The properties of the final-state hadronic system in antineutrino-proton charged-current interactions are presented. The events were observed in the Fermilab 15-foot hydrogen bubble chamber. The average energy of the events is ∼30 GeV, but there are some interactions beyond 100 GeV. The mean multiplicity of the charged hadrons varies as 〈nCH〉=(0.06±0.06)+(1.22±0.03)lnW2 for hadronic masses W in the range 1.0<W2<50 GeV2. By contrast, the multiplicity depends only weakly on the four-momentum transfer between the leptons. The mean pion multiplicities for events with three or more charged tracks are found to be 〈n−〉=1.64±0.04, 〈n0〉=1.16±0.13, for π− and π0 production, respectively. By comparing the number of positive tracks with π− data from neutrino production, we deduce a mean proton multiplicity 〈np〉 of 0.53 ± 0.15. The single-particle distributions in both longitudinal and transverse momentum are found to be similar to those for nondiffractive production in hadronic collisions. The fragmentation properties of the final-state d quarks are compared to the expectations of the quark-parton model. The fraction of observed neutral-strange-particle production for events with three or more charged tracks is 0.08 ± 0.015 and is consistent with coming completely from associated production.
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We have studied the K ππ system in the 14.3 GeV/ c reactions K − p → K − π + π − p, K − p → K 0 π − π 0 and K − p → K 0 π + π − n . The data have been obtained from a 500 000 picture exposure of the CERN 2m HBC. The first two final states are dominated by Q-production in the Kππ system; there is also an L-signal at M (K ππ ) ∼ 1.75 GeV. The reaction cross sections are compared to K − p data at other energies. We discuss the K ππ mass dependence of the diffractive production slope. Evidence is presented for a Q − p versus Q + p differential cross section cross-over around | t | = 0.17 GeV 2 . A t -channel isospin analysis for the KN → K ∗(890)π N channels in the Q-region shows that the I = 1 exchange amplitude is ⋍ 10% of the dominant I = 0 exchange amplitude. The K ππ decay distributions indicate a predominant J P = 1 + state in the Q-region, and an important J P = 2 − contribution in the L-region. We find neither s -channel nor t -channel helicity conservation at the meson vertex in the Q- or L-regions. The K π angular correlation moments within the K ππ diffractive system are characteristic of K π elastic scattering, suggesting a π -exchange Deck-type production mechanism. There is evidence for a Kf 0 and κπ contribution (where κ is the J P (K π ) = 0 + state) to the diffractive K ππ system. A fit to the K − π + π − and K 0 π − π 0 Dalitz-plot distributions for the Q-re gion indicates that the ratio of K ϱ to K ∗ π decay amplitudes decreases with increasing K ππ mass.
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Inclusive production of Σ + , Σ − and Σ 0 hyperons in K − p interactions at 14.3 GeV/ c has been studied and compared to Λ production. Cross sections are presented as a function of longitudinal and transverse momenta and compared to the pp → Σ + + anything data.
Results on the inclusive reactions K − p → K ∗− (890) + X + and K − p → K ∗0 (890) + X 0 at 14.3 GeV/c are presented. A comparison is made with previous data and with the reaction K − p → K 0 + X at 14.3 GeV /c . Predictions of a triple-Regge model for the variation of the unnatural and natural parity exchanges with the mass of the X system are examined. The experimental values of the structure functions are compared with those calculated from a quark model.
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AVERAGED OVER ALL PRODUCTION ANGLES.
We present measurements of the differential and polarization cross sections for the reactions KL0p→Ks0p, Λπ+, Σ0π+, and Λπ+π0 made in a hydrogen bubble chamber exposed to a beam of KL0 with incident momentum 550±35 MeV/c. The quasielastic data imposes additional constraints on the partial-wave analyses of the KN and K¯N systems. Our data show no strong energy-dependent effects in the region of the reported Σ(1580), JP=32− state. The phase of the forward regeneration amplitude was found to be about - 160° independent of KL0 momentum.
SYSTEMATIC ERRORS INCLUDED.
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The elastic and one-pion production channels from the pp interaction at four c.m. energies between 2150 and 2240 MeV are described. No evidence of formation of the narrow T(2195) meson is observed. The elastic differential cross section is measured in the range of squared four-momentum transfer ¦t¦ > 0.03 GeV2. This has been extrapolated to the forward direction where Re/Im parts of the amplitude are deduced. The one-pion final states are well described by assuming that they are dominated by Δ-production.
The reactions K L o p→K S o p, π + Λ , π + Σ o have been measured for center-of-mass energies from 1540 to 1610 MeV. Channel cross sections and coefficients of the Legendre polynomial expansion of the differential cross sections and hyperon polarizations are presented. We see no evidence in the πΛ channel for the suggested 3 2 − resonance at 1580 MeV. The cross section for the K S o p channel shows an energy dependence which is not predicted by the existing phase shift solutions based on charged kaon data.
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The K − p differential and total elastic cross-sections have been measured at 14.25 GeV/ c . The results have been compared with various Regge models.
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Differential and channel cross sections and hyperon polarizations are presented for the reactions K L o p → K S o p, π + Λ o , and π + Σ o at an average beam momentum of 550 MeV/ c . These data provide constraints on KN and K N amplitudes obtained from charged kaon reactions and reject one of the S = +1, I = 0 and one of the S = -1, I = 1 phase shift solutions.
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