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Upper limit on the η → π+π branching fraction with the KLOE experiment

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Based on an integrated luminosity of 1.61 fb1 e+e collision data collected with the KLOE detector at DAΦNE, the Frascati ϕ-factory, a search for the P- and CP-violating decay η → π+π has been performed. Radiative ϕ → ηγ decay is exploited to access the η mesons. No signal is observed in the π+π invariant mass spectrum, and the upper limit on the branching fraction at 90% confidence level is determined to be ℬ(η → π+π) < 4.9 × 106, which is approximately three times smaller than the previous KLOE result. From the combination of these two measurements we get ℬ(η → π+π) < 4.4 × 106 at 90% confidence level.


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Correspondence to X. Kang.

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ArXiv ePrint: 2006.14710

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The KLOE-2 collaboration., Babusci, D., Berlowski, M. et al. Upper limit on the η → π+π branching fraction with the KLOE experiment. J. High Energ. Phys. 2020, 47 (2020).

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  • Branching fraction
  • CP violation
  • e +-e Experiments
  • Rare decay