Monday, July 16, 2012

SUSY Stop Quark Signals At LHC?

Lubos Motl (a strong SUSY believer) is trumpeting experimental results at the LHC's CMS experiment and ATLAS experiment that he argues each show 2.5 sigma signals of 300 GeV stop quarks in the same detection channel, the supersymmetric boson that is the partner of the top quark and often expected to be the lightest of the superpartners of the Standard Model fermions.   Motl acknowledges, however, that neither CMS nor ATLAS are interpreting the overall results to be a meaningful stop quark signal as he does.

The ATLAS experiment powerpoint presentation (cited by SUSY skeptic and Motl nemesis Peter Woit) at the same conference that Motl discusses, however, dismisses this conclusion and instead argues that the experimental data are consistent with the Standard Model and show results in at least one channel that rules out a 300 GeV stop quark for most values of the relevant additional parameter that influences the expected signal at the 95% confidence level.

At least twenty-nine papers discussed SUSY prospects at the LHC (and in relation to that the utility of a new international linear collider for studying these issues). More of the papers discussed SUSY to some extent even though their titles don't disclose this fact. Most of the rest of the papers were purely experimental in orientation. No other specific class of theories had even two papers discussing it. SUSY variants remain the only really respectable, widely evaluated alternative to the plain vanilla Standard Model in beyond the Standard Model high energy physics.

Many proposals with expanded Higgs boson sectors are ruled out, but certain models with both singly and doubly charged Higgs bosons in addition to the Standard Model Higgs boson (Georgi-Machacek Model triplets), are not ruled out by the LHC data alone although they are disfavored by the Tevatron data.

Possible BSM values in the Standard Model CKM mixing matrix (potentially making it impossible to fit the model to the data because it is overconstrained) disappeared with more precise measurements from LHC.

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