Measurement of D*^± Production at Low Q² with the Beam-Pipe Calorimeter of ZEUS at HERA

Abstract

The production of D^* mesons in deep-inelastic ep-scattering has been studied using the ZEUS detector at HERA. The total D^* production cross-section and the differential cross-sections as functions of Q², y, p_t(D^*) and η(D^*) have been measured at low Q². The data sample used was collected during the period 1998-2000 and amount to an integrated luminosity of 82.2 pb^-1.<br /> The low Q² region could be reached using the beam-pipe calorimeter which measures the scattered electron at very small angles. Therefore special emphasis was put on the calibration of the BPC in order to reconstruct events in the kinematic range 0.05 < Q² < 0.7 Gev² and 0.02 < y < 0.85. The D^* mesons have been identified via the decay into lighter mesons D^*+-> K^-π⁺π⁺ and the charged conjugated decay in the kinematic region 1.5 < p_t(D^*) < 9.0 GeV and -1.5 < η(D^*) < 1.5. <br /> The measured cross-sections are in agreement with the predictions from perturbative QCD calculations. Previous ZEUS D^* production measurements could be extended towards lower values of Q² in agreement with the corresponding perturbative QCD predictions.