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Register a new userConstraints on the $K^0_{mathrm{S}}rightarrowmu^{+}mu^{-}$ branching fraction
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A search for the decay $K^0_{mathrm{S}}rightarrowmu^{+}mu^{-}$ is performed using proton-proton collision data, corresponding to an integrated luminosity of $5.6,text{fb}^{-1}$ and collected with the LHCb experiment during 2016, 2017 and 2018 at a center-of-mass energy of $13,mathrm{TeV}$. The observed signal yield is consistent with zero, yielding an upper limit of ${cal B}(K^0_{mathrm{S}}rightarrowmu^{+}mu^{-}) < 2.2 times 10^{-10}$ at 90% CL. The limit reduces to ${cal B}(K^0_{mathrm{S}}rightarrowmu^{+}mu^{-}) < 2.1 times 10^{-10}$ at 90% CL once combined with the result from data taken in 2011 and 2012.
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A search for the decay $K^0_{scriptscriptstyle S}tomu^+mu^-$ is performed, based on a data sample of proton-proton collisions corresponding to an integrated luminosity of 3 fb$^{-1}$, collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The observed yield is consistent with the background-only hypothesis, yielding a limit on the branching fraction of ${cal B}(K^0_{scriptscriptstyle S}tomu^+mu^-) < 0.8~(1.0) times 10^{-9}$ at $90%~(95%)$ confidence level. This result improves the previous upper limit on the branching fraction by an order of magnitude.
Based on 586 $rm{pb^{-1}}$ of $e^+e^-$ annihilation data collected at a center-of-mass energy of $sqrt{s}=4.6~rm{GeV}$ with the BESIII detector at the BEPCII collider, the absolute branching fraction of $Lambda_c^+ to p K^0_{mathrm{S}}eta$ decays is measured for the first time to be $mathcal{B}(Lambda_c^+ to p K^0_{mathrm{S}}eta) = (0.414 pm 0.084 pm 0.028)%$, where the first uncertainty is statistical and the second is systematic. The result is compatible with a previous CLEO result on the relative branching fraction $frac{mathcal{B}(Lambda_c^+ to p K^0_{mathrm{S}}eta)}{mathcal{B}(Lambda_c^+ to p K^-pi^+)}$, and consistent with theoretical predictions of SU(3) flavor symmetry.
The charmless three-body decays $B^0_{(s)} to K_{mathrm{scriptscriptstyle S}}^0 h^+ h^{prime -}$ (where $h^{(prime)} = pi, K$) are analysed using a sample of $pp$ collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of $3mbox{fb}^{-1}$. The branching fractions are measured relative to that of the $B^0 to K_{mathrm{scriptscriptstyle S}}^0 pi^{+} pi^{-}$ decay, and are determined to be: begin{eqnarray*} frac{{cal B}(B^0rightarrow K^0_{rm S}K^{pm}pi^{mp})}{{cal B}(B^0rightarrow K^0_{rm S}pi^{+}pi^{-})} = {} & 0.123 pm 0.009 ; mathrm{,(stat)}; pm 0.015 ; mathrm{,(syst)},, frac{{cal B}(B^0rightarrow K^0_{rm S}K^{+}K^{-})} {{cal B}(B^0rightarrow K^0_{rm S}pi^{+}pi^{-})} = {} & 0.549 pm 0.018 ; mathrm{,(stat)}; pm 0.033 ; mathrm{,(syst)},, frac{{cal B}(B_{s}^0rightarrow K^0_{rm S}pi^{+}pi^{-})}{{cal B}(B^0rightarrow K^0_{rm S}pi^{+}pi^{-})} = {} & 0.191 pm 0.027 ; mathrm{,(stat)}; pm 0.031 ; mathrm{,(syst)}; pm 0.011 ; (f_s/f_d) ,, frac{{cal B}(B_{s}^0rightarrow K^0_{rm S}K^{pm}pi^{mp})} {{cal B}(B^0rightarrow K^0_{rm S}pi^{+}pi^{-})} = {} & 1.70phantom{0} pm 0.07phantom{0} ; mathrm{,(stat)} ; pm 0.11phantom{0} ; mathrm{,(syst)}; pm 0.10phantom{0} ; (f_s/f_d) ,, frac{{cal B}(B_{s}^0rightarrow K^0_{rm S}K^{+}K^{-})}{{cal B}(B^0rightarrow K^0_{rm S}pi^{+}pi^{-})} in {} & [0.008 - 0.051] rm ~at~90%~confidence~level, end{eqnarray*} where $f_s/f_d$ represents the ratio of hadronisation fractions of the $B^0_s$ and $B^0$ mesons.
Utilizing a data set corresponding to an integrated luminosity of 6.32~$rm fb^{-1}$, recorded by the BESIII detector at center-of-mass energies between 4.178 and 4.226~GeV, we perform an amplitude analysis of the decay $D_{s}^{+} to K_{S}^{0}pi^{+}pi^{0}$ and determine the relative fractions and phase differences of different intermediate processes, which include $K_{S}^{0}rho(770)^{+}$, $K_{S}^{0}rho(1450)^{+}$, $K^{*}(892)^{0}pi^{+}$, $K^{*}(892)^{+}pi^{0}$, and $K^{*}(1410)^{0}pi^{+}$. Using a double-tag technique, and making an efficiency correction that relies on our knowledge of the phase-space distribution of the decays coming from the amplitude analysis, the absolute branching fraction is measured to be $mathcal{B}(D_{s}^{+} to K_{S}^{0}pi^{+}pi^{0})=(5.43pm0.30_{text{stat}}pm 0.15_{text{syst}})times 10^{-3}$.
A search for CP violation in Cabibbo-suppressed $D^{pm}rightarrow K^0_{mathrm{S}} K^{pm}$ and $D^{pm}_{s}rightarrow K^0_{mathrm{S}} pi^{pm}$ decays is performed using $pp$ collision data, corresponding to an integrated luminosity of 3~fb$^{-1}$, recorded by the LHCb experiment. The individual $CP$-violating asymmetries are measured to be begin{eqnarray*} mathcal{A}_{CP}^{D^{pm}rightarrow K^0_{mathrm{S}} K^{pm}} & = & (+0.03 pm 0.17 pm 0.14) % mathcal{A}_{CP}^{D^{pm}_{s}rightarrow K^0_{mathrm{S}} pi^{pm}} & = & (+0.38 pm 0.46 pm 0.17) %, end{eqnarray*} assuming that $CP$ violation in the Cabibbo-favoured decays is negligible. A combination of the measured asymmetries for the four decay modes $D^{pm}_{(s)}rightarrow K^0_{mathrm{S}} K^{pm}$ and $D^{pm}_{(s)}rightarrow K^0_{mathrm{S}} pi^{pm}$ gives the sum [ mathcal{A}_{CP}^{D^{pm}rightarrow K^0_{mathrm{S}} K^{pm}} + mathcal{A}_{CP}^{D^{pm}_{s}rightarrow K^0_{mathrm{S}} pi^{pm}} = (+0.41 pm 0.49 pm 0.26) %. ] In all cases, the first uncertainties are statistical and the second systematic. The results represent the most precise measurements of these asymmetries to date and show no evidence for CP violation.
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