All LHC, all the Time

The LHC media blitz is in full swing, with last week’s long New Yorker article now followed by an unusually long and detailed New York Times piece titled A Giant Takes On Physics’ Biggest Questions. Dennis Overbye does an excellent job of covering the story. Besides the experimentalists actually involved in building the machines, he quotes theorists John Ellis, Joe Lykken, Nima Arkani-Hamed and Michelangelo Mangano. To distinguish this piece from the New Yorker one, here it’s Mangano who is the one who consumes a lot of espresso. There are side-bars about the recent problem with the Fermilab magnets and about the implications for string theory (not much). There’s a multimedia component to the Times coverage, with interactive graphics, a slide show, a podcast (an interview with Arkani-Hamed, described as “one of the physicists at the center of the project”), and a video.

I do fear all this LHC coverage is peaking too early. With still probably at least a year to go before the machine even starts taking data, the coverage may already be generating an LHC overexposure problem: see Chad Orzel’s new posting Tired of the LHC. If Chad is already complaining about this, boy is he going to be grumpy about it by a year from now…

The New Yorker keeps its physics theme going this week with cover art that includes a blackboard full of basic equations from quantum mechanics.

The NY Times article includes the usual not very cogent explanation of the role of the Higgs. For something much better aimed at explaining Higgs-hunting to the general public, see the online interactive presentation Hunt for Higgs, part of a web-site about the LHC called Big Bang.

Blogging may be light the next week or so since I’ll be traveling. First stop is Trieste, where I’ll be speaking at 5pm on Friday as part of a large event there called FEST. From there I’ll make brief visits to Geneva, Paris and London, back here in New York late next week.

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71 Responses to All LHC, all the Time

  1. David B. says:

    Dear anon.

    There is one prediction of the MSSM that you seem to be missing and it is the most important prediction that makes the model testable: the lightest Higgs has to have a mass that is lower than the mass of the Z particle at tree level. With loop corrections one can make this number bigger, but not too big. The model barely gets by with the current precision data and bounds.

    Indeed, one of the most important reasons that made supersymmetric models appealing was that the higgs selfcoupling constant was
    unified with the gauge coupling constants of the standard model.
    Unfortunately because the MSSM does not break supersymmetry spontaneously, that was not enough to fit data. The extra parameters that are added to the MSSM to break susy in the most “general way that does not spoil the advantages of having supersymmetry” do not change this prediction.

    If the higgs that is found at the LHC is not sufficiently light, then the MSSM will be ruled out. I find that to be quite a useful prediction.

  2. Anti-Crackpot says:

    Anon,
    Since we do we claim that the supersymmetric partners are ‘invisible’. On the contrary, they should be observed at LHC if supersymmetry is right. In any case, if your alternative ideas are so good, then I would suggest writing a paper on them. If they turn out to be right, then you’ll win the Nobel. You should really refrain from lumping SUSY in with string theory. There is some relation between the two, but they are not entirely the same.

    If and when supersymmetry is discovered, the following work will be to understand the mechanism by which it is broken. At that point, we will be able to make some predictions, such as the relic neutralino (assuming this is LSP) density and from that get a handle on the composition of the dark matter. Are there any of you who believe dark matter isn’t real?

  3. Christine says:

    Are there any of you who believe dark matter isn’t real?

    Science is facts; just as houses are made of stone, so is science made of facts; but a pile of stones is not a house, and a collection of facts is not necessarily science.
    Jules Henri Poincaré (1854-1912)

    There are in fact two things, science and opinion; the former begets knowledge, the latter ignorance.

    Hippocrates (460 BC – 377 BC)

    I do not see how this is a question of believing or not.

    BTW, see http://arxiv.org/abs/0705.2462

    (sorry: html tag for the link seems not to be working in the preview)

  4. Christine says:

    BTW, I have worked for some time with dark matter models. So, as I said, it is not a question of believing or not.

  5. Anti-Crackpot says:

    Hi Christine,
    Sorry, I was a little loose with my language. What I meant was, is there anyone who denies that there is strong evidence for the existence of dark matter? There is a lot of evidence for it coming from many independent directions such as galactic rotation curves, microlensing and CMB. If it does indeed exist, then this is another line of evidence that the Standard Model needs to be extended since the dark matter cannot be baryonic or composed substantially of neutrinos.

  6. Walt says:

    Anti-Crackpot, you originally said “I think its likely that within two years, the particle physicists and string theorists will be sipping champagne, and all of the stupid people who think it will find nothing will dissappear into the vacuum.” There’s nothing in this statement about skeptics who spread information (whoever that is supposed to be); it’s about the existence of skeptics at all. It’s not a healthy attitude. Nature will turn out to do what nature does, whatever our aesthetic judgement tell us.

  7. M says:

    If supersymmetry will be found, “stupid people” will start working on it rather than sipping champagne or disappearing into the vacuum. However, supersymmetry missed a number of oppurtunities for showing up, and LHC is the last call. If supersymmetry will not be found, then those people who spent their life working on supersymmetry will be really upset.

    Peter thinks that it is unhealhy that so many string theorists have been hired, and here we could have a similar situation: various phenomenologists built their career working on supersymmetry, and LHC might tell that their research activity was irrelevant. Anti-Crackpot, do you guess who would pay for this situation? I mean: if you are a joung post-doc who works only on supersymmetry, you should consider extending your research activity.

