Improved lattice computation of proton decay matrix elements

By Y. Aoki, T. Izubuchi, E. Shintani, A. Soni. 2017

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We present an improved result for the lattice computation of the proton decay matrix elements in Nf=2+1 QCD. In this study, by adopting the error reduction technique of all-mode-averaging, a significant improvement of the statistical accuracy is achieved for the relevant form factor of proton (and also neutron) decay on the gauge ensemble of Nf=2+1 domain-wall fermions with mπ=0.34–0.69  GeV on a 2.7  fm3 lattice, as used in our previous work [1]. We improve the total accuracy of matrix elements to 10–15% from 30–40% for p→πe+ or from 20–40% for p→Kν¯. The accuracy of the low-energy constants α and β in the leading-order baryon chiral perturbation theory (BChPT) of proton decay are also improved. The relevant form factors of p→π estimated through the “direct” lattice calculation from the three-point function appear to be 1.4 times smaller than those from the “indirect” method using BChPT with α and β. It turns out that the utilization of our result will provide a factor 2–3 larger proton partial lifetime than that obtained using BChPT. We also discuss the use of these parameters in a dark matter model.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/64275c73707c666dfc2dd2b2fca8438925b38518