Eur. Phys. J. C 24, 261-270 (2002)
DOI: 10.1007/s100520200947
Exclusive decay of 1- quarkonia and Bc meson into a lepton pair combined with two pions
J.P. Ma1 and J.-S. Xu1, 21 Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100080, P.R. China
2 China Center of Advance Science and Technology (World Laboratory), Beijing 100080, P.R. China
(Received: 22 January 2002 / Revised version: 7 March 2002 / Published online: 8 May 2002 - © Springer-Verlag / Società Italiana di Fisica 2002 )
Abstract
We study the exclusive decay of
,
and
Bc
into a lepton pair combined with two pions in two kinematic
regions. One is
specified by the two pions having
large momenta, but a small invariant mass. The other is
specified by the two pions having small momenta.
In both cases we find that in the heavy quark limit the
decay amplitude takes a factorized form, in which the
non-perturbative effect related to the heavy meson is represented
by a
NRQCD matrix element. The non-perturbative effects related to
the two
pions are represented by some universal functions
characterizing the conversion of gluons into pions.
Using models for these universal functions and chiral perturbative
theory we
are able to obtain numerical predictions for the decay widths.
Our numerical results show that the
decay of
is of the order of
10-5 with
reasonable cuts and can be observed at BES II and the
proposed BES III and CLEO-C. For other decays the branching ratio
may be too small to be measured.
© Società Italiana di Fisica, Springer-Verlag 2002
