LHC News

JoAnne Hewett at Cosmic Variance reports that the latest LHC commissioning plan will not involve collisions at 14 TeV until 2008, with earliest physics run in April 2008. First collisions will be in November 2007, but at Tevatron energies. Until recently the plan had been to try for first collisions at full energy next summer, and some had hoped that a bit of new physics data could be acquired in 2007, but it looks like that is not to be. For a summary talk on the situation, see here.

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21 Responses to LHC News

  1. Hello Peter:
    Your blog has long been a source of enjoyment for many people. Thank you for the support in the recent mini-controversy. You can see that I have gone far beyond those student papers. The slings and arrows haven’t hurt at all. Bring it on!

  2. sunderpeeche says:

    Very rarely do accelerators achieve their top energy on the first pass (although w/ upgrades in *later years*, many have exceeded their original design energy). Especially with something as complicated as LHC, it will be a major feat just to demonstrate collisions and maintain a stable beam. Will all of the detectors be ready?

  3. JoAnne says:

    sunderpeeche: Both of the high p_T detectors (ATLAS and CMS) will be working good enough by Fall 07 to measure the interactions from the first collisions. Both, however, will be missing quite a few pieces (i.e., ATLAS will not have full muon coverage). It will take a long time to calibrate the detectors once the data starts pouring in.

    I have no knowledge of the status of LHCB and ALICE, but imagine they are in the same boat.

  4. Chuckles says:

    The Motls piece against Carroll is available via Google Cache. Very Impressive, I must say. So the argument is that the far left Carroll is basically the countertype of the far right Dembski – which makes Motl what exactly? A reactionary physicist pontificating about brains and sex, subjects in which he is eminently qualified, unlike Carroll and Woit pontificating about…ah, never mind.

    Cache ’em young:

    http://72.14.203.104/search?q=cache:n6ecH9UI44YJ:motls.blogspot.com/2006/06/sean-carroll-joins-peter-woit.html+&hl=en&gl=us&ct=clnk&cd=1

  5. absolutely says:

    Copy then paste the above link to your browser’s address bar. If you click directly you will get a Motl intercept (worth a look though for a laugh).

  6. JoAnne says:

    Could someone please tell me how the comment thread to this post – with a subject matter of the LHC and hard science with real experimental data – degenerated into an irrelevant thread about Lubos Motl, Peter’s book, and loop quantum gravity???

  7. Peter Woit says:

    Joanne,

    1. People love to post off-topic things here trying to turn the discussion away from the topic of the posting to whatever they would rather hear about.

    2. Unfortunately, there seem to be a lot fewer people out there who want to have an informed discussion about particle physics than would like to discuss Lubos or LQG.

    3. Last night I deleted some of the Lubos discussion and tried to see if WordPress had some way of moving the comment with the link to another posting but it doesn’t seem to have a way of doing this. Considered deleting this, decided not to since some people might find it amusing or enlightening, even if off-topic. Went to sleep, thus unable to moderate continuing off-topic comments…

    Someday I should write up a FAQ with answers to recurring questions like “What about LQG?”, no time now. Please, if you must discuss Lubos, use the recent thread devoted to him, and try and avoid posting comments unless you have something interesting to say about the topic of the posting. What many people continually do here is analogous to joining a discussion that has gotten going among a group of people and starting to go on about a different subject. It’s rude.

    Back to the topic of the LHC. Anyone want to guess how long it will be from April 2008 until the experiments have enough data to say something interesting, understand their backgrounds, and are ready to go public with results of the data analysis? How long did it take in the case of the Tevatron?

  8. sunderpeeche says:

    Others may have better info on the Tevatron, but FWIW it started operations in 1983

    http://www.fnal.gov/pub/news/history_tevatron.html

    It was initially a fixed-target machine (now it runs sometiimes as a collider and sometimes fixed-target). Antiproton beams were first circulated at Fermilab in 1985.

    http://history.fnal.gov/brochure.html#IV

    Don’t know about fixed-target expts, but the first collider detector was CDF which started taking data in 1985 (D0 came later). One of the earliest significant physics publications from CDF was a precise measurement of the Z mass (1989), the result was competitive with LEP at the time.

    http://prola.aps.org/abstract/PRL/v63/i7/p720_1

  9. Seth says:

    As a member of one of the experiments, something I would note is that this may be less of a delay in good physics results than it looks like. Even if the accelerator had started at 14 TeV CM energy, all the data from 2007 would likely have been used for detector commissioning. And many of those commissioning tasks can be done almost as well with 450 GeV beams.

  10. anonymous says:

    dear Seth,

    can you explain to a theorist the reason behind this decision?
    At “Cosmic Variance” it is said that it is safer to start with less energy stored in the machine, but why reducing the energy rather than the intensity of the beams, at the price of using magnetic fields much below their planned values?

  11. Seth says:

    I’m a few pay grades below management, but what it looks like Cosmic Variance says is that the much of the machine simply won’t be ready to run at all full energy in time, or at least not fully checked out. (There are more ways to break an accelerator than simply storing too much total energy into it, I’m sure.) So they prefer to run at low energy rather than not running at all.

