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.
The reaction gamma p --> K0 Sigma+ was measured in the photon energy range from threshold up to 2.6 GeV with the SAPHIR detector at the electron stretcher facility, ELSA, in Bonn. Results are presented on the reaction cross section and the polarization of the Sigma+ as a function of the kaon production angle in the centre-of-mass system, cos(Theta_K^{c.m.}), and the photon energy. The cross section is lower and varies less with photon energy and kaon production angle than that of gamma p --> K+ Sigma0. The Sigma+ is polarized predominantly at cos(Theta_K^{c.m.}) \approx 0. The data presented here are more precise than previous ones obtained with SAPHIR and extend the photon energy range to higher values. They are compared to isobar model calculations.
Polarization parameter of the SIGMA+ as a function of angle in two photon energy ranges.
Large-angle cross sections for γd→π0d are systematically measured in the photon energy range between 500 and 1000 MeV. A good fit is obtained by use of a Glauber-model calculation which includes the dibaryon resonances F33(2.26) and G41(2.51), but the fit has an unusual nature in the role of resonance and nonresonance contributions.
Liquid hydrogen target for final calibration.
The differential cross section for the reaction γp → π 0 p at forward angles has been measured in the energy region between 350 MeV and 1175 MeV. A phenomenological multiple analysis was carried out on the present data together with other data.
No description provided.
The differential cross sections for the γ + n → π O + n reaction have been measured at the photon energies of 500–900 MeV. The ratios, R oo = [ d δ d Ω(γ n → π o n ) ] [ d δ d Ω(γ p → π o p ) ] , have been obtained at the c.m. pion angles of 60 O , 90 O , 105 O , 120 O , and 140 O .
Axis error includes +- 0.0/0.0 contribution (8 TO 11////).
No description provided.
We report measurements of the two-photon processes e+e−→e+e−π+π− and e+e−→e+e−K+K−, at an e+e− center-of-mass energy of 29 GeV. In the π+π− data a high-statistics analysis of the f(1270) results in a γγ width Γ(γγ→f)=3.2±0.4 keV. The π+π− continuum below the f mass is well described by a QED Born approximation, whereas above the f mass it is consistent with a QCD-model calculation if a large contribution from the f is assumed. For the K+K− data we find agreement of the high-mass continuum with the QCD prediction; limits on f′(1520) and θ(1720) formation are presented.
Data read from graph. Additional overall systematic error 20% not included.
Data read from graph. Additional overall systematic error 20% not included.
The polarized target asymmetry for γ + p → π + + n was measured at c.m. angles around 130° for the energy range between 0.3 and 1.0 GeV. A magnetic spectrometer system was used to detect π + mesons from the polarized butanol target. The data show two prominent positive peaks at 0.4 and 0.8 GeV and a deep minimum at 0.6 GeV. These features are well reproduced by the phenomenological analysis made by us.
No description provided.
The polarized target asymmetry in the reaction γp→π°p has been measured at c.m. angles around 100° for photon energies between 0.4 and 1.0 GeV by detecting both the recoil proton and the π°. The result is compared with recent analyses.
No description provided.
We have observed exclusive production of K + K − and K S O K S O pairs and the excitation of the f′(1515) tensor meson in photon-photon collisions. Assuming the f′ to be production in a helicity 2 state, we determine Λ( f ′ → γγ) B( f ′ → K K ) = 0.11 ± 0.02 ± 0.04 keV . The non-strange quark of the f′ is found to be less than 3% (95% CL). For the θ(1640) we derive an upper limit for the product Λ(θ rarr; γγ K K ) < 0.03 keV (95% CL ) .
Data read from graph.. Errors are the square roots of the number of events.
Data read from graph.. Errors are the square roots of the number of events.
The polarized target asymmetry for the process γ p → π + n has been measured for incident photon energies below 1.02 GeV over a range of c.m. angles from 40° to 160°. π + mesons from a polarized butanol target were detected by a magnetic spectrometer. The results are compared with predictions given by existing analyses. A tentative interpretation of the data is performed, and a larger contribution of S-wave resonances is suggested. The photocouplings of dominant resonances were hardly changed by the inclusion of new data and they seem to be almost uniquely determined.
No description provided.
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