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arXiv · 1710.06523

Nucleon axial coupling from Lattice QCD

Chia Cheng Chang·Amy Nicholson·Enrico Rinaldi·Evan Berkowitz·Nicolas Garron·David Brantley·Henry Monge-Camacho·Chris Monahan·Chris Bouchard·M. A. Clark·Balint Joo·Thorsten Kurth·Kostas Orginos·Pavlos Vranas·Andre Walker-Loud
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Abstract

We present state-of-the-art results from a lattice QCD calculation of the nucleon axial coupling, $g_A$, using M\"obius Domain-Wall fermions solved on the dynamical $N_f = 2 + 1 + 1$ HISQ ensembles after they are smeared using the gradient-flow algorithm. Relevant three-point correlation functions are calculated using a method inspired by the Feynman-Hellmann theorem, and demonstrate significant improvement in signal for fixed stochastic samples. The calculation is performed at five pion masses of $m_\pi\sim \{400, 350, 310, 220, 130\}$~MeV, three lattice spacings of $a\sim\{0.15, 0.12, 0.09\}$~fm, and we do a dedicated volume study with $m_\pi L\sim\{3.22, 4.29, 5.36\}$. Control over all relevant sources of systematic uncertainty are demonstrated and quantified. We achieve a preliminary value of $g_A = 1.285(17)$, with a relative uncertainty of 1.33\%.

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Chia Cheng Chang, Amy Nicholson, Enrico Rinaldi, Evan Berkowitz, Nicolas Garron, David Brantley, Henry Monge-Camacho, Chris Monahan, Chris Bouchard, M. A. Clark, Balint Joo, Thorsten Kurth, Kostas Orginos, Pavlos Vranas, Andre Walker-Loud. 2017-10-17. Nucleon axial coupling from Lattice QCD. https://arxiv.org/abs/1710.06523

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