Tests of the Standard Model by means of $\Upsilon(3S)$ decays with the $BABAR$ detector

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Asynchronous Talk Flavor and Precision Physics Flavor and Precision Physics Session 2


Alexei Sibidanov (University of Victoria)


The $BABAR$ detector collected a sample of 122 million $\Upsilon(3S)$ mesons, corresponding to an integrated luminosity of 28 ${\mathrm{fb^-1}}$, operating the PEP-II $e^+e^-$ collider at a center-of-mass energy of 10.355 ${\mathrm{GeV}}/c^2$. This sample is the largest ever collected at that energy and provides unique opportunities to test several aspects of the Standard Model (SM).
We report on a precision measurement of the ratio $R_{\tau\mu} = BF(\Upsilon(3S)\to\tau^+\tau^-)/BF(\Upsilon(3S)\to\mu^+\mu^-)$ using data collected with the BABAR detector at the SLAC PEP-II $e^+e^-$ collider. The measured ratio is in agreement with the SM prediction. Its uncertainty is almost order of magnitude smaller than the only previous measurement reported by the CLEO collaboration.
We also present a search for the Lepton Flavour Violating decays $\Upsilon(3{\mathrm{S}}) \to e^{\pm}\mu^{\mp}$, unobservable in the SM, but predicted to be enhanced in several new physics extensions.

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