Wing, Matthew; (1999) The study of heavy quark production in high ET photoproduction at HERA using the ZEUS detector. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The production of heavy quarks has been studied in dijet photoproduction at HERA. Two high transverse energy jets provide a hard scale as well as the quark mass itself. Using data collected by the ZEUS detector during 1996 and 1997 with a total luminosity of 36.9 pb-1, we have performed two analyses to study heavy quark production. Firstly, we have considered decays of the D*(2010) meson in dijet events and measured the cross-section, dó/dxyobs, where xyobs is the fraction of the photon energy contributing to the two highest transverse energy jets. On comparison of the distribution with the predictions of Monte Carlo simulations, the component of resolved photon processes needed to describe the data is 43±5(stat.)%. Secondly, we have measured the same cross-section for the inclusive decays of quarks to electrons in the final state in a similar kinematic region. For this cross-section a significant contribution of resolved processes, equal to 29±5(stat.)%, was also required in the Monte Carlo to describe the data. Furthermore, to analyse the contribution of beauty quarks in the kinematic region, the cross-section, dó/dpTrel, was measured, where pTrel is the momentum of the electron transverse to the axis of the jet which the electron is closest to. On comparison of the data with Monte Carlo predictions, the component from decays of beauty quarks required to describe the cross-section was 15.6 ± 4.2(stat.)+12.9-7.0 (syst.)%. Therefore, the amount of beauty measured compared to the Monte Carlo is, 1.3 x MC < beauty < 4.9 x MC, in the one sigma limit. The 95% confidence level upper limit is, beauty < 6.5 x MC. In this thesis, we therefore obtain the first indication of open beauty production at ZEUS.

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