Heavy Flavor Theory: Overview

An introduction to the heavy quark effective theory and its symmetries is given. Some implications of the heavy quark spin and flavor symmetries are discussed. Recent results on fragmentation to quarkonium states are reviewed.Comment: 25 pages, phyzzx, CALT-68-1901, Talk given at the Lepton Photon Conferenc

The b-quark and Symmetries of the Strong Interaction

Applications of HQET and NRQCD to fragmentation are briefly reviewed. The special role of the b-quark in applications of heavy quark symmetry is discussed. Predictions of HQET for semileptonic B decays to excited charmed mesons are considered.Comment: 8 pages, Talk presented at the Twenty Beautiful Years of Bottom Physics Symposium, Chicago, IL, 1997. Discussion of fragmentation parameters is improve

Dedication to Nathan Isgur

Nathan passed away in July after a lengthy illness. I am sure most of you are familiar with his many contributions to heavy quark physics and it is certainly fitting that we take a few minutes to honor him at the beginning of this meeting. Actually Nathan's main physics interest was the strong interactions rather than heavy quark physics per se. He was already very well known for work he did with Gabriel Karl and others on the nonrelativistic quark model before the work that he did on heavy quark symmetry and its applications. However, Nathan understood the limitations of the nonrelativistic quark model, and was thrilled that the methods he helped develop allowed one to derive systematically from the theory of the strong interactions many properties of hadrons that contain a heavy quark

Yukawa Bound States of a Large Number of Fermions

We consider the bound state problem for a field theory that contains a Dirac fermion $\chi$ that Yukawa couples to a (light) scalar field $\phi$. We are interested in bound states with a large number $N$ of $\chi$ particles. A Fermi gas model is used to numerically determine the dependence of the radius $R$ of these bound states on $N$ and also the dependence of the binding energy on $N$. Since scalar interactions with relativistic $\chi$'s are suppressed two regimes emerge. For modest values of $N$ the state is composed of non-relativistic $\chi$ particles. In this regime as $N$ increases $R$ decreases. Eventually the core region becomes relativistic and the size of the state starts to increase as $N$ increases. As a result, for fixed Yukawa coupling and $\chi$ mass, there is a minimum sized state that occurs roughly at the value of $N$ where the core region first becomes relativistic. We also compute an elastic scattering form factor that can be relevant for direct detection if the dark matter is composed of such $\chi$ particles.Comment: 14 pages, 7 figure