Fundamental Symmetries Homepage

Welcome to the CINP Fundamental Symmetries Working Group

The Scientific Working Group "Fundamental Symmetries" provides a forum for all Canadian scientists working on tests of the Standard Model at low and intermediate energies, primarily using the techniques of nuclear and atomic physics. It facilitates communication and collaboration within the community by organizing workshops and topical sessions at conferences and fosters the interaction with closely related communities in high energy, nuclear and atomic physics, astrophysics and cosmology. Outreach activities promoting our research are an important part of the working group's mission, both to the general public and to undergraduate and graduate students.

For more information about this working group, please contact us.

Low energy tests of fundamental symmetries in nuclei and atoms have traditionally played an important role in the search for ‘new physics’ beyond the Standard Model. The field is more active than ever, particularly in Canada, where it is represented by the working group “Fundamental Symmetries” within the Canadian Institute of Nuclear Physics (CINP). The study of symmetries in subatomic physics is of key importance for two reasons. On one hand, the fundamental forces and conservation laws of nature are intimately linked to corresponding symmetries; the investigation of those symmetries and their violations gives unique insights. In addition, from a practical point of view, symmetries can be exploited to single out vanishingly small signatures of new physics in the presence of much larger ‘conventional’ interactions, giving low-energy experiments a physics reach to energy scales orders of magnitude higher, and keeping them competitive with direct searches conducted at colliders.

Francium atomic parity violation experiment at TRIUMF (© M. Kossin).

Our current understanding of the fundamental interactions and symmetries is reflected in the Standard Model; constructed 40 years ago, it is essentially still in agreement with experimental findings. It is a quantum field theory founded on the assumptions of Lorentz symmetry and invariance under the combined transformation of charge (C), parity (P), and time reversal (T), or CPT. Since the 1950s and 60s we know that C, P, CP, and T are violated separately. However, the Standard Model contains an uncomfortably large number of free parameters, and while the P and CP symmetry violations have been successfully incorporated, the Standard Model cannot explain their origin. In addition, no link exists between the Standard Model and gravity.

Theories such as quantum gravity and string theory are pursued intensely as a unifying approach valid up to the Planck scale. While they yield the Standard Model and general relativity in the low-energy regime, they frequently assume Lorentz and CPT violation. High precision, low-energy fundamental symmetry-type experiments in nuclei and atoms can probe for very faint remnants of these symmetry violations occurring at energies far beyond the current frontier of direct searches.

In Canada, there is currently a strong community of researchers working on fundamental symmetry tests. The work covers many of the hot topics and also has a remarkable breadth in the experimental approaches, from electron scattering experiments at the 10 GeV level to beta decay in laser traps using atoms at neV temperatures, a span of 19 orders of magnitude in energy!


Current efforts involving Canadian groups


Below we list links and images for ongoing efforts. More details about the physics can be found on the groups' respective webpages and in the CINP Nuclear Briefs and NSERC Long Range Plans .

  • Time-reversal violation: a search for a permanent electric dipole moment of the neutron - TUCAN at TRIUMF [ UCN webpage at TRIUMF ]
    Ultra-cold neutron facility at TRIUMF.


  • Time-reversal violation in radiative beta decay of laser-trapped 38mK at the TRINAT facility at TRIUMF [TRINAT page at TRIUMF ]

    TRINAT beta-neutrino correlation experiment at TRIUMF.


  • The weak charge of the proton via parity-violating electron scattering: The Qweak experiment at JLab [ Qweak home page at JLAB ]
    Qweak detector at JLAB.


  • Parity-violating electron-electron scattering: MOLLER at JLab [ MOLLER page at JLAB ]

    Layout of the future MOLLER experiment at JLAB.


  • Atomic parity violation in laser-trapped francium at TRIUMF [ Francium page at U Manitoba ]

    Francium magneto-optic trap at ISAC/TRIUMF (© M. Kossin).


  • CPT, Lorentz invariance and gravity tests with trapped anti-hydrogen: The ALPHA project at CERN [ ALPHA page at CERN ]




G. Gwinner, 2019

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