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Register a new userRadiative decays of the Sigma0(1385) and Lambda(1520) hyperons
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The electromagnetic decays of the Sig0(1385) and Lambda(1520) hyperons were studied in photon-induced reactions gamma p -> K+ Lambda(1116)gamma in the CLAS detector at the Thomas Jefferson National Accelerator Facility. We report the first observation of the radiative decay of the Sig0(1385) and a measurement of the Lambda(1520) radiative decay width. For the Sig0(1385) -> Lambda(1116)gamma transition, we measured a partial width of 479+/-120(stat)+81-100(sys) keV, larger than all of the existing model predictions. For the Lambda(1520) -> Lambda(1116)gamma transition, we obtained a partial width of 167+/-43(stat)+26-12(sys) keV.
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The radiative decay Lambda(1520) --> Lambda gamma was measured directly in the study of exclusive diffractive-like reaction p + N --> Lambda(1520) K^+ + N, Lambda(1520) --> Lambda gamma with the SPHINX spectrometer. The values of the branching and partial width of this radiative decay were obtained: BR[Lambda(1520) --> Lambda gamma] = (1.02+/-0.21(stat)+/-0.15(syst))x10^{-2} and Gamma[Lambda(1520) --> Lambda gamma] = 159+/-33(stat)+/-26(syst) keV.
We calculate the radiative decay widths of decuplet hyperons in a chiral constituent quark model including electromagnetic exchange currents between quarks. Exchange currents contribute significantly to the E2 transition amplitude, while they largely cancel for the M1 transition amplitude. Strangeness suppression of the radiative hyperon decays is found to be weakened by exchange currents. Differences and similarities between our results and other recent model predictions are discussed.
Differential cross sections and photon-beam asymmetries for the gamma p -> K+ Lambda(1520) reaction have been measured with linearly polarized photon beams at energies from the threshold to 2.4 GeV at 0.6<cos(theta)<1. A new bump structure was found at W=2.11 GeV in the cross sections. The bump is not well reproduced by theoretical calculations introducing a nucleon resonance with J<=3/2. This result suggests that the bump might be produced by a nucleon resonance possibly with J>=5/2 or by a new reaction process, for example an interference effect with the phi photoproduction having a similar bump structure in the cross sections.
We study the decays of the charmonium resonances $J/psi$ and $psi(3686)$ to the final states $Xi^{-}barXi^{+}$, $Sigma(1385)^{mp}barSigma(1385)^{pm}$ based on a single baryon tag method using data samples of $(223.7 pm 1.4) times 10^{6}$ $J/psi$ and $(106.4 pm 0.9) times 10^{6}$ $psi(3686)$ events collected with the BESIII detector at the BEPCII collider. The decay $psi(3686)rightarrowSigma(1385)^{mp}barSigma(1385)^{pm}$ is observed for the first time, and the measurements of the other processes, including the branching fractions and angular distributions, are in good agreement with and much more precise than the previously published results. Additionally, the ratios $frac{{cal{B}}(psi(3686)rightarrowXi^{-}barXi^{+})}{{cal{B}}(J/psirightarrowXi^{-}barXi^{+})}$, $frac{{cal{B}}(psi(3686)rightarrowSigma(1385)^{-}barSigma(1385)^{+})}{{cal{B}}(J/psirightarrowSigma(1385)^{-}barSigma(1385)^{+})}$ and $frac{{cal{B}}(psi(3686)rightarrowSigma(1385)^{+}barSigma(1385)^{-})}{{cal{B}}(J/psirightarrowSigma(1385)^{+}barSigma(1385)^{-})}$ are determined.
We present a search for ten baryon-number violating decay modes of $Lambda$ hyperons using the CLAS detector at Jefferson Laboratory. Nine of these decay modes result in a single meson and single lepton in the final state ($Lambda rightarrow m ell$) and conserve either the sum or the difference of baryon and lepton number ($B pm L$). The tenth decay mode ($Lambda rightarrow bar{p}pi^+$) represents a difference in baryon number of two units and no difference in lepton number. We observe no significant signal and set upper limits on the branching fractions of these reactions in the range $(4-200)times 10^{-7}$ at the $90%$ confidence level.
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