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Physics & Astronomy

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December 1, 2017 | 3:30 p.m. - 4:30 p.m.
Category: Seminar
Location: Physics #312 | Map
666 W. Hancock
Detroit, MI 48201
Cost: Free!
Audience: Academic Staff, Current Graduate Students, Current Undergraduate Students, Faculty

Title: The half-life of a free neutron from Lattice QCD

Speaker: Jason Chang (LBNL)

Abstract: The axial coupling of the nucleon, $g_A$, is a fundamental property of neutrons and protons. The long-range nuclear force between nucleons and the $beta$-decay rate of a free neutron both depend on $g_A^2$. This coupling therefore underpins all of low-energy nuclear physics, controlling, for example, the primordial composition of the universe. While the value of $g_A$ is, in principle, determined by the fundamental theory of nuclear strong interactions, Quantum Chromodynamics (QCD), it is daunting to compute, as QCD is non-perturbative and has evaded an analytic solution. Lattice QCD provides a rigorous, non-perturbative definition of the theory through a discretised formulation which can be numerically implemented.
Using an innovative computational method, we resolve the two outstanding challenges identified by the lattice QCD community for determining $g_A$: we demonstrably control excited state lattice artifacts and are able to utilise exponentially more precise numerical data resulting in the determination $g_A^{QCD} = 1.275 pm 0.012$, compatible with the experimentally measured value and with unprecedented precision of $0.95%$. This milestone calculation signals a new era of precision lattice QCD applications to high-impact experimental searches for physics beyond the Standard Model in nuclear environments.

For more information about this event, please contact Matt Barrett at +1 313 5770750 or