The structure of charm jets and the dead cone effect in deep-inelastic scattering at HERA

The structure of charm jets in deep-inelastic scattering is studied with the H1 detector at HERA using an integrated luminosity of 50 pb-1. The analysis is performed in the phase space region 2≤Q2≤100 GeV2 and 0.05 ≤y≤ 0.7. Charm events are tagged by a D*-meson required to have a transverse momentum pT,D*> 1.5 GeV and a pseudorapidity vertical stroke ηD* vertical stroke < 1.5. Furthermore, the events are required to have at least one jet containing the D*-meson (D* Jet). If there is a second jet (OtherJet) in the event, it must have, like the D*Jet, pT,Jet> 1.5 GeV and vertical stroke ηJet vertical stroke < 1.5. The structure of the D*Jet and the OtherJet is investigated by measuring jet shape variables and subject multiplicities. In addition the angle of subjects with respect to the jet axis of the D*Jet and the OtherJet is used to study gluon radiation at the parton level. Study of the latter distribution as well as the derived one of a characteristic angle α0EJet as a function of EJet is motivated by the expected suppression of soft gluon radiation from heavy quarks, the so-called 'Dead Cone' effect, predicted by QCD. In all distributions differences between the D*Jet and the OtherJet are observed. The data are found to be well described by the QCD model for charm production, which includes the suppression of soft gluon radiation, as implemented in RAPGAP 2.8 and JETSET 7.4. Various checks and a further analysis using higher statistics are presented in order to get a better understanding of the contribution from the 'Dead Cone' effect to the α0EJet vs. EJet distribution. (orig.)