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Register a new userSearch for the weak decays $J/psi to D^{(*)}_{s}e u_{e}$
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Using a sample of $2.25times 10^8$ $J/psi$ events collected with the BESIII detector at the BEPCII collider, we search for the $J/psi$ semi-leptonic weak decay $J/psi to D^{-}_{s} e^{+} u_{e}+c.c.$ with a much higher sensitivity than previous searches. We also perform the first search for $J/psi to D^{*-}_{s} e^{+} u_{e}+c.c.$ No significant excess of a signal above background is observed in either channel. At the $90%$ confidence level, the upper limits are determined to be $mathcal{B}(J/psi to D^{-}_{s}e^{+} u_{e}+c.c.)<1.3times10^{-6}$ and $mathcal{B}(J/psi to {D^{*}_{s}}^{-}e^{+} u_{e}+c.c.)<1.8times10^{-6}$, respectively. Both are consistent with Standard Model predictions.
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Using the data samples of $(1310.6pm7.2 )times 10^{6}$ $J/psi$ events and $(448.1pm2.9)times 10^{6}$ $psi(3686)$ events collected with the BESIII detector, we search for the rare decays $J/psi to D^{0} e^{+}e^{-} +c.c.$ and $psi(3686) to D^{0} e^{+}e^{-} +c.c.$. No significant signals are observed and the corresponding upper limits on the branching fractions at the $90%$ confidence level are determined to be $Br(J/psi to D^{0} e^{+}e^{-} +c.c.)< 8.5times 10^{-8}$ and $Br (psi(3686) to D^{0} e^{+}e^{-} +c.c.)<1.4times 10^{-7}$, respectively. Our limit on $Br(J/psi to D^{0} e^{+}e^{-} +c.c.)$ is more stringent by two orders of magnitude than the previous results, and the $Br(psi(3686) to D^{0} e^{+}e^{-} +c.c.)$ is measured for the first time.
In an analysis of a 2.92~fb$^{-1}$ data sample taken at 3.773~GeV with the BESIII detector operated at the BEPCII collider, we measure the absolute decay branching fractions to be $mathcal B(D^0 to K^-e^+ u_e)=(3.505pm 0.014 pm 0.033)%$ and $mathcal B(D^0 to pi^-e^+ u_e)=(0.295pm 0.004pm 0.003)%$. From a study of the differential decay rates we obtain the products of hadronic form factor and the magnitude of the CKM matrix element $f_{+}^K(0)|V_{cs}|=0.7172pm0.0025pm 0.0035$ and $f_{+}^{pi}(0)|V_{cd}|=0.1435pm0.0018pm 0.0009$. Combining these products with the values of $|V_{cs(d)}|$ from the SM constraint fit, we extract the hadronic form factors $f^K_+(0) = 0.7368pm0.0026pm 0.0036$ and $f^pi_+(0) = 0.6372pm0.0080pm 0.0044$, and their ratio $f_+^{pi}(0)/f_+^{K}(0)=0.8649pm 0.0112pm 0.0073$. These form factors and their ratio are used to test unquenched Lattice QCD calculations of the form factors and a light cone sum rule (LCSR) calculation of their ratio. The measured value of $f_+^{K(pi)}(0) |V_{cs(d)}|$ and the lattice QCD value for $f^{K(pi)}_+(0)$ are used to extract values of the CKM matrix elements of $|V_{cs}|=0.9601 pm 0.0033 pm 0.0047 pm 0.0239$ and $|V_{cd}|=0.2155 pm 0.0027 pm 0.0014 pm 0.0094$, where the third errors are due to the uncertainties in lattice QCD calculations of the form factors. Using the LCSR value for $f_+^pi(0)/f_+^K(0)$, we determine the ratio $|V_{cd}|/|V_{cs}|=0.238pm 0.004pm 0.002pm 0.011$, where the third error is from the uncertainty in the LCSR normalization. In addition, we measure form factor parameters for three different theoretical models that describe the weak hadronic charged currents for these two semileptonic decays. All of these measurements are the most precise to date.
Using $10.1times10^{9}$ $J/psi$ events produced by the Beijing Electron Positron Collider (BEPCII) at a center-of-mass energy $sqrt{s}=3.097~rm{GeV}$ and collected with the BESIII detector, we present a search for the rare semi-leptonic decay $J/psito D^{-}e^{+} u_{e}+c.c.$. No excess of signal above background is observed, and an upper limit on the branching fraction $mathcal{B}(J/psito D^{-}e^{+} u_{e}+c.c.)<7.1times10^{-8}$ is obtained at $90%$ confidence level. This is an improvement of more than two orders of magnitude over the previous best limit.
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 and the upper limit on the branching fraction is set to be $mathcal{B}(J/psi to phi e^+ e^-) < 1.2 times 10^{-7}$ at the 90% confidence level, which is still about one order of magnitude higher than the Standard Model prediction.
Using a $3.19~mathrm{fb}^{-1}$ data sample collected at the $sqrt{s}~=~4.178$ GeV with the BESIII detector, we search for the rare decay $D_{s}^{+} rightarrow p bar{p} e^{+} u_{e} $. No significant signal is observed, and an upper limit of $mathcal{B}(D_{s}^{+} rightarrow p bar{p} e^{+} u_{e}) < 2.0 times 10^{-4}$ is set at the 90% confidence level. This measurement is useful input in understanding the baryonic transition of $D_{s}^{+}$ mesons.
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