HEPData Search

We have measured the asymmetry of the cross section for γp→π+n from a polarized target at 5 and 16 GeV. The range of four-momentum transfer was 0.02<~−t<~1.0 GeV2. The π+ mesons were produced in a polarized butanol target and detected with the Stanford Linear Accelerator Center 20−GeVc spectrometer. A sizable asymmetry was found at both 5 and 16 GeV, a typical value being -0.6 near −t=0.3 GeV2. A small amount of data on the asymmetry of other photoproduction processes was also obtained.

5 data tables

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RECOIL PROTON POLARIZATION IN ETA PHOTOPRODUCTION

Heusch, C.A. ; Prescott, C.Y. ; Rochester, L.S. ; et al.

Phys.Rev.Lett. 25 (1970) 1381, 1970.

Inspire Record 61494 DOI 10.17182/hepdata.21581

We measured the polarization of the recoil proton in the process γp→pη0, at 90° in the center-of-mass system, at incoming photon energies from 0.8 to 1.1 GeV. Detection of all three particles in the final state pγγ permitted observation of this process with little background. Subsequent rescattering off carbon nuclei yielded sizable polarization values for the protons, indicating considerable S−P—wave interference in the production process.

1 data table

Table 1

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Photoproduction of k+ mesons and polarization of lambda0 hyperons in the 1-gev range

Fujii, T. ; Imanishi, A. ; Iwata, S. ; et al.

Phys.Rev.D 2 (1970) 439-448, 1970.

Inspire Record 61523 DOI 10.17182/hepdata.24271

Polarization of Λ hyperons and differential cross sections for the reaction γ+p→K++Λ were measured at the K+-meson center-of-mass angles around 45°, 70°, and 90° for the incident photon energies of 1054, 1100, and 1160 MeV. The K+ mesons were detected with a magnetic spectrometer and a velocity-selection system based on the energy loss and the time of flight. The polarization of Λ was determined by measuring the up-down asymmetry of protons in the decay Λ→pπ− with respect to the production plane. The results show a dominant sinθK* dependence of the polarization at the region of the third resonance and are consistent with a contribution of the P11 resonance with a mass of about 1700 MeV.

3 data tables

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Production of single negative pions from deuterium with polarized photons

Bar-Yam, Z. ; De Pagter, J. ; Dowd, J. ; et al.

Phys.Rev.Lett. 24 (1970) 1078-1081, 1970.

Inspire Record 62952 DOI 10.17182/hepdata.21628

The asymmetry A=(dσ⊥−dσ∥)(dσ⊥+dσ∥) of the differential cross section for the reaction γd→π−pp has been studied with linearly polarized photons of 3.0 GeV at squared four-momentum-transfers between 0.15 and 2.0 (GeV/c)2. The asymmetry was found to be positive at −t values below 0.3 (GeV/c)2, dipping to negative values between 0.4 and 0.6 (GeV/c)2, and then rising again to positive values above 0.7 (GeV/c)2.

1 data table

Table 1

Axis error includes +- 11/11 contribution.

Pi+ photoproduction from hydrogen with polarized photons

Bar-Yam, Z. ; De Pagter, J. ; Dowd, J. ; et al.

Phys.Rev.Lett. 25 (1970) 1053-1056, 1970.

Inspire Record 62861 DOI 10.17182/hepdata.21600

The reaction γ⊥,∥p→π+n has been studied with linearly polarized photons of energy 3.0 GeV at −t values between 0.15 and 1.2 (GeVc)2. The asymmetry A+=(dσ⊥−dσ∥)(dσ⊥+dσ∥) is found to be positive throughout this four-momentum-transfer range, implying the dominance of natural parity exchange in the t channel. Comparison of dσ⊥(γ⊥p→π+n) and dσ⊥p→π−p) from a previous experiment indicates strong interference between the isoscalar and isovector photon amplitudes for photons polarized perpendicular to the production plane.

3 data tables

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