CP violation in η(′) → π+π−μ+μ− decays Zillinger, Maximilian Kubis, Bastian Sanchez-Puertas, Pablo Chiral Lagrangian CP violation Effective Field Theories of QCD SMEFT Acknowledgments We are grateful to Hakan Akdag and Tobias Isken for providing us with parameterizations for phase shifts and Omnès functions, as well as for useful discussions. We thank Martin Hoferichter for helpful comments on the manuscript. Financial support was provided by the Swiss National Science Foundation under Project No. PCEFP2_181117, by the DFG (CRC 110, “Symmetries and the Emergence of Structure in QCD”), the European Union’s Horizon 2020 Research and Innovation Programme (grants no. 754510 [EU, H2020-MSCA-COFUND2016] and no. 824093 [H2020-INFRAIA-2018-1]), the Spanish MINECO, MCIN/AEI/10.13039/501100011033 (grants PID2020-112965GB-I00 and PID2020-114767GB-I00), and Junta de Andalucía (grants POSTDOC_21_00136 and FQM-225). It has been pointed out recently that a certain set of dimension-6 scalar P- and CP-violating light-quark-muon operators may be tested in η and η′ decays to various final states involving μ+μ− pairs, at a level not yet excluded by constraints from electric dipole moments. We here work out the hadronic matrix elements required for the predictions for the decays η, η′ → π+π−μ+μ−. We relate a new asymmetry in the angular distribution between the dipion and dimuon decay planes to the corresponding Wilson coefficients. Despite the advantage of not requiring the measurement of muon polarization, the projected sensitivities are shown to be moderate due to a combination of small phase space and chiral suppression. Such sensitivity studies are most timely in view of upcoming or planned high-statistics η(′) experiments such as the JLab eta factory or REDTOP. 2022-12-19T09:39:23Z 2022-12-19T09:39:23Z 2022-12-01 journal article Zillinger, M., Kubis, B. & Sánchez-Puertas, P. CP violation in η(′) → π+π−μ+μ− decays. J. High Energ. Phys. 2022, 1 (2022). [https://doi.org/10.1007/JHEP12(2022)001] https://hdl.handle.net/10481/78563 10.1007/JHEP12(2022)001 eng info:eu-repo/grantAgreement/EC/H2020/MSCA-COFUND2016/754510 info:eu-repo/grantAgreement/EC/H2020/-INFRAIA-2018-1/824093 http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional Springer Nature