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Register a new userAngular analysis of $B^0 to K^ast(892)^0 ell^+ ell^-$
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We present a measurement of angular observables, $P_4$, $P_5$, $P_6$, $P_8$, in the decay $B^0 to K^ast(892)^0 ell^+ ell^-$, where $ell^+ell^-$ is either $e^+e^-$ or $mu^+mu^-$. The analysis is performed on a data sample corresponding to an integrated luminosity of $711~mathrm{fb}^{-1}$ containing $772times 10^{6}$ $Bbar B$ pairs, collected at the $Upsilon(4S)$ resonance with the Belle detector at the asymmetric-energy $e^+e^-$ collider KEKB. Four angular observables, $P_{4,5,6,8}$ are extracted in five bins of the invariant mass squared of the lepton system, $q^2$. We compare our results for $P_{4,5,6,8}$ with Standard Model predictions including the $q^2$ region in which the LHCb collaboration reported the so-called $P_5$ anomaly.
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We present a measurement of angular observables and a test of lepton flavor universality in the $Bto K^ast ell^+ell^-$ decay, where $ell$ is either $e$ or $mu$. The analysis is performed on a data sample corresponding to an integrated luminosity of $711~mathrm{fb}^{-1}$ containing $772times 10^{6}$ $Bbar B$ pairs, collected at the $Upsilon(4S)$ resonance with the Belle detector at the asymmetric-energy $e^+e^-$ collider KEKB. The result is consistent with Standard Model (SM) expectations, where the largest discrepancy from a SM prediction is observed in the muon modes with a local significance of $2.6sigma$.
A test of lepton universality, performed by measuring the ratio of the branching fractions of the $B^{0} rightarrow K^{*0}mu^{+}mu^{-}$ and $B^{0} rightarrow K^{*0}e^{+}e^{-}$ decays, $R_{K^{*0}}$, is presented. The $K^{*0}$ meson is reconstructed in the final state $K^{+}pi^{-}$, which is required to have an invariant mass within 100$mathrm{,MeV}c^2$ of the known $K^{*}(892)^{0}$ mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of about 3$mathrm{,fb}^{-1}$, collected by the LHCb experiment at centre-of-mass energies of 7 and 8$mathrm{,TeV}$. The ratio is measured in two regions of the dilepton invariant mass squared, $q^{2}$, to be begin{eqnarray*} R_{K^{*0}} = begin{cases} 0.66~^{+~0.11}_{-~0.07}mathrm{,(stat)} pm 0.03mathrm{,(syst)} & textrm{for } 0.045 < q^{2} < 1.1~mathrm{,GeV^2}c^4 , , 0.69~^{+~0.11}_{-~0.07}mathrm{,(stat)} pm 0.05mathrm{,(syst)} & textrm{for } 1.1phantom{00} < q^{2} < 6.0~mathrm{,GeV^2}c^4 , . end{cases} end{eqnarray*} The corresponding 95.4% confidence level intervals are $[0.52, 0.89]$ and $[0.53, 0.94]$. The results, which represent the most precise measurements of $R_{K^{*0}}$ to date, are compatible with the Standard Model expectations at the level of 2.1--2.3 and 2.4--2.5 standard deviations in the two $q^{2}$ regions, respectively.
The ratio of branching fractions of the decays $Lambda^{0}_{b}to pK^{-}e^{+}e^{-}$ and $Lambda^{0}_{b}to pK^{-}mu^{+}mu^{-}$, $R^{-1}_{pK}$, is measured for the first time using proton-proton collision data corresponding to an integrated luminosity of 4.7 $fb^{-1}$ recorded with the LHCb experiment at center-of-mass energies of 7, 8 and 13 TeV. In the dilepton mass-squared range $0.1 < q^{2} < 6.0$ $GeV^{2}/c^{4}$ and the $pK^{-}$ mass range $m(pK^{-}) < 2600$ $MeV/c^{2}$, the ratio of branching fractions is measured to be $R^{-1}_{pK} = 1.17 ^{+0.18}_{-0.16} pm 0.07$, where the first uncertainty is statistical and the second systematic. This is the first test of lepton universality with b baryons and the first observation of the decay $Lambda^{0}_{b}to pK^{-}e^{+}e^{-}$.
We report a search for charmless hadronic decays of neutral $B$ mesons to $eta K^{*}(892)^{0}$. The results are based on a 711fb$^{-1}$ data sample that contains $772times 10^6 Boverline{B}$ pairs, collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric energy $e^+e^-$ collider. We observe the decay for the first time with a significance of 5.0 standard deviations and obtain its branching fraction ${cal B}[B^0toeta K^{*}(892)^{0}]=[2.6pm0.7{rm (stat)}pm0.2{rm (syst)}]times 10^{-6}$. We also measure the $CP$ violating asymmetry as ${cal A}_{CP}[B^0toeta K^{*}(892)^{0}]=-0.22pm0.29{rm (stat)}pm0.07{rm syst}$.
A measurement of the differential branching fraction of the decay ${B^{0}rightarrow K^{ast}(892)^{0}mu^{+}mu^{-}}$ is presented together with a determination of the S-wave fraction of the $K^+pi^-$ system in the decay $B^{0}rightarrow K^{+}pi^{-}mu^{+}mu^{-}$. The analysis is based on $pp$-collision data corresponding to an integrated luminosity of 3,fb$^{-1}$ collected with the LHCb experiment. The measurements are made in bins of the invariant mass squared of the dimuon system, $q^2$. Precise theoretical predictions for the differential branching fraction of $B^{0}rightarrow K^{ast}(892)^{0}mu^{+}mu^{-}$ decays are available for the $q^2$ region $1.1<q^2<6.0,{rm GeV}^2/c^4$. In this $q^2$ region, for the $K^+pi^-$ invariant mass range $796 < m_{Kpi} < 996,{rm MeV}/c^2$, the S-wave fraction of the $K^+pi^-$ system in $B^{0}rightarrow K^{+}pi^{-}mu^{+}mu^{-}$ decays is found to be begin{equation*} F_{rm S} = 0.101pm0.017({rm stat})pm0.009 ({rm syst}), end{equation*} and the differential branching fraction of $B^{0}rightarrow K^{ast}(892)^{0}mu^{+}mu^{-}$ decays is determined to be begin{equation*} {rm d}mathcal{B}/{rm d} q^2 = (0.342_{,-0.017}^{,+0.017}({rm stat})pm{0.009}({rm syst})pm0.023({rm norm}))times 10^{-7}c^{4}/{rm GeV}^{2}. end{equation*} The differential branching fraction measurements presented are the most precise to date and are found to be in agreement with Standard Model predictions.
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