Tevatron Higgs Exclusion

The combination of the CDF and DZero results previously described individually are now available. The main result is that there is an exclusion from 158 GeV to 175 GeV. This means that the ranges left for a Higgs are from 114 GeV to 158 GeV or from 175 GeV to 185 GeV. This will be described at ICHEP this afternoon by Ben Kilminster.

As for the Higgs-plus-bottom channel, it shows an excess of just over 2 sigma in the range 130 GeV to 160 GeV. Very tantalising but also very inconclusive. A 2-sigma effect is normally regarded as no more than noise in the experimental physics community. They need 3-sigma to call it an “observation”, and 5-sigma to call it a “discovery”. This result is based on only 2 inverse femtobarns of data at one of the experiments. Why did they not show a combined result as they didi for the Higgs searches?

There is one last plot of interest that shows binned signals on a hypothesis of a Higgs at 115 GeV. This has a clear anomaly over two or three bins. Be wary to draw too many conclusions.


17 Responses to Tevatron Higgs Exclusion

  1. Ervin Goldfain says:

    Phil,

    Any possible misinterpretation by the general audience can be avoided by simply saying that that Higgs has not been detected at Tevatron but that the combined detector reports have established new exclusion limits. I may be doing some hairsplitting here but it seems to me that “very tantalizing” is an open invitation to continue rumour mongering. We’ve had enough of this already…

    Cheers,

    Ervin

    • philipgibbs says:

      OK, I added some more words to give myself a clear conscience. Actually the speaker showed a slide that he said answered the question “what would the effect of a Higgs boson look like on this plot if there was one?”. The answer plot showed something like the shape observed, but less pronounced. That was a bit naughty.

      By the way, I found this definition of “tantalising” which makes me think I chose the right word: “arousing desire or expectation for something unattainable or mockingly out of reach”

  2. [...] still at large,” Resonaances, 26 July 2010 [también aquí]; philip Gibbs, “Tevatron Higgs Exclusion,” viXra log, July 26, 2010; y muchísimas [...]

  3. Luboš Motl says:

    Dear Ervin,

    the existence of tantalizing Higgs-like events is not just a rumor now: it is the official conclusion of the speaker who spoke on behalf of both Tevatron collaborations. The hints of a 113-115 GeV light Higgs are there and the “rumors” will surely continue to thrive because there’s a damn good reason to keep these events in mind. After all, most likely, they are real.

    There’s also a 2+ sigma excess in the MSSM 3b channel, assuming the H Higgs mass around 140 GeV. This is also an official fact now, not just a rumor. In this sense, both rumors have been officially confirmed. (And there’s a new rumor that an analysis gives a similar 3-sigma excess across the spectrum which wasn’t presented by Kilminster.) You may have had enough but that’s because you don’t really like discoveries in physics and you prefer to be told – incorrectly – that there won’t be any new discoveries made out of the observed data.

    Cheers
    Lubos

  4. philipgibbs says:

    I added in another plot that Lubos and Jester had on their reports:
    http://motls.blogspot.com/2010/07/combined-d0cdf-higgs-results-next.html ,
    http://resonaances.blogspot.com/2010/07/higgs-still-at-large.html ,
    It looks good but it is harder to interpret than the cheese and lettuce plots (At least for me)

    It is a real pity that they did not present more complete results (with the full integrated luminosity available) for the Higgs+bottom channel. Results with real observations at 3 sigma take longer to approve for publication than less significant results. The fact that it was not shown and that there was no excuse given, is going to stengthen the rumours. So perhaps we just have to wait for it.

    I think as theorists we can bias our interpretation with the assumption that the Higgs exists (or that it does not exists if you are Kea or Hawking) This makes you see a two sigma effect in a different way. The experimenters are not supposed to do that and for them a two-sigma signal must always be interpreted as possible noise.

    • Luboš Motl says:

      Dear Phil, these are interesting musings of yours.

      It’s somewhat paradoxical that uninteresting and weak results are faster in getting publicized – but it reflects the experimenters’ being careful not to publicize strong yet incorrect claims (weak but incorrect claims are OK in this optics haha). Thank God that particle physicists are thinking in this “reticent” way rather than the opposite one – trying to hype shocking results even if they’re likely to be incorrect.

      Concerning the duty you prescribed to the experimenters – that they’re never allowed to be “biased” towards the existence of the Higgs – I am not sure whether it’s possible. Experimenters always have to look somewhere and the right places to look and sensible expectations what may happen and what’s unlikely to happen is *always* dictated by some theory – whether a more or less complete one. Without a theory, experimenters wouldn’t know what to do.

      This fact doesn’t make their work “biased” in any sensible way. Two-sigma separation between some curves calculated in some method is still a two-sigma separation, and so on. But when one interprets the data, of course that he is allowed to think. A theory that has absolutely no Higgs is inconsistent below a TeV. So if someone needs to assume that something like the Higgs exists in some interval, well, he can surely assume it.

      I feel that if this reasoning – even when it comes to inconclusive signals – were taken seriously, the measured data already prefer MSSM over SM by one or two orders of magnitude in the odds.

    • Luboš Motl says:

      What I also wanted to say is that when you say that “2 sigma may be noise”, well, they surely can be noise. But they can also be noise separating us from a different theory than the Higgsless one. You seem to implicitly say that a theory without any new particles is always the “golden standard” that the experimenters have to be rooted in and defend. I disagree with that.

