Particle Physics at the Energy and Intensity Frontiers
Shrihari Gopalakrishna, Institute of Mathematical Sciences
Particle physics aims to understand the fundamental character of Nature at the tiniest distance scales accessible. To directly study new phenomena at the shortest distance scales, the highest energy probes are required, achieved in giant particle accelerators at the energy frontier. Another option is to study phenomena to the best possible precision to uncover the very rare effects of short-distance physics in experiments at the intensity frontier. Yet another avenue is to use the cosmic frontier to find imprints of new physics in the very hot early-universe.
Careful experimentation through these means for over a century has revealed that the fundamental building blocks in Nature are quarks and leptons. The quarks and leptons interact via the strong, electromagnetic, weak, and gravitational interactions. These properties are succinctly encoded in a very successful theoretical framework called the standard model of particle physics, which is a Poincare-group invariant quantum field theory with an SU(3)xSU(2)xU(1) gauge-group.
Although the standard model has been phenomenally successful in explaining experiments performed till date, there are various indications that our understanding is incomplete. Some observations that are yet to be explained are: what is the observed dark matter and dark energy, what gives rise to the baryon asymmetry, what is the neutrino mass generation mechanism, etc. Some theoretical puzzles that remain are: is there a deeper structure to what we see, is there new physics that restores naturalness in the Higgs sector, why this structure of the quark and lepton masses and mixings, why is there no CP-violation in the strong interactions, what is the consistent way to quantize gravity, etc.
We anticipate that the just upgraded Large Hadron Collider (LHC) at CERN, and future experiments, will reveal answers to many of these questions continuing to deepen our understanding of the fundamental aspects of Nature. The more we learn the more enigmatic it gets!