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Register a new userBranching fraction and CP asymmetry of the decays $B^+ to K_{rm scriptscriptstyle S}^0 pi^+$ and $B^+ to K_{rm scriptscriptstyle S}^0 K^+$
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An analysis of $B^+ to K_{rm scriptscriptstyle S}^0 pi^+$ and $B^+ to K_{rm scriptscriptstyle S}^0 K^+$ decays is performed with the LHCb experiment. The $pp$ collision data used correspond to integrated luminosities of $1{,fb}^{-1}$ and $2{,fb}^{-1}$ collected at centre-of-mass energies of $sqrt{s}=7mathrm{,Tekern -0.1em V}$ and $sqrt{s}=8mathrm{,Tekern -0.1em V}$, respectively. The ratio of branching fractions and the direct {it CP} asymmetries are measured to be $mathcal{B}(B^+ to K_{rm scriptscriptstyle S}^0 K^+)/mathcal{B}(B^+ to K_{rm scriptscriptstyle S}^0 pi^+) = 0.064 pm 0.009textrm{(stat.)} pm 0.004textrm{(syst.)}$, $mathcal{A}^{it CP}(B^+ to K_{rm scriptscriptstyle S}^0 pi^+) = -0.022 pm 0.025textrm{(stat.)} pm 0.010textrm{(syst.)}$ and $mathcal{A}^{it CP}(B^+ to K_{rm scriptscriptstyle S}^0 K^+) = -0.21 pm 0.14textrm{(stat.)} pm 0.01textrm{(syst.)}$. The data sample taken at $sqrt{s}=7mathrm{,Tekern -0.1em V}$ is used to search for $B_c^+ to K_{rm scriptscriptstyle S}^0 K^+$ decays and results in the upper limit $(f_ccdotmathcal{B}(B_c^+ to K_{rm scriptscriptstyle S}^0 K^+))/(f_ucdotmathcal{B}(B^+ to K_{rm scriptscriptstyle S}^0 pi^+)) < 5.8times10^{-2}textrm{at 90% confidence level}$, where $f_c$ and $f_u$ denote the hadronisation fractions of a $bar{b}$ quark into a $B_c^+$ or a $B^+$ meson, respectively.
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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.
A search for charmless three-body decays of $B^0$ and $B_{s}^0$ mesons with a $K_{rm S}^0$ meson in the final state is performed using the $pp$ collision data, corresponding to an integrated luminosity of $1.0,mbox{fb}^{-1}$, collected at a centre-of-mass energy of $7mathrm{,Tekern -0.1em V}$ recorded by the LHCb experiment. Branching fractions of the $B_{(s)}^0 to K_{rm S}^0 h^{+} h^{prime -}$ decay modes ($h^{(prime)} = pi, K$), relative to the well measured $B^0 to K_{rm S}^0 pi^{+} pi^{-}$ decay, are obtained. First observation of the decay modes $B_s^0 to K_{rm S}^0 K^{pm} pi^{mp}$ and $B_s^0 to K_{rm S}^0 pi^{+} pi^{-}$ and confirmation of the decay $B^0 to K_{rm S}^0 K^{pm} pi^{mp}$ are reported. The following relative branching fraction measurements or limits are obtained begin{eqnarray*} onumber frac{{cal B}(B^0 to K_{rm S}^0 K^{pm} pi^{mp})}{{cal B}(B^0 to K_{rm S}^0 pi^{+} pi^{-})} &=& 0.128 pm 0.017 , ({rm stat.}) pm 0.009 , ({rm syst.}) ,, onumber frac{{cal B}(B^0 to K_{rm S}^0 K^{+} K^{-} )}{{cal B}(B^0 to K_{rm S}^0 pi^{+} pi^{-})} &=& 0.385 pm 0.031 , ({rm stat.}) pm 0.023 , ({rm syst.}) ,, onumber frac{{cal B}(B_s^0 to K_{rm S}^0 pi^{+} pi^{-} )}{{cal B}(B^0 to K_{rm S}^0 pi^{+} pi^{-})} &=& 0.29phantom{0} pm 0.06phantom{0} , ({rm stat.}) pm 0.03phantom{0} , ({rm syst.}) pm 0.02 , (f_s/f_d) ,, onumber frac{{cal B}(B_s^0 to K_{rm S}^0 K^{pm} pi^{mp})}{{cal B}(B^0 to K_{rm S}^0 pi^{+} pi^{-})} &=& 1.48phantom{0} pm 0.12phantom{0} , ({rm stat.}) pm 0.08phantom{0} , ({rm syst.}) pm 0.12 , (f_s/f_d) ,, onumber frac{{cal B}(B_s^0 to K_{rm S}^0 K^{+} K^{-} )}{{cal B}(B^0 to K_{rm S}^0 pi^{+} pi^{-})} &in& [0.004;0.068] ; {rm at ;; 90% ; CL} ,. end{eqnarray*}
