First observation of the direct detection of positive D-meson into anti-K-long + 3 pions and negative D-meson into K-long + 3 pions with the Fermilab FOCUS experiment

Abstract

In this thesis the decays of positive D-mesons into neutral anti-K-mesons and three charged pions and of negative D-mesons into neutral K-mesons and three charged pions are reconstructed in both long and short neutral K-meson states. The data were taken with the Fermilab FOCUS spectrometer. This constitutes the first observation of these decays in the long K-meson mode. We detail the cuts necessary to find the branching ratio for the K-long to K-short modes for both positive and negative D-mesons, show that the ratio is 0.89, and detail further work that remains to be done. The K-long mode is reconstructed using the D-meson flight direction, the direction of the charged pions, and the energy deposited in the hadron calorimeter. The K-short decay is reconstructed directly using tracking information in the pi plus - pi minus decay mode.