Sunday, December 27, 2015

particle physics - What does the latest $B_s^0rightarrow mu^+mu^-$ results mean for SUSY?


A paper from the LHCb collaboration just came out last week, stating basically that the $B_s^0\rightarrow\mu^+\mu^-$ decay matches standard model predictions, and people are already shouting that SUSY is dead. Is SUSY actually in trouble or is it just hype again?



Answer



It is hype again. Whether such decays are affected by SUSY depends mostly on the masses of scalar superpartners and they have been known to be high enough from other considerations, so existing viable SUSY models, especially those derived from string theory, were predicting the muon pair branching ratio of B-mesons' decays close to the Standard Model i.e. close to the published LHCb observations. See Prof Gordon Kane's comments in this story:



http://motls.blogspot.com/2012/11/superstringy-compactifications.html?m=1




The models that would be falsified typically require either scalar superpartner masses below 1 TeV or very high values of $\tan\beta$. However, for the values of the masses and $\tan\beta$ mostly believed to be relevant these days, supersymmetry is compatible with the result.


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