# Ruling out the massless up-quark solution to the strong CP problem by computing the topological mass contribution with lattice QCD

@article{Alexandrou2020RulingOT, title={Ruling out the massless up-quark solution to the strong CP problem by computing the topological mass contribution with lattice QCD}, author={C. Alexandrou and J. Finkenrath and L. Funcke and K. Jansen and B. Kostrzewa and F. Pittler and C. Urbach}, journal={arXiv: High Energy Physics - Lattice}, year={2020} }

The infamous strong CP problem in particle physics can in principle be solved by a massless up quark. In particular, it was hypothesised that topological effects could substantially contribute to the observed non-zero up-quark mass without reintroducing CP violation. Alternatively to previous work using fits to chiral perturbation theory, in this letter we bound the strength of the topological mass contribution with direct lattice QCD simulations by computing the dependence of the pion mass on… CONTINUE READING

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