Production of the excited charm mesons D 1 and D 2* at HERA

The production of the excited charm mesons D 1 (2420) and D2*(2460) in ep collisions has been measured with the ZEUS detector at HERA using an integrated luminosity of 373pb -1 . The masses of the neutral and charged states, the widths of the neutral states, and the helicity parameter of D 1 (2420) 0 were determined and compared with other measurements and with theoretical expectations. The measured helicity parameter of the D10 allows for some mixing of S- and D-waves in its decay to D *± π Π . The result is also consistent with a pure D-wave decay. Ratios of branching fractions of the two decay modes of the D2*(2460)0 and D2*(2460)± states were measured and compared with previous measurements. The fractions of charm quarks hadronising into D 1 and D2* were measured and are consistent with those obtained in e + e - annihilations. © 2012 Elsevier B.V.