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Register a new userEvidence for the strangeness-changing weak decay $Xi_b^-toLambda_b^0pi^-$
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Using a $pp$ collision data sample corresponding to an integrated luminosity of 3.0~fb$^{-1}$, collected by the LHCb detector, we present the first search for the strangeness-changing weak decay $Xi_b^-toLambda_b^0pi^-$. No $b$ hadron decay of this type has been seen before. A signal for this decay, corresponding to a significance of 3.2 standard deviations, is reported. The relative rate is measured to be ${{f_{Xi_b^-}}over{f_{Lambda_b^0}}}{cal{B}}(Xi_b^-toLambda_b^0pi^-) = (5.7pm1.8^{+0.8}_{-0.9})times10^{-4}$, where $f_{Xi_b^-}$ and $f_{Lambda_b^0}$ are the $btoXi_b^-$ and $btoLambda_b^0$ fragmentation fractions, and ${cal{B}}(Xi_b^-toLambda_b^0pi^-)$ is the branching fraction. Assuming $f_{Xi_b^-}/f_{Lambda_b^0}$ is bounded between 0.1 and 0.3, the branching fraction ${cal{B}}(Xi_b^-toLambda_b^0pi^-)$ would lie in the range from $(0.57pm0.21)%$ to $(0.19pm0.07)%$.
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The first search for the rare radiative decay $Xi_b^- to Xi^- gamma$ is performed using data collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb$^{-1}$. The $Xi_b- to Xi^- J/psi$ channel is used as normalization. No $Xi_b^- to Xi^- gamma$ signal is found and an upper limit of $mathcal{B}(Xi_b^- to Xi^- gamma) < 1.3 times 10^{-4}$ at 95% confidence level is obtained.
In the SND experiment at VEPP-2M $e^+e^-$ collider the $phi(1020)topi^0pi^0gamma$ decay was studied and its branching ratio was measured: $B(phitopi^0pi^0gamma)=(1.221pm 0.098pm0.061)cdot10^{-4}$. It was shown, that $f_0(980)gamma$ intermediate state dominates in this decay and the $f_0(980)$-meson parameters were obtained.
Decays of the $Xi_b^-$ and $Omega_b^-$ baryons to the charmless final states $p h^{-}h^{prime -}$, where $h^{(prime)}$ denotes a kaon or pion, are searched for with the LHCb detector. The analysis is based on a sample of proton-proton collision data collected at centre-of-mass energies $sqrt{s} = 7$ and $8 TeV$, corresponding to an integrated luminosity of $3 {rm fb}^{-1}$. The decay $Xi_b^- to p K^-K^-$ is observed with a significance of $8.7$ standard deviations, and evidence at the level of $3.4$ standard deviations is found for the $Xi_b^- to p K^-pi^-$ decay. Results are reported, relative to the $B^-to K^+K^-K^-$ normalisation channel, for the products of branching fractions and $b$-hadron production fractions. The branching fractions of $Xi_b^- to p K^-pi^-$ and $Xi_b^- to p pi^-pi^-$ relative to $Xi_b^- to p K^-K^-$ decays are also measured.
Using $e^+e^-toLambda_c^+barLambda_c^-$ production from a 567 pb$^{-1}$ data sample collected by BESIII at 4.6 GeV, a full angular analysis is carried out simultaneously on the four decay modes of $Lambda_c^+to pK_S^0$, $Lambda pi^+$, $Sigma^+pi^0$, and $Sigma^0pi^+$. For the first time, the $Lambda_c^+$ transverse polarization is studied in unpolarized $e^+e^-$ collisions, where a non-zero effect is observed with a statistical significance of 2.1$sigma$. The decay asymmetry parameters of the $Lambda_c^+$ weak hadronic decays into $pK_S^0$, $Lambdapi^+$, $Sigma^+pi^0$ and $Sigma^0pi^+$ are measured to be $0.18pm0.43(rm{stat})pm0.14(rm{syst})$, $-0.80pm0.11(rm{stat})pm0.02(rm{syst})$, $-0.57pm0.10(rm{stat})pm0.07(rm{syst})$, and $-0.73pm0.17(rm{stat})pm0.07(rm{syst})$, respectively. In comparison with previous results, the measurements for the $Lambdapi^+$ and $Sigma^+pi^0$ modes are consistent but with improved precision, while the parameters for the $pK_S^0$ and $Sigma^0pi^+$ modes are measured for the first time.
We report a study of the decay $D^0 rightarrow bar{K}^0pi^-e^+ u_{e}$ based on a sample of $2.93~mathrm{fb}^{-1}$ $e^+e^-$ annihilation data collected at the center-of-mass energy of 3.773~GeV with the BESIII detector at the BEPCII collider. The total branching fraction is determined to be $mathcal{B}(D^0rightarrow bar{K}^0pi^-e^+ u_{e})=(1.434pm0.029({rm stat.})pm0.032({rm syst.}))%$, which is the most precise to date. According to a detailed analysis of the involved dynamics, we find this decay is dominated with the $K^{*}(892)^-$ contribution and present an improved measurement of its branching fraction to be $mathcal{B}(D^0rightarrow K^{*}(892)^-e^+ u_e)=(2.033pm0.046({rm stat.})pm0.047({rm syst.}))%$. We further access their hadronic form-factor ratios for the first time as $r_{V}=V(0)/A_1(0)=1.46pm0.07({rm stat.})pm0.02({rm syst.})$ and $r_{2}=A_2(0)/A_1(0)=0.67pm0.06({rm stat.})pm0.01({rm syst.})$. In addition, we observe a significant $bar{K}^0pi^-$ $S$-wave component accounting for $(5.51pm0.97({rm stat.})pm0.62({rm syst.}))%$ of the total decay rate.
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