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Register a new userObservation of $psi(3686) to nbar{n}$ and improved measurement of $psi(3686) to p bar{p}$
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We observe the decay $psi(3686) to n bar{n}$ for the first time and measure $psi(3686) to p bar{p}$ with improved accuracy by using $1.07times 10^8$ $psi(3686)$ events collected with the BESIII detector. The measured branching fractions are $mathcal{B}(psi(3686) to n bar{n}) = (3.06 pm 0.06 pm 0.14)times 10^{-4}$ and $mathcal{B}(psi(3686) to p bar{p}) = (3.05 pm 0.02 pm 0.12) times 10^{-4}$. Here, the first uncertainties are statistical and the second ones systematic. With the hypothesis that the polar angular distributions of the neutron and proton in the center-of-mass system obey $1+alpha cos^2theta$, we determine the $alpha$ parameters to be $alpha_{nbar{n}} = 0.68 pm 0.12 pm 0.11$ and $alpha_{pbar{p}} = 1.03 pm 0.06 pm 0.03$ for $psi(3686)to nbar{n}$ and $psi(3686)to pbar{p}$, respectively.
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We observe the process $psi(3686) to p bar{p} eta^{prime}$ for the first time, with a statistical significance higher than 10$sigma$, and measure the branching fraction of $J/psi to p bar{p} eta^{prime}$ with an improved accuracy compared to earlier studies. The measurements are based on $4.48 times 10^8$ $psi(3686)$ and $1.31 times 10^{9}$ $J/psi$ events collected by the BESIII detector operating at the BEPCII. The branching fractions are determined to be $B(psi(3686) to p bar{p} eta^{prime}) = (1.10pm0.10pm0.08)times10^{-5}$ and $B(J/psi to p bar{p} eta^{prime})=(1.26pm0.02pm 0.07)times10^{-4}$, where the first uncertainties are statistical and the second ones systematic. Additionally, the $eta-eta^{prime}$ mixing angle is determined to be $-24^{circ} pm 11^{circ}$ based on $psi(3686) to p bar{p} eta^{prime}$, and $-24^{circ} pm 9^{circ}$ based on $J/psi to p bar{p} eta^{prime}$, respectively.
Using a data sample of $4.48times10^{8}$ $psip$ events collected with the BESIII detector, we present a first observation of $psi(3686)to pbar{p}phi$, and we measure its branching fraction to be $[6.06pm0.38 ($stat.$) pm 0.48 ($syst.$)]times10^{-6}$. In contrast to the earlier discovery of a threshold enhancement in the $pbar{p}$-mass spectrum of the channel $J/psitogamma pbar p$, denoted as $X(pbar{p})$, we do not find a similar enhancement in $psi(3686)to pbar{p}phi$. An upper limit of $1.82times10^{-7}$ at the $90%$ confidence level on the branching fraction of $psi(3686)to X(pbar{p})phito pbar{p}phi$ is obtained.
Using a sample of $1.06times10^8 psip$ events produced in $e^+e^-$ collisions at $sqrt{s}$ = 3.686 GeV and collected with the BESIII detector at the BEPCII collider, we present studies of the decays $klx+c.c.$ and $gklx+c.c.$. We observe two hyperons, $Xi(1690)^-$ and $Xi(1820)^-$, in the $K^-Lambda$ invariant mass distribution in the decay $klx+c.c.$ with significances of $4.9 sigma$ and $6.2 sigma$, respectively. The branching fractions of $klx+c.c.$, $ksx+c.c.$, $psiptogamma chi_{cJ}to gamma K^- Lambda bar{Xi}^+ +c.c.$ $(J=0, 1, 2)$, and $psipto Xi(1690/1820)^{-} bar{Xi}^++c.c$ with subsequent decay $Xi(1690/1820)^-to K^-Lambda$ are measured for the first time.
Using a data sample of $448.1 times 10^6$ $psi(3686)$ events collected with the BESIII detector at the BEPCII collider, we report the first observation of the electromagnetic Dalitz decay $psi(3686) to eta e^+ e^-$, with significances of 7.0$sigma$ and 6.3$sigma$ when reconstructing the $eta$ meson via its decay modes $etatogamma pi^+ pi^-$ and $etatopi^+pi^-eta$ ($eta to gammagamma$), respectively. The weighted average branching fraction is determined to be $mathcal{B}(psi(3686) to eta e^+ e^-)= (1.90 pm 0.25 pm 0.11) times 10^{-6}$, where the first uncertainty is statistical and the second systematic.
Based on the data sample of $448.1times10^{6}$ $psi(3686)$ events collected with the BESIII detector at BEPCII, we present a study of the decays $psi(3686)rightarrowgammachi_{cJ}rightarrowgammabar{p}K^{*+}Lambda+c.c.$ and $psi(3686)rightarrowbar{p}K^{*+}Lambda+c.c.$. The branching fractions of $chi_{cJ}rightarrowbar{p}K^{*+}Lambda+c.c.$ ($J$=0, 1, 2) are measured to be $(4.8pm0.7pm0.5)times10^{-4}$, $(5.0pm0.5pm0.4)times10^{-4}$, and $(8.2pm0.9pm0.7)times10^{-4}$, respectively, where the first uncertainties are statistical and the second systematic. The branching fraction of $psi(3686)rightarrowbar{p}K^{*+}Lambda+c.c.$ is measured to be $(6.3pm0.5pm0.5)times10^{-5}$. All these decay modes are observed for the first time.
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