Lambda production is studied in K − p interactions at 10.1 GeV/ c , where the dominant reaction is K − p → Λ + pions. General characteristics such as the distributions of the double differential cross section in the lab system, of the variable x = p L ∗ p max ∗ , of p ⊥ 2 and of the missing mass to the lambda are presented. Total cross sections for Λ production and for the various channels are given. Differential cross sections d σ d t , d σ d t′ and d σ d u′ are presented. Forward and backward peaks are observed in the d σ d t′ and d σ d u′ distributions, respectively. It is found that the exponential slope of these distributions decreases with increasing missing mass to the lambda and, for d σ d t′ , also for increasing multiplicity in the final state. The polarization of the lambdas is studied as a function of multiplicity, p L ∗ , (Λπ ± ) effective mass, t ′ and u ′. The forward lambdas show
No description provided.
POSSIBLE FORWARD DIP.
Cross sections are presented for the K + p interacttions with 2, 3, 4 and 5 particles in the final state for incident momenta between 2.1 and 2.7 GeV/c. The results are compared with those from other experiments at nearby momenta.
Axis error includes +- 0.0/0.0 contribution (?////).
The non-strange four-prong events of π + p interactions at 3.5 GeV/ c are studied. Cross sections are calculated for all resonance productions in the channels π + p → p π + π + π − ( σ T = 3.18 ± 0.13 mb) and π + p → p π + π + π − π o ( σ T = 4.03 ± 0.16 mb). The dominant two body reactions Δ ++ ϱ o and Δ ++ ω o are investigated in detail, and production and decay distributions are presented as well as joint decay density matrix elements and joint correlation terms. The Δ ++ ϱ o reaction is compared to predictions of OPE with absorption and the Δ ++ ω o is compared to rho-exchange with sharp cutoff.
FOUR-PRONG, NON-STRANGE CROSS SECTIONS. SYSTEMATIC ERROR INCLUDED.
BREIT-WIGNER RESONANCE FITS, ALLOWING FOR PHASE SPACE AND RELEVANT REFLECTIONS, TO <P PI+ PI+ PI-> FINAL STATE.
BREIT-WIGNER RESONANCE FITS, ALLOWING FOR PHASE SPACE AND RELEVANT REFLECTIONS, TO <P PI+ PI+ PI- PI0> FINAL STATE.
The total cross sections of 18.7 GeV Σ − hyperons on protons and deutrons have been measured to be 34.0 ± 1.1 mb and 61.3 + 1.4 mb, respectively. The derived Σ − -neutron cross section is 30.0 ± 1.2 mb.
CROSS SECTIONS CORRECTED FOR FORWARD COULOMB AND NUCLEAR SCATTERING.
It is found in the reactions π ± p →( π ± π + π − )p, believed to be dominated by diffraction dissociation, that the d σ d t′ distributions show a “cross-over” effect at t ′ ≈ 0.15, similar to the effect observed in elastic scattering. This gives evidence for the interference of ( ϱ 0 , B 0 ,…)-exchanges with ( P , f 0 , …) -exchanges in pion diffraction dissociation reactions. No such evidence is found for baryon dissociation, π ± p → π ± (p π + π − ), at the same energy.
No description provided.
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We report on a measurement for the branching-ratio X 0 → 2γ X 0 ar all. Our result is X 0 → 2γ X 0 → all = (2.9 ± 0.9)% .
BY COMPARISON WITH THE KNOWN ETA PRODUCTION CROSS SECTION.
Data were taken at the energy 2 E = 990 MeV to search for multibody events, with the same large solid angle detector which has been used for the measurement of the ϱ , ω and φ production by e + e − annilations. Assuming a π + π − π 0 π 0 production by the quasi two-body process e + e − → ϱ → ωπ 0 we give the correspondi ng cross section σ (e + e − → π + π − π 0 π 0 ) = (1.1 ± 0.5) 10 −32 cm 2 . Since no events with 3 and 4 charged pions have been observed σ (e + e − → π + π − π 0 π − ) ⩽ 1.5 × 10 −33 cm 2 .
RATIO TO MUON PAIR PRODUCTION CALCULATED FROM CROSS SECTION. INCLUDING SYSTEMATIC ERRORS.
The Λ polarization in the reaction γp → K + Λ has been measured using the decay Λ → pπ − as an analyzer. It is found to be large and negative in the momentum transer range 0.2 ⩽ | t | ⩽ 1.0 (GeV/ c ) 2 .
No description provided.
The Λp, Λn, Λ p, and Λ n total cross-sections were measured in the Λ momentum interval 6–21 GeV/ c . Within the experimental uncertainties the cross-sections are momentum-independent in this interval and the momentum-averaged cross-sections are found to be: σ ( Λp ) = 34.6 ± 0.4 mb : σ ( Λn ) = 34.0 ± 0.8 mb ; σ ( Λp ) = 56 ± 11 mb ; σ ( Λn ) = 46 ± 20 mb . The first two results are in agreement with charge symmetry, and with simple quark model sum rules applied to previous results on pp, K - n, and π + p total cross-sections.
NO SIGNIFICANT MOMENTUM DEPENDENCE OVER THIS INTERVAL. 2.8 +- 0.3 MB SHADOWING CORRECTION APPLIED FOR NEUTRON CROSS SECTION.
6 MB SHADOWING CORRECTION APPLIED FOR NEUTRON CROSS SECTION.
A large solid angle detector has been used to observe two body events produced by electron-positron collisions in the Orsay storage ring. From the π + π − excitation curve in the ϱ region we have deduced the amplitude and the phase of the ω-ϱ interference, and the ϱ resonance paramaters: M ϱ = (775.4±7.3) MeV, Γ ϱ = (149.6 ± 23.2) MeV, √ B ( ω → π + π − ) = 0.19 ± 0.05, φ = (85.7 ± 15.3) 0 , σ ( e + e − → ϱ ) = (1.00 ± 0.13) μ b at S = M ϱ 2 , B ( ϱ → e + e − = (4.1 ± 0.5) × 10 −5 , Γ ( ϱ → e + e − ) = (6.1 ± 0.7) keV, ( g ϱ 2 /4 π ) = 2.26 ± 0.25, ( g ϱππ 2 /4 π ) = 2.84 ± 0.50.
STATISTICAL ERRORS ONLY. CROSS SECTION AT RHO0 PEAK IS 1.00 +- 0.13 MUB FROM FIT.
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