Production of the excited charm mesons image and image at HERA Original Research Article

The production of the excited charm mesons image and image in ep collisions has been measured with the ZEUS detector at HERA using an integrated luminosity of image. The masses of the neutral and charged states, the widths of the neutral states, and the helicity parameter of image were determined and compared with other measurements and with theoretical expectations. The measured helicity parameter of the image allows for some mixing of S- and D-waves in its decay to image. The result is also consistent with a pure D-wave decay. Ratios of branching fractions of the two decay modes of the image and image states were measured and compared with previous measurements. The fractions of charm quarks hadronising into image and image were measured and are consistent with those obtained in image annihilations.