Axial Vector Form Factors from Lattice QCD that Satisfy the PCAC Relation

Physical Review Letters
Yong-Chull JangTanmoy Bhattacharya

Abstract

Previous lattice QCD calculations of axial vector and pseudoscalar form factors show significant deviation from the partially conserved axial current (PCAC) relation between them. Since the original correlation functions satisfy PCAC, the observed deviations from the operator identity cast doubt on whether all of the systematics in the extraction of form factors from the correlation functions are under control. We identify the problematic systematic as a missed excited state, whose energy as a function of the momentum transfer squared Q^{2} is determined from the analysis of the three-point functions themselves. Its energy is much smaller than those of the excited states previously considered, and including it impacts the extraction of all of the ground state matrix elements. The form factors extracted using these mass and energy gaps satisfy PCAC and another consistency condition, and they validate the pion-pole dominance hypothesis. We also show that the extraction of the axial charge g_{A} is very sensitive to the value of the mass gaps of the excited states used, and current lattice data do not provide an unambiguous determination of these, unlike the Q^{2}≠0 case. To highlight the differences and improvement between the co...Continue Reading

References

Feb 7, 2013·Physical Review Letters·V A AndreevUNKNOWN MuCap Collaboration
May 2, 2018·Reports on Progress in Physics·Richard J HillAlberto Sirlin

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Citations

Feb 16, 2021·The European Physical Journal. A, Hadrons and Nuclei·Konstantin Ottnad

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