Subthreshold rho^0 photoproduction on 3He

A large reduction of the rho^0 mass in the nuclear medium is reported, inferred from dipion photoproduction spectra in the 1 GeV region, for the reaction 3He(gamma,pi+ pi-)X with a 10% duty factor tagged-photon beam and the TAGX multi-particle spectrometer. The energy range covered (800 < E(gamma) < 1120 MeV) lies mostly below the free rho^0 production threshold, a region which is believed sensitive to modifications of light vector-meson properties at nuclear-matter densities. The rho^0 masses extracted from the MC fitting of the data, m*(rho^0) = 642 +/- 40, 669 +/- 32, and 682 +/- 56 MeV/c^2 for E(gamma) in the 800-880, 880-960, and 960-1040 MeV regions respectively, are independently corroborated by a measured, assumption-free, kinematical observable. This mass shift, far exceeding current mean-field driven theoretical predictions, may be suggestive of rho^0 decay within the range of the nucleonic field.Comment: 40 pages, 13 figures, submitted to Phys. Rev.

Electron-induced neutron knockout from 4^{4}He

The differential cross section for electron-induced neutron knockout in the reaction 4He(e,e′n)3He has been measured for the first time with a statistical accuracy of 11%. The experiment was performed in quasielastic kinematics at a momentum transfer of 300  MeV/c and in the missing-momentum range of 25–70  MeV/c. The comparison of the data with theoretical calculations shows an impressive increase of the cross section resulting from final state interaction effects. Specifically , the p−n charge-exchange process dominates the cross section in this kinematical regime. (APS

Probing the DeltaNN component of 3He

The 3He(gamma,pi^+/- p) reactions were measured simultaneously over a tagged photon energy range of 800<E_gamma<1120 MeV, well above the Delta resonance region. An analysis was performed to kinematically isolate Delta knockout events from conventional Delta photoproduction events, and a statistically significant excess of pi+p events was identified, consistent with Delta++ knockout. Two methods were used to estimate the DeltaNN probability in the 3He ground state, corresponding to the observed knockout cross section. The first gave a lower probability limit of 1.5+/-0.6+/-0.5%; the second yielded an upper limit of about 2.6%.Comment: 14 page

Development of a small field-of-view scintimammography camera: Measurements and simulations

The authors report on studies of a small field of view scintimammography camera based on a position sensitive PMT and a crystal scintillator array. A 5-inch R3292 Hamamatsu PMT was coupled to a variety of scintillators, including pixelized NaI(TI), Csi (Na) and YAP. Laboratory and phantom studies were performed to compare performances of the above scintillator sensors with special emphasis on spatial resolution and scatter rejection. The results of Monte Carlo simulations for different pixel sizes are also presented

Analyzing powers for pi+- p polarized elastic scattering between 87-MeV and 263-MeV

Analyzing powers for \u3c0p elastic scattering were measured using the CHAOS spectrometer at energies spanning the \u394(1232) resonance. This work presents \u3c0+ data at the pion kinetic energies 117, 130, 139, 155, 169, 180, 193, 218, 241, and 267 MeV and \u3c0- data at 87, 117, 193, and 241 MeV, covering an angular range of 50\ub0<~\u3b8c.m.<~180\ub0 at the higher energies and 90\ub0<~\u3b8c.m.<~180\ub0 at the lower energies. Unique features of the spectrometer acceptance were employed to reduce systematic errors. Single-energy phase shift analyses indicate the resulting S11 and S31 phases favor the results of the SM95 phase shift analysis over that of the older KH80 analysis