Measurements of Branching Fractions and Decay Amplitudes in B-> J/\psi K^* decays

TL;DR

This paper reports precise measurements of branching fractions and decay amplitudes in B->J/psi K* decays, revealing dominance of CP-even components and providing detailed angular analyses using data from the Belle detector.

Contribution

It provides the first detailed angular analysis of B->J/psi K* decays, measuring decay amplitudes and branching fractions with high precision.

Findings

Branching fractions measured as approximately 1.29 x 10^{-3} for both neutral and charged modes.

Longitudinal amplitude |A_0|^2 = 0.62, transverse |A_perp|^2 = 0.19, indicating CP-even dominance.

CP-even component dominates in B^0 -> J/psi K*0 decay.

Abstract

The branching fractions and the decay amplitudes of B -> J/psi K^* decays are measured in a 29.4/fb data sample collected with the Belle detector at the KEKB electron-positron collider. The decay amplitudes of helicity states of the J/psi K^* system are determined from the full angular distribution of the final state particles in the transversity basis. The branching fractions are measured to be (1.29\pm0.05\pm0.13) \times 10^{-3} for neutral mesons and (1.28\pm0.07\pm0.14) \times 10^{-3} for charged mesons. The measured longitudinal and transverse (perpendicular to the transversity plane) amplitudes are |A_0|^2 = 0.62\pm0.02\pm0.03 and |A_{\perp}|^2 = 0.19\pm0.02\pm0.03, respectively. The value of |A_{\perp}|^2 shows that the CP even component dominates in the B^0 \to J/\psi K^{*0}(K_S\pi^0) decay.