Observation of New Resonances Decaying to J /ψ K+ and J /ψ ϕ

The first observation of exotic states with a new quark content c c ¯ u s ¯ decaying to the J /ψ K⁺ final state is reported with high significance from an amplitude analysis of the B⁺→J /ψ ϕ K⁺ decay. The analysis is carried out using proton-proton collision data corresponding to a total integrated luminosity of 9 fb^-1 collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV. The most significant state, Z_{c s}(4000 )^{+, has a mass of 4003 ±6_-14+4 MeV , a width of 131 ±15 ±26 MeV , and spin parity JP=1+, where the quoted uncertainties are statistical and systematic, respectively. A new 1+ X (4685 ) state decaying to the J /ψ ϕ final state is also observed with high significance. In addition, the four previously reported J /ψ ϕ states are confirmed and two more exotic states, Z_{c s}(4220 )+ and X (4630 ), are observed with significance exceeding 5 standard deviations.}