7 TeV collisions tonight…


… if all goes well. The LHC has been circulating two 3.5 TeV beams off and on for the past week, and tonight they plan to turn off the separators keeping them apart. We should then see the first 7 TeV collisions ever produced in a laboratory.  If there are any undiscovered particles with a mass in the new energy range that is being opened up, it would now become possible for them to be spontaneously produced in a detector where we can see them (as opposed to cosmic ray air showers).  Our view of particle physics is about to become three and a half times larger than it has ever been.

The plan at first is just to let the beams collide without focusing them, so the luminosity will be low, and the rate at which new particles could be produced would be correspondingly low.  As time goes on, the beams will be focused and the intensity will be raised, which increases the rate of collisions and therefore the probability of seeing new stuff.  This is the beginning of an 18–24 month period of continuous data-taking and open-ended exploration.

Tonight I’ll be following this from the Fermilab control room (the LHC is in Switzerland— this is a remote control room).  I’ll post any interesting updates as comments to this article (they won’t come up in RSS feeds).  Here are other sources of information, all more direct than this blog (I mostly try to avoid repeating them):

  • CERN twitter (from the LHC control room)
  • ATLAS control room blog
  • CMS e-commentary
  • LHC page 1: live update of machine status.  When I last looked, the energy was 3.5 TeV and the beam intensities were 1.5e10 (higher than the past few weeks).  The red and blue lines are intensities of the clockwise and counter-clockwise beams versus time.
  • CMS data aquisition: live update of CMS data collection.  The main plot is data accumulated versus time; it’s a constant slope for cosmic rays (no LHC beam), but could jump up if we get a lot of events from the beams.
  • CMS event display: pictures of the events as we see them (in three projections: face-on, side view, and 3D).  Yellow lines are particle trajectories, red and blue bars are calorimeter energy deposits.  If a yellow line goes beyond the calorimeters, it’s a muon!  Right now, I think it’s re-playing events from the low-energy collisions of 2009; that will change sometime tonight.

In my timezone, the sun is setting. Happy Passover!


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6 Responses to “7 TeV collisions tonight…”

  1. Jim Pivarski Says:

    I’d just like to point out one more thing: LHC page 1 currently says “Proton Physics: Stable Beams” with all status flags green. I’ve never seen that before. The message “enjoy .. will keep till ~2:30” refers to 2:30 AM at CERN, which is in 25 minutes.

  2. Jim Pivarski Says:

    The CMS Event Display is up to date. What appears there now is currently happening.

  3. Jim Pivarski Says:

    After two lost beams, each costing 1.5 hours, the third time was successful and now we’ve gone into stable beams! The CMS Event Displays are live, showing real proton collisions. The cumulative plots are also looking very good. Keep reloading the Event Display page to see 7 TeV proton collisions!

    If you’re reading this hours later, after this first fill is over, you can see some nice pictures on the CMS e-commentary page. Good night!

  4. John Armstrong Says:

    I’ll post any interesting updates as comments to this article (they won’t come up in RSS feeds).

    There’s a link right at the bottom of the page to


  5. Michael Schmitt Says:

    Hi Jim, glad to see you’re managing to blog a bit again – despite how busy you are on CMS! This is a great time to tell the world about our experiment and to celebrate the first major LHC success. More will surely follow…

  6. black hole of genf Says:

    And I was expecting the black hole to appear.

    But wait, it exists on the net 😛

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