Proton-proton total cross-sections have been measured at nine different energies between 179 and 555 MeV (607 and 1162 MeV/ c ) with a typical accuracy of 0.9%. The accuracy is limited by a poor knowledge of the Coulomb-nuclear interference region in elastic scattering.
No description provided.
A search for production of D*−'s using the decay chain D0π−, D0→K+π−, was carried out at the Brookhaven National Laboratory multiparticle spectrometer with a 16-GeV/c π− beam and a hydrogen target. At 95% confidence level the upper limits for the product of peripheral production cross section by branching ratio are 2.4 nb for inclusive D*− production and 1.3 nb for the exclusive channel π−p→D*−Λc.
UPPER LIMIT TO CROSS SECTIONS.
We report on a search for Ξ* production in the mass range 1.5-2.0 GeV / c2 in K−n interactions at 2.87 GeV / c. Upper limits on Ξ* production cross sections, as well as reaction cross sections for those final states in which Ξ*'s may be observed, are presented. In particular, an upper limit of 5.4 μb is placed on production of an isospin-−32 Ξ*−−.
CROSS SECTIONS ARE QUOTED FOR THE SAME FINAL STATE DERIVED FROM DIFFERENT TOPOLOGIES.
UPPER LIMITS AT 90 PCT CONFIDENCE LEVEL FOR RESONANCE ABOVE SMOOTH BACKGROUND.
No description provided.
Data on p p annihilations at rest into K 1 0 K 1 0 ω 0 and K + K − ω 0 are discuss New measurements for the mass, the width and the branching ratio of the ω 0 are presented. Evidence for quasi two-body annihilations p p → ϕπ, p ̄ p → S ∗ π is discussed.
PRODUCTION RATE FOR ANNIHILATION AT REST.
The measurement of different reactions of p d annihilation at rest in a gaseous target has been performed using the OBELIX spectrometer at LEAR (CERN). A strong deviation from the OZI-rule prediction was found from the measurement of the ratio R = φπ ωπ in two regions of proton momenta, P < 200 MeV/ c and P > 400 MeV/ c : R( φπ − ωπ − ) = (133 ± 26) × 10 −3 and (113 ± 30) × 10 −3 , respectively. These values are about 30 times greater than the theoretical prediction. For the first time the excitation of the †-resonance was observed among the final-state products of p d annihilation. The existence of a broad enhancement in the 4π invariant mass at m ≈ 1480 MeV, seen in previous experiments, was confirmed. A ≈ 100 MeV downward shift of the bump position, when the proton momentum increased up to P > 400 MeV/ c , was also observed, while the positions of ω, ϱ and f 2 (1270) did not change with the proton momentum. The following branching ratios were measured: BR( p d → π − φ p ) = (6.62 ± 0.49) × 10 −4 , for P < 200 MeV/ c ; BR( p d → π − φ p ) = (0.95 ± 0.22) × 10 −4 , for P > 400 MeV/ c ; BR( p d → π − ω p ) = (49.7 ± 8.9) × 10 −4 , for P < 200 MeV/ c ; BR( p d → π − ω p ) = (8.38 ± 1.09) × 10 −4 , for P > 400 MeV/ c ; BR( p d → 2π − π + p ) = (150 ± 6) × 10 −4 , for P < 200 MeV/ c ; BR( p d → 2π − π + p ) = (16.6 ± 0.9) × 10 −4 , for P > 400 MeV/ c ; BR( p d → 3π − 2π + p ) = (326 ± 12) × 10 −4 , for P < 200 MeV/ c ; BR( p d → 3π − 2π + p ) = (44 ± 7) × 10 −4 , for P > 400 MeV/ c ; BR( p d → Λ K + π − ) = (0.96 ± 0.19) × 10 −4 , for P > 400 MeV/ c ; BR( p d → Λ K + π − π 0 ) = (3.5 ± 0.8) × 10 −4 , for P > 400 MeV/ c ; BR( p p → 2π − 2π + ) = (540 ± 20) × 10 −4 ; BR( p p → 3π − 3π + ) = (251 ± 21) × 10 −4 .
We present cross sections for e+e−→hadrons, e+e−, and μ+μ− near 3095 MeV. The ψ(3095) resonance is established as having an assignment JPC=1−−. The mass is 3095 ±4 MeV. The partial width to electrons is Γe=4.8±0.6 keV and the total width Γ=69±15 keV. Total rates and interference measurements for the lepton channels are in accord with μ−e universality.
Total reaction cross sections σR of (30–60)AMeV 4,6,8He and 6,7,8,9,11Li on Pb, and 2n-removal cross sections σ−2n of 6,8He and 11Li on Pb, were measured by injecting magnetically separated, focused, monoenergetic, secondary beams of those projectiles into a telescope containing Pb targets separated by thin Si detectors. All these σR’s (except 4He), and σ−2n for 6He and 11Li, are underpredicted by microscopic model calculations which include only nuclear forces. Better agreement is achieved by including electromagnetic dissociation in the model, for those projectiles for which either the electric dipole response functions or the dominant photodissociation cross sections were known. The cross sections σ−4n for 8He, σ−xn for 7,8,9Li, and (σ−3n+σ−4n) for 11Li were found to be ⩽0.7 b. All σR’s were measured to better than 5% accuracy, showing that the method is usable for other target elements sandwiched into a Si telescope.
Attenuation measurements of reaction and total cross sections have been made for π− beams at 410, 464, and 492 MeV on targets of CD2, 6Li, C, Al, S, Ca, Cu, Zr, Sn, and Pb. These results are assisted by and compared to predictions from a recent eikonal optical model. Calculations with this model, which does not include pion absorption, agree with recent elastic scattering data, but are significantly below our measured reaction and total cross sections.
Fission fragment cross sections and angular anisotropies have been measured to high accuracy following fusion of 16O with the strongly deformed nucleus 182W, at bombarding energies spanning the fusion barrier region. Together with existing evaporation residue data, they show that at all the beam energies, the statistical transition state model adequately describes the fission properties measured. No significant evidence was found for a memory of the different configurations at fusion resulting from the target nucleus deformation, in contrast with previous measurements for deformed actinide nuclei.
In the reaction p p → 3π + 3π − 2227 events, and in the reaction p p → 3π + 3π − π 0 6578 events have been analyzed. The general characteristics of the reactions, such as total cross sections, angular and momentum distributions, the production of ϱ, f, ω and η mesons, and angular correlations are presented.
No description provided.
THETA being the angle between PI+ and P (or PI- and PBAR) in CMS.
THETA being the angle between PI+ and P (or PI- and PBAR) in CMS.
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