Section 11.1 Introduction
This chapter continues from the discussion begun in the previous chapter. We now have the tools that we need to study particle interactions at the most fundamental level of quarks and leptons. In this chapter, you'll learn how to sketch particle reactions to reveal the details of the fundamental interactions. And you'll learn how to predict a particle's decay scheme and lifetime from its mass and internal structure. We'll look at the three generations of quarks and leptons and make a case for grand unified theories (GUTs). And finally, we'll return to the early universe as the best laboratory for testing some of these ideas.