We present complete results concerning the five reactions K − p → Λω , K − p → Λφ , K − p → Σ 0 ϱ and K − p → Σ 0 φ . The experimental data are well described by exchange mechanisms and the agreement with the SU(3) symmetry predictions is excellent.
FORWARD AND BACKWARD CROSS SECTIONS ARE FOR COS(THETA) > AND < 0. SLOPE DETERMINED FOR -TP = 0.2 TO 1.0.
AUTHORS ALSO GIVE CORRELATIONS OF LAMBDA POLARIZATION WITH THE MESON POLARIZATION.
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The K − p reactions leading to charge exchange and hyperon final states have been studied at nine momenta between 862 and 1001 MeV/ c using data from a 600 000 picture exposure of the Lawrence Berkeley Laboratory 25″ liquid hydrogen bubble chamber. Partial cross sections are determined for all final states resolved by kinematic fitting. In addition, differential cross sections are presented for the two-body final states K o n , Λπ o and Σ +- π -+ along with hyperon polarization angular distributions for Λπ o and Σ + π − .
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Cross sections for γd and γn interactions and photoproduction of ϱ 0 and ω are studied at 4.3 GeV, using a linearly polarized photon beam in a deuterium bubble chamber. We find that σ T (γ n ) ⋍ σ T (γ p ) within about 5% and that the γn average charge multiplicity is lower than γp by 0.42±0.09. About 4000 ϱ 0 events and 70 coherent ω events are observed. We present total and differential cross sections for both xoherent and incoherent ϱ 0 production on deuterium, as well as decay angular distributions and density-matrix elements. We find that the t -channel isospin-one exchange amplitude in γ N → ϱ 0 N (e.g. A 2 exchange) is at most 5–13% of the dominant isoscalar amplituds. The ϱ 0 production mechanism is dominantly s -channel helicity-conserving (SHC) on both neutrons and protons. We find that relative to the SHC amplitudes, the single and double helicity-flip amplitudes at the γϱ 0 vertex are of the order of 10–15% for | t | > 0.25 GeV 2 , and have the same sign on both nucleons. This shows that helicity-flip is mainly due to isoscalar exchanges. The ratio of ω to ϱ 0 coherent forward cross sections is found to be 0.16±0.04. The natural-parity exchange part of γ N → ω N is strongly dominated by isoscalar exchanges, and the magnitude of the isovector-exchange is consistent with zero.
TOPOLOGICAL CROSS SECTIONS AND AVERAGE CHARGE MULTIPLICITIES GIVEN IN TABLE 1.
'PARAMETRIZATION'.
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The results are presented of two partial-wave analyses of the (3π) − system in 30 000 events of the reaction π − p → π − π − π + p at 11.2 GeV/ c . Both techniques incorporate the assumptions of the isobar model and are (a) the University of Illinois program which fits in terms of the (3π) density matrix elements and (b) an amplitude parametrisaton including possible effects of both spin non-flip and spin flip at the baryon vertex. The results obtained with these independent programs are found to be very close.
NORMALIZED TO A TOTAL REACTION CROSS SECTION OF 1.17 +- 0.24 MB. ALL QUOTED CROSS SECTIONS ARE FOR INTEGRATED BREIT-WIGNERS.
A2 2+D-WAVE FOR 1.2 < M(3PI) < 1.4 GEV. THE FIRST THREE COMBINATIONS OF DENSITY MATRIX ELEMENTS ARE FOR NATURAL PARITY EXCHANGE, AND THE REMAINDER UNNATURAL.
Data are presented from a high statistics bubble chamber experiment to K − p interactions over the c.m. energy range 1720 to 1796 MeV. Channel cross sections, differential cross sections and, where appropriate, polarisation distributions have been obtained for the final states K − p , K 0 n , π 0 Λ and π ± Σ ∓ . These data are compared with those from previously published experiments and with the predictions from the RL-IC 77 partial-wave amplitudes for each of these channels.
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EXTRAPOLATED FORWARD AND BACKWARD DIFFERENTIAL CROSS SECTIONS.