      A Higgsless Standard Model is just an incomplete theory that is OK for some data and that is simplest among such theories – but clearly, when it comes to the understanding of events with possible Higgs sector production, it’s just one possible hypothesis and surely not one of the more sensible ones. ;-)

      Theories with Higgs boson(s) describe the non-Higgs events as well, and they’re better in describing the possible (or future) Higgs-related events. So there’s surely no rational reason to discard them. The notion of minimality mentioned above is irrational.

      Another example. When they measure things, of course that they should have prior probabilities for the right theories to be SM or MSSM to be relatively comparable. Unless one can actually falsify a qualitative framework or a class of theories, he shouldn’t be trying to do so by twisting the evidence in the direction that “everything can be noise away from a preferred theory” because any such preference is a sign of bias.

  5. philipgibbs says:

    If anyone wants to review the talk, the video recording for yesterday afternoon is online at http://webcast.in2p3.fr/2010/ichep/index.php?video=lundiapresmidi.ram

    It’s five hours long and it is hard to get the video to forward to later talks but you can download the full file from http://webcast.in2p3.fr/2010/ichep/lundiapresmidi.ram (1.5 Gigabytes), then it it easier to view in real player.

    Perhaps they will edit it into individual talks later.

  6. ervin goldfain says:

    “You may have had enough but that’s because you don’t really like discoveries in physics and you prefer to be told – incorrectly – that there won’t be any new discoveries made out of the observed data.”

    Lubos,

    Contrary to what you say, I love new discoveries in HEP and physics in general. The hard reality is that, as of today, the Higgs signal remains inconclusive. This is an undeniable fact. Of course, the situation may change in the next few years with LHC running at full speed and more data being processed. Only time will tell.

    Cheers,

    Ervin

    • Luboš Motl says:

      Dear Ervin, no one is questioning that it’s “inconclusive”. However, a “fully conclusive” proof never exists in science. As the integrated luminosity gets up, the picture gets sharper but it will never get infinitely sharp.

      I think it’s not only exciting for science fans to look how the current inconclusive “score” looks like but it is also beginning to become relevant as a source of information that influences the research directions of the actual physicists in the field of phenomenology who actually care about the data.

      What is simply not clear to me is the motivation behind your attempt to choke the interest of the people about the current results and interesting hints, and the readiness of the media and others to bring the answers.

      • Ervin Goldfain says:

        Lubos,

        Let me make it clear that I have no intent whatsoever in suppressing anybody’s interests in new scientific results. I simply think that it is wise to stay cautious and refrain from hyping up conclusions a way or another when the available data is not pointing in a definitive direction.

        Cheers,

        Ervin

  7. Luboš Motl says:

    Dear Ervin, I just happen to think that there’s still a huge lack of interest in these stories in the media, surely not an excess of hype. That contrasts with the thousands of tweets about the Higgs boson on Twitter.

    And I am completely flabbergasted that the world is essentially silent about SUSY.

    Hints are highly suggestive that this most striking discovery of physics at least in 40 years is going to be made in one year by the LHC and no one is talking about it! It’s damn crazy, especially if contrasted with other disciplines such as the climate where the confidence levels are usually smaller than 2.5 sigma but similar conclusions are being hyper in thousands of articles every week.

    The world outside the HEP specialists will be completely un-ready for what is likely to take place soon.

    • ervin goldfain says:

      Lubos,

      Nowadays precision data is available on electroweak parameters as well as on the range of allowable Higgs masses. At least in principle, one ought to be able to prove or refute MSSM, which is based on two Higgs doublets, by computing its radiative corrections to Veltman’s rho-parameter. Available data on CP violation in B-meson decays may also be used towards the same goal.

      It seems to me that these calculations may either quickly reignite the interest in SUSY or may raise doubts about its validity.

      Cheers,

      Ervin

    • Ulla says:

      Sweet dreams, Lubos.

      It is highly surprising that you, of all people, talk for a possibility, and that at such a low probability value!

      To me all this looks like curtains of smoke only. Attention is focused on wrong things? No wonder people are cautious.

  8. Ulla says:

    Higgs bosons are produced at the Tevatron at Fermilab once every few days.

    Did you all knew that :) Said at Ben Kilminsters homepage. http://b0urpc.fnal.gov/~bjk/

  9. Ulla says:

    I just have to put this quote of Ben Kilminster here, from the ICHEP-blog.

    “”People keeps on asking how would the exclusion plot look like if there existed a Higgs boson. We did the exercise of injecting a 115 GeV SM Higgs boson signal in several channels, and that’s what we got”.
    And, guess what, – the results is that the exclusion curve jumps up like it had a 1 sigma fluctuation on a rather large mass range. Now, doesn’t this jump remind you of any feature we saw in another curve? There a region where the unspeakable dreams and hopes of many live, between a green and a yellow band.”

    He meant this second pic.

    I wonder how it would be possible to detect a signal from mr. Higgs if not even a fabricated one is detected? Is there something wrong with the procedure? The signal is spread out? It is after all bosonic.

  10. philipgibbs says:

    The fabricated signal mimicks the level of statistics they have so far. As the amount of data is increased the signal becomes clearer.

    Not sure but I think the channels they are looking at here would select integer spin particles so what they are seeing should be bosonic.

Follow

Get every new post delivered to your Inbox.

Join 270 other followers

%d bloggers like this: