New effective treatment of the light-front nonvalence contribution in timelike exclusive processes

We discuss a necessary nonvalence contribution in timelike exclusive processes. Following a Schwinger–Dyson type of approach, we relate the nonvalence contribution to an ordinary light-front wave function that has been extensively tested in the spacelike exclusive processes. A complicate four-body energy denominator is exactly cancelled in summing the light-front time-ordered amplitudes. Applying our method to Kℓ3 and D0→K−ℓ+νl where a rather substantial nonvalence contribution is expected, we find not only an improvement in comparing with the experimental data but also a covariance (i.e., frame-independence) of existing light-front constituent quark model.