LHC Restart

By John Conway | April 30, 2009 11:39 am

CERN announced today that the final replacement LHC magnet was lowered into the tunnel, and is making its way to Sector 3-4 (between collision points 3 and 4). Last September’s incident led to 53 magnets – about half a kilometer of the 27-km ring – having to be removed, repaired or cleaned, and replaced. Check out the video of the final dipole going in on April 16.


New systems are being installed to better detect incipient magnet quenches, and the helium pressure relief systems are being upgraded. My understanding is that this will be done on the greater part of the LHC magnets this year, but not all of them.

The plan is to complete the installation of the replacement magnets, and then cool down all sectors. At present, half the machine is being held at liquid nitrogen temperatures, and the other half is at room temperature. It will take a couple months, once they start, to cool the whole machine down to superconducting temperature, about 2 degrees K.

So, by late summer the LHC commissioning can begin where it left off last September. Assuming all goes well, physics collisions are foreseen at 10 TeV by late fall. The machine will not run at the design energy of 14 TeV at least until the entire machine is retrofit with the new quench detection and pressure relief systems. And, the beam intensity (and hence collision luminosity) will not be anywhere near the ultimate goal during the first physics run.

The usual running pattern at CERN is to start in the spring, and collide beams through the late fall, and do machine maintenance, etc. during the winter when electric power is more expensive in Europe (they heat with nukes, basically; we burn fossil fuel in the US in winter).

But a decision was reached earlier this year to run the LHC through next winter, with only a brief two-week shutdown for Christmas and New Year.

What we can reasonably expect is that if all goes well, we can accumulate something like 100 inverse picobarns of collisions by spring 2010, and perhaps 200 pb-1 by the end of the run in fall, 2010. Now, pb-1 this is a strange unit – it has dimensions of inverse area. Formally we call it integrated luminosity. Basically it tells you how many collisions you’ve had, in essence. To get the number of some type of interesting events, you need to know the cross section – which has units of area – for producing that type of event. Then you simply multiply the cross section times the integrated luminosity.

Once the machine shuts down in late 2010, and if we do have a sample of about 200 pb-1, there will ensue a long shut down in 2010-2011 to complete the magnet retrofit. The LHC will then not run until late 2011.

This means that the lower-energy, relatively small sample of physics data is all we will have to analyze until 2012, three years from now! The experiments have already been simulating collisions at the lower energy and retuning analyses.

Though everyone is waiting breathlessly for the LHC to discover the Higgs boson, with lower energy and a smaller sample, I would not bet on the LHC finding it any time before 2012. In fact, a full analysis of the Higgs sensitivity at 10 TeV is yet to be done in ATLAS and CMS. This is a huge task, and will take months, but there is no question that it is more difficult at the lower energy, and it’s already very hard for the LHC to see, say, a 120 GeV Higgs boson. As I wrote in my post in March, this is also very hard for the Tevatron in the same time period. Those of us looking for a standard model Higgs boson have to exercise a bit of patience while working very hard toward the ultimate goal!

Neverheless, there is a ton of new physics that *could* emerge from even the first LHC physics sample from the 2009/10 run. If nature has new high-mass particles giving observable pair-production resonances at energies not accessible at the Tevatron, they could stand out in sharp relief above the standard model. Similarly if there are extra dimensions of space time, we may see excess pair production of standard model particles. If supersymmetry exists, and the experiments manage to understand well the apparent missing momentum transverse to the beam direction (a big challenge) then a first observation of the presence of supersymmetric particles might be possible.

At this point, all you can do is admire the wisdom of the great Zen master Yogi Berra, who said “If this was easy it wouldn’t be so hard!” But then, maybe we’ll get lucky.

CATEGORIZED UNDER: News, Science, Technology
  • http://www.esa.int/SPECIALS/Operations/SEMO4HZTIVE_0.html QUASAR


  • http://- Manoj Bhardwaj

    The write up shows the degree of details the designers and operators need to go for making the trials successful!!
    All the best.
    Take care, May God Bless you.

