A more careful estimate of the charm content of eta'

Original · EN

We estimate the quantity |fₑta'(c)| which is associated with the charm content of eta' meson from the experimentally known ratio R=B(psi ->eta' gamma)/B(psi ->etac gamma). It is shown that due to the off-shellness of the c c component of eta', which has been overlooked so far, fₑta'(c) is further suppressed. Assuming that psi ->eta' gamma decay is dominated by psi ->etac transition, we obtain |fₑta'(c)| = 2.4 MeV which could imply that the (b -> c cs) mechanism does not play a major role in the B -> K eta' decay mode.