Measurement of the Dynamics of the Decays D-s(+) -> eta(('))e(+)nu(e)

Abstract

Using e(+)e(-) annihilation data corresponding to an integrated luminosity of 3.19 fb(-1) collected at a center-of-mass energy of 4.178 GeV with the BESIII detector, we measure the absolute branching fractions BDs+->eta e+nu e = (2.323 +/- 0.063(stat) +/- 0.063(syst))% and BDs+->eta'e+nu e = (0.824 +/- 0.073(stat) +/- 0.027(syst))% via a tagged analysis technique, where one D-s is fully reconstructed in a hadronic mode. Combining these measurements with previous BESIII measurements of BD+->eta(')e+nu e,the eta - eta' mixing angle in the quark flavor basis is determined to be phi(P) = (40.1 +/- 2.1(stat) +/- 0.7(syst))degrees. From the first measurements of the dynamics of D-s(+) -> eta(')e(+)nu(e) decays, the products of the hadronic form factors f(+)(eta('))(0) and the Cabibbo-Kobayashi-Maskawa matrix element vertical bar V-cs vertical bar are determined with different form factor parametrizations. For the two-parameter series expansion, the results are f(+)(eta) (0) vertical bar V-cs vertical bar = 0.4455 +/- 0.0053(stat) +/- 0.0044(syst) and f(+)(eta)' (0) vertical bar V-cs vertical bar and = 0.477 +/- 0.049(stat) +/- 0.011(syst).