Elementary fermions quarks

Presently we consider the quarks, which come in six different flavours, and the leptons, of which also six have been identified, as elementary fermions. 

Chemistry is the central science in the sense that it provides the tie between physics on the one hand and biology on the other. The world of physics, seen broadly, covers a wide spectrum. In general, the concerns of physics focus on entities smaller or larger than those of direct interest to chemistry. At the micro level physics unravels the mysteries of the elementary particles, known generally as fermions, which constimte all ordinary matter. Fermions include the quarks and their antiparticles, the antiquarks. There are six kinds of quarks, known as top, bottom, strange, charm,... 

Abstract The present experimental evidence seems to support the Standard Model of elementary particles, which interprets the world as consisting of 12 basic fermions six quarks and six leptons with their antiparticles, 13 hosons mediating the strong, electromagnetic and weak interactions, and the mysterious Hi s hoson. This chapter attempts to overview the basic features of the Standard Model with a minimal mathematical apparatus. 

On the other hand, no sign of baryon number violation has been observed to date in any elementary particle physics experiment. In the Standard Model, one cannot find any process that would involve the transformation of a proton into mesons or leptons. However, in the early 1970s, t Hooft (1976) showed that in the presence of specific configurations of electro-weak vector fields, fermions (leptons and quarks) can be created or annihilated, but the difference of the baryon number and of lepton number B—L) should stay constant (quarks and antiquarks actually carry 1/3 unit of baryon charge, while the lepton charge of the known species is 1). Today the chance for such transitions to occur is negligible (the probability is estimated to about 10 ). However, they must have occurred frequently when the temperature was of the order of 100 GeV (about 10 K). 

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