+CMS Higgs combination … It is … possible that the difference in position of the peak excess from the two experiments is giving some cause for delay while they improve their calibration methods to see if they can be brought closer together. …”:

    Matt Strassler said in his 9 Feb 2012 post “This Week’s Step Forward in the Search for the Higgs Particle” (especially Fig. 4) said:
    “… Note the line … drawn on all three plots dividing events above 125 GeV from events below 125 GeV.
    What you notice is that
    ATLAS’s largest excess (126-127) is at a point where CMS has a deficit,
    and that
    ATLAS has a deficit across some of CMS’s excess.

    If anyone tells you that the case for the Higgs is firm,
    ask them about this discrepancy,
    which … had better go away. …”.

    If pre-Moriond analysis shows that ATLAS and CMS data cancel each other out when combined,
    then will that be presented at Moriond
    with or without explicitly making the obvious conclusions
    that the 125 GeV bumps are probably not a Standard Model Higgs,
    that the Higgs is probably more complicated than a single SM particle (maybe multi-state SM as I prefer or some more exotic thing)?


  7. wl59 says:

    After adjusting the cable in the Neutrino – speed experiment, the ‘significant’ result of a supralightspeed disappeared. Now they could adjust the cable in the 2-gamma-experiment, so that that signal disappear too !! In the other channels is no indication of such a signal, although should be there. And, just at the sides of that signal in 2-gamma, a deficiency, and the integrated (or smoothed total value of events) is zero, or no net production of anything, in the best case a frequence shift of the background, by any known or unknown reason.

  8. Mike says:

    The energy in a scalar standing wave is E = (A^2)vsf, where A is the amplitude of the wave, v = velocity, s = mass-density of the medium and f = frequency of the wave. Also, E = hf, so setting enery equal in both formulas give h = (A^2)vs , which after substituting A = Planck’s length, v = c and s = mass-density of the universe (mass-universe = 10^53 kg / radius-universe = 10^26 m), h is found to be equal to 6.62 x 10-34 J-sec. The increments in energy of Planck’s constant are due to increments in amplitude of the wave (increments of Planck’s length, nA), and the energy of every particle thereafter is found as E = ((nA)^2)vsf, where f = c/(n*radius universe) for a standing wave so substiting for f, E = n(A^2)(Mass-universe*c^2/(radius-universe^2)).

    Based on this formula, a Higgs boson at 125 Gev would correspond to n = 8.5 x 10^43 (not an integer, but with these numbers it’s hard to be accurate except for A and the speed of light). A more interesting test is to take the ratio of the Higgs energy to the electron rest-energy to eliminate the cosmological variables and then it’s left as: 125.706 Gev / 0.511 Mev = n-Higgs / n-electron = 246000. To get an integer value for the Higgs means it’s energy would be close to125.706 GeV

  9. wl59 says:

    It don’t looks good fir Higgs. The newest results for the W and for the top Quark don’t rule out yet its mass in the aerea which remains by LHC, but its most probable mass would be something like 90.


  10. ondra says:

    Could the upcoming results of Bd/Bs -> mu mu searches in CMS and ATLAS, and hopefully LHCb, somehow significantly constrain 125 Higgs in terms of SM or SUSY signal?
    Thanks in advance.

  11. Nick says:

    They need to shut it off for the entire month of December this year so they don’t tempt the Mayan end of the world prophecy.

    • Philip Gibbs says:

      They usually shut it down in December but this year they will keep it running just to prove what nonsense that Mayan thing is. In any case if there were anything in prophesies any action to prevent it would be futile. (I know you are probably joking but so am I and there is no telling with blog comments)

  12. carla says:

    Do you know the reason for the 2012 schedule being available to people with a Cern password only?

  13. carla says:

    They’ve mangaged a Beta*=0.8m!! and later on 0.6m!!!! so things looking good so far. Note the exclamation marks are theirs and not mine, lol

    • Philip Gibbs says:

      Its worth the exclamation marks. Last year they ended at beta* = 1.0m so this could increase luminosity by 60% I just hope they can gets lots of good long runs

%d bloggers like this: