Scattering Amplitudes and Correlation Functions

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This award funds the research activities of Professor Andrei Belitsky at Arizona State University.The observable Universe is composed of atoms. Atoms, in turn, are formed by nuclei surrounded by clouds of electrons. Protons and neutrons are bound together to form these nuclei. Zooming further into the protons and neutrons, one encounters quarks and their antiparticles (antiquarks), which are the most fundamental components of matter. The quarks and antiquarks are attracted to each other by the Strong Force. This force is so strong that it is impossible to see individual quarks --- they are always bound together in various configurations. If one tries to pull them apart, the energy expended to do this is immediately converted into the creation of new quark-antiquark pairs from empty space, and those new particles in turn bind to the particles that one was attempting to isolate. A theory underlying these phenomena --- namely Quantum Chromodynamics (QCD) --- has been known since 1974. However, up to now no one has succeeded in solving this theory, and this is not due to a lack of effort. Uncovering the inner workings of the Strong Force will be of paramount importance for understanding the fundamental laws of physics, and is therefore in the national interest because it fosters the development of fundamental science in the United States. As part of this project, Professor Belitsky plans to develop theoretical methods for alleviating the complications one faces in understanding strongly interacting particles such as quarks. He is also engaged in advising and mentoring students at the graduate and undergraduate levels who will make valuable contributions to the project. Moreover, Professor Belitsky delivers popular presentations and also mentors and guides middle- and high-school students, thereby increasing the public awareness of particle physics.On a more technical level, Professor Belitsky will work on a promising paradigm to reformulate the theory of the strong force (QCD) as an effective theory of extended degrees of freedom. Over the past two decades, the field witnessed an explicit implementation of these ideas through the gauge/string correspondence for supersymmetric cousins of QCD. The Principal Investigator will develop and generalize tools for analyses of two types of observables in these models: spacetime S-matrices and correlators of gauge-invariant operators. The main approach is based on their geometrization and use of integrable dynamics of the resulting two-dimensional worldsheet. An explicit implementation includes a tessellation of emerging string worldsheets in terms of overlapping transitions which are then bootstrapped to all orders in coupling. Along these lines, the PI will also pursue a form-factor program for off-shell scattering amplitudes and the properties of its integrable dynamics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.