The differential cross section of the reaction γ + p → p + πo has been measured at the Deutsches Elektronen- Synchrotron, Hamburg, at mean phonon energies of 1.36, 2.0 and 3.0 GeV and pion center of mass angles between 0o and 70o. The results are compared with some theoretical calculations based on elementary and reggeized 1- meson exchange.
Axis error includes +- 12/12 contribution.
Axis error includes +- 12/12 contribution.
Axis error includes +- 12/12 contribution.
The differential cross-section of the reaction γ + p → p + π 0 was measured at the Deutsches Elektronen-Synchrotron, Hamburg, at mean photon energies of 4.0, 5.0 and 5.8 GeV and pion center of mass angles between 0° and 60°. The results are compared wiht theoretical calculations based on Reggeized vector meson exchange.
Axis error includes +- 7/7 contribution.
Axis error includes +- 7/7 contribution.
Axis error includes +- 7/7 contribution.
The polarization of the recoil proton from the reaction 7+p--->~pi0+p has been measured using liquid helium as polarization analyser. The photon energy has been varied between 250 and 360 MeV, the pion angle (CM) between 58 and 100.
No description provided.
Some cross-sections for the photo-production of ~z~ from hydrogen for pion c.m. angles in the range 60~ ~ are presented. The data have been obtained by measuring proton yields from a hydrogen target, thus permitting separation of single-pion production from the strong background caused by double-pion production. The values, which extend from 360 to 938 MeV, show reasonable agreement with the results of a recent phase-shift analysis
No description provided.
The angular distribution of the polarization of the recoil protons from the reactionγ+p→π 0+p has been measured at a photon energy of 360 MeV and at pion CM angles of 58°, 75°, 96° and 105°. The polarization of the protons has been determined by the left to right ratio in scattering on a helium gas target. The trajectory of each scattered proton has been measured by a system of spark chambers.
No description provided.
Differential cross sections for the gamma p -> pi^0 p reaction have been measured with the A2 tagged-photon facilities at the Mainz Microtron, MAMI C, up to the center-of-mass energy W=1.9 GeV. The new results, obtained with a fine energy and angular binning, increase the existing quantity of pi^0 photoproduction data by ~47%. Owing to the unprecedented statistical accuracy and the full angular coverage, the results are sensitive to high partial-wave amplitudes. This is demonstrated by the decomposition of the differential cross sections in terms of Legendre polynomials and by further comparison to model predictions. A new solution of the SAID partial-wave analysis obtained after adding the new data into the fit is presented.
Run 1. Total cross section as a function of c.m. energy W.
Excitation function at cos(Theta_eta)= -0.967
Excitation function at cos(Theta_eta)= -0.900
The polarization of the recoil proton in γ + p → p + π0 has been measured at photon energies of 725 MeV and 900 MeV for centerof-mass angles near 90° using a small propane-ethane gas bubble chamber. Protons emerging from a liquid hydrogen target are momentum-analysed with a magnet, and the scattering from carbon observed in the bubble chamber. A counter telescope rejects pions and electrons, and protons from multiple pion processes are discriminated against by keeping the peak bremsstrahlung energy just above the mean photon energy. The visual method of observing scattering asymmetries has the advantage of being insensitive to systematic asymmetries in the incoming proton flux. It also quickly eliminates strongly inelastic scatters (stars), and provides a complete angular distribution from which the fraction of scatters which are inelastic can be deduced. The effect of inelastic scatters upon the scattering asymmetry is large when the energy-loss resolution is poor, an inherent problem with bremsstrahlung beams. The counting rate for this small chamber (3.4g/cm2 carbon scatterer) was 11 scatters/hour using every 5th synchrotron pulse; larger chambers with more dense scatterers (such as Freon) could give higher counting rates. Results are fork = 725MeV and ϑ (pion) = 87° (cm.), P=0.74±0.20, and for k=900MeV and ϑ (pion) = 70°, P=.51±.7. P is taken to be positive along the directionK xp, wherep is the momentum of the outgoing proton.
No description provided.
New results are presented on the differential cross-section for the reaction α+p→π0+p, at energies between 600 and 1000 MeV, and c.m. pion angles Θ*π=40° and Θ*π=60°. The present data, together with that at Θ*π=40° already published (11), show an angle-independent position of the second resonance at about 750 MeV. Rather flat angular distributions in the forward c.m. hemisphere are also favoured by these data. On comparing the cross-sections obtained when detecting both the neutral pion and the recoil proton, and when detecting only the latter, estimates of the background of «ghost protons» are obtained, in agreement with the empirical curve proposed in ref. (11).
No description provided.
The elastic scattering of photons by protons has been measured for 100 MeV to 290 MeV photons at 90° c.m.s. and 139° c.m.s. scattering angles. The expected large increase in cross-section is observed at energies approaching that of (3/2, 3/2) pion-nucleon resonance. The scattering can be qualitatively explained by the ordinary Thomson amplitude combined with that of the (3/2, 3/2) resonance. A more detailed examination of the cross-section in the region just above the photo-meson threshold has shown that it is sensitive to the π0 photon coupling. From the experimental data, one may conclude that the π0 mean life should be between 10−16 and 10−18 s.
No description provided.
The polarization of the recoil proton in the photoproduction process γ+p→p+π0 has been measured with the beam of the Frascati electrosynchrotron at an angle of 90° in the c.m. system, in the energy interval (500÷900) MeV. A counter technique has been used, and the polarization of the proton was revealed by the left to right asymmetry in the elastic scattering of the protons in a carbon target. The experimental results are given in Table III and in Fig. 10. A definite polarization is found, always of the same sign and equal to −0.4±.14, −0.63±.23, −0.6±.25, −0.57±.12, −0.38±.09, −0.5±.17, −0.5±.22 at the γ-ray energies of 560, 610, 650, 700, 750, 800, 850 MeV respectively. The discussion of these experimental results, together with the data of angular dstributions, allows to conclude that they are in agreement with the hypothesis that the second resonance is a transition (E 1,d 3/2) and the third one is a transition (E 2,f 3/2).
No description provided.
Forum