Answer to Question #89983 in Atomic and Nuclear Physics for Ben

Question

the discovery of the higgs particle was an important contribution to our understanding to particle physics. describe the standard model of subatomic particle.you should identify the fundamental particles and the composition of the particles we can observe

Answer 1

The Standard Model contains of 12 matter fermion fields, divided into two subgroups: quarks and leptons, which are also divided into two families: (u, c, t) quarks, (d, s, b) quarks, (e, mu, tau) leptons and (e, mu, tau) neutrinos. These particles interact with each with three gauge interactions: electromagnetic, weak and strong. Electromagnetic field interacts with charged particles, which are all the fermions except neutrinos and described by U(1) gauge group, its only generator corresponds to a vector boson called a photon. W, Z-bosons, particles associated with generators of SU(2) gauge group of weak interaction, connect (u,c,t) quarks with (d,s,b), as well as (e, mu, tau) leptons with corresponding neutrinos. Particles of the strong interaction are called gluons, there 8 of them due to 8 generators of SU(3) gauge group of strong interaction. However, in the Standard Model, there is a scalar field called Higgs field, which was included in the theory to explain how can gauge W, Z-bosons obtain masses. In the space, there is a nonzero value of Higgs field, and the interaction with it gives masses to all quarks, (e, mu, tau) leptons and W, Z-bosons. Of course, this field on the quantum level also has its particle, called Higgs boson. Gravitation is not included in the Standard Model due to problems with its quantization.

Quarks cannot be seen in free states due to the strong interaction between them. They unite in "uncharged" particles, which are called hadrons and divided into mesons (if it is a quark + antiquark system) or baryons (if it is a 3 quarks system). Well known examples are a proton, neutron (both are baryons), pion or kaon (mesons).