A study of quark fragmentation using kaons produced in association with prompt Ds(+ and -)/D(+ and -) mesons .

摘要

Quarks are considered to be the fundamental constituents of hadronic matter, but they have never been observed as free particles. When quarks are produced at high energy colliders, they quickly form bound colorless states, which then decay to produce the particles observed in experiments. The process by which an initially free quark combines with other quarks to form a hadronic particle is called quark fragmentation and has been described using phenomenological models since quarks were first proposed. Since then, several models have been developed to describe the quark fragmentation phenomenon, and these have been tuned to reproduce many average properties of hadrons produced in high energy collisions.;In this dissertation, we describe an analysis that probes the properties of particles produced in association with a hadron containing a charm quark that provides a way, for the first time, to study what is thought of as the second particle produced in the process of heavy quark fragmentation. Data from proton anti-proton collisions was used to carry out this research, which were collected with the CDF II detector at the Fermilab Tevatron and corresponds to 360 pb–1 of integrated luminosity. We reconstruct D±s and D± mesons, which contain charm quarks, and identify the kaons produced in association with them. The kinematic properties of these kaons are compared with predictions of the fragmentation models implemented in the PYTHIA and HERWIG event generators. We find that kaon production in association with D±s mesons is enhanced at levels that are in agreement with the fragmentation models but observe differences in production rates of kaons that are produced later in the fragmentation process.