Observation of charmed strange meson pair production in Y(2S) decays and in e+e− annihilation at sqrt(s)=10.52 GeV

We observe the process Y(2S)→D(*)+s D−sJ and continuum production e+e-→D(*)+s D-sJ at sqrt(s)=10.52  GeV (and their charge conjugates) using the data samples collected by the Belle detector at KEKB, where D-sJ is Ds1(2536)− or D*s2(2573)−. Both D-sJ states are identified through their decay into KD(*). We measure the products of branching fractions B(Y(2S)→D(*)+s D−sJ)B(D-sJ→KD(*)) and the Born cross sections σBorn(e+e-→D(*)+s D-sJ)B(D-sJ→KD(*)), and then compare the ratios R1=B(Y(2S)→D(*)+s D−sJ)/B(Y(2S)→μ+μ−) for Y(2S) decays and R1=σBorn(e+e-→D(*)+s D-sJ)/σBorn(e+e-→μ+μ−) for continuum production. We obtain R1/R2=9.7±2.3±1.1, 6.8±2.1±0.8, 10.2±3.3±2.5, and 3.4±2.1±0.8 for the D+s Ds1(2536)−, D*+s Ds1(2536)−, D+s D*s2(2573)−, and D*+s D*s2(2573)− final states in the D-sJ→K−D(*)0 modes, respectively. The measured R1/R2 values indicate that the strong decay dominates in Y(2S)→D(*)+s D−sJ processes. We also measure the ratios of branching fractions B(Ds1(2536)−→K0SD*(2010)−)/B(Ds1(2536)−→K-D*(2007)0)=0.48±0.07±0.02 and B(D*s2(2573)−→K0SD-)/B(D*s2(2573)−→K-D0)=0.49±0.10±0.02, which are consistent with isospin symmetry. The second ratio is the first measurement of this quantity. Here, the first uncertainties are statistical and the second are systematic.