LHC Updates: Watch this Space


Hi everyone,

I’d like to try something unusually blog-like on The Everything Seminar. As some of you know, the Large Hadron Collider (LHC) will come online sometime this fall to answer basic questions in particle physics, and some of these questions have been waiting for 20, 30, or even 40 years (the Higgs mechanism was proposed in 1964).  My day-job is to commission the Compact Muon Solenoid (CMS) experiment, one of the two general-purpose particle detectors on the ring (the other is ATLAS), “general-purpose” meaning that it is designed for surprises, a discovery machine.  Since it seems that I won’t be interrupting any math conversations, I’d like to give short updates on what’s going on and when things will be working, and maybe correct some newspapers.  I’ll be spending some of the first data runs in the CMS Centre at CERN, and can relay a little bit of what it’s like in the first days of a new particle physics experiment.

This morning, I discovered LHCCountdown.com, which says that the LHC will “start” in two days and several hours.  It’s unclear which milestone to take as the actual “start” of the LHC— the first beam in the machine, the first beam to go all the way around the machine, the first counter-rotating beams, the first collisions, the first collisions at full energy (whether you take that to be 10 TeV or 14 TeV)— but for any reasonable definition, the LHC will not “start” on Thursday.  It isn’t even possible to run a beam around the full circle until the experiments are completely closed, which will happen in the last week of August for CMS.  The Official LHC start-date is September 2, 2008, though it’s not clear that this will correspond to any specific milestone.  Certainly not colliding beams.

The problem, other than a litany of specific technical issues that all had to be corrected and the unyielding fact that schedules slip, is that the people who are building and commissioning the LHC are the same people who make the schedules.  I’ve even seen schedules presented with the caveat, “This is wrong, but we don’t want to divert people to update it.”  So even the experimenters are guessing at the start dates.  The concensus of rumors has first collisions happening sometime in October, a total integrated luminosity (amount of data) for 2008 of about 10 pb-1, a collision energy of 10 TeV (rather than the design 14 TeV), and then a shut-down at the end of the year to allow the beam and the detectors to fix everything we found out was wrong in the first few months.

This is modest.  It won’t be the final word on anything: most predictions for the LHC require more data than 10 pb-1 to be distinguished from familiar Standard Model signals.  But if there are any “obvious” new physics signals, like excessive decays to easily-identified electrons or muons, or better yet, resonances that form spikes or cascade decays that form triangular edges on top of the smooth Standard Model distributions, we’ll see them right away.  The 2008 run represents a factor of 5 increase in energy above the Tevatron, so anything that was just out of reach before will now be in plain view, as long as the signal we’re considering obviously can’t be produced by the Standard Model or a detector malfunction.

For my part, I’m studying high-energy muons.  Every few weeks now, we read in about a week’s worth of cosmic ray muon data and I use them to study the alignment of the detectors.  (Super-precise position measurements don’t do you any good if you don’t know where the measuring devices are!)  Meanwhile, our muon detectors are moved every time someone needs to install or wire something up in the core of CMS, so the algorithms that were designed to identify misalignments on the micron-to-millimeter scale first need to search for the detectors, sometimes meters from their design positions.  And oh yeah, these detectors are five stories tall.

There are some nice pictures in the Boston Globe.  More later.


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15 Responses to “LHC Updates: Watch this Space”

  1. John Armstrong Says:

    Welcome! I’m sure you’ll find a receptive audience. I don’t know a mathematician who isn’t at least curious about the LHC, even if it’s not in his bailiwick. I, for one, am looking forward to hearing from the horse’s mouth.

  2. Charles Says:

    This has been one of those weeks where I regret having stopped studying physics as intently as I did for awhile as an undergrad, with ICHEP in Philly this year. Definitely interested in finding out how things go at LHC.

  3. Greg Muller Says:

    Oh, awesome idea Jim. Feel free to use this blog as you see fit, as I don’t really see myself returning to regular blogging for a few months yet (I’m in Work/Finish/Publish mode right now). Its a shame theres no really good milestone to celebrate with the LHC; I was toying with the idea of having a party for the occasion.

    In other mathy particle-collider news, the latest article at Non-Commutative Geometry


    is about how the Tevatron just ruled out the Higgs mass predicted by the version of the Standard model coming from non-commutative geometry. A set-back and a missed opportunity, though to quote my Nuclei and Particles professor: “Everytime the universe seems to act in a random or inelegant way, its just because our tools or imagination can’t yet get to the true beauty of what’s going on.”

  4. John Armstrong Says:

    Its a shame theres no really good milestone to celebrate with the LHC; I was toying with the idea of having a party for the occasion.

    Or we could turn it around the other way: there are a dozen reasons to celebrate. First beam, first circulation, first crossing (orthodox), first crossing (observed)…

  5. Kea Says:

    Great! Thanks!! I nearly fell off my chair this morning when the news headlines mentioned the LHC. The news here is prone to stories about local politics, health issues, armed robberies, missing children, mountain accidents and the like; not to stories about science.

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  10. Matthias Says:

    Any new findings so far (i.e. as of January 5, 2009)?

  11. Boff Says:


    All you brainiac physicists, mathematicians and scientists are book smart, but have absolutely ZERO common sense. The LHC will lead to our ultimate demise.

    So go ahead, cheer, and “Fire the ring!”


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