Theoretical Physics Colloquium

What's up with Beyond the Standard Model of Particle Physics?

by Prof. Kaustubh Agashe (University of Maryland, USA)

Tuesday, January 1, 2019 from to (Asia/Kolkata)
at AG 69
I will present the status of selected topics going beyond the Standard Model (BSM) of particle physics. One of the motivations to extend the SM is to address it's "hierarchy problem''. Namely, a condensate of the Higgs boson determines the range of the weak nuclear force. However, one finds that quantum corrections generically shift this range to a much smaller value than what is observed. Conventional solutions to this mystery  include supersymmetry (postulating the existence of a partner for every SM particle with spin differing by 1/2) and the idea that the Higgs boson is a composite particle (made up of constituents which are tightly bound by a new force), which is conjectured to be related to theories with a warped extra dimension. These proposals are being highly constrained by various experimental searches. This has inspired new approaches such as the possibility that the new particles which solve the hierarchy problem do not feel the forces of the SM (unlike the above two cases), thereby making them difficult to search for or using the cosmological evolution of the universe to account for the size of the Higgs condensate. Another reason to invoke new particles is to make up the dark matter (DM) of the universe, where the more popular option has been weakly interacting massive particles (WIMPs) which often arise in solutions to the hierarchy problem. Once again, the null results of searches for such particles has led to proposals that the DM is much lighter and revival of interest in an old idea, namely, a particle called the axion (in turn, originally invoked in order to solve one of the puzzles of the strong nuclear force).