Of Particular Significance

A Very Brief Comment About Yesterday’s Post

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 07/17/2012

I got a question after yesterday’s post that motivates me to make a comment.

My post yesterday said that “the LHC is gradually moving from broad searches to precision tests.”

The question I received was “Does this mean that the LHC experiments are giving up on looking for supersymmetry [for now]?”

The answer is: “Of course not.”  There’s a complete logical disconnect between those two statements.  The first would imply the second ONLY if it were true that the way to find supersymmetry (or anything else new) was in broad searches rather than in precision measurements.  But that premise is false.

New particles and forces (such as, but not limited to, those predicted by supersymmetry) are easy to find in broad searches if they generate collisions that look very distinctive and are much more common than similar collisions predicted by known phenomena.

New particles and forces (such as, but not limited to, those predicted by supersymmetry) are impossible to find in broad searches if they generate collisions that are either not so distinctive or are not very common compared to similar events predicted by known phenomena.  For these you need to measure and predict known phenomena much more precisely.

Some variants of supersymmetry (including many of the more popular ones) generate large distinctive signals.  Some don’t.  Broad searches only rule out the first class (and I should mention that not all the broad searches have even been done yet.)

The same goes for many other theories with as-yet unknown particles and forces.  There’s nothing special about supersymmetry in this regard.

So no, the new phase of the LHC research program is not about giving up on looking for this or that.  It’s about working even harder than before, in order to find what might be hiding a bit below the surface.  In fact, that was the major topic of this weekend’s workshop (including my own talk).

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13 Responses

  1. P.S. : what kind of logic is able to justify that if we have ( n) values with unknown mechanism for their specifications , then if we have ( n+m) values all specifications will be explained ?
    That is exactly the SM vs. BSM deception adopted by some !!

  2. As it is a proven logical axiom that no formal system can in principle be explained from within , then would you please clarify why many physicists insist that the BSM will explain the SM.

    1. See the previous answer; the issue is that a Beyond-the-Standard-Model theory may have fewer unknowns, or at least a very different set, than the Standard Model itself, which has something like 20 parameters and an assortment of particles that don’t seem entirely satisfactory.

      Think about how quantum mechanics and particle physics explain the periodic table of the elements; there really is an explanation there, even though new questions are raised.

  3. Dear professor Matt . : is it logical to assume that discovering new particles and forces can explain all of the S.M. ……
    or the expanded BSM will need a still higher level of explanation ?

    1. If you’re asking whether a complete theory can explain itself, no, there will always be the question of “why this Beyond The Standard Model (BSM) theory and not a different one?” But at least the number of unknowns might decrease as we learn more. I personally don’t believe we’re likely to get a “final” answer.

  4. Fine , then if the new particle is 100% S.M. higgs , BUT nothing new or BSM was discovered thru the LHC,,,,,,does that mean stagnation of physics ?
    What other windows do we have ?

    1. the LHC is still in early stages… there is plenty of time left, and plenty of searching to do.

      IF nothing else is discovered at the LHC, then the future will depend on what my colleagues and I figure out in the meantime. Maybe someone will have a good idea. There are certainly other routes to pursue, though the LHC seemed to me to be the best bet for the near term.

      At worst, only particle physics (and probably not all of it) will stagnate. Physics of other sorts will continue on just fine.

  5. When will the 2012(until june) 8 TeV data data made public?

    Of course, I want to say about anything else (mainly SUSY) than the already shown 8 Tev data used to discover the Higgs particle.

  6. What will be the situation if the new particle properties proved to deviate from the S,M higgs but nothing else whatsoever was discovered thru the LHC ? nothing new , nothing BSM ? then what ? the end of physics ?

  7. The best line about Susy comes from 2012 ICHEP – “The huge number of SUSY presentations at this conference is inversely proportional to the number of evidence for it!” Would the same apply to strings ?

    1. At a string theory conference, perhaps. Not at ICHEP; there were probably one or two talks with a string theory connection.

      Supersymmetry is both over- and under-sold; way too many people believe(d) in it without good evidence, but on the other hand, many types of searches for supersymmetry are also useful for finding other types of physics, so there’s not really too much harm in this over-zealous devotion to the theory on the part of some. I remain agnostic on the likelihood of the idea being true, as I’ve been for years; if true as originally sold, supersymmetry should have been discovered in the early 90s, at LEP.

      1. Dear Prof. Strassler,
        is it then in your opinion still worthwhile trying to learn more about and understand better BSM physics such as supersymmetry, etc … ?

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