The electroproduction of π0 on the proton was measured from 0 to 2.5 MeV above threshold for virtual-photon 4-momenta of -0.05 and -0.1 (GeV/c)2. The sum of the lowest-order contributing multipoles, a0=‖E0+‖2-εL‖L0+‖2, was determined with a precision an order of magnitude better than previously possible. Our results for a0 are consistent with present calculations. Our extracted value for ‖L0+‖2 at the ‘‘photon point’’ is in agreement with recent predictions.
Joined statistics for two incident electron energy of 300 and 500 MeV.
Angular and momentum distributions have been measured for positrons from electron-positron pairs created in peripheral collisions of 6.4-TeV sulfur ions with fixed targets of Al, Pd, and Au. The data are compared with results of several theoretical treatments. Measured differential cross sections peak at low momentum (≤1 MeV/c), extend significantly to much higher momenta (>17 MeV/c), and concentrate sharply in the forward direction, along the ion-beam axis. Positron yields scale as the square of the target nuclear charge as predicted by theory.
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With 4.36×106 events, spin precession in a magnetic field has been used to measure the magnetic moment of the Ξ− hyperon as -0.6505±0.0025 nuclear magnetons.
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We report measurements of asymmetries in quasielastic scattering of polarized electrons from polarized He3 at Q2=-0.2 GeV/c)2. We measure AT′=(-2.6±0.9±0.46)% and ATL′=(+1.75±1.2±0.31)%. The asymmetry AT′ depends predominantly on the previously measured neutron magnetic form factor and provides a test of theories of spin-dependent quasielastic scattering. Our result for AT′ is consistent with a previously reported measurement and suggests that the current theoretical picture is incomplete and final-state-interaction and meson-exchange corrections are necessary if the electric form factor of the neutron is to be reliably extracted from the asymmetry of ATL′.
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The polarization of quasifree Λ hyperons produced by the (π+K+) reaction on C12 and on the deuteron was measured for the first time. The asymmetry of pions from weak decay of the Λ hyperon was used to determine the polarization. The polarization for the deuterium target was found to be consistent with that for the elementary n(π+,K+)Λ reaction. The polarization of the Λ produced by the quasifree process from C12 is consistent with that for the elementary reaction, which demonstrates that the spin characteristics of the elementary reaction are not modified by the nuclear medium.
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We present the first polarization measurements for pion absorption on a nucleus heavier than the deuteron. The polarization of protons resulting from π+ absorption in the He3 was measured at bombarding energies of 120 and 250 MeV. Protons from absorption in a quasideuteron were selected by applying kinematical constraints. A significant discrepancy was observed between the experimental results and theoretical predictions. At 120 MeV the measured polarizations for He3 are consistent with those of the deuteron. At 250 MeV the angular distribution of the polarization is significantly different than for the deuteron, showing sensitivity to the nuclear density, and thus may be sensitive to short range correlations between nucleons.
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We report measurements of d¯, p¯, K−, and π− produced at 0° in collisions of 14.6A GeV/c Si28 on Al, Cu, and Au targets. A beam-line focusing spectrometer was used to identify particles at rigidities from -2 to -8 GV. The ratio of d¯/p¯ invariant cross sections at midrapidity (y=1.7) is (1±0.7)×10−5, larger than expected from a calculation of dd¯ direct production but smaller than predicted by a simple coalescence model. We also report limits on the production of exotic particles.
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The B0 B¯ 0 average mixing parameter χ has been extracted from eμ and ee events produced in pp¯ collisions at √s =1.8 TeV. In a sample of 900 eμ events, the like-sign to opposite-sign charge ratio R is measured to be 0.556±0.048(stat)−0.042+0.035(syst). In the absence of mixing, the expected value of R would be 0.23±0.06. The corresponding number for 212 ee events is 0.573±0.116(stat)±0.047(syst) with an expected nonmixing value of 0.24±0.07. The observed excess in R leads to a combined determination of χ=0.176±0.031(stat+syst) ±0.032 (model), where the last uncertainty is due to Monte Carlo modeling.
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Antiproton induced fission probabilities of U238, Bi209, Pb208 and Au177 are reported together with the mass distribution of the fission fragments in the U238 and Bi209 cases. The charged particles multiplicities observed in co-incidence with fission have, also, been measured for U and Bi and are presented.
TOTAL AVERAGE MASSES AND KINETIC ENERGIES OF FISSION FRAGMENTS. Mean mass is in proton mass units.
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NUCLEUS IS P, C, AL, CU.
NUCLEUS IS P, C, AL, CU.
NUCLEUS IS P, C, AL, CU.
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