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[PAST EVENT] Physics Colloquium
Abstract:
Hadron physics has recently entered a new era, with the emergence of a comprehensive approach to the description of hadron structure, through the Wigner distributions of the fundamental constituents. Wigner distributions are a quantum mechanical concept analogous to the classical notion of a phase space distribution and encode information on both the spatial and momentum tomography of a bound state. A simpler, precursor concept is that of hadron light-front wave functions. They have a probability interpretation and therefore provide a connection between dynamical properties of a quantum field theory and notions familiar from quantum mechanics. An important example is the pion's parton distribution amplitude (PDA), which is a critical piece of the explanation for the behaviour of this interesting hadron. This presentation will draw these threads together, tying the pion's PDA to real-world observables and statements about just when QCD might be perturbative. It will also illustrate the connection between Wigner distributions and transverse momentum dependent parton distribution functions (TMDs), and how light-front wave functions can be used to calculate TMDs for the pion, nucleon, and spin-one targets like the rho and deuteron.