Elementary Particle Physics in a Nutshell

Thanks to the birth of the Large Hadron Collider, a new era has dawned in particle physics. Elementary Particle Physics in a Nutshell summarizes our insights to date, with Christopher Tully spotlighting the current status of theory and experiments alike.

A survey of the Standard Model

An introductory chapter offers an overview of elementary particle physics. By pinpointing the building blocks of matter and their interactions, we can learn not only about the universe today but also its distant past. Beginning with the notion of an “elementary particle,” Tully walks us through the highlights of the Standard Model. This framework consists of six quarks, six leptons, and four forces, as well as the Higgs boson, a major target of the LHC.

We next turn to address one of the most profound equations in particle physics, the Dirac equation, along with quantum electrodynamics. Consider a spin-1/2 particle such as an electron; the rotations of its spin and the states of the system are easily describable. Now take the electron and “Lorentz boost” it into a frame moving to the right. How do we construct a wavefunction of a relativistic electron? The answer leads us to the Dirac equation, which introduces antiparticles—the first of several symmetry extensions to the structure of matter.

From here, we investigate gauge theories, which originate from the existence of degrees of freedom in the description of elementary particle states that are indeterminate and have no effect on the predicted outcomes of any experiment. The “gauge principle” states that the existence and form of an interaction may be deduced from the existence of physically indeterminate, gaugeable quantities.

Tully proceeds to describe the properties of hadrons, composite particles made of quarks held together by the strong force. We see how these particles manifest themselves from the confinement of quarks and gluons into “color-neutral bound states,” a concept that arises from the theory of the strong interaction, also known as quantum chromodynamics.

A focus on experimental insights

We move to the experimental side of the field with a chapter on detectors and measurements. Rather than profiling types of devices and their uses as a starting point, Tully organizes his discussion from the perspective of the particle type to be measured, followed by a review of the experimental methods involved.

A separate chapter includes a look at neutrino oscillations. The realization that one type of neutrino can change into a separate type has helped to resolve a longstanding problem concerning the measured production rate of neutrinos in the Sun’s interior, and suggested that they possess mass.

An extensive number of processes in high-energy electron-positron collider physics have been predicted and measured to high precision; and an entire chapter is devoted to this phenomenon. Among the interactions we study is the “two-photon reaction,” which is described by the collision of two photons, each emitted from the incoming electron and positron, to form a two-fermion final state in addition to the scattered electron and positron.

The energy frontier in experimental particle physics is at hadron colliders, and it is to these that we turn next. Superconducting magnets permit high-momentum protons and antiprotons to be accumulated and ramped to the highest energies with negligible energy loss. The collisions of hadrons probe a wide range of length scales.

Finally, Tully addresses Higgs physics. The Higgs mechanism, which consists of a spontaneous breaking of the electroweak symmetry, is an elegant solution to several outstanding problems in particle physics. It is the quarry of a large-scale search at the LHC, and Tully explores the motivation and status of this hunt.

Complete with end-of-chapter exercises, Elementary Particle Physics in a Nutshell offers an exhilarating tour of this fast-evolving field.