Invariant-mass distribution of c(c)over-bar in Y (1S) -> c(c)over-bar + X

Abstract

We calculate the invariant-mass distribution for the c (c) over bar pair produced in the inclusive Y(1S) decay based on the color-singlet mechanism of the nonrelativistic quantum chromodynamics factorization approach at leading order in the bottom-quark velocity v(b) in the meson rest frame. As the short-distance processes, we consider b (b) over bar -> g* gg followed by g* -> c (c) over bar and b (b) over bar -> gamma* -> c (c) over bar at leading order in the strong coupling. The invariant-mass distribution of the b (b) over bar -> c (c) over bar gg contribution has a sharp peak just above the threshold and that of the b (b) over bar -> gamma* -> c (c) over bar channel is concentrated at the maximally allowed kinematic end point. We predict that Gamma[Y(1S) -> c (c) over bar + X]/Gamma[Y(1S) -> light hadrons] = (0.065 +/- 0.048)alpha(s), which is in agreement with a previous result within errors.