We report updated measurements of branching fractions ($mathcal{B}$) and CP-violating charge asymmetries ($mathcal{A_{rm CP}}$) for charmless $B$ decays at Belle II, which operates on or near the $Upsilon$(4S) resonance at the SuperKEKB asymmetric energy $e^{+}e^{-}$ collider. We use samples of 2019 and 2020 data corresponding to 62.8 fb$^{-1}$ of integrated luminosity. The samples are analysed using two-dimensional fits in $Delta E$ and $M_{it bc}$ to determine signal yields of approximately 568, 103, and 115 decays for the channels $B^0 to K^+pi^-$, $B^+ to K_{rm S}^0pi^+$, and $B^0 to pi^+pi^-$, respectively. Signal yields are corrected for efficiencies determined from simulation and control data samples to obtain branching fractions and CP-violating asymmetries for flavour-specific channels. The results are compatible with known determinations and contribute important information to an early assessment of Belle II detector performance.
Decays of the form $B^{0}_{(s)}rightarrow J/psi K_{{rm S}}^{0} h^+ h^{left(primeright) -}$ ($h^{(prime)} = K, pi$) are searched for in proton-proton collision data corresponding to an integrated luminosity of $1.0 , {rm fb}^{-1}$ recorded with the LHCb detector. The first observation of the $B^{0}_{s}rightarrow J/psi K_{{rm S}}^{0} K^{pm} pi^{mp}$ decay is reported, with significance in excess of 10 standard deviations. The $B^{0}rightarrow J/psi K_{{rm S}}^{0} K^{+} K^{-}$ decay is also observed for the first time. The branching fraction of $B^{0}rightarrow J/psi K_{{rm S}}^{0} pi^{+} pi^{-}$ is determined, to significantly better precision than previous measurements, using $B^0 rightarrow J/psi K_{{rm S}}^{0}$ as a normalisation channel. Branching fractions and upper limits of the other $B^{0}_{(s)}rightarrow J/psi K_{{rm S}}^{0} h^+ h^{left(primeright) -}$ modes are determined relative to that of the $B^{0}rightarrow J/psi K_{{rm S}}^{0} pi^{+} pi^{-}$ decay.
A binned Dalitz plot analysis of the decays $B^0 to D K^{ast 0}$, with $D to K_{S}^{0} pi^{+} pi^{-}$ and $K_{S}^{0} K^{+} K^{-}$, is performed to measure the observables $x_pm$ and $y_pm$, which are related to the CKM angle $gamma$ and the hadronic parameters of the decays. The $D$ decay strong phase variation over the Dalitz plot is taken from measurements performed at the CLEO-c experiment, making the analysis independent of the $D$ decay model. With a sample of proton-proton collision data, corresponding to an integrated luminosity of $3.0,rm{fb}^{-1}$, collected by the LHCb experiment, the values of the $CP$ violation parameters are found to be $x_+ = 0.05 pm 0.35 pm 0.02$, $x_-=-0.31pm 0.20 pm 0.04$, $y_+=-0.81pm 0.28pm 0.06$ and $y_-=0.31pm 0.21 pm 0.05$, where the first uncertainties are statistical and the second systematic. These observables correspond to values $gamma$ = $(71 pm 20)^circ$, $r_{B^0} = 0.56pm 0.17$ and $delta_{B^0} = (204,^{+21}_{-20})^circ$. The parameters $r_{B^0}$ and $delta_{B^0}$ are the magnitude ratio and strong phase difference between the suppressed and favoured $B^0$ decay amplitudes, and have been measured in a region of $pm 50$ MeV/$c^2$ around the $K^{ast}(892)^{0}$ mass and with the magnitude of the cosine of the $K^{ast}(892)^{0}$ helicity angle larger than 0.4.
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