  • joulesm

    Oh good, I’m looking forward to the restart!!

    Btw, any of you guys heard about the “rebirth of cold fusion”??
    (please see http://www.eurekalert.org/pub_releases/2009-03/acs-fr031709.php)
    I can’t seem to find any trust-worthy source that published this, but I’m a bit surprised that it was announced at an American Chemical Society meeting. I guess I would have expected a better filter from the ACS…

  • Low Math, Meekly Interacting

    As the great Yogi said, “You can observe a lot just by watching.” I’m no physicist, but I can’t wait to see what the data reveals.

  • http://sacrilicio.us madcap

    Now witness the firepower of this fully ARMED and OPERATIONAL battle station!

  • MIKE


  • nobody

    I am actually worried about the following:
    If every experiment has to be duplicated by a totally independent team using totally independent equipment in order to be considered valid, how should we trust the results LHC or any other multibillion accelerator that will come in the future?

  • Tszap

    I’ve always thought that “inverse picobarns” was a needlessly obscure unit. “Events per picobarn” is completely equivalent and much more intuitive.

  • John

    I take it none of you people have children. If you did, you wouldn’t even fathom going through with this experiment that puts billions of lives in danger. I’m not a religious nut or anything, I just believe there is just way too much uncertainty to do this. Many reputable scientists have agreed that this thing could create black holes that would destroy the Earth. Hawking radiation has yet to be proven……if it turns out to be false, we’re dead.

  • nobody

    “Many reputable scientists…” this is one of the best examples of weasel words I have ever seen 😀

  • John

    The John whose comment two above this one is colored, as if it were from me (the real John, who wrote the post) is not me.

  • John

    Anyway, “John” (not me) I think it’s clear that no “reputable scientist” believes there is even the slightest chance of creating earth-destroying black holes at the LHC. If there were, we’d see astronomical objects blowing up all the time, due to the interstellar cosmic rays raining down on them, and we simply don’t. There is less uncertainty in this regard than in just about any scientific claim I have ever heard.

  • John

    nobody: There are two large independent general-purpose experiments at the LHC called ATLAS and CMS. They look at the same kind of collisions at the same time, with detectors that are quite similar but nevertheless different. The two collaborations analyze data and look for new phenomena completely separately, and so can confirm or dispute each other when one experiment claims to have made a discovery.

    You are right that the ultimate test in science is reproducibility, and the experiments are quite similar. So it is a vali question to ask what *both* experiments might be missing. Particle theorists have been quite ingenious in coming up with new physics models for which the present detectors are not well designed to discover…I literally lay awake at nights worrying about such things.

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  • nobody

    Hi (real) John,
    thanks for taking the time to answer, I really appreciate it.

  • Amos Zeeberg (Discover Web Editor)

    Note: We had a little technical problem there that made the non-Conway John’s comment show up in a colored box. The problem’s now been fixed, and only the appropriate comments are highlighted.

    Game on!

  • Phil

    John C,
    When you wrote “… if there are extra dimensions of space time, we may see excess pair production of standard model particles.”

    Are you referring to Hawking Radiation(HR) pairs ? If so, then you are saying that 10 TeV is enough to support HR which implies that a BH must exist if HR represents energy loss (evaporation) from a BH right ? I ask this only because “extra dimensions” are cited as a necessary pre-condition for BH creation in LHC.

    I expect you are likely referring simply to created pairs which would not have a blackbody spectrum (no previous interaction history) right ? Can you confirm there is no (at all likely) BH creation at 10 TeV even if given the presence of extra dimensions ?

    In passing, like other_John (probably), I have been a little disturbed by the “Don’t worry your pretty little heads ….” attitude that professional Science has taken over this question of BH creation at the LHC. Reminds me of Lord Kelvin’s (was it ?) pontifications about everything “…nothing left to be discovered (paraphrasing) …” in the years just prior to the discovery of QM.

