Observation of the h_c(1P) using e^+e^- collisions above DDbar threshold

TL;DR

This paper reports the first observation of the h_c(1P) state in e^+e^- collisions above the D Dbar threshold, measuring its production cross section and providing evidence for related processes at specific energies.

Contribution

The study presents the first measurement of e^+e^- --> pi^+ pi^- h_c(1P) cross section and evidence for e^+e^- --> eta h_c(1P) at 4170 MeV, expanding understanding of charmonium production.

Findings

Measured cross section of 15.6 pb for e^+e^- --> pi^+ pi^- h_c(1P)

Evidence for e^+e^- --> eta h_c(1P) at 4170 MeV

Hints of increased cross section at 4260 MeV

Abstract

Using 586pb^-1 of e^+e^- collision data at E_CM = 4170MeV, produced at the CESR collider and collected with the CLEO-c detector, we observe the process e^+e^- --> pi^+ pi^- h_c(1P). We measure its cross section to be 15.6+-2.3+-1.9+-3.0pb, where the third error is due to the external uncertainty on the branching fraction of psi(2S) --> pi^0 h_c(1P), which we use for normalization. We also find evidence for e^+e^- --> eta h_c(1P) at 4170MeV at the 3sigma level, and see hints of a rise in the e^+e^- --> pi^+ pi^- h_c(1P) cross section at 4260MeV.