Differential cross sections for neutral-pion photoproduction on hydrogen in the region of the first resonance have been measured by two independent experiments detecting the recoil protons. The results of both measurements have been combined into one set of cross sections covering the photon energy range from 200 to 440 MeV at pion c.m. angles between 50 and 160 degrees.
No description provided.
No description provided.
No description provided.
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 asymmetry A = (σ + −σ − ) (σ + +σ − ) of the reaction γ p↑↓ → π 0 p was measured at the Deutsches Elektronen Synchrotron DESY, Hamburg at a mean photon energy of 4.0 GeV in the four-momentum transfer range 0.2 (GeV/ c ) 2 ⩽ −t ⩽ 1.1 (GeV/ c ) 2 in steps of approximately 0.08 (GeV/ c ) 2 . The π 0 -meson and the proton were detected in coincidence. The asymmetry is compatible with zero in the t -range 0.2 (GeV/ c ) 2 ⩽ − t ⩽ 0.4 (GeV/ c ) 2 and negative in the t -range ⩾ 0.5 (GeV/ c ) 2 .
No description provided.
The differential cross-section of the reaction γ p→ η p has been measured at the Deutsches Elektronen Synchrotron (DESY) at mean photon energies of 4 and 6 GeV in the momentum transfer range between zero and 1.4 GeV 2 . The data show a slight maximum around t =−0.15 GeV 2 and fall off smoothly till t =−1.4 GeV 2 . There is no indication of a dip around t =−0.5 GeV 2 .
Axis error includes +- 19/19 contribution.
Axis error includes +- 19/19 contribution.
The ratio R = (d σ /d t )( γ d → ( π 0 n)p)/(d σ /d t )( γ d → ( π 0 p)n), was measured at the Deutsches Elektronen-Synchrotron DESY, Hamburg at a mean photon energy of 4.0 GeV in the four-momentum transfer range between t = − 0.2 (GeV/ c ) 2 and t = − 1.2 (GeV/ c ) 2 in steps of approximately 0.08 (GeV/ c ) 2 . The ratio R is less than 1 up to t = − 0.9 (GeV/ c ) 2 and shows a broad minimum around t = − 0.6 (GeV/ c ) 2 . Corrections for nuclear effects in the deuterium were not applied but are shown to be small.
No description provided.
The differential cross section of the reaction γ p → π 0 p has been measured at the Deutsches Elektronen Synchrotron DESY, Hamburg, at a mean photon energy of 4.0 GeV in the four-momentum transfer range between t = −0.2 (GeV/ c ) 2 and t = −1,2 (GeV/ c ) 2 in steps of approximately 0.08 (GeV/ c ) 2 . The experiment was carried out in connection with the measurements of the photoproduction of π 0 mesons on deuterium, which were described in the preceding article. In the present paper the contributions arising from background reactions are discussed in more detail.
No description provided.
Production of charmed mesons in γγ-interactions at PETRA energies has been observed in the TASSO detector. Cross sections for inclusiveD*± and\(D^0 \bar D^0 \) production have been measured. Neutral and charged meson pairs are estimated to be produced with comparable cross sections, and their sum seems to account for a sizeable fraction of σtot(γγ→hadrons) near the\(c\bar c\) threshold.
No description provided.
No description provided.
Statistical error only.
The process γγ→π+π−π+π− has been investigated in reactions of the typee+e−→e+e−π+π−π+π− in the single tag mode. The range of the four momentum squared of one of the virtual photons was 0.28 GeV2/c2≦Q2≦3.6 GeV2/c2, the average being 〈Q2〉=0.92 GeV2/c2; the other photon was quasi real. The reaction is mainly described by the channels γγ→ρ0ρ0 and γγ→4π (phase space), occuring with about equal probability. TheQ2-dependence of the cross section is in agreement with the ρ form factor.
Data read from graph.. Additional overall systematic error 25%.
Data read from graph.. Additional overall systematic error 25%.. The Q**2 approx 0 datum is deduced from the earlier TASSO paper, Brandelik et al, Phys. Lett. 97B(1980)448, (<a href=http://durpdg.dur.ac.uk/scripts/reacsearch.csh/TESTREAC/red+1151> RED = 1151 </a>) on rho0 rho0 production.
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.
Production of the p p π + π − final state by two-photon scattering was observed. The cross section for γγ→p p π + π − was determined assuming phase space production. No evidence was found for the production or formation of resonances. Upper limits are given for Λ and Δ pair production, for production of p p ϱ 0 and for the two-photon excitation of c c bound states.
No description provided.
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