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Abstract:
Lattice QCD is a unique numerical approach that is able to calculate hadronic quantities including nonperturbative QCD effects fully with statistical and systematical errors quantified. Lattice QCD has gold-plated calculations in flavor physics that achieved percent-level or even smaller errors. These inputs are crucial for stringent tests of the Standard Model. For example, precise determination of the CKM matrix elements is essential to test the CP-violation in the Standard Model quark sector. Hadronic matrix elements, e.g., decay constants and form factors, are essential inputs from lattice QCD to determine the CKM matrix elements.
In this talk, I will present a high-precision lattice QCD calculation of B to D (D*) semileptonic decays form factors. This calculation adopts highly improved lattice heavy quark action and current operators that could suppress heavy quark discretization error up to the third order in heavy quark effective theory power-counting.
All the methodology developed to bring precision results for flavor physics can be transferred to the nucleon structure calculations. Nucleon particularly suffers from a notorious signal-to-noise ratio problem. However, enormous statistics are accumulated with modern supercomputing systems together with the theoretical development of variance reduction techniques. So, the benchmarking calculations of nucleon axial charges approach to percent-level errors.
In the later part of this talk, I will present a recent advancement in excited state control of nucleon form factors. The advancement in the analysis method makes it possible to incorporate low-energy nucleon-pion excites states, which supposedly exist but have not been shown explicitly from simulation data, thus omitted. The impact of including these low-energy excited states is substantial for the nucleon axial form factor and moderate for the electromagnetic form factors. Particularly, this advancement better shapes the lattice determination of the nucleon axial form factor for the upcoming neutrino experiments using nuclear targets. These neutrino experiments are aiming to better understand neutrino oscillation and thus the CP-violation in the lepton sector that is not described by the Standard Model.
Biography:
I am a postdoctoral research scientist at Columbia University in the City of New York. Before joining the Columbia lattice group in the physics department, I was a postdoctoral research associate at Brookhaven National Laboratory and Los Alamos National Laboratory after receiving a Ph.D. in 2015 from Seoul National University, South Korea. My primary field of research is lattice QCD for precision tests of the Standard Model. Research interests include applications of effective field theories for the lattice QCD and numerical algorithms and software development for high-performance computing.
Online meeting room： https://meeting.tencent.com/dm/n7JC8qdASNSP
ID: 912343663 Password: 123456
Video:
https://vshare.sjtu.edu.cn/play/146a43af8f200f8c2f116d667e577c47