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Inclusive charm production in Υ(nS) decay

Daekyoung Kang1,2, Taewon Kim1, Jungil Lee1,2, and Chaehyun Yu1

  • 1Department of Physics, Korea University, Seoul 136-701, Korea
  • 2Physics Department, Ohio State University, Columbus, Ohio 43210, USA

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Phys. Rev. D 76, 114018 – Published 27 December, 2007

DOI: https://doi.org/10.1103/PhysRevD.76.114018

Abstract

Based on the nonrelativistic QCD (NRQCD) factorization formalism, we calculate the inclusive charm production rate in Υ(nS) decay at leading order in the strong coupling constant αs and the relative velocity v of the b quark in the quarkonium rest frame. The branching fractions for Υ(nS) to charm for n=1, 2, and 3 are all around 7%–9%. About 60% of the branching fraction into charm is from annihilation of the color-singlet bb¯ pair into γ*→cc¯. Most of the remaining branching fraction is from annihilation of the color-singlet bb¯ pair decaying into cc¯gg. We also compute the momentum distributions of the charm quark and charmed hadrons in the decays. The virtual-photon contribution to the charm-quark momentum distribution is concentrated at the end point while the cc¯gg contribution is broad. The momentum distributions for charmed hadrons are obtained by convolving the charm-quark momentum distribution with charm fragmentation functions. This makes the momentum distributions for charmed hadrons softer than that for the charm quark. This effect is particularly significant in the virtual-photon contribution.

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Phys. Rev. D 76, 114018– Published 27 December, 2007
  • Received 27 July 2007

© 2007 American Physical Society

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