This Week’s Leak

Everyone in the HEP community is breathlessly awaiting the release of results from the 2011 LHC run, expected to come at the EPS-HEP 2011 conference in Grenoble starting July 21. A public press conference has been announced for July 25. Presumably the new results will further tighten limits on supersymmetric particles, extra-dimensional models and other exotica, but the real excitement surrounds the question of what the news about the Higgs will be. The latest LHC data should finally allow competition on this front with the Tevatron.

Philip Gibbs at viXra log has posted here what looks like the bottom line for CMS. They are not yet able to exclude a Higgs at lower masses, including the range where the Tevatron has an exclusion region, but are able to exclude (at 95% confidence level) a SM Higgs in a higher mass region (about 275-425 GeV). This sort of result is not quite what it looks like, since precision electroweak measurements already rule out such a SM Higgs, and recall that the Higgs self-coupling increases with Higgs mass, meaning that one is entering into a region where one is not sure that perturbation theory applies. If the Higgs is not a weakly coupled field, life becomes much more complicated.

The source of the plot is variously described as “shown [July 8] at a seminar which as far as I know was public”, from “a public part of the CERN repository”, and “not yet public but was made accessible on a Fermilab site”.

ATLAS, the competition for CMS, presumably has a similar plot up its sleeve just about ready for release at EPS-HEP 2011. Once the two experiments have made public their independent results at this conference, they intend to immediately get to work producing a combined plot, with goal of releasing it at Lepton-Photon 2011, which will take place in Mumbai August 22-27.

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11 Responses to This Week’s Leak

  1. DB says:

    Minor typo Peter, the EPS-HEP conference begins on July 21st.

    I think it’s too early to expect anything really interesting out of the LHC this time around. I suspect that the inexorable closing off of the SUSY parameter space is a bit of a sideshow for most. It’s like dutifully visiting a terminally ill relative you never really got along with.

    This is the year to celebrate the machine’s performance after the initial disastrous startup. ICHEP 2012 in Melbourne, or especially EPS-HEP 2013 in Stockholm should be another story altogether.

  2. Peter Woit says:

    Thanks DB,

    Absent surprises, the most interesting thing should be whether a Higgs is seen in the expected region of 114-158 GeV. Do you really think it will take that long for ATLAS/CMS to be able to exclude or start to see something in this region?

  3. DB says:

    I’m a Higgs agnostic myself, Peter, and I won’t be hugely surprised if they don’t see it, which is why I think it will take until 2013 before we know one way or another.

  4. GS says:

    I really enjoy the high quality of the discussions in this blog. Even though my comment may not be living up to the level of the rest, I just wanted to mention–as a (very speculative) side remark–the CERN announcement for the press conference http://www.interactions.org/cms/?pid=1030888
    Notice topic three: “The LHC and other projects: what strategy should Europe adopt for particle physics? by Michel Spiro, President of the CERN Council and CNRS Scientific Director for the Alpes region.” This may be exaggerated, but it sounds suspiciously like they are preparing to present no revolutionary results there.

    Best,
    GS

  5. P. says:

    CDF has seen B_s -> mu+mu-

    Talk on friday:
    http://theory.fnal.gov/jetp/

  6. Peter Woit says:

    P.

    Thanks, very interesting! I’m assuming for them to see this, the signal must be too large to be compatible with the SM, right?

    At the KITP, they were guessing that this seminar would be “possible…D0 ttbar asymmetry measurement”, see

    http://lhc11.wikispaces.com/Talks+%26+Discussions

  7. Peter Woit says:

    P.

    The CDF paper is out tonight:

    http://arxiv.org/abs/1107.2304

    They do claim to see an excess of B_s -> mu+mu- above expected background + SM value, with 1.9% probability of such an excess if the Standard Model is correct. They conclude

    “Although of moderate statistical significance, this is the first indication of a B_s -> mu+mu- signal”

    Not yet a convincing violation of the SM, but intriguing. Can D0 also see this?

  8. PA says:

    A seriously garbled html version of the CMS presentation remains in the Google cache. It’s very preliminary, so who knows what will really be the result presented. The bottom line is that although “strong statements” about the Higgs are now possible, the upward fluctuations seen in Phil G.’s plot are fully consistent with statistical expectations. So as of now, it looks like CMS will firmly exclude some models (SM Higgs + 4th generation), but a little more patience will be needed for the vanilla Higgs.

  9. anonymous says:

    “This sort of result is not quite what it looks like, since precision electroweak measurements already rule out such a SM Higgs, and recall that the Higgs self-coupling increases with Higgs mass, meaning that one is entering into a region where one is not sure that perturbation theory applies.”

    Does this suggest that we may not be able to confidently detect a more massive Higgs if it exists? Does the vanilla Higgs show a better signature over all mass regions?

  10. chris says:

    no, it just means that this was primarily ruling out technicolor Higgses, which are not so popular anyways.

  11. Peter Woit says:

    chris,

    It’s not clear to me that ruling out a high-mass Higgs described by SM Feynman rules actually tells you anything about a Higgs in a technicolor theory, which will have a different behavior.

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