ABSTRACT

We introduced two quarks in Ch. 8, and discussed hadrons which are made up of these two quarks. We also saw how an SU(2) symmetry, viz., the isospin symmetry, helps us understand various properties of these hadrons. At the time when the idea of quarks was introduced, there already existed some hadrons which could not be understood with only the u and the d quarks. So the quark model was born with three types of quarks. We begin this chapter with the reasons for assuming the third quark, and discuss the physics of different hadrons made from the three types of quarks.