The inclusive production of Ks0, Λ, Λ¯, and Ks0Λ in the p¯Ta reaction at 4 GeV/c was measured and compared with that in the p¯p reaction. The total inelastic and topological cross sections were also measured. The number of Λ’s produced in the p¯Ta reaction was 11.3 times larger than that expected from the geometrical cross section, which is defined as A2/3 times the cross section for the p¯p reaction. The yield ratio Λ¯/Λ was found to be 2×10−2. These values cannot be accounted for by a straightforward extension of the p¯N reaction. Besides, a correlation of 2 vees like Ks0-Λ could not prove their simultaneous production. Nuclear temperatures of 135 and 97 MeV were obtained from the kinetic energy spectra of Ks0 and Λ, respectively. The kinematical characteristics of the Ks0 and Λ produced were analyzed in terms of the fireball model.
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The PS185 experiment at the CERN Low Energy Antiproton Ring (LEAR) has studied the reaction p ̄ p → \ ̄ gLΛ at several momenta. In this paper results from two runs with high statistics at 1.546 GeV/ c and 1.695 GeV/ c are described. Based on 4063 and 11362 analysed events, respectively, differential and integrated cross sections, polarizations and spin correlations are presented. The singlet fraction, extracted from the spin correlations, is consistent with zero at both momenta, showing that the \ ̄ gLΛ pairs are produced in a pure triplet state. A comparison of the decay asymmetry parameters of Λ and \ ̄ gL reduces the upper limits for the violation of the CP invariance for this system.
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THE BESTFIT WITH LMAX=3, HI2=1.204.
THE BESTFIT WITH LMAX=6, HI2=0.547.
A complete set of polarization-transfer observables has been measured for quasifree (p→,n→) reactions on H2, C12, and Ca40 at a bombarding energy of 495 MeV and a laboratory scattering angle of 18°. The data span an energy-loss range from 0 to 160 MeV, with a corresponding momentum transfer range of qc.m.=1.7–1.9 fm−1. The laboratory observables are used to construct partial cross sections proportional to the nonspin response and three orthogonal spin responses. These results are compared to the transverse spin response measured in deep inelastic electron scattering and to nuclear responses based on the random phase approximation. The polarization observables for all three targets are remarkably similar and reveal no evidence for an enhancement of the spin-longitudinal nuclear response relative to the spin-transverse response. These results suggest the need for substantial modifications to the standard form assumed for the residual particle-hole interaction.
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Interest in the production of hyperon-antihyperon pairs following antiproton-proton annihilation stems largely from attempts to understand the nature of flavor production. To date the major focus of both the experimental and the theoretical effort has been on the p¯p→Λ¯Λ reaction. In this paper, we present data on the complementary channels p¯p→Σ¯0Λ and p¯p→Λ¯Σ0. Events from the kinematically similar p¯p→Λ¯Λ reaction were obtained in parallel. The procedure to distinguish these three separate reactions is described and results for all channels are presented. These include the total and differential cross sections, hyperon polarizations, and spin correlation coefficients. Data were obtained at incident antiproton lab momenta of 1.726 and 1.771 GeV/c which correspond to excess kinetic energies in the p¯p→Λ¯Σ0+c.c. reaction of 26 and 40 MeV, respectively, above threshold. Comparisons are made to earlier work at similar excess energies in the p¯p→Λ¯Λ channel. The low-energy regime has been highlighted in this experiment to reduce the complexity in the theoretical analysis. © 1996 The American Physical Society.
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Axis error includes +- 2.3/2.3 contribution.
Axis error includes +- 2.3/2.3 contribution.
Angular distributions for the differential cross section and three deuteron analyzing powers iT11, T20, and T22 of the reaction d→p→3Heπ0 have been measured over the whole angular domain at 20 energies close to threshold (0.03<Tπc.m.<10.2 MeV). The differential cross section and tensor analyzing power T20 both show strong variation in energy and angle due to interference between S- and P-wave pion production, whereas iT11 and T22 remain consistent with zero over the whole experimental range. All the data at different energies and angles fall on universal curves when plotted as functions of the single variable pπcosΘ, evaluated in the c.m. The broad features of the results are in line with theoretical expectations. © 1996 The American Physical Society.
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