An analysis of π−p two-prong interactions at 4.16 GeV/c is presented. The total two-prong cross section is 19.11±0.40 mb, based on 33 672 events. The elastic-scattering differential cross section shows an exponential behavior, Kexp(−AΔ2). With A=7.36±0.14 GeV−2, the "absorption parameters" are derived as C+=0.846±0.017 and γ+=0.040±0.001. The final-state π−π0p exhibits a strong ρ−, and the π−π+n a strong ρ0 and f0. The partial cross sections for the dominant resonant channels pρ−, π−Δ+(1236) (→pπ0), ρ0n, and f0n are 0.59±0.03, 0.17±0.01, 1.15±0.05, and 0.53±0.06 mb, respectively. The ρ− production and decay angular distributions do not agree with the predictions of the absorption-modified one-pion-exchange model. However, an inclusion of the contribution from ω exchange adequately accounts for the discrepancy. The ρ0 asymmetry is interpreted as a result of an interference of the resonant P wave and isospin-zero S wave, and the corresponding spin-density matrix elements are obtained. In the final state π−p+neutrals, a clear peak for the η meson and some evidence for the ω meson are seen.
Axis error includes +- 0.0/0.0 contribution (?////EVENT NORMALIZATION).
The reaction π−+p→Λ+K0 in the 72-in. hydrogen chamber was used to produce 7220 K0 mesons associated with a visible decay Λ→p+π−. The time dependence and absolute yield of the subsequent strong interactions of K0 and K0 in hydrogen were used to determine all the parameters of the neutral K system, without the assumption of CPT invariance or other assumptions about the weak interactions of neutral K's. From the time distribution of 59 events of the type K¯0+p→hyperon, we find the magnitude of the KS0−KL0 mass difference. We then determine the mixing parameters p, q, p′, q′ of the neutral K system by means of the time dependence and absolute yield of 11 charge-exchange events, K0+p→K++n, and the absolute yield of 49 two-body interactions, K¯0+p→hyperon+pion. The results are consistent with CPT invariance and with values of the mixing parameters determined by means of weak interactions. We find the Biswas ratio R≡σ(KLp→KSp)σ(KLp→hyperon) to be R=0.41±0.13 averaged over KL momenta from about 200 to 600 MeVc. This agrees with solution I of Kim and with the results of Kadyk et al. Our absolute yields for K¯0+p→hyperon+pion are in good agreement with the predictions of charge independence and the measured rates for K−+p→hyperon+pion. For the front-back asymmetry of the Λ in K¯0+p→Λ+π+, we find (F−B)(F+B)=−0.48±0.18, indicating that the P wave cannot be neglected relative to the S wave in our momentum range.
TOTAL NUMBER EVENTS=22.
TOTAL NUMBER EVENTS=18.
TOTAL NUMBER EVENTS=9.
The differential cross sections for KL0p→KS0p scattering are presented in several momentum intervals between 1 and 10 GeVc. The data are strongly peaked in the forward direction, characteristic of a large s-channel helicity-nonflip scattering amplitude in this reaction, and a distinct break in the differential cross section occurs at |t|=0.3 GeV2. The phase of the forward scattering amplitude, φ, is consistent with being independent of momentum. The average value of the phase, φ=−133.9±4.0∘, corresponds to a Regge trajectory α(0)=0.49±0.05 in agreement with the canonical ρ, ω0 Regge intercept, α(0)∼0.5. However, this result disagrees with the Regge trajectory determined from the energy dependence of the forward cross section, α(0)=0.30±0.03, indicating a breaking of the Regge phase-energy relation. Comparisons of KL0p→KS0p and π−p→π0n scattering data reveal substantial differences in the energy dependence of the differential cross sections. Comparisons to KN charge-exchange data then suggest that direct-channel (absorption) effects may explain the differences in πN and KN channels.
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A study has been made of the individual channels that contribute to the reaction K − p → Λ 0 + neutrals in the K − momentum range from 525 to 820 MeV/ c . Total cross sections are presented for the K − p → Λ 0 η 0 , Σ 0 Σ 0 π 0 , Λ 0 π 0 , Σ 0 π 0 and Σ 0 π 0 π 0 channels and differential cross sections for K − p → Λ 0 π 0 . The data were obtained in a heavy liquid bubble chamber experiment with an average gamma detection efficiency of 70%. Only events with all decay gammas detected were used for analysis. This is the first of a series of papers on this subject and presents the experimental technique in detail.
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Cross sections, differential cross sections, and hyperon polarization results are presented for the reactions K¯0p→Λπ+ and K¯0p→Σ0π+ in the momentum interval 1 to 12 GeV/c. Emphasis is placed on the comparison of Λ and Σ channels, and on the momentum dependences of the data. In particular, the Λ polarization data are consistent with being independent of energy above 2 GeV/c; and the slopes of the forward cross sections are found to increase toward the slope values for the line-reversed reactions πp→K(Λ,Σ) as energy increases.
