Precise determination of the properties of X(3872) and of its isovector partner Wc1.

We perform a simultaneous fit to BESIII data on e+e-→γ(D0D‾0π0/J/ψπ+π-) and LHCb data on B+→K+(J/ψπ+π-) to precisely determine the properties of the X(3872), with full consideration of three-body effects from D∗→Dπ decay, respecting both analyticity and unitarity. The X(3872) is determined to be a quasi-bound state with a significance of 2.7σ, representing the most precise determination to date. Its pole is located at -160-74+57-125-38+23ikeV, relative to the nominal D0D‾*0 threshold. Moreover, we confirm the presence of an isovector partner state, Wc1. It is found as a virtual state at 3.1±0.7+1.3-0.6+1.9iMeV relative to the D+D*- threshold on an unphysical Riemann sheet, strongly supporting a molecular nature of both X(3872) and Wc1. As a highly nontrivial prediction, we show that the Wc1 leads to nontrivial lineshapes around 3.88 GeV in B0→K0X(3872)→K0D0D¯0π0 and K0J/ψπ+π--thus the scheme presented here can be tested further by improved measurements.