اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدMeasurement of $mathcal{B}(J/psi to eta e^+ e^- $) and search for a dark photon
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Using a data sample of $(1310.6pm7.0)times10^{6}$ $J/psi$ decay events collected with the BESIII detector at BEPCII, we study the electromagnetic Dalitz decay $J/psi to eta e^+e^-$ with two dominant $eta$ decay modes, $eta to gamma pi^+ pi^-$ and $eta to pi^+pi^-eta$. The branching fraction is determined to be $mathcal{B}(J/psi to eta e^+e^-) = (6.59pm0.07pm0.17) times 10^{-5}$, which improves in precision by a factor of 2 over the previous BESIII measurement. A search for the dark photon ($gamma $) is performed via $J/psi toeta gamma , gamma to e^{+}e^{-}$. Excluding the $omega$ and $phi$ mass regions, no significant signal is observed in the mass range from 0.1 to 2.1 GeV/$c^{2}$. We set upper limits at the 90% confidence level on $mathcal{B}(J/psi to eta gamma )timesmathcal{B}(gamma to e^+e^-)$, $mathcal{B}(J/psi toeta gamma$) and the mixing strength as a function of dark photon mass. This is among the first searches for dark photons in charmonium decays.
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Using a data sample of $448.1times10^6$ $psi(3686)$ events collected at $sqrt{s}=$ 3.686 GeV with the BESIII detector at the BEPCII, we search for the rare decay $J/psi to phi e^+ e^-$ via $psi(3686) to pi^+pi^- J/psi $. No signal events are observed
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