Measurement of the Branching Fraction of and Search for a CP-Violating Asymmetry in ${\eta }^{\prime }\to {\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$ at BESIII

Abstract

The rare decay ${\eta }^{\prime }\to {\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$ is studied using a sample of $1.3\times 10^9$ $J/\psi$ events collected with the BESIII detector at BEPCII in 2009 and 2012. The branching fraction is measured with improved precision to be $\left(2.42\pm 0.05_{stat.}\pm 0.08_{syst.}\right)\times 10^{-3}$. Due to the inclusion of new data, this result supersedes the last BESIII result on this branching fraction. In addition, the CP-violating asymmetry in the angle between the decay planes of the ${\pi }^{+}{\pi }^{-}$-pair and the $e^{+}{e}^{-}$-pair is investigated. A measurable value would indicate physics beyond the standard model; the result is ${\mathcal{A}}_{CP}=\left(2.9\pm 3.7_{stat.}\pm 1.1_{syst.}\right)\%$, which is consistent with the standard model expectation of no CP-violation. The precision is comparable to the asymmetry measurement in the $K_L^0\to {\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$ decay where the observed $(14\pm 2)\%$ effect is driven by a standard model mechanism.

arXiv comment10 pages, 8 figures, 3 tables

References in corpus (18)

• Design and Construction of the BESIII Detector
• The Precision Monte Carlo Event Generator KK For Two-Fermion Final States In e+e- Collisions
• Future Physics Programme of BESIII
• Detailed measurement of the e+e- pair continuum in p+p and Au+Au collisions at sqrt(s_NN)=200 GeV and implications for direct photon production
• Branching fraction measurements of χ_{c0} and χ_{c2} to π^0π^0 and ηη
• Observation of CP Violation in K(L)->pi+pi-e+e- Decays
• Determination of the number of $J/\psi$ events with inclusive $J/\psi$ decays
• Precision Study of ${\eta }^{\prime }\to \gamma {\pi }^{+}{\pi }^{-}$ Decay Dynamics
• Charmonium decays to gamma pi0, gamma eta, and gamma eta'
• eta, eta-prime --> pi+ pi- l+ l- in a chiral unitary approach
• Observation of ${\eta }^{\prime }$ decays to ${\pi }^{+}{\pi }^{-}{\pi }^0$ and $π^+π^-\e^+e^-$
• The CP-violating asymmetry in η\toπ^+ π^- e^+e^-
• Measurement of the branching ratio and search for a CP violating asymmetry in the eta -> pi+pi-e+e-(gamma) decay at KLOE
• Measurement of ${\eta }^{\prime }\to {\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$ and ${\eta }^{\prime }\to {\pi }^{+}{\pi }^{-}{\mu }^{+}{\mu }^{-}$
• Measurements of Branching Ratios for $\eta$ Decays into Charged Particles
• Precision measurement of the branching fractions of ${\eta }^{\prime }$ decays
• CP Violation in the Decay $\eta \to {\pi }^{+}{\pi }^{-}\gamma$
• Results on CP Violation from the NA48 experiment at CERN