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    LHC About to Reach The 1/fb Goal
    By Tommaso Dorigo | June 14th 2011 07:30 AM | 22 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 LHC has been running very well in the last few weeks, and I can announce, with some anticipation, that the 1-inverse-femtobarn line will be crossed in the next few days. Check it out in the figure below, which shows, together with the delivered luminosity (red line), the one acquired by the CMS experiment (that is, the part acquired with CMS fully operational).

    The total bounty available before the next shutdown (end of June) is probably going to amount to 1.3-1.4/fb. Expect exciting new results by ATLAS and CMS for the summer 2011 conferences!

    Comments

    Since that plot was last updated more than 60/pb have been delivered, and it does not include the 47/pb from 2010. Passing the 1/fb mark was yesterdays news and was confirmed in today's morning report http://lhc-commissioning.web.cern.ch/lhc-commissioning/news-2011/present...

    That's the delivered luminosity, as you can see on the last slide, the (more important) recorded luminosity did not yet reach 1 fb-1, which is shown on the last slide of the presentation you linked to. This is expected to happen today

    June shutdown? I thought it is going until the end of 2012. And when are these conferences you speak of with such ill warranted excitement? I can make a solid prediction on the new "results." WE FOUND NOTHING NEW.

    Every few weeks (was 6 but now seems to be every 8weeks or so) the LHC goes into a period of MD followed by a TS (machine development and a technical stop) -- fancy terms for proactive maintenance and calibration on each of the experiments etc.

    While the most likely outcome of the various summer conferences will be what you say above, that is still significant in and of itself (duh!) Like Tommaso mentioned in a previous post, we're about to exclude a very large range of masses that the Higgs could be hiding within (validating Tevatron's results and many other measurements as well). Additionally there will be countless other refinements and new ranges defined for 'exotic' processes like SUSY at various masses.

    Tommaso, at what point will you (personally and off the official record :)) begin to get worried about the Higgs just not existing. It seems that with a combined CMS+Atlas search with all of 2011 data this Decemeber (possibly close to 6fb-1 combined) that the Higgs may just not be there...

    dorigo
    Dear Anon,

    before I start to worry (or rather, get excited about) that the Higgs boson does not exist we must have excluded at 99% the full relevant mass region (ie. below 200 GeV). I think what I would start to believe next is that the Higgs is hiding in some unobservable decay mode, such as gluon pairs.

    Cheers,
    T.
    Daniel de França MTd2

    Tommaso,
    and why do you give Higgs preference to be hidden in gluon pair decay mode?
    Hi Tommaso,

    what if we start by seeing nothing above 130 GeV? Wouldn't that be exciting news already?
    It is my understanding that evidence of a "light" Higgs would also be (indirect) evidence of new physics to come, is that correct? (I've read contradicting opinions about that, just wanted to hear your views)

    dorigo
    Hi Daniel,

    the H->gg is just an idea... It would be a way for the Higgs to hide indefinitely from our view.

    Cheers,
    T.
    Daniel de França MTd2
    How would that idea work? Can you show us any paper about that?
    dorigo
    Uh... No. With many heavy quark generations, the branching fraction of H to gluon pairs through triangle loops would saturate to a value very close to 100% (other decays involving photon pairs or other boson pairs). Of course the production rate would also increase, but it might make the Higgs much harder to detect.

    I will look around for papers discussing this... The only input I have is an old book by Okun!

    Cheers,
    T.
    dorigo
    Ok, for instance in
    http://arxiv.org/PS_cache/arxiv/pdf/1102/1102.2920v1.pdf ...

    Cheers,
    T.
    Daniel de França MTd2
    You mean, for that to work, you'd have to increase the number of generations?
    dorigo
    Well, yes... Bounds on additional generations are based on a number of assumptions which need not hold.
    Cheers,
    T.

    Cheers,
    T.
    dorigo
    Hmm, no, I deny that a light higgs is an indication of anything, unless you already have a prior bias in favour of MSSM and other Supersymmetric theories.

    Best,
    T.
    ... and why would H->gg not be visible as a nice dijet resonance?

    Because of the overwhelming dijet QCD background. That's one reason why we know, for instance, that the claims this year of new bumps at around 115 or 150 GeV couldn't be the SM Higgs. Wayyy too many events.

    Seeing nothing may be significant to you. But it will have a very different significance to those providing funds for your circus. Like Heuer said: seeing nothing is not an option. Seriously. In 3-4 years or less you'd better detect something or you will have killed high energy physics for a long time if not forever. No amount of positive spin will save you given the current global finances and some other factors. Like CERN's numerous list of failures and delays. Personally, I hope you find something.

    Which circus?

    Anonymous above writes:

    "And when are these conferences you speak of with such ill warranted excitement? I can make a solid prediction on the new "results." WE FOUND NOTHING NEW."

    Null results may not meet expectations of many but are still the voice of Nature. Not finding Higgs, SUSY or new generations of heavy states is also forward progress as it forces us to go back to square one and rethink the foundations.

    Cheers,

    Ervin

    Hank
    The 1% of people who understand the value of null results will be outvoted by the many others who see that they could have spent billions less to have something not exist no one knew existed anyway.

    Big HEP projects are already dead in the US thanks to overblown hyperbole (and understating cost) of the SSC and finding a null result in Europe would also be bad for the ILC that will be needed to figure out anything the LHC would find anyway.    That leaves us with China to fund the next big project if Europe passes, and they won't even let people access Facebook so they sure won't let Tommaso write a blog from there.
    Why are you people talking about not seeing anything? If the Higgs is at 120 GeV (say) you'll have to wait. If SUSY is around the corner slightly heavier than 1 TeV, you'll have to wait. Be patient and stop complaining, you bunch of mental teenagers.