Results are presented on π + p and K + p elastic scattering at 250 GeV/ c , the highest momentum so far reached for positive meson beams. The experiment (NA22) was performed with the european hybrid spectrometer. The π + p elastic cross section stays constant with energy while the K + p cross section increases.
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ERRORS IN ELASTIC CROSS SECTIONS INCLUDE SYSTEMATIC ERRORS.
Elastic Σ − p and π − p cross section have been measured at 17.2 GeV/ c in the t interval −0.12, −0.38 (GeV/ c ) 2 . The Σ − p slope is b = 8.12 ± 0.35 (GeV/ c ) −2 .
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Backward elastic scattering of π± on protons has been measured for incident pion momenta between 30 and 90 GeV/c and 0≤−u≤0.5 (GeV/c)2. The u dependence of the cross sections is similar to that observed at lower momenta, and Regge models give acceptable fits to the data.
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We present results from a measurement of the differential cross sections for Σ−p, Ξ−p, and π−p elastic scattering at 23 GeV/c. We have collected samples of 6200 Σ−p events, 67 Ξ−p events, and 30 000 π−p events in the interval 0.10<|t|<0.23 (GeV/c)2.
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Measurements of π±p backward elastic scattering have been made for incident pion momenta between 30 and 90 GeV/c and for 0<−u<0.5 (GeV/c)2. The momentum dependence of the cross sections is of a form expected from a simple Regge model, and the u dependence of the cross sections is similar to that observed at lower momenta.
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We present results of an analysis of two-prong events for elastic scattering and single-pion production in K−p interactions at 5.5 GeVc. The resonance parameters for the charged and neutral K*(890) and K*(1420) are determined and the observed production and decay properties of the charged and neutral K*(890) are compared with the theoretical predictions of an absorptive one-particle-exchange model and a Regge model. The K*(1420) differential cross section and density-matrix elements are presented and the question of whether more than one resonance exists in this mass range is considered. A search for resonance effects at Kπ mass beyond 1500 MeV is made. In particular, the recently reported state at 1800 MeV is discussed. A B5-model analysis of the reaction K−p→K¯0π−p is also presented.
NORMALIZED TO SIG(K- P --> ANYTHING) OF 24.3 +- 0.8 MB.
FORWARD CROSS SECTION OPTICAL POINT FROM TWO PARAMETER EXPONENTIAL FIT OVER 0.12 < -T < 0.68 GEV**2.
The Fermilab hybrid 30-in. bubble-chamber spectrometer was exposed to a tagged 147-GeV/c positive beam containing π+, K+, and p. A sample of 3003 K+p, 19410 pp, and 20745 π+p interactions is used to derive σn, 〈n〉, f2cc, and 〈nc〉D for each beam particle. These values are compared to values obtained at other, mostly lower, beam momenta. The overall dependence of 〈n〉 on Ea, the available center-of-mass energy, for these three reactions as well as π−p and pp interactions has been determined.
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Results of a high-statistics study of elastic scattering and meson resonances produced by π−p interactions at 8 GeV/c are presented. Large statistics and small systematic errors permit examination of the complete kinematic region. Total differential cross sections are given for ρ0,−, f0, g0,−, Δ±, Δ0, and N* resonances. Spin-density matrix elements and Legendre-polynomial moments are given for ρ, f, and Δ resonances. The results for ρ0 and f0 resonances are compared with the predictions of a Regge-pole-exchange model. Properties of the above resonances are compared and discussed. In particular, we present evidence that the ρ0 and f0 production mechanisms are similar. The similarity of the g0 t distribution to that of the ρ0 and f0 suggests a common production mechanism for all three resonances.
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SLOPE REFERS TO EXPONENTIAL FIT IN U.
A study of 205-GeV/c π−p interactions has been made with a 48 800-picture exposure in the bare Fermilab 30-inch hydrogen bubble chamber. The average number of charged particles produced per inelastic interaction is 7.99±0.06. The elastic cross section is 3.18±0.13 mb and the total cross section is 24.19±0.44 mb. The inclusive cross sections for neutral-particle production are: σ(γ)=171.3±15.3 mb, σ(KS0)=3.64±0.61 mb (x<0.3), σ(Λ)=1.71±0.34 mb (x<0.3), and σ(Λ¯)=0.59±0.23 mb (x<0.1). The average number of π0's produced per inelastic collision is consistent with a linear rise with the number of charged particles, and about equal to the number of produced π− or π+. The average number of K0's, Λ's, and Λ¯'s is consistent with very little dependence on the number of charged particles. General characteristics of neutral-particle production are presented and compared with other experiments. For each topology the produced neutral energy is ∼13 of the incident energy.
THE ERRORS INCLUDE THOSE DUE TO VARIOUS CORRECTIONS.
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Measurements of the total cross section have been performed at the ISR with c.m. energies between 23.5 GeV and 62.5 GeV. Two independent experimental methods have been applied, a measurement of total interaction rate and of small angle elastic scattering. Both experiments give consistent results showing that the total cross section increases by (11.8±1.5) % over the ISR energy range. This experiment has also measured the slope of the forward diffraction peak in elastic scattering at small momentum transfer. The elastic cross section shows the same relative rise as the total cross section, and the ratio λ of elastic to total cross section approaches a constant value of λ =0.178±0.003.
TOTAL ELASTIC CROSS SECTION FROM INTEGRATING THE PARAMETRIZED DIFFERENTIAL CROSS SECTION, USING ALL OPTICAL POINT DATA AND AT LARGE -T RESULTS OF OTHER EXPERIMENTS.
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