Measurement of e⁺e⁻→γχ_c0,c1,c2 cross sections at center-of-mass energies between 3.77 and 4.60 GeV

The e+e−→γχcJ (J=0, 1, 2) processes are studied at center-of-mass energies ranging from 3.773 to 4.600 GeV, using a total integrated luminosity of 19.3  fb−1 e+e− annihilation data accumulated with the BESIII detector at BEPCII. We observe for the first time e+e−→γχc1,c2 signals at √s=4.180  GeV with statistical significances of 7.6σ and 6.0σ, respectively. The production cross section of e+e−→γχc1,c2 at each center-of-mass energy is also measured. We find that the line shape of the e+e−→γχc1 cross section can be described with conventional charmonium states ψ(3686), ψ(3770), ψ(4040), ψ(4160). Compared with this, for the e+e−→γχc2 channel, one more additional resonance is added to describe the cross section line shape. Its mass and width are measured to be M=4371.7±7.5±1.8  MeV/c2 and Γtot=51.1±17.6±1.9  MeV, where the first uncertainties are statistical and the second systematic. The significance of this resonance is estimated to be 5.8σ, and its parameters agree with the Y(4360) resonance previously reported in e+e−→π+π−ψ(3686), and the Y(4390) in e+e−→π+π−hc within uncertainties. No significant signal for the e+e−→γχc0 process is observed, and the upper limits of Born cross sections σB(e+e−→γχc0) at 90% confidence level are reported.