Observation of a new charged charmoniumlike state in B -> J/psi K pi decays

Understand

We present the results of an amplitude analysis of anti-B0 -> J/psi K- pi+ decays.

• A new charged charmoniumlike state Zc(4200)+ decaying to J/psi pi+ is observed with a significance of 6.2 sigma.
• The mass and width of the Zc(4200)+ are 4196 +31-29 +17-13 MeV/c^2 and 370 +70-70 +70-132 MeV, respectively; the preferred assignment of the quantum numbers is J^P = 1^+.
• In addition, we find evidence for Zc(4430)+ -> J/psi pi+.