Higgs Live Blogging 4 - Big Expectations
    By Tommaso Dorigo | July 4th 2012 12:39 AM | 6 comments | Print | E-mail | Track Comments
    About Tommaso

    I am an experimental particle physicist working with the CMS experiment at CERN. In my spare time I play chess, abuse the piano, and aim my dobson...

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    [ The first three entries of this live blogging series are available here (part 1) and here (part 2) and here (part 3)]

    7.30 AM People have started flowing in the Main Auditorium. It seems things worked out well in the end - I can detect no drama. I must tell you that I have decided to use a more comfortable position to blog about the event: I have abandoned the idea of getting a lousy seat in the auditorium, with bad internet connection and no power outlet fit for my plug (dommage), and moved to one of the conference rooms of Building 40, the headquarters of ATLAS and CMS. From here I have all the benefits, except the one of breathing the very same air as the five theorists who conceived the Higgs field in the first place.

    7.40 AM The name of the event is "Higgs search update". Just another sign that CERN is downplaying this as much as possible. I wonder if this is actually a cunning move to raise even more interest in the press... I recall that CERN handled exceptionally well the September 10 2009 event, when the startup of LHC made headlines around the world. In a way it would make sense: keep a low profile while everybody claims you are going to make a huge announcement, to hold everybody's breath until the end.
    Or could it be that somebody high-up in the CERN management has bet a large sum against the Higgs discovery being published in 2012 ? ;-) Nah, I know people would want to drag me in front of an execution ploton if I said that! On the other hand, a colleague yesterday did suggest that some less than noble reason might be involved in CERN feet-dragging attitude. We'll see...

    7.50 AM The Main Auditorium, I am told, holds 340 seats. Now it appears that they will not allow more people to get in and sit in the aisles, so apparently I did the right thing in choosing a secondary location - I would not have made it in. But in any case, the main issue was the wireless...

    8 AM Free discussions are going on leisurely in the conference room I am seated in. It is a relaxed atmosphere which I much prefer to the tension of the main auditorium, where this kind of discussions are not taking place. People here seem to agree that the word "discovery" should be used, and that it is actually silly not to use it.

    8.10 AM so about the fundamental bits... I realize I had promised a few already in the former post. Let me make a quick list for those of you who have not followed the discussion on the Higgs boson in the recent pat here...

    - The seminars will explain a bit in general all the details of the experimental apparata, the fundamental bits on the Higgs boson phenomenology, and the data taking. Do not expect them to focus immediately on the Higgs search: both CMS (who will go first) and ATLAS (second) will need to introduce their searches by explaining just how good their detectors are.

    - If you follow the live stream, you will see first of all lots of plots showing how the experiments detect their electrons, photons, muons, and jets. Don't try to grasp everything - it is almost impossible for an outsider. The experiment spokespersons know that the audience in the Main Auditorium will include ambassadors and politicians and people who know nothing about the whole thing, but they are determined to drop them out very early on. No attempt will be made at explaining things at a laymen level in the seminars: these are scientific seminars designed to answer the questions of the scientific community, not

    - You will hear the search channels described one by one, but not in detail - don't forget that this event is also meant to be the open event of ICHEP, which takes place in Melbourne this week. In Melbourne the details of all searches of the Higgs boson will be presented in separate talks, and so the experiments will only give the results of the various search channels, with little detail. In any case it would be impossible to be detailed, since both CMS and ATLAS have just 45 minutes for the whole thing.


    Dozens of hardcore fans of particle physics also open a chat box and will chat during the seminar in one hour - it's already taking place now. Open: 

    One may also open the chat box in a separate window (link beneath the box).
    What does it mean if each experiment has found a Higgs at different masses (like 124 and 126)? Would 1 of them have to be an error?

    Measurements come with an error HR, otherwise they are utterly meaningless.
    124 and 126 mean zero without an error. In any case it is 125.3+-0.6 for CMS and 126.something, with a larger error, for ATLAS. They are perfectly compatible.
    Dear Tommaso, so it was discovered a usual SM Higgs? What about the compatibility with MSSM or NMSSM? Thanks

    Dear oi,

    the signal is fully compatible with the one expected for a SM HIggs, but it will take a long time to be sure. As for SUSY, there are many different possibilities so one can always find a theory which fits the data better, but as I said if the original hypothesis is good I do not see much meaning in alternative hypotheses. In any case any theory with a increased coupling to photons might be favoured, with the caveats that the production occurs via loops of fermions, so one must balance the various components. A similar attempt has already been done by CMS, who produced a figure with a fit to "coupling modifiers" cv and cf. The best fit wants cf to be 0.5 or so, and cv about 1. But the SM (1,1) is less than 2 sigma away. You can find that figure in my posting on yesterday's CMS seminar.
    Do you know what Stephen Wolfram of the Mathematica fame has to say about the Higgs boson discovery, the Higgs mechanism as an idea, and his decades in particle physics and what it means in general?