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RESONANCE REGION CROSS SECTIONS.
Results on the channels K − p → Λ 0 η 0 , Λ 0 π 0 , Σ 0 π 0 , Λ 0 π 0 π 0 and Σ 0 π 0 π 0 are obtained in a K − p formation experiment using 1 million photographs taken in a heavy liquid bubble chamber filled with a CF 3 BrC 3 H 8 mixture. The results are compared with hydrogen bubble chamber (HBC) experiments and with experiments having full or partial gamma-ray detection. Our Λ 0 π 0 and Λ 0 + neutral cross section agree with HBC results. Our Σ 0 π 0 cross section does not exhibit a bump at 1670 MeV as previously seen in HBC experiments. Our Λ 0 π 0 π 0 data are dominated by a Σ (1385) π 0 production. Our Σ 0 π 0 π 0 data is consistent with the presence of some Σ (1405) π 0 production.
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The differential cross sections and density matrix elements for the φ and ϱ 0 mesons have been measured in the reactions K − p → K − K + ( Λ , Σ 0 ) and K − p → π − π + ( Λ , Σ 0 ) at 13 GeV using a wire chamber spectrometer. The analysis shows that while the vector meson production is dominated by the natural parity exchange amplitude, some unnatural parity exchange is also required. Furthermore the φ and ϱ natural exchange cross sections are identical in shape and have the 2:1 relative strength expected in the quark model with K ∗ and K ∗∗ exchange degeneracy. The analysis of the clear peak-dip ϱ 0 − ω interference pattern observed in the π − π + data indicates that the ω production is in phase with the ϱ and of similar magnitude. Both the S ∗ and f′ meson are clearly observed in this experiment. The S ∗ data are found to be consistent with S ∗ parameters deduced from ππ scattering analyses. The f′ density matrix elements and a new limit of the f′ → π − π + branching ratio are presented.
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CROSS SECTIONS CORRECTED FOR EVENTS OUTSIDE THE PHI MASS CUT. <T-CHANNEL>.
CROSS SECTIONS CORRECTED FOR EVENTS OUTSIDE THE PHI MASS CUT. <S-CHANNEL>.
Differential cross sections for the reactions K−p→K¯0n, K−p→K¯0Δ0, and K+p→K0Δ++ in the region 0<|t|<1.2 GeV2 are presented from a wire-spark-chamber spectrometer experiment performed in a 13-GeV/c separated beam. The results are based on 20 000 Δ++ events, 4600 Δ0 events, and 8500 n events. The line-reversed pair of Δ reactions is used to test Regge exchange degeneracy and an SU(3) sum rule. The energy dependence of all three reactions is studied by comparison with other experiments.
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TMIN IS SO MUCH LESS THAN THE RESOLUTION THAT TP DOES NOT DIFFER SIGNIFICANTLY FROM T.
We present high-statistics data on differential cross sections and density matrix elements for K*±(890) production obtained in a 13-Gev/c SLAC experiment. The most remarkable features of the data are the dominance of natural-parity exchange and significant differences between K*+ and K*− production by natural-parity isoscalar exchange. We present two exchange models which successfully describe this difference, as well as the overall t dependence: model A including Pomeron plus strongly exchange-degenerate Regge poles and model B involving broken exchange degeneracy for the f and ω exchanges. These two phenomenological models lead to different predictions for the energy dependence of K*± production, for the relative K*(1420)K*(890) production rate, and for the SU(3)-related ρ± production processes.
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On 8 K events of the reaction p p π + π − at 7.23 GeV/ c simple selection on angular parameters is performed yielding a sample of events with the typical features of diffraction dissociation. A cross section of 1.22 ± 0.08 mb (in two vertices) and a slope of the t distribution of 12.6 ± 1.0 GeV −2 for − t < 0.1 GeV 2 are obtained for the diffraction fraction dissociation p → p π + π − + c.c. Using an analogous selection procedure, another sample of events is isolated that is characterized by double resonance production. Cross sections for Δ Δ and Δ Δ ′ + c.c. production amount to 1.27 ± 0.09 mb and 0.23 ± 0.07 mb respectively. Diffraction dissociation and double resonance production together make up for 87% of the total cross section for the reaction p p → p p π + π − , which is 3.11 ± 0.13 mb.
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EXPONENTIAL FIT TO D(SIG)/DT IN THREE REGIONS OF T. FOR EVENTS WITH M(P PI+) AND M(AP PI-) < 1.4 GEV.
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