M. Pratap

General features of charged particle production in pp interactions at 100 GeV/c

Abstract We present new data on charged particle production in p p interactions at 100 GeV/c. Comparisons are made between p p annihilations (estimated by differences) between corresponding p p and pp data samples) and e+e− annihilation into hadrons. A technique for separating the inclusive proton and pion spectra is described and the resulting pion spectra are studied in terms of Feynman x, rapidity and pT. Comparison with pp data allows us to estimate the pion spectra in p p annihilations and we find agreement with predictions of Mueller-Regge theory. We also present results on semi-inclusive π± and proton production, give updated topological cross sections and describe further attempts to isolate effects due to annihilations. Finally we investigate the diffractive excitation of the antiproton into low-mass states by studying events with a slow recoil proton.

Inclusive production of π0, Ks0, Λ0, and Λ0 in 100, 200 and 360 GeV/c π−p interactions

Inclusive cross sections for π0, Ks0, Λ0 and Λ0 production in 100, 200 and 360 GeV/c π−p interactions are presented and compared with data at other energies. Invariant cross sections for γ, Ks0, Λ0 and Λ0 production are presented in terms of Feynman x, the rapidity y, and transverse momentum squared, pT2. A comparison of the observed γ spectrum is made with the spectra computed assuming that the π0 momentum distribution is identical to that of the observed π+ orπ−.

A study of inclusive Λ, > Σ0 and Σ(1385) production in K−p interactions at 8.25 GeV/c

Abstract Inclusive Λ production has been studied in K−p interactions at 8.25 GeV/c using about 69 000 events; the total cross section is found to be 3.35 ± 0.20 mb. A comparison has been made with Σ0 and Σ(1385) inclusive production. Their influence on the inclusive Λ production is discussed. The inclusive Λ cross section and polarization is interpreted in terms of the triple-Regge model. In the target fragmentation region an effective Regge trajectory is determined which lies closer to the K than to the K∗. In the beam fragmentation region the cross-section data indicate an effective Regge trajectory which corresponds to the nucleon, while the polarization data require additional Regge exchanges to be present.

Observation of a narrow hyperon state of mass 3.17 GeV

Abstract We present evidence for a narrow Y∗ with a mass of 3.17 GeV and a width ⩽ 20 MeV decaying to ΣKK + pions, ΛKK + pions and ΞK + pions. The data come from two high statistics K−p bubble chamber experiments with a sensitivity of ≈100 eV/μb at 8.25 GeV/c and ≈ 45 eV/μb at 6.5 GeV/c.

production in 100 GeV/c interactions

We present results on inclusive Δ++ (1236) production in 100 GeV/c pp interactions. In the region |t| < 1 GeV2 we find a cross section of 1.29 ± 0.15 mb. Comparisons with pp interactions at high energies show Δ++ production in pp and pp interactions to be very similar. The decay angular distributions of the Δ++ are consistent with production predominantly through pion-exchange and the properties of the system recoiling from the Δ++ are similar to those of real π+p interactions. However, the pπ+ background is found to show qualitatively similar behaviour. In contrast to the indications of Δ++ production through pion exchange we also find evidence that events proceeding through diffraction dissociation are more likely to contain Δ++ than other events. We present results on the forward production of Δ++ in association with Δ++ and protons.

Δ++ and Δ++ production in 100 GeV/c pp interactions

We present results on inclusive Δ++ (1236) production in 100 GeV/c pp interactions. In the region |t| < 1 GeV2 we find a cross section of 1.29 ± 0.15 mb. Comparisons with pp interactions at high energies show Δ++ production in pp and pp interactions to be very similar. The decay angular distributions of the Δ++ are consistent with production predominantly through pion-exchange and the properties of the system recoiling from the Δ++ are similar to those of real π+p interactions. However, the pπ+ background is found to show qualitatively similar behaviour. In contrast to the indications of Δ++ production through pion exchange we also find evidence that events proceeding through diffraction dissociation are more likely to contain Δ++ than other events. We present results on the forward production of Δ++ in association with Δ++ and protons.

A study of the reactions K−p → Λπ0, Λη, Λη at 8.25 GeV/c incident K− momentum

Abstract Differential cross sections and polarizations are presented for the reactions K − p → Λπ 0 , Λη , Λη ′ at 8.25 GeV/ c incident K − momentum. The data, which come from a high statistics experiment in the CERN 2 m bubble chamber, are compared with previous experimental results on the same reactions and with current theoretical ideas.

Evidence for a Λp resonance with spin-parity 2−

A moments analysis of the Λp system produced forwards (t< 1 GeV2) by 8.25 GeV/c K− mesons in the reaction K−p → Λpp has been performed. Significant structure is observed in the double moments H(LMlm) describing the decay of the Λp system and the subsequent Λ decay for L ⩽ 4. This structure can be interpreted in terms of the production of a resonance of spin-parity JP = 2−, with a mass and width of 2235±50 MeV and ∼ 200 MeV, respectively. The production cross section for the Λp decay mode is ∼ 1.5 μb.

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

Abstract We observe production of a Ξ*(2370) in the reactions K−p→ [ Y K ¯ π ] K, [ Y K ¯ π ] 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.

A study of inclusive Ξ−, Ξ(1530) and Ω− production in K−p interactions at 8.25 GeV/c

Inclusive Ξ− production is studied in K−p interactions at 8.25 GeV/c using about 8000 events. An analysis based on the triple-Regge model shows that the Λα − Λγ and Σβ − Σδ exchanges explain the forward Ξ− production. Ξ(1530) properties are also studied and are found to be similar to those of Ξ−s. Finally, a study of the production of Ω− based on 67 events shows that Ωs are also produced by hyperon exchange.