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Register a new user$K^+Lambda$ and $K^+Sigma^0$ photoproduction with fine center-of-mass energy resolution
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Measurements of $gamma p rightarrow K^{+} Lambda$ and $gamma p rightarrow K^{+} Sigma^0$ cross-sections have been obtained with the photon tagging facility and the Crystal Ball calorimeter at MAMI-C. The measurement uses a novel $K^+$ meson identification technique in which the weak decay products are characterized using the energy and timing characteristics of the energy deposit in the calorimeter, a method that has the potential to be applied at many other facilities. The fine center-of-mass energy ($W$) resolution and statistical accuracy of the new data results in a significant impact on partial wave analyses aiming to better establish the excitation spectrum of the nucleon. The new analyses disfavor a strong role for quark-diquark dynamics in the nucleon.
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We report the first measurements of the $E$ beam-target helicity asymmetry for the $vec{gamma} vec{n} to K^{0}Lambda$, and $K^{0}Sigma^{0}$ channels in the energy range 1.70$leq Wleq$2.34 GeV. The CLAS system at Jefferson Lab uses a circularly polarized photon beam and a target consisting of longitudinally polarized solid molecular hydrogen deuteride with low background contamination for the measurements. The multivariate analysis method boosted decision trees was used to isolate the reactions of interest. Comparisons with predictions from the KaonMAID, SAID, and Bonn-Gatchina models are presented. These results will help separate the isospin $I=0$ and $I=1$ photo-coupling transition amplitudes in pseudoscalar meson photoproduction.
We report measurements of the exclusive electroproduction of $K^+Lambda$ and $K^+Sigma^0$ final states from an unpolarized proton target using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The separated structure functions $sigma_U$, $sigma_{LT}$, $sigma_{TT}$, and $sigma_{LT}$ were extracted from the $Phi$-dependent differential cross sections acquired with a longitudinally polarized 5.499 GeV electron beam. The data span a broad range of momentum transfers $Q^2$ from 1.4 to 3.9 GeV$^2$, invariant energy $W$ from threshold to 2.6 GeV, and nearly the full center-of-mass angular range of the kaon. The separated structure functions provide an unprecedented data sample, which in conjunction with other meson photo- and electroproduction data, will help to constrain the higher-level analyses being performed to search for missing baryon resonances.
$K^+Lambda(1405)$ photoproduction has been studied at the BGOOD experiment via the all neutral decay, $Lambda(1405)rightarrowSigma^0pi^0$. BGOODs unique experimental setup allows both the cross section and $Lambda(1405)$ invariant mass distribution (line shape) to be measured over a broad $K^+$ polar angle range, extending to extreme forward $K^+$ angles unattainable at previous experiments. The line shape was determined to be in agreement with the previous results of CLAS and ANKE, and appear consistent with two poles derived in $chi$PT based models. %with hints of a double peak structure which may have been observed in the ANKE results At forward $K^+$ angles the relative strength of the peaks appear to change, however more statistics are required for a firm conclusion. Evidence is provided for the role of a triangle singularity driven by the $N^*(2030)$ resonance, which appears to significantly contribute to $K^+Lambda(1405)$ photoproduction. This is observed in both the angular distributions and the integrated cross section which was determined with unprecedented energy resolution.
$gamma p rightarrow K^+ Lambda$ differential cross sections and recoil polarisation data from threshold for extremely forward angles are presented. The measurements were performed at the BGOOD experiment at ELSA, utilising the high angular and momentum resolution forward spectrometer for charged particle identification. The data discriminates between conflicting results in the world data set and enable extraction of the cross section as the minimum momentum transfer to the recoiling hyperon is approached.
Differential cross sections and hyperon polarizations have been measured for $bar{K}^0 n$, $pi^0 Lambda$, and $pi^0 Sigma^0$ production in $K^- p$ interactions at eight $K^-$ momenta between 514 and 750 MeV/$c$. The experiment detected the multiphoton final states with the Crystal Ball spectrometer using a $K^-$ beam from the Alternating Gradient Synchrotron of BNL. The results provide significantly greater precision than the existing data, allowing a detailed reexamination of the excited hyperon states in our energy range.
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