Observation of the Ληo resonance in π−p interactions at 1.0 GeV/c

The radiative decays of resonances with Λ^o hyperons involved have been studied in the 24-liter propane bubble chamber exposed to 4.0 GeV/c negative pions. The M_Λγ effective mass distribution exhibits a peak which can be explained by the existence of the Λη^o-resonance with mass of about 1680 MeV. The kinematic influence of the known hyperon resonances on the distributions is discussed. An attempt is being made to determine the Λη^o-spin.     

Observation of ω1− production in K−p interactions at 11 GeV/c

Clear evidence is presented for the production of an Ω¹⁻ resonance of mass 2253±13 MeV/c² and width 81±38 MeV/c² in K⁻p interactions at 11 GeV/c. The state is observed in the Ξ (1530)K̄ decay mode, and the corresponding inclusive cross section is estimated to be 630±180 nb. Comparisons are made with theoretical predictions and with similar states observed inhyperon beam induced data.     

Decay asymmetry of the K− π+ system in K− nucleon interactions at 3 GeV/c

The decay asymmetry of the K⁻π⁺ system was measured in two reactions and found to be equal to that observed for K⁺π⁻ systems, in agreement with its intepretation as an S waves effect in Kπ scattering.     

Observation of a narrowK s 0 K s 0 π+π− state at 1.97 GeV produced inK + p interactions at 32 GeV/c

Evidence is provided for a new resonance in theK _s ⁰ K _s ⁰ π⁺π^? system with a mass of 1.97±0.01 GeV and width 40±20 MeV. It is produced with an inclusive cross section of ～6μb in the beam fragmentation process of 4-prongK ⁺ p interactions with at least 2 associatedV ⁰'s at 32 GeV/c and decays dominantly into theK ^{* ±} (892)K _s ⁰ π^? mode.     

Observation of the reaction π−p → at 6 GeV / c

In studying a sample of events representing the π⁻p→π⁻pπ⁻π⁺ reaction with high momentum transfer to the final proton, we have observed a nucleon isobar with mass near 1700 MeV decaying into π⁺pπ⁻.     

Six-prong events produced in 16 GeV/c π−p interactions

About 12 000 events with six prongs have been measured in 16 GeV/c π⁻p interactions. Cross sections for the various reaction channels and for the production of mesonic baryonic resonances are given. In the reaction π⁻p → pπ⁺π⁺π⁻π⁻π⁻, the (π⁻π⁻π⁺) effective mass spectrum shows indications of enhancements near the A₁, A_1.5 and A₂-meson masses. The longitudinal momentum distributions and the average transverse momenta are presented. The distribution of the angles between pairs of pions is studied and it is shown that in π⁻p interactions the average opening angle for pairs of positive pions is smaller than that for pairs of negative pions.     

Study of theπ + π − γ system centrally produced in the reactionpp→p f (π + π − γ)p s at 300 GeV/c

The reactionppp _f ( ^{+ –} )p _s , where the ^{+ –} system is centrally produced, has been studied at 300 GeV/c. The ^{+ –} mass spectrum shows evidence for a ⁰ decay mode of the (958) andf ₁ (1285). The branching ratio (f ₁(1285) ^{+ +})/(f ₁(1285) ⁰ ) is found to be 5.0±0.7. No evidence is found for a ⁰(770) decay mode of theE/f ₁ (1420) for which an upper limit BR (E/f ₁(1420) ⁰ )<0.08 at=" 95%=" cl=" is=">     

Production of a Y11 (1700) in K−p collisions at 6 GeV/c

An enhancement is observed in Λ⁰π⁺ effective mass in the reaction K⁻ + p → Λ⁰ + π⁺ + π⁻ at 6 GeV/c. The lack of any large enhancements in other final states, as well as the shape and position of the peak, suggest that it is due to the new hyperon resonance, the Y₁¹ (1700), since it cannot be explained in terms of the known Y₁¹ (1660) and Y₁¹ (1765).     

Observation of a Ξ*(2370) produced in 8.25 GeV/c K−p interactions

We observe production of a Ξ^*(2370) in the reactions K^?p→$[Y\overline{K}\pi ]$K, $[Y\overline{K}\pi ]$Kπ and [ΩK] (K or Kπ) at 8.25 GeV/c in a high statistics bubble chamber experiment. The mass and width are determined to be 2373 ± 8 MeV and 80 ± 25 MeV, respectively. The I = 1/2 assignment is strongly favoured.     

Comparison of K1(890) production in K−n and K−p interactions near 4.5 GeV/c

The production and decay angular distributions of the K¹(890) in K⁻n and K⁻p interactions at 4.5 GeV/c are compared. We have studied 377 K¹(890) events in the former and 743 in the latter, corresponding to cross sections of 224 ± 20 μb and 250 ± 20 μb respectively. The data are compared with absorption and Reggepole models.     

Resonance production in K−-neutron interactions at K− momenta of 1.45 and 1.65 GeV/c

Results are reported on K⁻-neutron interactions at c.m. energies near 2 GeV. The interactions are dominated by strong production of hyperon resonances, particularly Σ(1385), Λ(1405) and Λ(1520). Production cross sections and angular distributions are given for the Σ(1385), Λ(1405) and Λ(1520) and branching fractions to decay modes observed in the experiment are given for Σ(1385) and Λ(1520). The strong energy dependence of some features of the data suggests that s-channel effects are dominant.     

K−p elastic scattering at 10 GeV/c

Results are presented on elastic scattering of 10.1 GeV/c K⁻ mesons on protons, based on a sample of 16 261 kinematically-fitted bubble-chamber events. The differential cross section is given over the |t|- range of 0.06 to 2.5 GeV² and is fitted with the expressions a e^bt, A e^Bt+Ct2 and (P e^Qt+Re^St) over various intervals of t. The results are compared with those of other experiments at nearby energies. Upper limits of |α| < 0.28 and σ_B < 0.4 μb (both at a 90% confidence level) are given for the ratio of real to imaginary part of the forward-scattering amplitude and the backward-elastic-scattering cross section, respectively.