This week at the University of Pittsburgh the Phenomenology 2012 Symposium has talks reviewing the current situation in particle physics phenomenology. Not much new, but there is one plenary talk on string phenomenology, Cumrun Vafa’s Stringy Predictions for Particle Physics. Mostly this deals with Vafa’s ideas about F-theory “predictions” for the fermion mass and mixing matrices. Quite a few assumptions and rather little string theory (the predictions are “stringy”) goes into this, and except for the one recently measured neutrino mixing angle, these are all postdictions, not predictions. I suspect that most string theorists are no more sold on these as predictions of string theory than they are on Kane’s Higgs mass prediction. For example, Vafa’s colleague Andy Strominger in recent talks (and not so recent ones) gives string theory an “F” in the area of making unambiguous testable predictions, and I assume he’s well aware of Vafa’s work.

Pre-LHC, Vafa had been claiming F-theory predictions for SUSY at the LHC (see for example here, here and here). The most dramatic one, the focus of the Harvard Gazette story, was for a stable stau. One of the papers linked to has various detailed calculations for what such an stau would look like, with typical masses around 200 GeV.

At the conference on Monday, this talk gives recent CMS results relevant to such an stau, listing new mass limits of 314 GeV for a “cascade-decay” scenario, 223 GeV for a “pair-produced” one. Vafa only briefly mentions SUSY at the end of his talk, with his final slide “We will wait to see if SUSY plays any role at the weak scale!” I’m guessing he’s getting resigned to the idea that the answer is probably No.

**Update**: Also on the No SUSY news front this evening, there’s a preprint entitled Should we still believe in constrained supersymmetry? analyzing the current situation with one popular version of SUSY, the CMSSM, which concludes:

We find that LEP and the LHC strongly shatter our trust in the CMSSM (with M_0 and M_{1/2} below 2 TeV) reducing its posterior odds by a factor of approximately three orders of magnitude.

Similar statements about the naturalness problem of CMSSM SUSY had been made already after LEP, see

http://arxiv.org/abs/hep-ph/9904247

“The Bayes theorem says how much one must reduce its confidence in SUSY after knowing the LEP2 results”

After LEP the confidence dropped to 5%. Now down to 0.1%.

Nowadays pointing out that SUSY & strings have problems is like shooting on the red cross.

a)Theorists putting such effort into a Bayesian analysis to quantify what we “know” may be quite a sign of the times–and not a good one.

b)After reviewing the C. Vafa cartoonical slides, I must say that I prefer xkcd.

c)In some other universe there is an S. Glashow who is not quite as nice as the one in this bubble (who decades ago taught stupid me Group Theory without making me feel stupid). This not-so-nice Glashow multiverse-twin is rolling his eyes and saying I told you so.

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