Measurement of the effective leptonic weak mixing angle at LHCb

by Menglin Xu (University of Warwick (GB))

Tuesday 23 Jul 2024, 11:00 → 12:00 Europe/Zurich

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In the Standard Model, the weak mixing angle sets the relative coupling strength of the weak hypercharge and weak isospin gauge symmetries. It is precisely predicted including higher order corrections; direct measurements are sensitive to possible effects of physics beyond the Standard Model. It is also a key parameter in global studies of the electroweak sector. New measurements are essential given the long-standing 3sigma discrepancy between the two best measurements to date at LEP and SLD, and in the light of the anomalously large W boson mass measured by CDF. A new result based on data from the LHCb experiment is presented, making use of the proton-proton collision dataset recorded during 2016-2018 at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.3 fb${}^{-1}$. The forward-backward asymmetry in the $pp\to Z/{\gamma }^{\ast }\to {\mu }^{+}{\mu }^{-}$ process is measured, and theoretical predictions are used to translate this to a determination of the effective leptonic weak mixing angle. The result is compared with previous measurements of the weak mixing angle and with the predicted value from the global electroweak fit.

CERN_Seminar.pdf