First determination of $|V_{cb}|$ and $B_s\rightarrow D_s^*$ hadronic form factors using $B_s$ semileptonic decays in LHCb

About

Semileptonic decays of heavy hadrons are commonly used to measure the parameters of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, as they involve only one hadronic current, parametrised in terms of scalar functions known as form factors. Two complementary methods have been used to determine the matrix element $|V_{cb}|$ that encodes the coupling between the $b$ and $c$ quarks. The determination of $|V_{cb}|$ using $B\rightarrow D^{(*)}\mu\nu$ decays or via the inclusive sum of all hadronic $B\rightarrow X_c l\nu$ decay channels are approximately three standard deviations apart, and this represents a long-standing puzzle in flavour physics. The exclusive determination relies heavily on the modeling of the form factors, and several different parametrisations have been proposed. Semileptonic $B_s$ decays have not previously been used to measure either $|V_{cb}|$ or the form-factor parameters. In this talk, the first measurement of the CKM matrix element $|V_{cb}|$ using $B_s \to D_s^{(*)}\mu\nu$ decays from the Run 1 dataset will be presented, as well as the differential decay rate and parameters of the leading form factors from $B_s\rightarrow D_s^*\mu\nu$ decays using Run 2 data. .

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