LHC passes 1/fb/year peak luminosity

After yesterday’s great run at the Large Hadron Collider that CERN DG Rolf Heuer described in management speak as “a game-changing fill“, they have done it again today. With 104 bunches and over 10 trillion protons per beam the peak luminosity has been pushed up to 36/μb/s which nearly doubles the record for the second day in a row. This is also 1.13/fb/year which is significant because their target is to collect 1/fb during 2012. Of course they will need to go higher to reach that target because the peak luminosity cannot be maintained continuously, but another factor of 5 or so should suffice and that is now looking quite achievable.

With just a few weeks left of proton physics this year, the recent pace of development has been faster than at any point since they first started to ramp up the luminosity.  If this run continues to a healthy completion tomorrow morning they should be able to collect 1/pb in a single run. It is only a few weeks since they celebrated collecting 1/pb in total.

Update: The fill did indeed surpass 1/pb for CMS, LHCb and ATLAS taking the total delivered past 5/pb

Update (30.sep.2010): There was a short run last night with 152 bunches reaching a new record luminosity of about 48/μb/s. This is nearly half way to the target luminosity for 2010 but hopefully the second half will be much quicker than the first.

11 Responses to LHC passes 1/fb/year peak luminosity

  1. Luboš Motl says:

    Cool, I am convinced that a factor of 5 will be added, given your previously hinted plans for a factor of 10 within October…

  2. Philip Gibbs says:

    They have already gained a factor of 3.6 in the last few days. With fills to 384 bunches they have scope to increase by another factor of 4 so they should exceed their target of 100/μb/s by at least 40%.

    If things go really well they might try squeezing further to get near 200/μb/s which should be enough to comfortably meet the 1/fb target next year. They also have the option to decrease the bunch spacing to 75ns or even 50ns to give a further factor of 2 or 3, but that would take too long to set up for this year. This is all based on Steve Myers off-the-cuff remarks last week, so it is not part of the current plan, but the potential is there.

  3. Luboš Motl says:

    Thanks. I hope that October will really look more active to daily observers than September. 😉

    By the way, atlas.ch says 362 billion collisions in total so far. At 1 trillion collisions – which could be in a week or two, right? – pretty believable points of the supersymmetry may display signals.

    • Bill K says:


      Could you explain how that works? I’ve heard people say that finding supersymmetry may come rather quickly, but also some comments that to the contrary it will not be so easy.
      The initial collision makes squarks and/or gluinos, which decay into jets, lepton-antilepton pairs, and LSPs that carry off missing energy. But since the LSPs must occur in pairs, there will not be a peak in energy but rather a very broad enhancement to the background. You must therefore have a good understanding of the background before you can say whether they are there or not. One source indicated that about 500/pb would be necessary to resolve the question.

      • Luboš Motl says:

        Dear Bill, look e.g. at these two recent papers:


        They say that SUSY may be seen already after 100/pb or even 10/pb of data; the latter is equal to what has been accumulated by ATLAS and CMS combined. The more ambitious, 10/pb claim is mostly based on decays of the lightest colored superpartners – that surprisingly often involve highly multi-lepton decays.

        The 100/pb SUSY discovery paper shows that each of the models they try is discoverable at 5-sigma in one of the channels, and I guess that they’re generally similar – morally – to the previous paper I mentioned.

        I think that what you wrote – and some people write and say the same things – means that you only looked into one (wrong) channels, found that it is not good enough to discover SUSY, and generalized it to all channels – which is a fallacious reasoning.

        There are probably other papers that claim methods to find SUSY in these ways, but to say the least, if you want to insist on your claim, you would have to show what’s wrong with both papers above.


      • Lawrence B. Crowell says:

        I have only read part of the fist paper, and looked at the graphs. I must confess I find these types of papers very difficult to read. From what I see it appears that gluoino and chargino production may exist in jets. These in the .4-2TeV mass range should exist. I am not sure the authors in any way claim these data exist now.

      • Luboš Motl says:

        I probably don’t understand you at all, Lawrence. Of course that they don’t claim that “the data” that prove supersymmetry out of 100/pb “exist now”. 100/pb haven’t yet been collected.

        They say that once they collected, and if SUSY is right at one of the general representative points they study, it will be possible to deduce it from the data.

        The second paper talks about as little as 10/pb which will be collected in a week but it will take some time to send the data through the communication-and-analysis filters to see whether it’s there.

        I don’t know what to do with Bill’s good point about the continuity of the spectrum of decaying pairs. Do they say that they will be able to read masses from the events?

      • Lawrence B. Crowell says:

        What you indicate is largely what I gleened from this paper. The paper was about raising estimates given SUSY production.

      • Luboš Motl says:

        Apologies but I don’t understand: what else should have been the paper be about?

  4. Philip Gibbs says:

    Next step could be 150ns_152b_140_16_140_8bpi, another 50% increase. A trillion collisions should not take long at this rate, but problems such as cryo loss can cause several days of delays at any time. Last week they were aiming for 50/pb by end of October, so 10 times current total!

  5. […] "LHC Update," Not Even Wrong, September 24th, 2010]. Ver también Philip Gibbs, “LHC passes 1/fb/year peak luminosity,” viXra log, September 25, […]

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