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arXiv · 2512.19265

Comparison of the mixed-fermion-action Effects using different fermion and gauge actions with 2+1 and 2+1+1 flavors

Zun-Xian Zhang·Mengchu Cai·Bolun Hu·Xiangyu Jiang·Xiao-Lan Meng·Yi-Bo Yang·Dian-Jun Zhao
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Abstract

The leading-order low-energy constant $\Delta_{\rm mix}$ in mixed-action chiral perturbation theory is calculated using $2+1+1$-flavor gauge ensembles with HISQ fermions and a tadpole-improved Symanzik gauge action at four lattice spacings $a \in [0.048, 0.111]$ fm. By comparing our results to those from different actions and a $2+1$-flavor case, We find that the fermion action has the dominant impact, the gauge action has a secondary but measurable effect, and the contribution from charm quark loops is negligible within our current uncertainties.

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Zun-Xian Zhang, Mengchu Cai, Bolun Hu, Xiangyu Jiang, Xiao-Lan Meng, Yi-Bo Yang, Dian-Jun Zhao. 2025-12-22. Comparison of the mixed-fermion-action Effects using different fermion and gauge actions with 2+1 and 2+1+1 flavors. https://arxiv.org/abs/2512.19265

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