Determination of spin and parity of the Z_c(3900)

2017/06/13 by BESIII Collaboration, M. Ablikim, M. N. Achasov +424 · 1 citation
Physics and Astronomy · #hep-ex

paper · pdf · doi:10.1103/physrevlett.119.072001

published as Phys. Rev. Lett. 119, 072001 (2017) · 8 pages, 2 figures, 1 table

arxiv created 2017/06/13 · arxiv updated 2017/08/23

Abstract

The spin and parity of the Z_c(3900)^± state are determined to be J^P=1⁺ with a statistical significance larger than 7σ over other quantum numbers in a partial wave analysis of the process e⁺e^-→ π⁺π^-J/ψ. We use a data sample of 1.92 fb^-1 accumulated at √(s)=4.23 and 4.26 GeV with the BESIII experiment. When parameterizing the Z_c(3900)^± with a Flatte-like formula, we determine its pole mass M_\textrmpole=(3881.2±4.2_\textrmstat±52.7_\textrmsyst)\textrmMeV/c² and pole width Γ_\textrmpole=(51.8±4.6_\textrmstat±36.0_\textrmsyst)\textrmMeV. We also measure cross sections for the process e⁺e^-→ Z_c(3900)⁺π^-+c.c.→ J/ψπ⁺π^- and determine an upper limit at the 90% confidence level for the process e⁺e^-→ Z_c(4020)⁺π^-+c.c.→ J/ψπ⁺π^-.

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