Search for the CP-violating strong decays $η→π^+π^−$ and $η′(958)→π^+π^−$

LHCb Collaboration; Bernet, R; Müller, K; Steinkamp, O; Straumann, U; Vollhardt, A; et al (2017). Search for the CP-violating strong decays $η→π^+π^−$ and $η′(958)→π^+π^−$. Physics Letters B, 764:233-240.

Abstract

A search for the CP-violating strong decays $η→π^+π^−$ and $η′(958)→π^+π^−$ has been performed using approximately 2.5×107 events of each of the decays $D^+→π^+π^+π^−$ and $D^+_s→π^+π^+π^−$, 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 $D^+_{(s)}→π^+η^{(')}$ with $η^{(')}→π^+π^−$, and upper limits at 90% confidence level are set on the branching fractions, $\mathcal{B}(η→π^+π^−)<1.6×10^{−5}$ and $\mathcal{B}(η′→π^+π^−)<1.8×10^{−5}$. The limit for the η decay is comparable with the existing one, while that for the η′ is a factor of three smaller than the previous limit.

Abstract

A search for the CP-violating strong decays $η→π^+π^−$ and $η′(958)→π^+π^−$ has been performed using approximately 2.5×107 events of each of the decays $D^+→π^+π^+π^−$ and $D^+_s→π^+π^+π^−$, 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 $D^+_{(s)}→π^+η^{(')}$ with $η^{(')}→π^+π^−$, and upper limits at 90% confidence level are set on the branching fractions, $\mathcal{B}(η→π^+π^−)<1.6×10^{−5}$ and $\mathcal{B}(η′→π^+π^−)<1.8×10^{−5}$. The limit for the η decay is comparable with the existing one, while that for the η′ is a factor of three smaller than the previous limit.

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