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Register a new userSearch for baryon and lepton number violating decays $D^+tobarLambda(barSigma^0)e^+$ and $D^+toLambda(Sigma^0)e^+$
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Using a 2.93 fb$^{-1}$ data sample of electron-positron collisions taken with the BESIII detector at a center-of-mass energy of 3.773 GeV, which corresponds to $(8296pm31pm64)times10^3 D^+D^-$ pairs, we search for the baryon and lepton number violating decays $D^+tobarLambda(barSigma^0)e^+$ and $D^+toLambda(Sigma^0)e^+$. No obvious signals are found with the current statistics and upper limits on the branching fractions of these four decays are set at the level of $10^{-6}$ at 90% confidence level.
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We present a search for seven lepton-flavor-violating neutral charm decays of the type $D^{0}rightarrow X^{0} e^{pm} mu^{mp}$, where $X^{0}$ represents a $pi^{0}$, $K^{0}_{rm S}$, $bar{K^{*0}}$, $rho^{0}$, $phi$, $omega$, or $eta$ meson. The analysis is based on $468$ fb$^{-1}$ of $e^+e^-$ annihilation data collected at or close to the $Upsilon(4S)$ resonance with the BaBar detector at the SLAC National Accelerator Laboratory. No significant signals are observed, and we establish 90% confidence level upper limits on the branching fractions in the range $(5.0 - 22.5)times 10^{-7}$. The limits are between one and two orders of magnitude more stringent than previous measurements.
Using 1.8 million DDbar pairs and a neutrino reconstruction technique, we have studied the decays D^0 -> K^- e^+ nu_e, D^0 -> pi^- e^+ nu_e, D^+ -> Kbar^0 e^+ nu_e, and D^+ -> pi^0 e^+ nu_e. We find B(D^0 -> pi^- e^+ nu_e) = 0.299(11)(9)%, B(D^+ -> pi^0 e^+ nu_e) = 0.373(22)(13)%, B(D^0 -> K^- e^+ nu_e) = 3.56(3)(9)%, and B(D^+ -> Kbar^0 e^+ nu_e) = 8.53(13)(23)%. In addition, form factors are studied through fits to the partial branching fractions obtained in five q^2 ranges. By combining our results with recent unquenched lattice calculations, we obtain |Vcd| = 0.217(9)(4)(23) and |Vcs| = 1.015(10)(11)(106).
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.
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.
Using the data sample of an integrated luminosity of 2.93 fb$^{-1}$ taken at the center-of-mass energy of 3.773 GeV, we search for the Majorana neutrino in the lepton number violating decays $Dto K pi e^+ e^+$. No significant signal is observed, and the upper limits on the branching fraction at the 90% confidence level are set to be $mathcal{B},(D^0 to K^- pi^- e^+ e^+)<2.8times10^{-6}$, $mathcal{B},(D^+ to K_S^0 pi^- e^+ e^+)<3.3times10^{-6}$ and $mathcal{B},(D^+ to K^- pi^0 e^+ e^+)<8.5times10^{-6}$. The Majorana neutrino is searched for with different mass assumptions ranging from 0.25 to 1.0 GeV/$c^2$ in the decays $D^0to K^- e^+ u_N(pi^- e^+)$ and $D^+to K_S^0 e^+ u_N(pi^- e^+)$, and the upper limits on the branching fraction at the 90% confidence level are extracted to be at the level of $10^{-7} sim 10^{-6}$, depending on the mass of Majorana neutrino. The constraints on the mixing matrix element $|V_{eN}|^2$ are also evaluated.
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