    Anyway other_John, what are the chances Hawking ( whose reasoning about these Quantum Gravity issues) comes to us from 1975, is wrong ? After all, Hawking’s reasoning seems unassailable depending as it does( in my understanding of the issue) on the sacred cow of Conservation of Energy(CE)and no one is going to get anywhere in Physics questioning that right ?

    So don’t worry your pretty head about it. Hawking Radiation simply MUST be coming from inside the BH since there is nowhere else it could be coming from you see. Hawking’s (apparent) newtonian view of SpaceTime as an empty container interprets HR energy as the appearance of energy ex nihilo which violates CE so that can’t be right. Matter Creation of this sort went out with Hoyle,Bondi,Gold Steady State Theory of the mid ’60s when the Hot Big Bang model rose to prominence.

    So at first, he argued ( if i’m not mistaken) that this violation had to be “compensated” for by the BH preferentially swallowing the antimatter partners of HR and these anti particles would “cancel” some of the matter within the BH thus “reducing the BH mass” ( but not its energy meThinks). Clearly, that flaky reasoning had to be abandoned. No Thought Experiment can begin by blatantly violating CE. It wouldn’t be a “Principle” if exceptions could happen and after the fact compensation is not a remedy to this fatal error of reasoning.

    So, now, in abject violation of the very definition of BH’s that “nothing escapes”, we see the argument that HR itself represents energy tunneling out of the BH SINCE THERE IS NOWHERE ELSE this energy could be coming from -assumes Hawking. Black Hole Evaporation depends on this assumption being correct however, I believe the emperor is worse than naked in this regard.

    What about if one of the compactified dimensions we know and love is the source of this energy ? Namely, what about the Dirac Sea ? You know, that null energy well consisting of particle-antiparticle pairs that we invoke to explain those failed tunneling events called Virtual Particles ?

    What if the energy of HR is simply the now succesful tunneling of energy from the Dirac Sea induced by the extreme curvature of the SpaceTime manifold near the event horizon of a BH ? In that instance, HR does not violate CE and the energy is coming from somewhere other that the BH. Thus Evaporation does NOT occur and the BH can only grow which, it seems to me, preserves consistency with that pesky Hawking-Penrose Theorem about BHs never shrinking.

    Nor should you even worry, other_John, about those sticky open issues called The Information Loss problem and the Baryon Asymmetry (missing antimatter) problem or the Evaporation Remnant question after all, what possible bearing could these open questions have on any of this compared to all the professional reassurances you are getting on this question. You should remain especially unworried about the fact that since HR became a tunneling_from_BH phenomenon, the question of Evaporation has become synonymous with HR rather than being a conjecture separate from HR.

    You certainly shouldn’t listen to me about all this. I might have no credentials at all you see and am perhaps incapable of seeing these things with Forrest Gump_like clarity.

    Given that the Dirac Sea is everywhere present and that it is (likely) not unreasonable to think of it as a compactified “dimension” beyond the scope of direct measurement thus fitting with the notion of “extra” dimensions, I ask: why can’t the origin of HR energy be the Dirac Sea ? Anyone … ?
    Can anyone provide a link to where this idea has been refuted ?
    Thanks in advance-

  • DP in CA

    “Now, pb-1 this is a strange unit – it has dimensions of inverse area. Formally we call it integrated luminosity.”

    Or you could call it “fuel efficiency”! As in “How many per-acres does your car get?” Think about it.

  • Adam A

    Phil –
    You don’t need black hole production in order to have enhanced standard model production due to extra dimensions. Normally, the graviton (the quantization of the gravitation field) couples so weakly to elementary particles that we do not consider them in the possible interactions we can see. In theories with extra dimensions, the coupling of the graviton increases with energy faster than we would expect in non-extra dimensional theories. In the right extra dimensional scenario ~10 TeV could be enough energy that gravitational interactions become important. In that case, we would expect gravitons to participate in loop diagrams which would modify the expected cross sections of various processes.

    As John already mentioned, very high energy cosmic rays hit our atmosphere and all astronomical objects constantly. These cosmic rays have much more energy than we are capable of producing at the LHC. If it were possible for TeV scale energies to produce a micro black hole capable of devouring the earth, it would have happened already.

