Search for the $CP$-violating strong decays $\eta \to {\pi }^{+}{\pi }^{-}$ and ${\eta }^{\prime }(958)\to {\pi }^{+}{\pi }^{-}$

Abstract

A search for the $CP$-violating strong decays $\eta \to {\pi }^{+}{\pi }^{-}$ and ${\eta }^{\prime }(958)\to {\pi }^{+}{\pi }^{-}$ has been performed using approximately $2.5\times 10^7$ events of each of the decays $D^{+}\to {\pi }^{+}{\pi }^{+}{\pi }^{-}$ and $D_s^{+}\to {\pi }^{+}{\pi }^{+}{\pi }^{-}$, recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0 fb${}^{-1}$ of $pp$ collision data recorded during LHC Run 1 and 0.3 fb${}^{-1}$ recorded in Run 2. No evidence is seen for $D_{(s)}^{+}\to {\pi }^{+}{\eta }^{(\prime )}$ with ${\eta }^{(\prime )}\to {\pi }^{+}{\pi }^{-}$, and upper limits at 90% confidence level are set on the branching fractions, $\mathcal{B}(\eta \to {\pi }^{+}{\pi }^{-})<1.6\times 10^{-5}$ and $\mathcal{B}({\eta }^{\prime }\to {\pi }^{+}{\pi }^{-})<1.8\times 10^{-5}$. The limit for the $\eta$ decay is comparable with the existing one, while that for the ${\eta }^{\prime }$ is a factor of three smaller than the previous limit.

All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-046.html

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• PYTHIA 6.4 Physics and Manual
• Big-Bang Nucleosynthesis
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Cited by in corpus (2)

• CP-violating decays of the pseudoscalars eta and eta' and their connection to the electric dipole moment of the neutron
• Updated limits on the CP violating $\eta \pi \pi$ and ${\eta }^{\prime }\pi \pi$ couplings derived from the neutron EDM