Measurements of e+ e- ? ?c?+?-?0, ?c?+?-, and ?c?0? at ?s from 4.18 to 4.60 GeV, and search for a Zc state close to the D(D)over-bar threshold decaying to ?c? at ?s=4.23 GeV

Abstract

We study eta(c) production at center-of-mass energies root s from 4.18 to 4.60 GeV in e(+)e(-) annihilation data collected with the BESIII detector operating at the BEPCII storage ring, corresponding to 7.3 fb(-1) of integrated luminosity. We measure the cross sections of the three different exclusive reactions e(+)e(-) -> eta(c)pi(+)pi(-)pi(0), e(+)e(-) -> eta(c)pi(+)pi(-), and e(+)e(-) -> eta(c)pi(0)gamma. We find significant eta(c) production in e(+)e(-) -> eta(c)pi(+)pi(-)pi(0) at root s of 4.23 GeV and 4.26 GeV and observe a significant energy-dependent Born cross section that we measure to be consistent with the production via the intermediate Y(4260) resonance. In addition, we perform a search for a charmoniumlike Z(c) state close to the D (D) over bar threshold that decays to eta(c)pi, involving ground state charmonium, and observe no signal. Corresponding upper limits on the cross section of eta(c) and Z(c) production am provided, where the yields are not found to be significant.