    I’m not sure what the Dirac sea has to do with anything at all. The Dirac sea is kind of a superfluous concept. Dirac came up with it to explain why electrons, as described by his equation, don’t radiate infinitely as they drop into negative energy states. However, a modern view of the vacuum does not require the Dirac sea to keep electrons from dropping into negative energy states. In addition, the Dirac sea is not a useful concept to explain boson pair production. It’s also not terribly clear why you would need to invoke the Dirac sea to understand virtual particles. Virtual particles, unlike the Dirac sea, are actually real in a definable way. Although virtual particles were thought of originally as just a necessary mathematical tool, it became clear through the Casimir effect and the Lamb shift that the pair produced virtual particles that pop out of the vacuum actually have measurable, physical effects.

  • Phil

    Thanks for your reply.
    Re: Paragraph-1, I do not think gravity is quantized into gravitons at all and view the concept of a graviton as a simplistic extrapolation from field theory. Based on your explanation, I am therefore glad to hear that TeV production of a micro BH requires participation of these non exixtent gravitons. Unless of course this was just particle_speak for saying that the formation of a BH depends on the self synergy effects of gravity ( however it is quantized) in which case I have no dispute with your explanation.

    Re: paragraph-2, I don’t believe that unconfined TeV energy cosmic rays hitting comparatively stationary atmospheric targets can in any way be likened to confined TeV energy collisions occuring at a rate of 40 million collisions per second in LHC. I view this as an apples and oranges comparison. Why did it come as a surprise that Quark Gluon Plasmas are more liquid_like than plasma_like ? The answer is that professional understanding of these high energy regimes is not as complete as some would like to believe.

    Re: paragraph-3, I defer to your recounting of the history behind the concept of the Dirac Sea but I cited that only to point out that spacetime is full of latent energy ( zero point, vacuum energy, compactified dimensions, whatever) and that therefore Hawking’s simplistic assumption from 1975 that the energy of Hawking Radiation MUST be coming from the black hole is hasty and unwarranted as our curent understanding of the possible nature of the spacetime manifold leaves plenty of room to imagine that this HR energy could be originating from elsewhere than the black hole itself. So, just to be clear, i have no trouble with the assertion that HR occurs but simply do not believe that BH Evaporation follows as a consequence of HR.

    The thrust of my post was that I never see anyone questioning Hawking’s assumption regarding any alternative locus of origin of this HR energy.
    Thanks again.

  • Manny

    Maybe they will invite the other mass boson theorists to CERN for this restart – Guralnik, Hagen, Kibble, Brout, and Englert. I seem to remember pictures of Peter in a helmet last time this happened.

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  • Tammy

    i just found out that it tests the theory of extra dimensions, not alternate realities-which i thought was the same thing. bummer..

  • pi

    the lhc is a quark cannon that wil produce quark/fermion condensates. In haifa they have done an atom/boson condensate and didnt evaporate. they are based in the same laws. only 4000 rubidium atoms made the boson condensate. A quark condesante however acts with the strong force 100 times stronger, in 3 dimensional space 100^3=1 million times faster. Such superfluid fermion condensate of quarks moving at 1 million times the sound speed of Haifa’s dumb hole (ergo at light speed) will be in all akin to a black hole except that it wont evaporate and accrete the earth, if it follows the laws of fermion condensates. Because CERN will mass together up to 1 million quarks it is within its range. the totalitarian principle of gell-mann affirms that all particles that can be created and are not forbidden will be created. thus a fermion quark condensate, a quark hole will form. It will prove that Einstein is double right, because black holes will be as he thought, frozen stars, made of a cut-off substance (quarks) not mathematical singularities as quantum entropy theorists proposed. and it will show that black holes dont evaporate because size has nothing to do with ‘relativity laws’ (ergo the name size is relative to the observer). Of course we wont be here to honor Mr. Einstein but life seems, as i can see for these comments, something not relevant for scientists, eager to sacrifice their lives for the ‘dumb’ scientist. Carpe Diem.

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