The asymmetry of the cross section for π + photoproduction from a polarized butanol target has been measured at a c.m. angle 90° and photon energies between 300 and 900 MeV by a single-arm spectrometer detecting positive pions. Our results indicate that the asymmetry has clear positive peaks at photon energies 400 and 700 MeV with a deep valley at about 600 MeV. The general feature of the results is well reproduced by the phenomenological analyses made by Walker and ourselves; however, the best fit to the polarized target asymmetry data seems to give a somewhat different set of parameters from that given by Walker.
No description provided.
SMC is progressing a series of experiments to reveal the spin structure of nucleon at CERN. The first experiment on deuteron has been performed in 1992. We will report here the data on deuteron and discuss the present status of nucleon spin structure using all data including SMC and also E142(SLAC) data recently reported.
First moment of the spin-dependent structure function G1.
An experimental study was made of a ωπ 0 system produced in the charge exchange reaction π − p→ ωπ 0 n at 8.95 GeV/ c . The moment analysis was performed to study the spin-parity of the system in the mass region between 1.04 and 1.88 GeV. A clear peak of b 1 (1235) was observed in the J PC = 1 +− wave. No significant structure was seen in the 1 −− wave. An upper limit is obtained to be at most 1.9 μb for σ ( π − p→X 0 n)Br(X 0 → ωπ 0 ) for X 0 with a width of 130 MeV at 1480 MeV, where C(1480) meson with J PC = 1 −− has been reported in a φπ 0 decay mode.
Upper limit for pi- p --> X0 n (X0 --> omega pi0) with width 130 MeV at 1480 MeV where the C(1480) has been reported with JPC = 1-- in the phi pi0 decay mode.
High statistics data of the ηππ system in π − p → ηπ + π − n were obtained. A partial wave analysis was performed in the mass region between 1.37 and 1.85 GeV. Resonant structures were observed in the IJ PC = 11 −− wave around 1.6 GeV and in 13 −− around 1.7 GeV. The structure in 11 −− was fitted with a single Breit-Wigner and also fitted with two Breit-Wigner's. The result suggests the possible existence of two vector resonances around 1.6 GeV. The structure in 13 −− is considered to be the π 3 (1690).
Result of single Breit Wigner fit around 1.6 GeV. Called here $M(1635).
Results of double Breit Wigner fit around 1.6 GeV. $M(1446) and $M(1701).
Result of Breit Wigner fit around 1.7 GeV.
The tensor analyzing power T20 for the reaction d↑+12C→p(0°)+X has been measured in the region of proton internal momenta k in light-cone dynamics up to 1 GeV/ c. Measurements have been carried out at Dubna Synchrophasotron with polarized deuteron beam at deuteron momenta up to 9 GeV/ c. When k increases the experimental values of T20 have a tendency to approach the value ( −0.3) obtained by the calculation based on the reduced nuclear amplitude method in which the quark degrees of freedom are taken into account.
The differential cross section of the deuteron photodisintegration was measured at a protion c.m. angle of 180 degrees and for photon energies between 180 and 730 MeV. The protons were detected in a magnetic spectrometer. The proton energy resolution varied between 30 MeV and 50 MeV FWHM. Since these are the first data at 180 degrees in this energy range a comparison can only be done with data from other laboratories extrapolated to 180 degrees and with theoretical predictions. The agreement with existing calculations is poor. Contributions of dibaryons to the cross section seem not to improve the situation.
The tensor analyzing power T 20 for the reaction d ↑ + 12 C → π ± (0°) + X has been measured with a polarized deuteron beam from 6.2 to 9.0 GeV/ c at a pion momentum3.0 GeV/ c . This experiment is focused on “cumulatively produced pions”, which are produced beyond the kinematically allowed limit for free nucleon-nucleon collisions. The measured values of T 20 turn out to be close to zero. They are in disagreement with the results of our impulse approximation calculation which is based on a single NN → πNN interaction and takes into account the internal motion of nucleons in the deuteron. Possible explanations of the result are discussed.
The analyzing power for elastic pd scattering at 3.5 GeV has been measured in the region 0.1⩽−t⩽1.5 (GeV/ c ) 2 , using the polarized proton beam at KEK. The angular distribution shows a behavior similar to that in the lower energy region. It is reproduced fairly well by the predictions of a multiple scattering model based on the Glauber theory.
A measurement of the spin correlation parameters A xx (90° cm) and A yy (90° cm) of 47.5 MeV proton-proton scattering has been performed by means of polarized beam and a polarized target.
No description provided.
The polarized target asymmetry in the reaction γ p → π 0 p has been measured at c.m. angles of 30°, 80°, 105° and 120° for incident photon energies below 1 GeV. Two decay photons from π 0 were detected in coincidence at 30°, and at the other angles recoil protons and single photons from π 0 were detected. The results are compared with recent phenomenological analyses.
No description provided.
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