From July 9th to July 10th this year, the Canadian Institute of Nuclear Physics (CINP) held a workshop on Fundamental Symmetries at TRIUMF, Canada’s national laboratory for particle and nuclear physics, and Green College, as a satellite meeting to the International Nuclear Physics Conference (INPC 2010). TRIUMF Director Nigel Lockyer attended the whole of Saturday of the conference.
The study of fundamental symmetries lies at the intersection of nuclear, atomic, and particle physics. The workshop joined physicists of each of those areas of study from Canada and fourteen other nations. The workshop attendees participated in topics including beta decay, parity violation in atoms and nuclei, EDMs (electric dipole moment), muon decay, Lorentz and CPT invariance, neutrons, neutrinos, and others.
The highlight of the conference was a talk on the size of the proton as measured in muonic hydrogen. In a recent discovery, protons were found to be slightly smaller than previously thought, so particle physicists now have a more accurate and precise value to work with.
"Numerous new initiatives were presented, giving a bright outlook for the field of low-energy fundamental symmetry measurements," said Gerald Gwinner, chair of the workshop. "This first successful CINP Fundamental Symmetries workshop hopefully will be the beginning of regular meetings between Canadian researchers in fundamental symmetries and their colleagues from around the world."
But what are fundamental symmetries anyway?
Physicists understand the universe as having certain physical properties that have a balance on two sides. You may have heard of antimatter, a counterpart to our matter - all of the things we interact with every day that our universe is made of. Matter and antimatter are, in physics, supposed to be created in precisely equal quantities in an event like the Big Bang. Antimatter is nearly exactly the same as matter except for one small difference, a change in the charge or spin of the particle. For instance, take the antimatter electron, also known as a positron. The positron is the same as an electron, only positively charged instead of negatively charged. When antimatter meets its matter twin, they are supposed to annihilate each other into pure energy.
There is a problem with this theory though: there is much more matter in the universe than there is antimatter. So where would all of the antimatter have gone? This is an asymmetry, in what is supposed to be symmetrical - the same on both sides. That means it is a violation of our current fundamental understanding of the universe.
The basic theory for elementary particles describes three different principles of symmetry: P for parity, C is the symmetry of charge, and T is the symmetry of time.
All forces in the universe have equal and opposite reactions, and this is the reason why there is supposed to be an antimatter counterpart to our matter - something equal and opposite to matter should have been created at the start of the universe. But where is all the antimatter?
Researchers at TRIUMF partner with CERN at the Large Hadron Collider's (LHC) LHCb experiment, which investigates the question of what happened to all the antimatter by studying its properties. A related question is, why our universe is made of matter and not antimatter in the first place? That is to say, why are our protons positively charged and our electrons negatively charged, and not the other way around?
One of the symmetries physicists believe the universe is supposed to follow is Charge-Parity. Charge-symmetry necessitates that a particle's charge does not alter how it follows the laws of nature, but this rule is broken by certain particles. Parity-symmetry necessitates that a nucleus will behave the same way regardless of its orientation in space, which is also broken by certain particles. The resultant theory is that perhaps the symmetry is actually preserved when charge and parity symmetries are broken together. Even this symmetry could not stand alone though, so the thought now is that the symmetry is actually one of Charge, Parity, and Time, all taken together.
Time-symmetry dictates that events that happen to particles must happen the same way both forwards and backwards. For instance, if a particle is moving and it splits into two different particles, we should be able to reverse the process - which would mean taking those two remaining particles and colliding them back together into the original. It is currently believed that Time symmetry must be broken when Charge and Parity symmetry are broken.
Why is the study of fundamental symmetry important, or relevant to everyday life?
To understand the way the universe works on a basic, fundamental, level is the kind of thing that results in many completely unexpected developments in science and technology. Typically when discoveries are made about why something is strange in science and physics, that knowledge gives us a whole new ability with which to approach the development of new technologies. Several experiments are underway to explore these symmetries, including such as experiments by Makoto Fujiwara to understand the properties of anti-matter hydrogen that his team successfully trapped. Other experiments presented include the searches for permanent electric dipole moment (EDM), an intrinsic charge polarization of elementary particles, which is directly related to the violation of time and parity symmetry. Others are in preparation, such as Gerald Gwinner and colleagues’ experiment to measure parity violation in radioactive francium atoms, which will help physicists understand the violation of symmetries in more detail.
"We were thrilled with the level of interest in this workshop,” said Makoto Fujiwara, co-chair of the workshop. "I think it is a reflection of the vibrancy in the field of Fundamental Symmetries studies, both nationally and internationally."
The Fundamental Symmetries Workshop, in addition to drawing greater interest in the field, was also important to prepare for long range planning of goal, and the next five-year plan for subatomic physics funding. It also highlighted the major Canadian contributions made to the study of fundamental symmetries, including the project to trap anti-matter (which succeeded later in November), experiments on ultra-cold neutrons, and the ISAC experiments at TRIUMF. There are also Canadians researching at the Jefferson Lab in the United States, at the TREK experiment (search for Time Reversal violation at KEK) and the Muon g-2 experiment at KEK in Japan, and at the TWIST and PIENU experiments.
- Jessica Coccimiglio, Communications Assistant