HEP News

Besides the dramatic new CMS results mentioned in the last two postings, there’s other news from the high-energy frontier as it moves from Illinois to Geneva.

Earlier this week the MCTP hosted a workshop on LHC First Data. Today at CERN was the LHC end-of-year jamboree, talks available here.

Plans for next year’s LHC run were made at Evian last week and will be finalized at Chamonix next month. Beam re-commissioning will start February 21, and it looks like the goal will be to run the machine at 4 TeV/beam (up from 3.5 this year) and accumulate a total luminosity of 1-3 inverse femtobarns. Instead of shutting down during 2012 to fix magnet interconnections, the plan now is for the LHC to continue running through 2012, accumulating enough data to definitively see or rule out a Standard Model Higgs and finally put the Tevatron out of business.

Today at Fermilab people are looking backwards, with a symposium celebrating the 25th anniversary of first collisions at the Tevatron. While a proposal has been put forth to keep the machine running through FY 2014, the budgetary situation looks increasingly likely to put them out of business, no matter what CERN does. The dysfunctional nature of the US federal budget process means that the laboratory is already several months into FY 2011, with no budget, operating under a “continuing resolution” that allows them to spend money at the same rate as last year. Last night, an effort to pass an “omnibus” spending bill for the rest of FY 2011 allocating total spending at the same level of FY2010 was defeated. This means that until February and the next Congress, Fermilab and the rest of the government will operate without a budget. At some point after that, the Republicans plan to try and pass a budget cutting spending from the FY2010 level. Fermilab could very well find itself this Spring finally finding out that its FY2011 budget has been cut, with only a few months left to get spending down to the appropriated level. Budgetary problems are not just affecting the Tevatron, with plans for an underground laboratory in South Dakota dedicated to neutrino and other experiments now up in the air as the NSF has withdrawn its support for the project.

President Obama did make an inspiring speech about his dedication to support Research and Development spending.

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10 Responses to HEP News

  1. HET student says:

    I think you meant 4 TeV beams, not Gev. This would be a disappointing performance by the LHC.

  2. Peter Woit says:

    Thanks HET student. Fixed.

  3. Nickle Berry says:

    I suppose Obama pans to pay for scientific research with tax cuts for the rich.

  4. Chris Austin says:

    Is anything more known about the little dip at M_Inv = 1.6 TeV and the following bump at M_Inv = 1.9 TeV in the 3rd plot, labelled ATLAS-CONF-2010-088, in the top row of the graphs on page 28 of the Atlas talk? The dip seems to be 3 sigma, and since the data follow a smooth curve, with a dip and a bump that is not in the Monte Carlo, one could argue that the significance is more than that. But M_Inv of what? The vertical axis shows Entries/0.1 TeV, but Entries of what? The integrated luminosity for the plot seems to be just 295 per nb, so has that signal now vanished, or is it still there?

  5. Anonymous says:

    “…the plan now is for the LHC to continue running through 2012, accumulating enough data to definitively see or rule out a Standard Model Higgs…”

    So what happens if the Higgs is ruled out by the end of 2012? What do we look for next?

  6. Chris Austin says:

    One possibility would be a fourth Standard Model generation, which would also allow the Higgs to be heavier.

    With reference to page 15 of the Atlas talk, it is not clear to me how the lack of structure in what appears to be the 2-jet invariant mass can exclude the production of excited quarks, by which I assume they mean quarks of a 4th Standard Model generation, with masses in the range 0.3 to 1.5 TeV.

    For from the graph of cross sections that appears on pages 6, 7, 9, 13, etc., it appears that sigma_b = sigma_{4.2 GeV} is about 3 x 10^5 nb at 7 TeV, and sigma_t = sigma_{172 GeV} is about 0.2 nb, so the heavy quark production rate scales with mass as about m^{-3.83}. So we expect sigma_{600 GeV} to be around 0.002 nb, which for an integrated luminosity of 3.1 per pb corresponds to about 6 events, against a background of 10^3 events. And we expect sigma_{900 GeV} to be around 0.4 pb, which corresponds to about 1 event, against a background of 100 events. And we expect sigma_{1500 GeV} to be around 0.05 pb, which corresponds to about 0.2 events, against a background of 6 events.

