Predictions Of Partial-wave Analyses Research Articles

MEASUREMENT OF POLARIZATION OBSERVABLES IN NEUTRAL DOUBLE PION PHOTOPRODUCTION OFF THE PROTON WITH THE CBELSA/TAPS EXPERIMENT

The Crystal Barrel/TAPS experiment is ideally suited to measure neutral mesons decaying into photons due to its high detection efficiency for photons, good energy resolution, and the nearly complete solid angle coverage. In combination with a longitudinally or transversely polarized target and an energy tagged, linearly or circularly polarized photon beam the experiment allows the measurement of a large set of polarization observables. The presented preliminary results for polarization observables of neutral double pion production obtained with a transversely polarized target show significant deviations from current predictions of partial wave analyses. This clearly indicates that 2π0-photoproduction is not yet understood.

Polarization parameters of elastic pp scattering in the angular range 22.5°–42.5° at an energy of 1 GeV and partial-wave analysis of data

The polarization properties of elastic scattering are studied experimentally for pp interaction at 1 GeV. The respective experimental results are presented for the spin-transfer parameter Kn00n and the polarization Pn000 at c.m. angles of 22.5°, 27.5°, 32.5°, and 42.5° and for the analyzing power A000n at c.m. angles of 22.5° and 27.5°. The experiment employed an unpolarized proton beam from the accelerator of the Petersburg Nuclear Physics Institute, a polarized proton target, and a high-resolution magnetic spectrometer. The data from this experiment are analyzed and compared with the predictions of partial-wave analyses.

Measurements of spin rotation parameter A in pion–proton elastic scattering at 1.62 GeV/c

The ITEP-PNPI Collaboration presents the results of the measurements of the spin rotation parameter A in the elastic scattering of positive and negative pions on protons at P beam=1.62 GeV/c. The setup included a longitudinally-polarized proton target with superconductive magnet, multiwire spark chambers and a carbon polarimeter with thick filter. Results are compared with the predictions of partial wave analyses. The experiment was performed at the ITEP proton synchrotron, Moscow.

Recoil-proton polarization in pi p elastic scattering at 547 and 625 MeV/c.

The polarization of the recoil proton in ${\ensuremath{\pi}}^{+}$p and ${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$p elastic scattering using a liquid-hydrogen target has been measured for backward angles at 547 and 625 MeV/c. The scattered pion and recoil proton were detected in coincidence using the large-acceptance spectrometer to detect and analyze the momentum of the pions and the JANUS polarimeter to identify and measure the polarization of the protons. Results from this experiment agree with other measurements of the recoil polarization, with analyzing-power data previously taken by this group, and with predictions of partial-wave analyses.

Measurmennt of recoil proton polarization in the process of π− photoproduction from neutrons in the energy range between 700 and 1200 MeV

The recoil proton polarization for γn → π −p was measured around the third resonance region. Both momentum vectors of the proton and the pion were determined by the magnetic spectrometers. The proton polarization was measured by means of proton-carbon scattering in the polarization analyzer located behind the proton spectrometer. Below 900 MeV incident photon energy, our data are consistent with the other existing experimental data ( θ π ∗ = 90° ) and the predictions of partial-wave analyses. Above 1000 MeV, however, a large discrepancy was observed between our data and the predictions of the partial-wave analyses. The discrepancy stands out as the pion c.m. angle increases. A new partial-wave analysis was made for γn → π −p including our polarization data, and the accuracy of the experimentally determined electromagnetic coupling constant of the third resonances were greatly improved. In particular, a finite amount of the helicity 3 2 amplitude for the γn → F 15(1688) resonance was obtained against the predictions of the quark models, by Copley, Karl and Obryk and by Feynman, Kislinger and Ravendal but in agreement with the relativistic quark models of Sugimoto and Toya, and Kubota and Ohta.