Seema Choudhury ; Soumen Halder ; Lopamudra Nayak ; Saurabh Sandilya ; Gagan Mohanty ; Anjan Giri

01 March 2022

Abstract: This paper report the BR measurement of B → K∗ℓℓ decays using 189.26/fb of data collected during 2019–2021 by the Belle II experiment at the SuperKEKB e+e− asymmetric-energy collider, corresponding to (197.2±5.7)×106 BB ̄ events. The final states considered are B0 → K∗0(K+π−)ℓℓ, B+ → K∗+(KS0π+,K+π0)ℓℓ, where ℓ = e or μ. The yield of signal for the decays B → K∗μμ, B → K∗ee, and B → K∗ℓℓ are 22 ± 6, 18 ± 6, and 38 ± 9, respectively. The uncertainties quoted for the signal yield are statistical only. We report the branching fraction of these decays for the entire q2 (invariant mass square of lepton pair) range excluding the charmonium resonances to be: B(B → K∗μμ) = (1.19 ± 0.31±+0.09) × 10−6, B(B → K∗ee) = (1.42 ± 0.48 ± 0.10) × 10−6, B(B → K∗ℓℓ) = (1.25 ± 0.30±+0.09) × 10−6, here, the first and second uncertainties are statistical and systematic, respectively. The results are statistically limited, but are compatible with the world average within uncertainty. These are the first measurements of B → K∗ℓℓ decays from Belle II experiments.

Keyword(s): FCNC, BR, Belle II, EWP, K*ll