LHC Update, More

According to John Conway, the decision coming out of Chamonix is to go with the first of the two scenarios described here: stay at 3.5 TeV/beam, then a long shutdown to fix all the splices. The idea is to run at 3.5 TeV during 2010 and 2011, stopping for shutdown either when 1 fb-1 has been accumulated, or end of 2011, whichever comes first. The LHC will thus be off throughout 2012, coming back in 2013 for a run at or near the design energy of 7 TeV/beam.

With the Tevatron counting on having around 12 fb-1 of data at 1 TeV/beam by October 2011, it should remain competitive with the LHC for many sorts of searches, including the search for the Higgs, for much longer than expected. This should be true for more than 3 years from now, until after the LHC has accumulated a significant amount of data at full energy in 2013. The current planning is for Tevatron operation only through FY2011, I wonder whether this will change…

Update: Science has a story from Adrian Cho here. The D0 co-spokesperson says the decision on running the Tevatron in 2012 “won’t have to be made for several months.” CERN experimenters are quoted as saying that they will still be searching for supersymmetry and extra dimensions. I haven’t seen any studies of exactly what 1 fb-1 at 7 TeV will make possible in terms of doing better than Tevatron limits on such processes and on the Higgs.

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5 Responses to LHC Update, More

  1. DB says:

    The LHC won’t even be runnng when the Aztec calendar ends in 2012? There goes one doomsday theory! :-)

  2. Teva says:

    “The current planning is for Tevatron operation only through FY2011, I wonder whether this will change…”

    Let’s bear in mind that many particle accelerators became famous (or perhaps I should say many significant HEP expt discoveries were obtained) for reasons completely different from why they were proposed. Pre-WW2 machines didn’t usually have names, but post-WW2, the Bevatron was designed to produce the antiproton (it did, and a physics NP), but it really became famous for Luis Alvarez and the bubble chamber and finding many resonances. The AGS proton synchrotron at BNL was built to reach higher energies, but nobody anticipated the 3 NP winning discoveries it produced (J of J/psi, CP violation, 2 types of neutrino species) — there was also the Omega- (Eightfold way). The AGS runs to this day (as an injector for RHIC). SPEAR? Nobody really expected the psi of J/psi, nor the tau lepton (although the idea of a charmed quark had been floated). The SLAC linac and deep inelastic scattering? The PS at CERN was a proton synchrotron of comparable energy to the AGS, and discovered weak neutral currents (Gargamelle bubble chamber), while the SPS at CERN was again a higher-energy proton synchrotron, but it really made history as a p-pbar collider. The muon g-2 storage ring at CERN indeed stored muons and gave a high-precision value for (g-2)_mu, but after that it was used for ICE (Initial Cooling Experiment) to demonstrate the feasibility of stochastic cooling.

    The Tevatron? It has produced the top quark, although the existence of the top was predicted as soon as the b quark was discovered (1977), albeit without a precise prediction for the mass. So … if the Tevatron finds a signal (or possible evidence for a signal … this is very subjective), then indeed the funding profile of the Tevatron will change. Why not?

  3. Pietro says:

    Nobel Prize winner Veltman (who won the Prize on issues around the unification of the weak interaction) thinks that the Higgs does not exist, and says so in each of his talks, citing a paper of his from 1991 which he wrote with his daughter. He predicts that there are some subtle changes in longitudinal W and Z boson scattering, but nothing else to be discovered at energies of a few TeV.

    If he is correct, both machines will see very little new physics. It will be fantastically interesting to see who is right: the majority or the “lonely” researcher Veltman.

  4. Ralph says:

    Re: “The current planning is for Tevatron operation only through FY2011, I wonder whether this will change…”

    My guess is that the only thing that is certain is that plans will change, the question is how :-)

    If we get to the end of 2011 and it looks like something interesting is in sight, it might make sense to run LHC at 2*3.5TeV through 2012 also and aim for many fb^{-1} at that energy – in which case keeping Tevatron running would be pretty much irrelevant?

  5. Anon says:

    The “rule of thumb” is that you need ~3 times more luminosity at 7 TeV center-of-mass energy to get the same sensitivity as at 10 TeV center-of-mass energy. This is approximate and depends on production mechanism and the mass of the thing you’re trying to discover and the backgrounds which can scale differently. Keeping this in mind there’s a write-up from last year with some interesting information at:

    https://espace.cern.ch/acc-tec-sector/Chamonix/Chamx2009/papers/MFL_9_01.pdf

    and

    https://espace.cern.ch/acc-tec-sector/Chamonix/Chamx2009/talks/MFL_9_01_talk.pdf

    You should bear in mind that most of the these studies were done quickly making assumptions about how things scale with energy, rather than full simulation.

    In short for Higgs, LHC will overtake Tevatron in sensitivity at high masses but will struggle to be competitive at low masses with 1 fb-1. It seems the Tevatron will not discover a low mass Higgs at the 5 sigma level, but may see evidence for a low mass Higgs with 10-12 fb-1 of data. For SUSY and exotics, LHC should be in new territory.

    In reply to the comment about Veltman, there are many people who have studied theories without a Higgs, he may have been the first, but it’s an entirely conventional avenue of research now. In many ways the most exciting discovery would be one that nobody has thought of, and discovering nothing would also be enormously important since the whole Standard Model would need a re-think.

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