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Register a new userEvidence for exotic hadron contributions to $Lambda_b^0 to J/psi p pi^-$ decays
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A full amplitude analysis of $Lambda_b^0 to J/psi p pi^-$ decays is performed with a data sample acquired with the LHCb detector from 7 and 8 TeV $pp$ collisions, corresponding to an integrated luminosity of 3 fb$^{-1}$. A significantly better description of the data is achieved when, in addition to the previously observed nucleon excitations $Nto ppi^-$, either the $P_c(4380)^+$ and $P_c(4450)^+to J/psi p$ states, previously observed in $Lambda_b^0 to J/psi p K^-$ decays, or the $Z_c(4200)^-to J/psi pi^-$ state, previously reported in $B^0 to J/psi K^+ pi^-$ decays, or all three, are included in the amplitude models. The data support a model containing all three exotic states, with a significance of more than three standard deviations. Within uncertainties, the data are consistent with the $P_c(4380)^+$ and $P_c(4450)^+$ production rates expected from their previous observation taking account of Cabibbo suppression.
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The data sample of $Lambda_b^0to J/psi p K^-$ decays acquired with the LHCb detector from 7 and 8~TeV $pp$ collisions, corresponding to an integrated luminosity of 3 fb$^{-1}$, is inspected for the presence of $J/psi p$ or $J/psi K^-$ contributions with minimal assumptions about $K^- p$ contributions. It is demonstrated at more than 9 standard deviations that $Lambda_b^0to J/psi p K^-$ decays cannot be described with $K^- p$ contributions alone, and that $J/psi p$ contributions play a dominant role in this incompatibility. These model-independent results support the previously obtained model-dependent evidence for $P_c^+to J/psi p$ charmonium-pentaquark states in the same data sample.
The decays $ Lambda_b^0 to psi(2S)pK^-$ and $ Lambda_b^0 to J/psi pi^+ pi^- pK^-$ are observed in a data sample corresponding to an integrated luminosity of 3fb$^{-1}$, collected in proton-proton collisions at 7 and 8TeV centre-of-mass energies by the LHCb detector. The $psi(2S)$ mesons are reconstructed through the decay modes $psi(2S)tomu^+mu^-$ and $psi(2S)to J/psipi^+pi^-$. The branching fractions relative to that of $ Lambda_b^0 to J/psi pK^-$ are measured to be begin{eqnarray*} frac{mathcal{B}(Lambda_b^0 to psi(2S) pK^-)} {mathcal{B}(Lambda_b^0 to J/psi pK^-)} & = & (20.70pm 0.76pm 0.46pm 0.37)times10^{-2} ,, frac{mathcal{B}(Lambda_b^0 to J/psi pi^+ pi^- pK^-)} {mathcal{B}(Lambda_b^0 to J/psi pK^-)} & = & (20.86pm 0.96pm 1.34)times10^{-2} ,, end{eqnarray*} where the first uncertainties are statistical, the second are systematic and the third is related to the knowledge of $J/psi$ and $psi(2S)$ branching fractions. The mass of the $Lambda_b^0$ baryon is measured to be $$ M(Lambda_b^0) = 5619.65 pm 0.17 pm 0.17mathrm{MeV}/c^2,$$ where the uncertainties are statistical and systematic.
An angular analysis of $B^0to J/psi K^+pi^-$ decays is performed, using proton-proton collision data corresponding to an integrated luminosity of 3~${rm fb}^{-1}$ collected with the LHCb detector. The $m(K^+pi^-)$ spectrum is divided into fine bins. In each $m(K^+pi^-)$ bin, the hypothesis that the three-dimensional angular distribution can be described by structures induced only by $K^ast$ resonances is examined, making minimal assumptions about the $K^+pi^-$ system. The data reject the $K^ast$-only hypothesis with a large significance, implying the observation of exotic contributions in a model-independent fashion. Inspection of the $m(J/psipi^-)$ versus $m(K^+pi^-)$ plane suggests structures near $m(J/psipi^-)=4200$~MeV and 4600~MeV.
The results of searches for $B^{0}_{(s)} rightarrow J/{psi} p overline{p}$ and $B^{+} to J/{psi} p overline{p} {pi}^{+}$ decays are reported. The analysis is based on a data sample, corresponding to an integrated luminosity of 1.0 fb$^{-1}$ of $pp$ collisions, collected with the LHCb detector. An excess with 2.8$,sigma$ significance is seen for the decay $B^{0}_{s} to J/{psi} p overline{p}$ and an upper limit on the branching fraction is set at the 90 % confidence level: ${cal B}(B^{0}_{s} to J/{psi} p overline{p}) < 4.8 times 10^{-6}$, which is the first such limit. No significant signals are seen for $B^{0} to J/{psi} p overline{p}$ and $B^{+} to J/{psi} p overline{p} {pi}^{+}$ decays, for which the corresponding limits are set: ${cal{B}}(B^{0} to J/{psi} p overline{p}) < 5.2 times 10^{-7}$, which significantly improves the existing limit; and ${cal{B}}(B^{+} to J/{psi} p overline{p} {pi}^{+}) < 5.0 times 10^{-7}$, which is the first limit on this branching fraction.
An amplitude analysis of flavour-untagged $B_s^0 to J/psi p bar{p}$ decays is performed using a sample of $797pm31$ decays reconstructed with the LHCb detector. The data, collected in proton-proton collisions between 2011 and 2018, correspond to an integrated luminosity of 9 $text{fb}^{-1}$. Evidence for a new structure in the $J/psi p$ and $J/psi bar{p}$ systems with a mass of $4337 ^{+7}_{-4} ^{+2}_{-2}~text{MeV}$ and a width of $29 ^{+26}_{-12} ^{+14}_{-14}~text{MeV}$ is found, where the first uncertainty is statistical and the second systematic, with a significance in the range of 3.1 to 3.7 $sigma$, depending on the assigned $J^P$ hypothesis.
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