Ph.D Thesis


Ph.D StudentAmnon Harel
SubjectA Measurement of the Inclusive Branching Ratio
of Neutral D Mesons to Phi Mesons
DepartmentDepartment of Physics
Supervisor Professor Rozen Yoram


Abstract

The high luminosity B factories of recent years increased the need for a more detailed understanding of charmed meson decay, and in particular, of inclusive branching ratios. We evaluated a technique for measuring the Br(D0à ΦX) at OPAL using a slow-pion tag for the initial state. The slow-pion tag uses the fact that the momentum release in the decay D* à D0 π is only 39MeV. We have examined the applicability of three variations of this technique for measuring Br(D0à ΦX) and found them wanting.


By reconstructing another Φ meson instead of the pion, we get an indirect tag for decay chain Bs à Ds+Ds-(X) followed by two DsàΦX decays.  Since the Bs production rate at the Z resonance is well known, this allows us to measure Br(Bsà Ds+Ds-). This decay is predominantly CP-even, and it may account for the lifetime difference between the Bs’s CP-odd and CP-even eigenstates. We present a measurement that employs an unusual artificial neural net selection: the same ANN is applied to each track using that track's kinematics, geometry and energy loss rate. We measured Br(Bsà Ds+Ds-) = , where the systematic uncertainty can be significantly reduced when a better measurement of Br (Ds(*)àΦX) is available.


Finally, the control system of the ATLAS detector's Thin Gap Chambers is described. The system’s novel design places a significant  part of the system intelligence in microprocessors right on the detector, reducing the bandwidth required to transmit data and commands and allows performing complex tasks with the reliable but slow CAN bus system.  The software of the local control system, whose development was my responsibility, is described in detail.