Measurement of the Photon Beam Asymmetry in \u3ci\u3eγP\u3c/i\u3e → \u3ci\u3eK\u3c/i\u3e\u3csup\u3e+\u3c/sup\u3eΣ\u3csup\u3e0\u3c/sup\u3e at \u3ci\u3eE\u3csub\u3eγ\u3c/sub\u3e\u3c/i\u3e = 8.5 GeV with GlueX

In this work the photon beam asymmetry Σ for the reaction γp K+ Σ0(1193) is measured using the GlueX experiment in Hall D at Jefferson Lab. The analysis used data that were collected using a linearly polarized photon beam in the energy range (8.2 - 8.8) GeV incident on a liquid hydrogen target. The beam asymmetries are measured as a function of the Mandelstam variable t and as a single value for the low u region. These are the first exclusive measurements of the photon beam asymmetry Σ in this reaction at energies above the baryon resonance region. For the t-channel, results are close to unity and show that the reaction is dominated by the natural-parity exchange of the K*(892) Regge trajectory as predicted by theoretical models. A value of Σ = 0.410±0.090 is obtained for the u-channel and suggests the exchange of both Σ(J = 1/2) and Y*(J = 3/2) trajectory contributions to the production of K+Σ0

Decay of the Λ(1405) hyperon to Σ

Among the light baryons, the Jπ = 1/2− Λ(1405) hyperon is an important special case as it sits just below the N K̅ threshold and decays almost exclusively to Σπ. Some long-standing hypotheses for Λ(1405) are that it could be a N K̅ bound state or a Σπ continuum resonance. It may also be considered as a simple quark-model resonance, the P-wave companion of the Λ(1520). In recent years chiral unitary models have suggested that there are two isospin zero poles present in this mass region, and that the “line shape" of the Λ(1405) depends to what extent each of the two poles are stimulated in a given reaction. Below the N K̅ threshold, the Λ(1405) decays to the three Σπ charge combinations. The Σ0π0 mode is purely I = 0 and it is uncontaminated by complications arising from I = 1 scattering processes contributing to the reaction mechanism in the Σ+π− and Σ−π+ decays. It is also not affected from production and decay of the nearby Σ0(1385) hyperon. The GlueX experiment at Jefferson Lab has been used to study the Λ(1405) → Σ0π0 decay mode. We focus on the preliminary results of dσ/dMΣ0π0 and fits to the line shape of the Λ(1405) region in the −(t − tmin) range 0 - 1.5 GeV2 from analyzing the reaction γp → K+Λ* using the data collected during the first phase of the GlueX program

Strange Hadron Spectroscopy with Secondary KL Beam in Hall D

Final version of the KLF Proposal [C12-19-001] approved by JLab PAC48. The intermediate version of the proposal was posted in arXiv:1707.05284 [hep-ex]. 103 pages, 52 figures, 8 tables, 324 references. Several typos were fixedWe propose to create a secondary beam of neutral kaons in Hall D at Jefferson Lab to be used with the GlueX experimental setup for strange hadron spectroscopy. The superior CEBAF electron beam will enable a flux on the order of $1\times 10^4~K_L/sec$, which exceeds the flux of that previously attained at SLAC by three orders of magnitude. The use of a deuteron target will provide first measurements ever with neutral kaons on neutrons. The experiment will measure both differential cross sections and self-analyzed polarizations of the produced $\Lambda$, $\Sigma$, $\Xi$, and $\Omega$ hyperons using the GlueX detector at the Jefferson Lab Hall D. The measurements will span CM $\cos\theta$ from $-0.95$ to 0.95 in the range W = 1490 MeV to 2500 MeV. The new data will significantly constrain the partial wave analyses and reduce model-dependent uncertainties in the extraction of the properties and pole positions of the strange hyperon resonances, and establish the orbitally excited multiplets in the spectra of the $\Xi$ and $\Omega$ hyperons. Comparison with the corresponding multiplets in the spectra of the charm and bottom hyperons will provide insight into he accuracy of QCD-based calculations over a large range of masses. The proposed facility will have a defining impact in the strange meson sector through measurements of the final state $K\pi$ system up to 2 GeV invariant mass. This will allow the determination of pole positions and widths of all relevant $K^\ast(K\pi)$ $S$-,$P$-,$D$-,$F$-, and $G$-wave resonances, settle the question of the existence or nonexistence of scalar meson $\kappa/K_0^\ast(700)$ and improve the constrains on their pole parameters. Subsequently improving our knowledge of the low-lying scalar nonet in general

Measurement of the J/ψ\psi photoproduction cross section over the full near-threshold kinematic region

We report the total and differential cross sections for J / ψ photoproduction with the large acceptance GlueX spectrometer for photon beam energies from the threshold at 8.2 GeV up to 11.44 GeV and over the full kinematic range of momentum transfer squared, t . Such coverage facilitates the extrapolation of the differential cross sections to the forward ( t = 0 ) point beyond the physical region. The forward cross section is used by many theoretical models and plays an important role in understanding J / ψ photoproduction and its relation to the J / ψ -proton interaction. These measurements of J / ψ photoproduction near threshold are also crucial inputs to theoretical models that are used to study important aspects of the gluon structure of the proton, such as the gluon generalized parton distribution of the proton, the mass radius of the proton, and the trace anomaly contribution to the proton mass. We observe possible structures in the total cross section energy dependence and find evidence for contributions beyond gluon exchange in the differential cross section close to threshold, both of which are consistent with contributions from open-charm intermediate states