اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدSearch for the rare decay $D^+ to D^0 e^+ u_e$
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We search for the rare decay $D^+to D^0 e^+ u_{e}$, using a data set with an integrated luminosity of 2.93 $rm fb^{-1}$ collected at $sqrt{s}=3.773$ GeV with the BESIII detector operating at the BEPCII storage rings. No signals are observed. We set the upper limit on the branching fraction for $D^+to D^0 e^+ u_e$ to be $1.0times 10^{-4}$ at the 90% confidence level.
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Using $2.93~mathrm{fb}^{-1}$ of $e^+e^-$ annihilation data collected at a center-of-mass energy $sqrt{s}=3.773$ GeV with the BESIII detector operating at the BEPCII collider, we search for the semileptonic $D^{0(+)}$ decays into a $b_1(1235)^{-(0)}$
axial-vector meson for the first time. No significant signal is observed for either charge combination. The upper limits on the product branching fractions are ${mathcal B}_{D^0to b_1(1235)^- e^+ u_e}cdot {mathcal B}_{b_1(1235)^-to omegapi^-}<1.12times 10^{-4}$ and ${mathcal B}_{D^+to b_1(1235)^0 e^+ u_e}cdot {mathcal B}_{b_1(1235)^0to omegapi^0}<1.75times 10^{-4}$ at the 90% confidence level.
Using an $e^+e^-$ collision data sample of 2.93 fb$^{-1}$ collected at a center-of-mass energy of 3.773 GeV by the BESIII detector at BEPCII, we report the observation of $D^0 to a_0(980)^- e^+ u_e$ and evidence for $D^+ to a_0(980)^0 e^+ u_e~$ wit
h significances of $6.4sigma$ and $2.9sigma$, respectively. The absolute branching fractions are determined to be $mathcal{B}(D^0 to a_0(980)^- e^+ u_e)timesmathcal{B}(a_0(980)^- to eta pi^-) = (1.33_{-0.29}^{+0.33}({rm stat})pm0.09({rm syst}))times10^{-4}~$ and $mathcal{B}(D^+ to a_0(980)^0 e^+ u_e)timesmathcal{B}(a_0(980)^0 to eta pi^0) = (1.66_{-0.66}^{+0.81}({rm stat})pm0.11({rm syst}))times10^{-4}~$. An upper limit of $mathcal{B}(D^+ to a_0(980)^0 e^+ u_e)timesmathcal{B}(a_0(980)^0 to eta pi^0)<3.0times10^{-4}~$ is also determined at the $90%~$ confidence level.
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.
Using 2.93 fb$^{-1}$ of $e^+e^-$ collision data collected with the BESIII detector at a center-of-mass energy of 3.773 GeV, we measure the absolute branching fractions of the decays $D^0to K^-e^+ u_e$ and $D^+to bar K^0 e^+ u_e$ to be $(3.567pm0.031_
{rm stat}pm 0.025_{rm syst})%$ and $(8.68pm0.14_{rm stat}pm 0.16_{rm syst})%$, respectively. Starting with the process $e^+e^-to Dbar{D}$, a new reconstruction method is employed to select events that contain candidates for both $Dto bar Ke^+ u_e$ and $bar Dto Ke^-bar u_e$ decays. The branching fractions reported in this work are consistent within uncertainties with previous BESIII measurements that selected events containing $Dto bar Ke^+ u_e$ and hadronic $bar D$ decays. Combining our results with the lifetimes of the $D^0$ and $D^+$ mesons and the previous BESIII measurements leads to a ratio of the two decay partial widths of $frac{bar Gamma_{D^0to K^{-}e^+ u_{e}}}{bar Gamma_{D^{+}to bar K^{0}e^+ u_{e}}}=1.039pm0.021$. This ratio supports isospin symmetry in the $D^0to K^-e^+ u_e$ and $D^+to bar K^0 e^+ u_e$ decays within $1.9sigma$.
A search for the lepton-flavour violating decay $D^0 to e^pm mu^mp$ is made with a dataset corresponding to an integrated luminosity of 3.0 fb$^{-1}$ of proton-proton collisions at centre-of-mass energies of $7$ TeV and $8$ TeV, collected by the LHCb
experiment. Candidate $D^0$ mesons are selected using the decay $D^{*+} to D^0 pi^+$ and the $D^0 to e^pm mu^mp$ branching fraction is measured using the decay mode $D^0 to K^-pi^+$ as a normalisation channel. No significant excess of $D^0 to e^pm mu^mp$ candidates over the expected background is seen, and a limit is set on the branching fraction, $mathcal{B}(D^0 to e^pm mu^mp) < 1.3 times 10^{-8}$, at 90 % confidence level. This is an order of magnitude lower than the previous limit and it further constrains the parameter space in some leptoquark models and in supersymmetric models with R-parity violation.
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