Measurement of D*± electroproduction at HERA

Open charm production in deep-inelastic scattering has been studied with the ZEUS detector in collisions between 27.5 GeV positrons and 820 GeV protons at the HERA storage ring. The decay of D*(2010)± mesons has been observed in the 1995 data set by reconstructing the daughter particles of the decay mode D*+ → (D0→K-π+)πs+ (and the charge-conjugated channel) in the central tracking detector (CTD). In the course of this work, a new analysis program shell (EZ) has been developed, which simplifies especially the study of individual particles and their decays. Furthermore, the potential of the ionisation energy loss (dE/dx) in the CTD for particle identification has been studied in detail. In the restricted region of the D* phase space, 1.5<p perpendiculartoD*<10 GeV and vertical stroke ηD* vertical stroke <1.5, the integrated cross-section for D* production has been measured to be 9.11±0.63-0.50+0.55 nb fo r the kinematic range y<0.7 and 1<Q2<600 GeV2, and 5.24±0.42-0.40+0.45 nb for 5< Q2<100 GeV. Differential cross-sections have been measured as functions of Q2, W, p perpendiculartoD* and ηD*, and are compared to NLO predictions of perturbative QCD. The good agreement observed permits use of the NLO calculation for the extrapolation of the measured cross-sections to the full phase space, allowing the determination of the charm contribution F2c(x,Q2) to the proton structure function F2, where x is the Bjorken scaling variable. For fixed Q2, F2c has been found to rise rapidly as x→0. NLO predictions for F2c, based on the gluon density g(x,Q2) in the proton as determined from the scaling violations of F2, agree with the data; this presents an important test of the DGLAP evolution mechanism of perturbative QCD. (orig.)