ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2014, vol. 112, p. -
Observation of a charged (D D ̄ *) ± mass peak in e + e - → π D D ̄ * at s = 4.26 GeV
We report on a study of the process e+e-→π±(DD̄*) - at s=4.26 GeV using a 525 pb-1 data sample collected with the BESIII detector at the BEPCII storage ring. A distinct charged structure is observed in the (DD̄*)- invariant mass distribution. When fitted to a mass-dependent-width Breit-Wigner line shape, the pole mass and width are determined to be Mpole=(3883.9±1.5(stat)±4.2(syst)) MeV/c2 and Γpole=(24.8±3.3(stat)±11.0(syst)) MeV. The mass and width of the structure, which we refer to as Zc(3885), are 2σ and 1σ, respectively, below those of the Zc(3900)→π±J/ψ peak observed by BESIII and Belle in π+π-J/ψ final states produced at the same center-of-mass energy. The angular distribution of the πZc(3885) system favors a JP=1+ quantum number assignment for the structure and disfavors 1- or 0-. The Born cross section times the DD̄* branching fraction of the Zc(3885) is measured to be σ(e+e-→π±Zc(3885)-) ×B(Zc(3885)- →(DD̄*)-)=(83.5±6.6(stat)±22. 0(syst)) pb. Assuming the Zc(3885)→DD̄* signal reported here and the Zc(3900)→πJ/ψ signal are from the same source, the partial width ratio (Γ(Zc(3885)→DD̄*)/Γ(Zc(3900)→πJ/ ψ))=6.2±1.1(stat)±2.7(syst) is determined. © 2014 American Physical Society.