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Register a new userObservation of the decay $Lambda_b^0rightarrowchi_{c1}ppi^-$
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The Cabibbo-suppressed decay $Lambda_b^0rightarrowchi_{c1}ppi^-$ is observed for the first time using data from proton-proton collisions corresponding to an integrated luminosity of 6fb$^{-1}$, collected with the LHCb detector at a centre-of-mass energy of 13TeV. Evidence for the $Lambda_b^0rightarrowchi_{c2}ppi^-$ decay is also found. Using the $Lambda_b^0rightarrowchi_{c1}pK^-$ decay as normalisation channel, the ratios of branching fractions are measured to be $$begin{array}{rcl} frac{ mathcal{B} (Lambda_b^0rightarrowchi_{c1}ppi^-)}{mathcal{B} (Lambda_b^0rightarrowchi_{c1}pK^-)} & = & (6.59 pm 1.01 pm 0.22 ) times 10^{-2} ,, frac{mathcal{B} (Lambda_b^0rightarrowchi_{c2}ppi^-)}{mathcal{B} (Lambda_b^0rightarrowchi_{c1}ppi^-)} & = & 0.95 pm 0.30 pm 0.04 pm 0.04 ,, frac{mathcal{B} (Lambda_b^0rightarrowchi_{c2}pK^-)}{mathcal{B} (Lambda_b^0rightarrowchi_{c1}pK^-)} & = & 1.06 pm 0.05 pm 0.04 pm 0.04 ,,end{array}$$ where the first uncertainty is statistical, the second is systematic and the third is due to the uncertainties in the branching fractions of $chi_{c1,2}rightarrow J/psigamma$ decays.
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Using proton-proton collision data, collected with the LHCb detector and corresponding to 1.0, 2.0 and 1.9fb$^{-1}$ of integrated luminosity at the centre-of-mass energies of 7, 8, and 13 TeV, respectively, the decay $Lambda_b^0to chi_{c1}(3872)pK^-$ with $chi_{c1}to J/psipi^+pi^-$ is observed for the first time. The significance of the observed signal is in excess of seven standard deviations. It is found that $(58pm15)%$ of the decays proceed via the two-body intermediate state $chi_{c1}(3872)Lambda(1520)$. The~branching fraction with respect to that of the $Lambda_brightarrowpsi(2S)p K^{-}$ decay mode, where the $psi(2S)$~meson is reconstructed in the $J/psi pi^+pi^-$ final state, is measured to be: begin{equation*} frac{Lambda_b^0tochi_{c1}(3872)pK^-}{Lambda_btopsi(2S)p K^-} times frac{mathcal{B}(chi_{c1} to J/psi pi^+pi^-)}{mathcal{B}(psi(2S)to J/psi pi^+pi^-)} = left(5.4 pm 1.1 pm 0.2right)times 10^{-2},, end{equation*} where the first uncertainty is statistical and the second is systematic.
The $Lambda_b^0toLambdaphi$ decay is observed using data corresponding to an integrated luminosity of 3.0fb$^{-1}$ recorded by the LHCb experiment. The decay proceeds at leading order via a $bto sbar{s}s$ loop transition and is therefore sensitive to the possible presence of particles beyond the Standard Model. A first observation is reported with a significance of $5.9$ standard deviations. The value of the branching fraction is measured to be $(5.18pm1.04pm0.35,^{+0.67}_{-0.62})times10^{-6}$, where the first uncertainty is statistical, the second is systematic, and the third is related to external inputs. Triple-product asymmetries are measured to be consistent with zero.
The Cabibbo-suppressed decay $Lambda^0_brightarrowpsi(2S)ppi^-$ is observed for the first time using a data sample collected by the LHCb experiment in proton-proton collisions corresponding to 1.0, 2.0 and 1.9fb$^{-1}$ of integrated luminosity at centre-of-mass energies of 7, 8 and 13TeV, respectively. The $psi(2S)$ mesons are reconstructed in the $mu^+mu^-$ final state. The~branching fraction with respect to that of the $Lambda^0_brightarrowpsi(2S)pK^-$ decay mode is measured to be $$frac{mathcal{B}left(Lambda^0_brightarrowpsi(2S)ppi^- right)} {mathcal{B}left(Lambda^0_brightarrowpsi(2S)pK^-right)}=left(11.4 pm 1.3 pm 0.2right)!%,,$$ where the first uncertainty is statistical and the second is systematic. The $psi(2S)p$ and $psi(2S)pi^-$ mass spectra are investigated and no evidence for exotic resonances is found.
The first observation of the decays $Lambda_b^0 to chi_{c1} p K^-$ and $Lambda_b^0 to chi_{c2} p K^-$ is reported using a data sample corresponding to an integrated luminosity of $3.0$ fb$^{-1}$, collected by the LHCb experiment in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV. The following ratios of branching fractions are measured begin{eqnarray*} frac{{cal B}(Lambda_b^0 to chi_{c1} p K^-)}{{cal B}(Lambda_b^0 to J/psi p K^-)} = 0.242 pm 0.014 pm 0.013 pm 0.009, frac{{cal B}(Lambda_b^0 to chi_{c2} p K^-)}{{cal B}(Lambda_b^0 to J/psi p K^-)} = 0.248 pm 0.020 pm 0.014 pm 0.009, frac{{cal B}(Lambda_b^0 to chi_{c2} p K^-)}{{cal B}(Lambda_b^0 to chi_{c1} p K^-)} = 1.02 pm 0.10 pm 0.02 pm 0.05, end{eqnarray*} where the first uncertainty is statistical, the second systematic and the third due to the uncertainty on the branching fractions of the $chi_{c1}to J/psigamma$ and $chi_{c2} to J/psigamma$ decays. Using both decay modes, the mass of the $Lambda_b^0$ baryon is also measured to be $m_{Lambda_b^0} = 5619.44 pm 0.28 pm 0.26$ MeV/$c^2$, where the first and second uncertainties are statistical and systematic, respectively.
The first observation of the Cabibbo-suppressed decay $Lambda_b^0rightarrow J/psi p pi^-$ is reported using a data sample of proton-proton collisions at 7 and 8 TeV, corresponding to an integrated luminosity of 3 $rm fb^{-1}$. A prominent signal is observed and the branching fraction relative to the decay mode $Lambda_b^0rightarrow J/psi p K^-$ is determined to be $$ frac{{cal B}(Lambda_b^0rightarrow J/psi p pi^-)}{{cal B}(Lambda_b^0rightarrow J/psi p K^-)}=0.0824pm0.0025:(text{stat})pm0.0042:(text{syst}). $$ A search for direct CP violation is performed. The difference in the CP asymmetries between these two decays is found to be $$ {cal A}_{CP}(Lambda_b^0rightarrow J/psi p pi^-)-{cal A}_{CP}(Lambda_b^0rightarrow J/psi p K^-)=(+5.7pm 2.4:(text{stat})pm1.2:(text{syst}))%, $$ which is compatible with CP symmetry at the $2.2sigma$ level.
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