Observation of the h{sub c}({sup 1}P{sub 1}) State of Charmonium

The h{sub c}({sup 1}P{sub 1}) state of charmonium has been observed in the reaction {psi}(2S){yields}{pi}{sup 0}h{sub c}{yields}({gamma}{gamma})({gamma}{eta}{sub c}) using 3.08x10{sup 6} {psi}(2S) decays recorded in the CLEO detector. Data have been analyzed both for the inclusive reaction, where the decay products of the {eta}{sub c} are not identified, and for exclusive reactions, in which {eta}{sub c} decays are reconstructed in seven hadronic decay channels. We find M(h{sub c})=3524.4{+-}0.6{+-}0.4 MeV which corresponds to a hyperfine splitting {delta}M{sub hf}(1P){identical_to}-M({sup 1}P{sub 1})=+1.0{+-}0.6{+-}0.4 MeV, and B({psi}(2S){yields}{pi}{sup 0}h{sub c})xB(h{sub c}{yields}{gamma}{eta}{sub c})=(4.0{+-}0.8{+-}0.7)x10{sup -4}.