  8. anon. says:

    Christine: thanks for that link to http://arxiv.org/abs/0705.2462 which is important. The ‘evidence’ for dark matter and dark energy is based on mainstream consensus in a very weak way, like claiming that the existence gravity is evidence for M-theory because M-theory predicts gravity, or claiming that SUSY must be real because, if you don’t have SUSY, the three SM force strengths won’t naturally converge at the Planck scale.

  9. anon. says:

    There is one prediction of the MSSM that you seem to be missing and it is the most important prediction that makes the model testable: the lightest Higgs has to have a mass that is lower than the mass of the Z particle at tree level. … – David B.

    Unless the model makes a prediction which is unique enough (which usually means precise enough) that no other theories are likely to make the same prediction, then the prediction is not a convincing test for the model. Even if the MSSM was the only possible SUSY, the confirmation of that prediction would still be dubious. If the MSSM Higgs isn’t found then they can just find another SUSY model which is even harder to experimentally refute.

    Similarly, in the case the string theory landscape, individual vacua are testable, since each has a definite set of parameters and therefore makes concrete predictions; the problem is that there are so many different vacua that it isn’t falsifiable. A theory which comes in many versions, like epicycles or string and SUSY, is likely to contain superficially impressive models by sheer coincidence.

  10. Michele says:

    Is there a way to get your talk at FEST? I would have liked to be there but I missed it. Thanks.

  11. Speaking of SUSY at the LHC, Marcela Carena gave a nice seminar in CDF yesterday. You might want to give a look at two plots she showed about discovery reaches of a MSSM Higgs by Atlas and CMS, in my blog.

    Cheers,
    T.

  12. Anti-Crackpot says:

    Anon and Walt,
    For some reason I keep having to make this point, but supersymmetry is testable directly as the supersymmetric partners of the known fermions and gauge bosons may be produced and detected in collisons at the LHC. The present situation is no different than the previous search for the top quark, which took twenty years to be discovered after the bottom. Why? Because of it’s very large mass! Now, you guys, arm-chair scientists that you are, should be aware that such a large mass was anticipated by those working with no-scale supergravity and radiative electroweak symmetry breaking, where a large top mass is required to drive the Higgs mass-squared to a negative value.

  13. sinus says:

    such a large mass was anticipated by those working with no-scale supergravity and radiative electroweak symmetry breaking,

    Today there are models with Higgs masses large, small, and intermediate. Those are not really predictions, since there are no solid reasons which one of those models is experimentally correct, if any. Some of those models may even give Higgs masses in the correct range, and still be completely wrong.

    To give another example, naive SU(5) gives essentially all the correct low energy physics, since it contains the SM, yet it doesn’t work.

    If radiative SB and supergravity models (of which there are many) were validated by the large top mass, as you seem to suggest, why is people wasting their time with other approaches that ostensibly failed to predict the top mass?

  14. Anti-Crackpot says:

    Sinus,
    Regarding SU(5), there is one piece of low-energy physics on which it is spectaculary wrong: neutrino masses. As far as the Higgs is concerned, it’s mass is very sensitive to such things as the top mass and the type of soft-SUSY breaking that is assumed. In the models, one can change the top mass by a few GeV and this causes the Higgs mass to change a lot. In the minimal supergravity models (mSUGRA), the gaugino masses (m_{1/2}) and scalar masses (m_0) are universal, but their actual values are unknown. The Higgs mass and low energy superpartner spectrum depends very much on these values.

  15. Haelfix says:

    Susy is still fine, but its getting perilously close to where its not fine anymore. Everyone hopes the lightest superpartner as well as the Higgs arises somewhere before 140 GEV or else we run into major phenomology problems elsewhere. Things become much less well motivated, nonminimal and contrived.

    If we find SUSY at say 500 GEV, and nothing other than a bare Higgs scalar before that, everyone will be horribly confused.

  16. L-Train says:

    CW:

    Thanks for your reply, but this blog may actually be a useful place to get some info on the topic of SUSY, and whether a transition to a SUSY state is possible at this point in the evolution of the universe, as predicted by Clavelli. You guys, after all, are debating about SUSY.

  17. Anti-Crackpot says:

    For the anti-stringers, there is a guest post at CV by Joe Polchinksi in reaction to Smolin’s reponse to his earlier review.

  18. Peter Woit says:

    I’m still traveling, won’t be back home until late Thursday. So, for now I won’t write anything much about the Polchinski posting. In any case, it’s mostly specifically an on-going discussion with Lee Smolin, and I know I don’t like it if, when someone is arguing a question with me, someone else tries to be helpful by taking my side, often making arguments I wouldn’t really agree with.

    It’s also true that Polchinski is just writing about quantum gravity, not about particle physics, where he’s well known to be a proponent of the anthropic landscape point of view. I’m not too interested in getting involved in arguments about who has the better theory of quantum gravity that can’t be tested. It would be interesting to see Polchinski try and defend the idea of 10/11 d string-theory based unification against the claim that virtually no predictions are possible, except vague sorts of statistical “predictions” that are often wrong.

  19. elzoro says:

    Off-topic but worth mentionning: Fields medalist Richard Borcherds (known among other things for his work on the Leech lattice, Monstruous Moonshine and axiomatic QFT) now has a blog http://borcherds.wordpress.com/

  20. Peter Woit says:

    Thanks elzoro,

    Maybe soon every Fields medalist will have a blog…

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