Next-to-leading-logarithm kT resummation for Bc → J/ψ decays

Abstract We derive the k T resummation for a transverse-momentum-dependent charmonium wave function, which involves the bottom quark mass m b , the charm quark mass m c , and the charm quark transverse momentum k T , up to the next-to-leading-logarithm (NLL) accuracy under the hierarchy m b ≫ m c ≫ k T . The resultant Sudakov factor is employed in the perturbative QCD (PQCD) approach to the B c → J / ψ transition form factor A 0 B c → J / Ψ ( 0 ) and the B c + → J / ψ π + decay. We compare the NLL resummation effect on these processes with the leading-logarithm one in the literature, and find a ( 5 − 10 ) % enhancement to the form factor A 0 B c → J / Ψ ( 0 ) and a ( 10 − 20 ) % enhancement to the decay rate B R ( B c + → J / Ψ π + ) . The improved k T resummation formalism is applicable to the PQCD analysis of heavy meson decays to other charmonia.