LHC Status and Plans

The Heavy Ion runs are continuing at the Large Hadron Collider with 69 bunches per beam being circulated. Next they will increase to 121 bunches. Watching live collisions is very impressive when these runs are active. The live 3D CMS display is especially worth looking at but you need to keep refreshing the image.

Meanwhile plans for next year are beginning to take shape and a presentation by Mike Lamont yesterday gave some details.  Although no definite decisions have been taken, they are now talking in terms of a slight energy increase to 4 TeV per beam. The amount of luminosity collected will depend on the exact parameters used and how efficiently the collider runs. Using “reasonable” numbers (936 bunches, beta* = 2.5m, 120 billion protons per bunch, 3 micron emittance) it should be possible to collect about 2.2/fb, more than twice the target value. With “Ultimate” numbers (1400 bunches, beta* = 2m, 150 billion protons per bunch, 2.5 micron emittance) , it may be possible to reach 7.6/fb next year. Reality is likely to be somewhere between these two numbers.

Update (14-Nov-2010): Overnight there was a clean run using 121 bunches that ran for eight hours. Here is a clip showing the entire run as seen from CMS

9 Responses to LHC Status and Plans

  1. Bornerdogge says:

    Here’s an “auto-refreshing” event display for CMS: http://cms.web.cern.ch/cms/FireworksLive.html

    Not exactly the same, but still impressive when the tracker is turned on!

    • Philip Gibbs says:

      The ATLAS display at http://atlas-live.cern.ch/ is good too. The ALICE live public display does not seem to work so well, but they have done some great animations and pictures.

      • Luboš Motl says:

        Did you see? ATLAS live just created an excited string. And its shape imprinted the sentence “String theory is the language in which God wrote the world” into the ATLAS detector. Well, let’s hope that they won’t censor this story… ;-)

      • Philip Gibbs says:

        I seem to have missed it. I hope you got a screen shot. From now on I will spend more time watching the live displays :)

  2. Bill K says:

    Certainly good news! Both the increased energy and the increased luminosity target will bring the Higgs that much closer. And in our lifetime! The plan has “always been” (since the accident) to start at 3.5 TeV and then go to 4.0 or 4.5 if possible. Question: is it worth it?

    The danger point is believed to be at 5 TeV, so 4.0 seems safe. But the LHC has only been commissioned for 3.5, so an energy increase will require another round of hardware commissioning, which they have allowed for in the schedule, most of February, with beams to start in March. What do we gain by this?

    Two things. Much increased sensitivity for heavier particles (whichever heavier particles you happen to believe in, plus also heavier Higgs.) Also somewhat larger cross-section for Higgs production in general.

    Especially if the luminosity can also be increased to the levels they indicate. A recent analysis from ATLAS concludes: “If 2/fb at 8 TeV is collected, and expected or planned analysis improvements are implemented, then the median exclusion region covers a range of Higgs boson masses from 114 to well over 500 GeV.”

    • Philip Gibbs says:

      Good points. These expectations for next year should really make an extension of the Tevatron a non-starter. The LHC will be well ahead of them even before the next shutdown.

      One point though, I think the danger point was 5 TeV in 2008 but that was because of one bad splice. The tests they did on other splices and other potential failure points suggests that the danger point is now at about 6.5 TeV

    • Bill K says:

      I don’t know, it’s all a big gamble and there seems to be a variety of opinions, even among those directly involved. This report from the 2010 Chamonix meeting: http://tinyurl.com/yezbg6f was unequivocal: “5 TeV running is excluded without major repairs.”

  3. Anders Lund says:

    I wonder if there is something in the data gathered so far, that makes them go to 4TeV, maybe a heavy SUSY particle which has a much larger cross section at 4TeV. Could that be likely?

    • Philip Gibbs says:

      They were hinting they might increase the energy next year even before they had gathered any data, but you never know…

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