    So the graph on page 15 seems to me only to limit the couplings of 4th generation quarks to be less than values somewhat larger than the Standard Model couplings.

  7. neo says:

    Does it make any sense to continue to run the Fermilab TEV now that the LHC is operational? Can it expect to compete with the reams of data being turned out by the LHC detectors?

  8. Peter Woit says:

    neo,

    Whether to keep the Tevatron operational is currently being debated. For the moment it is far ahead of the LHC in the Higgs search business, and the argument has been made that it could remain competitive for a few more years as it accumulates data faster (although at lower energy) than the LHC. But that was based on the assumption that the LHC would shutdown for at more than a year after reaching 1 inverse femtobarn in luminosity sometime next year. If the LHC acquires 3 inverse femtobarns in 2011 and keeps going through 2012, then it will definitively outclass the Tevatron in the Higgs search.

    The way the US budget situation is going, this may be a moot point anyway. It’s still unclear whether there will be funds to get through this fiscal year, much less funds to run the Tevatron in FY 2012.

  9. Chris Austin says:

    With reference to my first comment above, a Google search for ATLAS-CONF-2010-088 turned up the full report, “Search for new physics in multi-body final states at high invariant masses with ATLAS”, dated August 21, 2010. They selected events with at least three objects such as jets or leptons in the final state and an invariant mass above 800 GeV and total p_T greater than 700 GeV. The initial large peak is due to the cut on m_Inv at 800 GeV and the fact that the Standard Model background is rapidly decreasing. The graph appears on pages 8 and 9. The dip at 1.6 TeV and the peak at 1.9 TeV are definitely not in the Standard Model background. The data follow a very smooth curve, i.e. with almost no scatter, that departs substantially from the Monte Carlo, so although the dip is only 3 sigma below and the bump is only 1 sigma above the Monte Carlo, one could argue that the significance of the whole smooth curve is more than 3 sigma.

    The analysis used just under 300 per nb of data, but ATLAS now has 45 per pb, i.e. 150 times more, so if the trend shown in the graph has continued, it will be a discovery by now. There is no update available yet in the ATLAS Conference Notes, nor on arXiv. It would be very interesting to hear from someone in ATLAS about the current status of this signal.

    The search was designed to look for evidence of TeV-scale gravity, in the shape of high mass states decaying democratically to Standard Model states. The discussion on pages 10 and 11 refers only to semi-classical black holes, for which no evidence was seen. The bump could be a Kaluza-Klein graviton in the Randall-Sundrum-1 model, or it could be a KK mode of the graviton multiplet in the geometry of subsection 2.5 of my article arXiv:0704.1476, which is totally different from the Randall-Sundrum geometry, but also has the lightest massive gravitational KK modes around a TeV: their wavefunctions are pushed up against our boundary of the Horava-Witten interval by the warp factor.

    The only way I know to force the subsection 2.5 geometry to occur uses very large electric fluxes of the 4-form, whose dual 7-form fluxes wrap the de Sitter 3-sphere times a 3-cycle of the compact hyperbolic 6-manifold times the Horava-Witten interval. Choosing the quantized flux numbers to be about 10^{126} forces the cosmological constant to be about right, i.e. the de Sitter radius is forced to be about 10^{26} metres, and Newton’s constant and the electroweak breaking mass are also forced to be about right.

    The flux quantization condition is invariant under the full de Sitter group, but the fluxes are not. However it seems possible that the only significant observable Lorentz violations will be in the dynamics of the massive gravitational KK modes, so it would be worth checking if the size or position of the dip and the bump vary in synchrony with the Earth’s sidereal rotation, i.e. the Earth’s absolute rotation with respect to the stars. (A sidereal day is approximately 23 hours and 56 minutes.)

  10. Shantanu says:

    Peter, maybe slightly OT,
    but see the slides of NNN 2010 conference at Toyama
    http://www-sk.icrr.u-tokyo.ac.jp/NNN10/
    See in particular the talks by Nomura and concluding talk
    by Jung. (again emphasis of this conference is proton decay
    and underground detectors)