Production of excited charm and charm-strange mesons at HERA

TL;DR

This paper reports measurements of excited charm and charm-strange mesons produced in ep collisions at HERA, including their properties, production rates, and a search for radially excited states, providing data to test theoretical models.

Contribution

It presents the first detailed measurements of masses, widths, helicity parameters, and production rates of specific excited charm mesons at HERA, including a search for radially excited states.

Findings

Measured masses, widths, and helicity parameters of D_1(2420)^0, D_2^*(2460)^0, and D_{s1}(2536)^+-

Determined production rates and branching fraction ratios for these mesons

Conducted a search for the radially excited D^{*'}(2640)^+- meson

Abstract

The production of excited charm, D_1(2420)^0 and D_2^*(2460)^0, and charm-strange, D_{s1}(2536)^+-, mesons in ep collisions was measured with the ZEUS detector at HERA using an integrated luminosity of 126 pb^-1. Masses, widths and helicity parameters were determined. The measured yields were converted to the rates of c quarks hadronising as a given excited charm meson and to the ratios of the dominant D_2^*(2460)^0 and D_{s1}(2536)^+- branching fractions. A search for the radially excited charm meson, D^{*'}(2640)^+-, was also performed. The results are compared with those measured previously and with theoretical expectations.