Introduction to Particle Physics

Fragment Zoo

Physical scientists thought there were only three basic elements for most of the first half of the twentieth century: the known proton, neutron, and electron. Nonetheless, by the mid-1960s, that image had shifted. Improvements to particle accelerators and detector technology set the stage for the discovery of a seemingly infinite number of new particles. The so-called ‘particle zoo’ of the day lacked simplicity and elegance, which are indications of an excellent theory in science. Investigators began looking for a much simpler, unifying theory to explain the particles fundamentally.

Incomplete, but Elegant

Over the following decades, a theory known as the Standard Model of Particle Physics arose. The model explains the fundamental structure behind the particle zoo with unbelievable ‘accuracy.’ Presently, the theory is one of the most well-supported scientific theories in history.

The theory distinguishes two types of particles: fermions, which comprise all about us, and bosons, which mediate how fermions communicate with one another. Two typical examples are the electron (a fermion) and a photon (a boson), the particle of light that lugs the electromagnetic force. Fermions are then separated right into quarks – which make up protons and neutrons – and leptons – that include electrons in addition to muons, taus, and the elusive, barely-massive neutrinos.

The Standard Model estimates the properties of particles with unbelievable precision.

For a while, it indeed appeared to be the fundamental theory that physicists of the ‘particle zoo’ days looked for so fervently. Yet, one significant issue persisted – the theory can not explain why any particle has mass, much less estimate the masses of individual particles.

The Higgs and Beyond

Peter Higgs, François Englert, and others theorized an expansion to the Standard Design to solve this issue. They predicted the existence of an important field that exists everywhere, all the time, and provides mass to fundamental particles. Additionally, they proposed that excitation of this field could be observed as a particle – the famous Higgs Boson. In July 2012, almost fifty years after the first theorization of the Higgs Boson, CERN confirmed that both the CMS and Atlas experiments had observed the elusive particle.

This first observation of the Higgs caused nearly as many answers as questions. Physicists have found out little about the boson’s properties from experimental data. More data must be collected to verify the extent to which the observed particle matches the estimated one. And, despite its successes, the Standard Model has some drawbacks. It can not consider the majority of the mass in the universe, which is bound up in Dark Matter. Nor can it explain why deep space is filled with matter and not made of equal parts matter and anti-matter. And don’t even think of including gravity in the picture! There are several concerns to explore concerning the universe and subatomic particles.

Originally published on Stanford. Read the original article.