Upper limit on the $\eta \to {\pi }^{+}{\pi }^{-}$ branching fraction with the KLOE experiment

Abstract

Based on an integrated luminosity of 1.61 fb${}^{-1}$ $e^{+}{e}^{-}$ collision data collected with the KLOE detector at DA$\Phi$NE, the Frascati $\varphi$-factory, a search for the $P$- and $CP$-violating decay $\eta \to {\pi }^{+}{\pi }^{-}$ has been performed. Radiative $\varphi \to \eta \gamma$ decay is exploited to access the $\eta$ mesons. No signal is observed in the ${\pi }^{+}{\pi }^{-}$ invariant mass spectrum, and the upper limit on the branching fraction at 90\% confidence level is determined to be $\mathcal{B}(\eta \to {\pi }^{+}{\pi }^{-})<4.9\times 10^{-6}$, which is approximately three times smaller than the previous KLOE result. From the combination of these two measurements we get $\mathcal{B}(\eta \to {\pi }^{+}{\pi }^{-})<4.4\times 10^{-6}$ at 90\% confidence level.

arXiv comment11 pages, 3 figures

References in corpus (6)

• Confidence Level Computation for Combining Searches with Small Statistics
• Data handling, reconstruction, and simulation for the KLOE experiment
• Measurement of the DA$\Phi$NE luminosity with the KLOE detector using large angle Bhabha scattering
• CP-violating decays of the pseudoscalars eta and eta' and their connection to the electric dipole moment of the neutron
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Cited by in corpus (1)

• Novel approach to investigate $\eta$ decays via ${\eta }^{\prime }\to \pi \pi \eta$