[en] The ratios of inclusive electron scattering cross sections of 4He, 12C, and 56Fe to 3He have been measured for the first time. It is shown that these ratios are independent of xB at Q2 > 1.4 GeV2 for xB > 1.5, where the inclusive cross section depends primarily on the high momentum components of the nuclear wave function. The observed scaling shows that the momentum distributions at high-momenta have the same shape for all nuclei and differ only by a scale factor. The observed onset of the scaling at Q2 > 1.4 GeV2 and xB > 1.5 is consistent with the kinematical expectation that two-nucleon short range correlations (SRC) dominate the nuclear wave function at pm300 MeV/c. The values of these ratios in the scaling region can be related to the relative probabilities of SRC in nuclei with A3. Our data, combined with calculations and other measurements of the 3He/deuterium ratio, demonstrate that for nuclei with A12 these probabilities are 4.9-5.9 times larger than in deuterium, while for 4He it is larger by a factor of about 3.8

[en] We examine the results of two measurements by the CLAS collaboration, one of which claimed evidence for a Θ⁺ pentaquark, whilst the other found no such evidence. The unique feature of these two experiments was that they were performed with the same experimental setup. Using a Bayesian analysis we find that the results of the two experiments are in fact compatible with each other, but that the first measurement did not contain sufficient information to determine unambiguously the existence of a Θ⁺. Further, we suggest a means by which the existence of a new candidate particle can be tested in a rigorous manner

[en] New cross sections for the reaction ep → e(prime)ηp are reported for total center of mass energy W=1.5--2.3 GeV and invariant squared momentum transfer Q²=0.13--3.3 GeV². This large kinematic range allows extraction of new information about response functions, photocouplings, and ηN coupling strengths of baryon resonances. A sharp structure is seen at W ∼ 1.7 GeV. The shape of the differential cross section is indicative of the presence of a P-wave resonance that persists to high Q². Improved values are derived for the photon coupling amplitude for the S₁₁(1535) resonance. The new data greatly expands the Q² range covered and an interpretation of all data with a consistent parameterization is provided

[en] For the first time, the reaction gamma d -> Lambda n K+ has been analyzed in order to search for the exotic pentaquark baryon Theta+(1540). The data were taken at Jefferson Lab, using the Hall-B tagged-photon beam of energy between 0.8 and 3.6 GeV and the CEBAF Large Acceptance Spectrometer (CLAS). No statistically significant structures were observed in the nK+ invariant mass distribution. The upper limit on the gamma d -> Lambda Theta+ integrated cross section has been calculated and found to be between 5 and 25 nb, depending on the production model assumed. The upper limit on the differential cross section is also reported

[en] The reaction ²H(e,e(prime) p)n has been studied with full kinematic coverage for photon virtuality 1.75 < 5.5 ∼ GeV². Comparisons of experimental data with theory indicate that for very low values of neutron recoil momentum (p_n < 100 MeV/c) the neutron is primarily a spectator and the reaction can be described by the plane-wave impulse approximation. For 100 < 750 MeV/c proton-neutron rescattering dominates the cross section, while Δ production followed by the NΔ → NN transition is the primary contribution at higher momenta

[en] The cross section and decay angular distributions for the coherent φ meson photoproduction on the deuteron have been measured for the first time up to a squared four-momentum transfer t =(p_γ-p_φ)² = -2 GeV²/c², using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The cross sections are compared with predictions from a re-scattering model. In a framework of vector meson dominance, the data are consistent with the total φ-N cross section σ_φN at about 10 mb. If vector meson dominance is violated, a larger σ_φN is possible by introducing larger t-slope for the φN → φN process than that for the γN → φN process. The decay angular distributions of the φ are consistent with helicity conservation