    From the standpoint of the detector folks, this has positives and negatives; one positive I discussed in my last comment, but a major negative is we won’t have as much time to get our detectors fully installed as if they delayed until 2008. The detector installation on the two major experiments is running on an extremely tight schedule still, even though there is some delay in when the experiments will be closed in the new LHC schedule.

  12. sunderpeeche says:

    To reach top energy the magnets must run at full magnetic field, regardless of how many particles are stored in the beam. This is especially risky/difficult when dealing with superconducting magnets.

  13. Fred Diether says:

    Peter,

    The HyperCP collaboration had one of the biggest data set captured from experiments and it took them about 5-6 years to find the 214 MeV X particle. And they are still analyzing data. I would expect that LHC will have even bigger data sets than HyperCP. So it could be quite a few years before new physics is found if at all. Hopefully not though. 😉 They are definitely going to need a lot of data crunching capability.

    Fred

  14. Hi all,

    not only will CMS and Atlas be short of a few components, but – to me, more to the point – they will have to work a lot before they make sense of their triggers.

    The delays in CDF physics somebody mentioned above were due to precisely this problem: triggering in a hadronic environment is a nightmare in its own right.

    I am in CMS, but I do not care if the 2007 run is taken at 2 TeV, 2 GeV or 2 PeV. The data will not be useful for significant physics measurements. Rather, it will allow us to start making sense of our trigger primitives. Calibrations ? Calibrations come later. As was mentioned, W and Z boson physics measured by CDF was an early successful measurement, where that experiment beat the 630 GeV competition. But still, quite some time after the first shot.

    Now flame me if you must, but I predict that no physics measurement will be published by CMS and Atlas before summer 2009. That includes the total inelastic cross section 🙂

    Cheers,
    T.

  15. sunderpeeche says:

    nothing in over 24h? it’s curious how posts about expt hep generate so few responses, but something on theory generates volumes of the most appaling trash

  16. Peter Woit says:

    sunderpeeche,

    Probably just too few experimentalists willing to spend their time slumming here among the theorists.
    My tactic on the last posting of turning off comments and telling people to discuss on Cosmic Variance inflicted some of the usual suspects on them, forcing Sean Carroll (instead of me) to spend his time deleting people’s off-topic comments.  Maybe I should do that more often (sorry Sean…)

  17. JoAnne says:

    Peter: your prose is brilliant.

    Sunderpeeche: it is disappointing, isn’t it (the lack of interest in blog posts on experimental/phenomenological issues). I try not to let it get me down or stop me from posting, but sometimes….

    Tommaso: I agree that caution is needed, given some of the particularly wild forecasts of discovering SUSY at the LHC in the first 3 minutes! However, there will be physics papers in 2008, I think. Even if they are only about Z/W or top production. I am betting the accelerator & detectors will work well enough to get at least these measurements out. Plus, if there really are blackholes at a TeV, or if there is a heavy gauge boson (or Randall-Sundrum type graviton Kaluza-Klein resonances) at 2-3 TeV, then we will know very quickly. Probably during the 2008 physics run. However, missing energy signatures or the Higgs to gamma gamma channel will most likely take a few YEARS, in my opinion. As you know, those signatures require exact calibration and knowledge of the detector and Standard Model background. So, the wait for new physics depends on what nature has in store for us!

  18. Marty Tysanner says:

    JoAnne,

    Am wondering what your perspective is of the impact on grad students who are hoping to base a thesis on LHC data. Do you think the LHC schedule change will cause many experimentalists to delay graduation due to a need to wait additional time for data? Do you foresee many experimentalists switching to a different experiment as an alternative, or is that even a realistic option for those who have already committed themselves to the LHC?

  19. Chris Oakley says:

    nothing in over 24h? it’s curious how posts about expt hep generate so few responses, but something on theory generates volumes of the most appaling trash

    Sunderpeeche seems to be forgetting that most of the readers here are theorists, former theorists or wannabe theorists. The lack of posts should just be interpreted as a quiet confidence that the experimentalists are doing a good job, and that lacking any specific expertise on the matter, many of us do not see the benefit of making comments.

    But here is one anyway: IMHO text books with the emphasis on experiment – I’m thinking of Perkins’ “Introduction to High Energy Physics” specifically here – do a better job at theory than most theory text books. They almost completely ignore QFT, doing all calculations with elementary quantum mechanics. Those who think that reproducing QM is not a requirement for a properly-formulated QFT should take note.

  20. Walt says:

    Jo Anne: The biggest mistake anyone can make about blogging is thinking that there is any relationship between interest and comments. People don’t comment when they’re interested; they comment when they’re irritated. Lubos: irritating. LHC: not irritating. Guess what’s going to draw the comments.

  21. JoAnne says:

    Walt – how true!

    Marty – The effect on grad students working on the LHC will be small. Everybody expects new accelerators and detectors to be delayed and we are all delighted that this delay with the LHC is so *short.* It’s only a couple of months!!! It could have been years….(of course we don’t know how the actual start of operations will go). If the commissioning phase goes well, the students will get plenty of data for their theses during the 2008 run. Even just observing Standard Model processses such as gauge boson or top-quark production at energies of 14 TeV makes a great thesis! And, thanks for being concerned about the younsters.

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