The confining interaction and the M1 decay rates of heavy quarkonia

The M1 transition rates of heavy quarkonium states depend on the matrix ele ments of the effective confining interaction through the associated two-qua rk exchange current operator. The Hamiltonian model based on a scalar linea r confining interaction with a single gluon exchange hyperfine term describ es the J/psi --> eta(c)gamma and psi(2S) --> eta(c)gamma decay widths once the relativistic single quark magnetic moment operator is treated without a pproximation and the exchange current is taken into account.