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تسجيل مستخدم جديدModel-independent evidence for $J/psi p$ contributions to $Lambda_b^0to J/psi p K^-$ decays
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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.
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Observations of exotic structures in the $J/psi p$ channel, that we refer to as pentaquark-charmonium states, in $Lambda_b^0to J/psi K^- p$ decays are presented. The data sample corresponds to an integrated luminosity of 3/fb acquired with the LHCb d
etector from 7 and 8 TeV pp collisions. An amplitude analysis is performed on the three-body final-state that reproduces the two-body mass and angular distributions. To obtain a satisfactory fit of the structures seen in the $J/psi p$ mass spectrum, it is necessary to include two Breit-Wigner amplitudes that each describe a resonant state. The significance of each of these resonances is more than 9 standard deviations. One has a mass of $4380pm 8pm 29$ MeV and a width of $205pm 18pm 86$ MeV, while the second is narrower, with a mass of $4449.8pm 1.7pm 2.5$ MeV and a width of $39pm 5pm 19$ MeV. The preferred $J^P$ assignments are of opposite parity, with one state having spin 3/2 and the other 5/2.
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 descri
ption 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.
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.
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 i
ntegrated 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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