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 -->(K) over bara(1). The K-1A -K-1B mixing angle of the strange axial-vector mesons is found to be approximate to +/-37degrees or +/-58degrees from tau --> K(1)nu(tau) decays. The study of D --> K-1(1270) pi, K-1(1400) pi decays excludes the positive mixing-angle solutions. It is pointed out that an observation of the decay D-0 --> K-(1) over bar(1400) pi(+) at the level of 5x10(-4) will rule out thetaapproximate to-37degrees and favor the solution thetaapproximate to -58degrees. Though the decays D-0-->(K) over bar (0)(1)pi(0) are color suppressed, they are comparable to and even larger than the color-allowed counterparts (K) over bar (0)(1)(1270) pi(0) similar to K-1(-)(1270) pi(+) and (K) over bar (0)(1)(1400) pi(0) > K-1(-)(1400) pi(+). The finite width effect of the axial-vector resonance is examined. It becomes important for a(1)(1260) in particular when its width is near 600 MeV.