M. Cerrada

A partial-wave analysis of the 3π system in the reaction K−p → π+π−π0 Λ at 4.2 GeV/c

A partial-wave analysis of the (3π)0 system produced peripherally in the reaction K−p → π+π−π0 Λ at 4.2 GeV/c is presented. The observation of the weak Λ decay allows a determination of all the transversity production amplitudes except for two phases. The production of known resonances having decay modes other than 3π is used to test the isobar model ansatz. Significant ω(783), φ(1020) and A2(1310) production is observed. The spin parity of the ω∗(1675) is established as 3−. No evidence for production of other resonances, such as axial vector-mesons, is found.

Observation of double ø-meson production in 100 and 175 GeV π−-Be interactions

Abstract Inclusive oo production has been studied in π−-Be interactions for 100 and 175 GeV incident momentum. An upper limit of 72 nb has been set for σ(π − Be → η c (2980) + X ) s BR (η c → oo) at 175 GeV . At both momenta the number of oo events is larger than expected for uncorrelated o pairs. A narrow width enhancement is observed at Moo≈2100 MeV with a 4 standard deviation significance.

Properties of pp annihilations into strange particles at 702 and 757 MeV/c

Abstract p p annihilations, leading to the production of at least one neutral K meson in the final state, have been studied in the incident momentum region of 700–760 MeV/ c . Topological cross sections and cross sections for the various exclusive final states are presented. Detailed analyses of the different final states have been carried out to study the importance of resonance production and of quasi two-body and quasi three-body processes. A detailed study of the K K π system in the four-body final states shows that the F 1 meson is a spurious effect due to systematic biases. In the momentum range investigated, the C = +1 final states are strongly suppressed.

Spin-parity structure of the (Kππ)0 system produced in the charge-exchange reaction K−p → (K0π+π−)n at 4.2 GeVc

Abstract A partial wave analysis of the K 0 π + π − system produced in the charge exchange reaction K − p → ( K 0 π + π − ) n at 4.2 GeV/ c has been performed both as a function of Kππ mass and of t ′. The 1 + S wave forms the largest contribution to the K ππ system and peaks at roughly the same mass as the Q in diffractive K ππ production. The polarization properties of the 1 + S ( K ∗ π) and 1 + S (Kϱ) waves differ fromt those of the diffractive 1 + wave. There is some evidence for a resonance contribution to 1 + S ( K ∗ π) . The strong 2 + wave the K ∗ (1420) and the K ϱ/ K ∗ ϱ decay branching ratio determined to be 0.36±0.10. An enhancement with spin-parity 1 − is observed under K ∗ (1420) .

Spin Parity Structure of the (anti-K pi pi)0 System Produced in the Charge Exchange Reaction K- p --> (anti-K0 pi+ pi-) n at 4.2-GeV/c

Abstract A partial wave analysis of the K 0 π + π − system produced in the charge exchange reaction K − p → ( K 0 π + π − ) n at 4.2 GeV/ c has been performed both as a function of Kππ mass and of t ′. The 1 + S wave forms the largest contribution to the K ππ system and peaks at roughly the same mass as the Q in diffractive K ππ production. The polarization properties of the 1 + S ( K ∗ π) and 1 + S (Kϱ) waves differ fromt those of the diffractive 1 + wave. There is some evidence for a resonance contribution to 1 + S ( K ∗ π) . The strong 2 + wave the K ∗ (1420) and the K ϱ/ K ∗ ϱ decay branching ratio determined to be 0.36±0.10. An enhancement with spin-parity 1 − is observed under K ∗ (1420) .

π − ω interference in the reactions K− p → π+ π− (Λ, ϵ0) at 4.2 GeV/c

Abstract π − ω interference is studied in the reactions K − p → π + π − (Λ 0 , ϵ) at 4.2 GeV/ c using data from a high statistics experiments in the CERN 2m HBC. The phenomenon is analysed in terms of the conventional formalism as well as in terms of a new model for π − ω interference proposed by Earles and Srivastava. Satisfactory agreement with the data is found for both models. The rate of ω → 2π obtained in the latter model is in agreement with the VMD (Vector Meson Dominance) prediction for ω → γ → ϱ → 2π.

Upper Limits for Charm Production in 150-{GeV}

Abstract A search has been made for the hadronic production of charmed baryons and mesons with a large aperture forward magnetic spectrometer using 150 GeV protons originating from the CERN-SPS. A prompt electron trigger was used as a signature for charm. Upper limits at 90% confidence level have been obtained for the production of Λ c + D 0 , D 0 D + and D − : σ(Λ c ) ⩽ 8 μ b , σ( D 0 ) ⩽ 64 μ b , σ( D 0 ) b , σ( D + ) ⩽ 51 μ b and σ( D − ) ⩽ 49 μ b per nucleon, assuming linear A dependence. Systematic errors due to uncertainties in branching ratios and to model dependence of the acceptance calculation are discussed.

p

Abstract A search for the S(1936) has been made in the invariant mass spectrum of pp-pairs produced inclusively in proton-beryllium interactions at 100 GeV incident momentum. No enhancement is observed, giving a 3 standard deviation upper limit on the cross section of 220 nb/nucleon for production of a narrow pp state around ≈ 1940 MeV in the x F range 0.18 x F

Be Interactions

Abstract π − ω interference is studied in the reactions K − p → π + π − (Λ 0 , ϵ) at 4.2 GeV/ c using data from a high statistics experiments in the CERN 2m HBC. The phenomenon is analysed in terms of the conventional formalism as well as in terms of a new model for π − ω interference proposed by Earles and Srivastava. Satisfactory agreement with the data is found for both models. The rate of ω → 2π obtained in the latter model is in agreement with the VMD (Vector Meson Dominance) prediction for ω → γ → ϱ → 2π.

A search for the S(1936) in 100 GeV pBe interactions

Abstract We show that if one uses a coupled channel parametrisation for the I = 0 S-wave in processes ππ → ππ, ππ → K K and KK → KK (the last deduced from a p p → ππ + K 1 0 K 1 0 experiment ) taking properly into account the analytic structure of these waves, then it is possible to fit simultaneously all cross-sections for the above processes, in the ranges 700 1 2 MeV for the first fit, 2M K 1 2 MeV for the second, 2M K 1 2 Mev for the last. None of the three usually claimed resonances ϵ, S ∗ , ϵ′ show up in the corresponding eigenphase analysis.