Hadronic Charmed Meson Decays Involving Axial Vector Mesons

Cabibbo-allowed charmed meson decays into a pseudoscalar meson and an axial-vector meson are studied. The charm to axial-vector meson transition form factors are evaluated in the Isgur-Scora-Grinstein-Wise quark model. The dipole momentum dependence of the D → K transition form factor and the presence of a sizable long-distance W -exchange are the two key ingredients for understanding the data of D → Ka1. The K1A − K1B mixing angle of the strange axial-vector mesons is found to be ≈ ±37◦ or ±58◦ from τ → K1ντ decays. The study of D → K1(1270)π, K1(1400)π decays excludes the positive mixing-angle solutions. It is pointed out that an observation of the decay D0 → K− 1 (1400)π+ at the level of 5× 10−4 will rule out θ ≈ −37◦ and favor the solution θ ≈ −58◦. Though the decays D0 → K01π are color suppressed, they are comparable to and even larger than the color-allowed counterparts: K01(1270)π 0 ∼ K− 1 (1270)π+ and K01(1400)π > K − 1 (1400)π +. The finite width effect of the axial-vector resonance is examined. It becomes important for a1(1260) in particular when its width is near 600 MeV.