Nuclear Physics

From McGill (University) website:  Nuclear Physics

Nuclear physics began with the discovery of radioactivity, transmutation of matter, and the discovery of the nucleus. The latter two discoveries were made by Sir Ernest Rutherford. McGill University's long and strong tradition of excellence in nuclear physics began with Rutherford's tenure at McGill between 1898 and 1907 during which he discovered the transmutation of matter. The same tradition of excellence continues on to this day.
Today, nuclear physics encompasses a wide range of modern physics. The traditional study of nuclei and their reactions is still a vibrant part of modern nuclear physics. In the latter part of the 20th century, however, a new and exciting field of nuclear physics started to emerge, the study of nuclear matter under extreme conditions.

Nuclear Theory at McGill
(C. Gale, S. Jeon)

Soon after the advent of Quantum Chromodynamics (QCD), the theory of the strong nuclear force, physicists began to realize that at extreme temperatures of trillions of Kelvin, the protons and neutrons in nuclei should, in effect, melt, and the released quarks and gluons should form a completely new phase of matter. The hunt for this new state of matter, dubbed the Quark-Gluon Plasma (QGP), soon began and the powerful relativistic heavy ion colliders at the Brookhaven National Laboratory and at CERN have now confirmed that under this extreme and highly relativistic condition, QGP is indeed the phase of the nuclear matter. Yet, many properties of the produced QGP, such as the lowest viscosity ever measured, were completely unexpected.

To put QGP in perspective, this kind of temperature (about a billion times hotter than the surface of the sun) existed in nature only when the Universe was about a micro-second old, about 1 cubic millimeter of QGP contains enough energy that it could power current Canadian economy for few hundred million years, yet it flows more freely than the superfluid helium!
The study of QGP is the new frontier of modern nuclear physics. The Nuclear Theory Group at McGill has long been playing a central role in the development of this exciting new field. The group currently consists of two professors (Charles Gale and Sangyong Jeon) and more than a dozen students and postdoctoral fellows. The group also has strong ties to researchers in the high energy theory group at McGill and collaborators in the US, Europe and Asia. The main focus of our study is QGP and the relativistic heavy ion collisions in which it is made. The research topics vary widely from purely theoretical to numerical simulations. What ties all of our efforts together is the question, How does one use heavy ion collision phenomenology to learn about QGP? This calls for a comprehensive model of the full evolution of heavy ion collisions.

Evolution of jets in QGP

To achieve the extreme conditions necessary to produce QGP, heavy nuclei such as gold or lead are accelerated to almost the speed of light and made to collide with each other. The produced QGP then cools as it expands and eventually turns back into ordinary matter. To accurately describe and predict the behavior of these processes requires understanding of the initial nuclei, energy and entropy release during the collision, formation of QGP, expansion and cooling, and finally the phase transition back to ordinary nuclear matter. While all these are happening, high energy quarks (called the jets) may traverse QGP shedding some of its energy, and photons from black-body radiation are being produced at each stage. To understand all of the above is a challenging task to say the least. Yet, the goal of the our group is nothing short of building a comprehensive model of the full heavy ion collision and QGP evolution encompassing the essence of all of the above!
To achieve this goal, some of us are working on applying string theory techniques to the study of QGP, some of us are studying quantum field theories at extremely high temperatures, some are building the most advanced hydrodynamic models of the QGP evolution, and some are studying the effect of QGP on ultrarelativistic particles that are traversing it. Yet, there are many important un-answered questions such as What is the nature of the initial conditions? How does the QGP form so quickly? that are waiting for bright minds.
To add excitement, the LHC has started to produce a copious amount of new heavy ion collision data which contains more surprises that await theoretical resolution. Our group is fully engaged in studying all aspects of these issues. This is an exciting time to be a nuclear physicist, especially at McGill!

A hydrodynamic simulation of QGP evolution

Nuclear Experiment at McGill
(F. Buchinger)

The formation of the elements that make up our universe, from the remnants of the big bang that created it, continues to be a fascinating mystery. It is thought that at least part of the production of the heavier elements took place during explosive astrophysical events (supernovae, x-ray bursts etc.) that are powered by nuclear reactions among short-lived, radioactive nuclides at the limits of nuclear binding. The atomic masses of these nuclei are essential to understanding these processes because they determine the energy released and determine the path of the nuclear reaction chains that take place in these events. Furthermore, the atomic masses of nuclei that participate in super-allowed beta-decay provide a unique opportunity for tests of fundamental symmetries in the standard model for particle physics.
Nuclear mass measurements are done using the Canadian Penning Trap Mass Spectrometer (CPT) at the Argonne national Laboratory that collects short life nuclei produced in reactions at the ATLAS heavy-ion accelerator. With this system, nuclear masses of isotopes with lifetimes as short as 30 milliseconds are measured with very high accuracy and sensitivity. Nuclear mass measurements are also performed using the TITAN facility at TRIUMF in Vancouver where the unstable nuclei are produced by a different process; nuclear spallation.
In recent years, techniques originally used for atomic spectroscopy have been applied to measure such nuclear properties as spin, electric and magnetic moments, and the change of charge-radius between neighboring isotopes. These techniques are based on the precise measurement of atomic hyperfine structure in the interaction of laser beams with atomic beams obtained from isotope separators. The laboratory has pioneered in the development of a number of high sensitivity techniques for such studies.
Our group participates in a program of such measurements at the ISAC radioactive beam facility at TRIUMF. Using a spectroscopic method known as collinear fast beam laser spectroscopy and by making use of existing facilities such as the TITAN ion trapping system and material science beta-NMR and beta-NQR it is possible to perform spectroscopy measurements on ion beams with intensities as low as a few tens of ions per second.