Topological Susceptibility and QCD at Finite Theta Angle
Claudio Bonanno, Claudio Bonati, Massimo D'Elia
TLDR
This paper introduces QCD topology and θ-dependence, reviewing theoretical predictions and numerical results for its phenomenological implications.
Key contributions
- Provides a pedagogical introduction to QCD topology and θ-dependence, covering theoretical aspects.
- Explores phenomenological relevance in Standard Model, including η′ physics and neutron electric dipole moment.
- Addresses beyond-Standard Model issues like the strong CP problem and the axion solution.
- Reviews analytic predictions and recent numerical results from lattice QCD simulations.
Why it matters
This paper provides a comprehensive overview of QCD topology and θ-dependence, crucial for understanding fundamental particle physics. It bridges theoretical predictions with numerical simulations, addressing key issues from the Standard Model to the strong CP problem and axion physics.
Original Abstract
In this chapter we provide a pedagogical introduction to the main theoretical aspects related to topology and $θ$-dependence in Quantum Chromo-Dynamics (QCD), and to their phenomenological relevance in the Standard Model ($η^\prime$ physics, neutron electric dipole moment) and beyond (strong CP problem and the axion solution). We then provide an overview of the main analytic predictions for $θ$-dependence obtained using several different approaches (chiral effective theories, large-$N$ arguments, semiclassical methods) and their regimes of validity, as well as a selection of the most recent numerical results about QCD topology obtained via Monte Carlo simulations of the lattice-discretized theory.
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