LHC has delivered 2/fb to ATLAS

The Large Hadron Collider has delivered 2 inverse femtobarns of integrated luminosity to ATLAS. This means that the experiments now have nearly twice the amounts of data used at the recent EPS-HEP conference in Grenoble. The additional statistics this provides would make significant advance in the search for the Higgs boson.

In the recent results the collaborations working on the CMS and ATLAS detectors saw tantalising hints of an excess at around 140 GeV indicating the possible presence of the long sought after boson, but the signal was not entirely consistent with the standard model expectations or the electroweak fits. A low mass Higgs multiplet may be a better match. At the Lepton-Photon conference in Mumbai this month they will show the full combination of the data analysed so far, with the likelihood that it will strengthen the signal seen separately by the two experiments.

To get a better handle on what they are really seeing they will need to add more data but we do not yet know when they will produce a new update with more than 2/fb per experiment. This would be enough to make a significant difference.

As ATLAS passes the 2/fb mark for integrated luminosity delivered over 2010 and 2011, this is just the beginning of a series of 2/fb  milestones because not everyone agrees which figure is most significant. The detectors only record 90% to 95% of the data delivered and some people disregard the 48/pb delivered in 2010. The recorded luminosity for ATLAS in 2011 is around 1.9/fb but CMS has fallen behind with now only 1.75/fb recorded. Over the next few days all the figures will pass 2/fb but at viXra we like to start the celebrations as early as possible.

Update 6-Aug-2011: A record run lasting 26 hours has delivered over 100/pb to ATLAS and just slightly less to CMS. This takes ATLAS to over 2/pb recorded including 2010 and 2011 data. We have seen 370/pb delivered in just 5 days. In April I predicted that they would reach 70/pb per day. It has taken two months longer than I thought but they got there and still have the potential to go higher.

With this rate of delivery they should be able to reach 3/fb before start of the next break for development and maintenance on the 24th August. Can they still get 10/fb this year? It would require doubling the luminosity for the whole of last eight week run after the stop. That’s a stretch but not quite impossible.


12 Responses to LHC has delivered 2/fb to ATLAS

  1. josch222 says:

    Hi,
    I don’t think CMS has lost that much of the int. lumi.
    From https://lhc-statistics.web.cern.ch/LHC-Statistics/
    they lost 0.08 fb^-1 in the last 10 fills compared to Atlas.
    The data of the last 100 fills from https://j2eeps.cern.ch/test-supertable/
    shows that the difference should be even less. But that data is somewhat strange, for fill 1999 it shows the int. lumi nearly the same as in Atlas
    but in the “last 10 fills” – table there is a lack of 0.03 fb^-1
    In the plots from http://lpc.web.cern.ch/lpc/lumiplots.htm CMS-data seems to be a few fills behind most of the time.
    A bit confusing with all this different data sources.

  2. Philip Gibbs says:

    There are different numbers floating around but the plot at https://lhc-statistics.web.cern.ch/LHC-Statistics/# puts CMS 0.078/fb behind on delivered luminosity overall.

    ATLAS are showing 1.93/fb recorded while CMS are showing only 1.76/fb recorded, so they are about 10% behind on recorded luminosity.

  3. josch222 says:

    Now I got it where the “recorded” data comes from, you took it from the collaborations web appearances.

  4. paolo says:

    do not be distracted by nice LHC performance and abandon every hope
    for anything unusual
    see paper arXiv:1108.1183
    how depressing and ‘nightmarish’
    (‘nightmare scenario’ is even mentioned in this paper)

    • Bill K says:

      As nightmare scenarios go, this one’s impressive. First, for the use of the term ‘attobarn’. (Which I take it is not a German highway!) Second for the mention of particles with width exceeding 0.5 TeV. This paper, if correct, belies the oft-repeated statement that the LHC must find the cause of EWSB – it could be invisible, or out of reach.

    • Philip Gibbs says:

      Where did anyone say that the LHC must find the cause of EWSB?

      What people should say is that it will either find the Higgs boson or rule it out. If it rules it out then it has a good chance to find an alternative cause but since we don’t know for sure what that could be it would be rash to say that the LHC will succeed.

  5. Bill K says:

    You’re kidding! Well, quoting from a typical source:

    Something must happen in Vector Boson Scattering (VBS) at the Large Hadron Collider (LHC)
    Naive Standard Model: Scattering of longitudinal W’s rises in finitely
    But: optical theorem limits partial wave amplitudes
    Perturbation theory violates unitarity above s = √ 1.2TeV
    WW scattering at LHC (√spp =14 TeV) reaches this limit

    Note he never mentions a specific need for the Higgs boson, just says “something must happen” in a region accessible to the LHC. One could argue that this guy didn’t know what he was talking about, but many other people have said the same thing. So maybe none of them know what they’re talking about, or maybe I’m misunderstanding them all. Maybe the reference to perturbation theory is the catch. Or maybe the “something” that saves unitarity at LHC energies only postpones the crisis, and is not the same something that later causes EWSB.

    Glancing over the present paper, I get the impression that the main author Adam Falkowski does know what he is talking about.

    • Philip Gibbs says:

      I think that saying something must happen at that energy scale is different from saying that something must happen that the LHC must be able to detect. I would hope that with 3000/fb not much would escape it but there are limits to how well the background can be modeled so it is not certain.

  6. algernon says:

    I just hope they’re gonna take the opportunity offered by the MD/TS starting on 8/24 and begin work on an update of their Higgs searches in all of the channels… they could deliver updated results in the first half of October featuring 2.5-3/fb per detector.

    That’d be a nice way to bridge the gap till the winter conferences 😉

  7. carla says:

    They’ve increased the bunch intensity, yet the peak luminosity remains around 2/nb/s. I thought they might be doing some sort of luminosity leveling, but the beam llifetime remains at around 14 hours

  8. Tony Smith says:

    Mumbai Lepton-Photon 2011 (22-27 August) program shows
    Higgs Physics from 10:45 to 12:15 on Monday 22 August
    and
    lists 4 talks about Higgs
    Higgs Theory: A. Djouadi, Orsay
    Higgs Searches at ATLAS: Aleandro Nisati, Rome
    Higgs Searches at CMS: Vivek Sharma, UC San Diego
    Higgs Searches at Tevatron: Marco Verzocchi, FNAL

    Since the Higgs talks are all 2 days before to the LHC break on 24 August,
    is it unlikely that analysis of 2/fb or more would be announced there ?

    If 3/fb were to be collected by the LHC break on 24 August,
    when would analysis of it likely be announced ?

    Tony

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