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Register a new userMeasurement of the radiative decay width Gamma[Lambda(1520) --> Lambda gamma] with the SPHINX spectrometer
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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.
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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.
The radiative decay $Lambda_{b}^{0} to Lambda gamma$ is observed for the first time using a data sample of proton-proton collisions corresponding to an integrated luminosity of $1.7,fb^{-1}$ collected by the LHCb experiment at a center-of-mass energy of $13,TeV$. Its branching fraction is measured exploiting the $B^{0} to K^{*0} gamma$ decay as a normalization mode and is found to be $mathcal{B}(Lambda_{b}^{0} to Lambda gamma)= (7.1 pm 1.5 pm 0.6 pm 0.7) times 10^{-6}$, where the quoted uncertainties are statistical, systematic and systematic from external inputs, respectively. This is the first observation of a radiative decay of a beauty baryon.
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.
Differential cross sections for $K^-$ radiative capture in flight on the proton, leading to the $gammaLambda$ and $gammaSigma^0$ final states, have been measured at eight $K^-$ momenta between 514 and 750 MeV/$c$. The data were obtained with the Crystal Ball multiphoton spectrometer installed at the separated $K/pi$ beam line C6 of the BNL Alternating Gradient Synchrotron. The results substantially improve the existing experimental data available for studying radiative decays of excited hyperon states. An exploratory theoretical analysis is performed within the Regge-plus-resonance approach. According to this analysis, the $gammaSigma^0$ final state is dominated by hyperonresonance exchange and hints at an important role for a resonance in the mass region of 1700 MeV. In the $gammaLambda$ final state, on the other hand, the resonant contributions account for only half the strength, and the data suggest the importance of a resonance in the mass region of 1550 MeV.
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.
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