Results on the channels K − p → Λ 0 η 0 , Λ 0 π 0 , Σ 0 π 0 , Λ 0 π 0 π 0 and Σ 0 π 0 π 0 are obtained in a K − p formation experiment using 1 million photographs taken in a heavy liquid bubble chamber filled with a CF 3 BrC 3 H 8 mixture. The results are compared with hydrogen bubble chamber (HBC) experiments and with experiments having full or partial gamma-ray detection. Our Λ 0 π 0 and Λ 0 + neutral cross section agree with HBC results. Our Σ 0 π 0 cross section does not exhibit a bump at 1670 MeV as previously seen in HBC experiments. Our Λ 0 π 0 π 0 data are dominated by a Σ (1385) π 0 production. Our Σ 0 π 0 π 0 data is consistent with the presence of some Σ (1405) π 0 production.
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The ratio of π - to π + electroproduction cross sections from deuterium has been measured in the resonance region, at a four-momentum transfer squared close to −1.0 (GeV/ c ) 2 . Results in the forward direction are presented and a comparison is made with predictions based on SU(6) W and the Melosh transformation.
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The first measurements are reported of the asymmetry in resonance-region scattering of longitudinally polarized electrons by longitudinally polarized protons. Data have been obtained at Q2=0.5 and 1.5 (GeV/c)2 in the missing-mass range W=1.1−1.9 GeV. Results are compatible with a multipole analysis of single-pion electroproduction. The spin-dependent behavior is consistent with a duality mechanism as in the unpolarized case.
ELECTRON ASYMMETRY AT Q**2 ABOUT 0.5 GEV**2.
ELECTRON ASYMMETRY AT Q**2 ABOUT 1.5 GEV**2.
PHOTON ASYMMETRY AT Q**2 ABOUT 0.5 GEV**2.
The ratio of π − to π + electroproduction cross sections from deuterons has been measured in the resonance region at an average four-momentum transfer squared of 0.5 (GeV/ c ) 2 . Results are presented over a wide range of pion production angles and comparisons are made with theoretical predictions based on SU(6) w symmetry and the Melosh transformation.
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We have used the momentum spectrum of leptons produced in semileptonic B-meson decays to set a 90%-confidence-level upper limit on Γ(b→ulν)Γ(b→clν) of 4%. We also measure the semileptonic branching fractions of the B meson to be (12.0±0.7±0.5)% for electrons and (10.8±0.6±1.0)% for muons.
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The e + e − → ηπ + π − reaction has been measured in the center of mass energy interval 1350–2400 MeV by the magnetic detector DM2 at the Orsay storage ring DCI. Under the hypothesis of only one large resonance the cross section is not fit in a satisfactory way. The branching ratio τ − → η − π 0 ν τ =(0.13 ± 0.02)% is deduced via CVC from the above measurement.
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At the tagged photon facility PHOENICS at the Bonn accelerator ELSA a measurement of the target asymmetry of the reaction γp→pη from threshold to 1150 MeV has been performed. Simultaneously the reaction γp→pπ0 has been measured in the first resonance region. Results are presented for both reactions. The target asymmetry data are suited to put considerable constraints on the model parameters used for the theoretical description of meson photoproduction.
The errors include statistical and systematic errors added in quadrature. The target asymmetry determines as the rates belonging to different polarization states: (N_pol-up-N_pol_down)/(N_pol-up+N_pol_down).
The errors include statistical and systematic errors added in quadrature. The target asymmetry determines as the rates belonging to different polarization states: (N_pol-up-N_pol_down)/(N_pol-up+N_pol_down).
The errors include statistical and systematic errors added in quadrature. The target asymmetry determines as the rates belonging to different polarization states: (N_pol-up-N_pol_down)/(N_pol-up+N_pol_down).
We have measured the transverse asymmetry from inclusive scattering of longitudinally polarized electrons from polarized 3He nuclei at quasi-elastic kinematics in Hall A at Jefferson Lab with high statistical and systematic precision. The neutron magnetic form factor was extracted based on Faddeev calculations with an experimental uncertainty of less than 2 %.
Ratio of neutron magnetic form-factor to dipole value.
We report the first measurement of the neutron electric form factor $G_E^n$ via $\vec{d}(\vec{e},e'n)p$ using a solid polarized target. $G_E^n$ was determined from the beam-target asymmetry in the scattering of longitudinally polarized electrons from polarized deuterated ammonia, $^{15}$ND$_3$. The measurement was performed in Hall C at Thomas Jefferson National Accelerator Facility (TJNAF) in quasi free kinematics with the target polarization perpendicular to the momentum transfer. The electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle segmented detector. We find $G_E^n = 0.04632\pm0.00616 (stat.) \pm0.00341 (syst.)$ at $Q^2 = 0.495$ (GeV/c)$^2$.
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We measured the inclusive electron-proton cross section in the nucleon resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2 with the CLAS detector. The large acceptance of CLAS allowed for the first time the measurement of the cross section in a large, contiguous two-dimensional range of Q**2 and x, making it possible to perform an integration of the data at fixed Q**2 over the whole significant x-interval. From these data we extracted the structure function F2 and, by including other world data, we studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate higher twist contributions. The small statistical and systematic uncertainties of the CLAS data allow a precise extraction of the higher twists and demand significant improvements in theoretical predictions for a meaningful comparison with new experimental results.
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