2019-05-22 14:00  P7F

Size and Shape of Proton and Holography

Tan, Chung-I

The notion of size of a particle is well-defined classically. Under a Lorentz boost, its transverse size would not change. For a proton at rest, its classical size can be measured by a “weak probe”, e.g., a photon. However, quantum mechanically, a ``probe” is a scattering process. Proton-proton differential and total cross sections, while providing information on shape and size of hadrons, also probe the strong interactions, Quantum Chromodynamics (QCD), at high energy. Surprisingly, one observes that total cross increases with energy. After briefly reviewing experimental data, including that from the Large Hadron Collider at CERN, (LHC), I will turn to a discussion on the modern holographic approach to gauge theories, focusing on their “gravity duals”. In this approach, increasing proton-proton total cross section observed at LHC can be understood in terms of a novel notion of QCD Graviton.