Magnetism of amorphous metal-metal alloys

Study of the I=2 ππ scattering from the reaction π−d → π−π−psp at 9.0 GeV/c

The interaction of nucleons with antinucleons II. Narrow mesons near threshold—Experiments and theory

Single and double dissociation in π - p collisions at 11 and 16 GeV/ c

Coherent production of pions on nuclei determination of unstable boson-nucleon total cross sections

We use the modified multi-Regge model by Chan, Łoskiewiez and Allison (CLA) to calculate one-particle distributions of transverse and longitudinal momenta,pt andpl*, and invariant-mass distributions of the reactions$\pi ^ - p \to {\mathcal{N}} + (n - 1)\pi $ with multiplicitiesn ranging from 3 to 7 and an incident momentum of 11 GeV/c. We apply the model in a way that allows us to distinguish between differently charged pions. In order to account for the experimentally observed neutral pions in the forward direction, we have to take for the trajectory withG-parity +1 the ρ and not the Pomeron used by CLA. A comparison between the multi-Regge calculations and the experiment shows a good overall agreement. A remarkable feature of the reaction π−p→pπ+π−π−π0 is that almost no Δ++ production can be observed, when the prediction of the multi-Regge model is taken as a representation of the background in the pπ+ mass plot. However, this does not necessarily mean that no Δ++ production is present, but it might be an indication of the local duality now under discussion.

Application of a Reggeized multiperipheral model to π − p interactions at 11 GeV/c

In this paper we present an analysis of 1268 π−p → nπ+π− interactions obtained in the 1.5 m BNHBC and in the 2 m CERN HBC exposed at the CERN proton-synchrotron to a π− beam of 11 GeV/c momentum. The total cross-section of this channel is evaluated to be σ=(0.7±0.1) mb, while the production cross-sections for the ρ0, f0 and g0 resonances are determined as$\sigma _{\rho ^0 } = \left( {110 \pm 14} \right)$ μb,$\sigma _{f^0 } = \left( {75 \pm 14} \right)$ μb,$\sigma _{g^0 } = \left( {55 \pm 14} \right)$ μb. Some experimental behaviour of the π0 production is compared with the predictions of the OPE model with Durr-Pilkuhn form factors, the OPE absorptive model, the Regge model and the absorptive Regge model.

Some aspects of the reaction π−p → nπ+π− at 11 GeV/c

Experimental investigation on helicity conservation

Cross-sections for $eta ^ - p$ reactions at 11 GeV/c and theirt-dependencereactions at 11 GeV/c and theirt-dependence

Production of the A1 and A2 mesons is observed in the π+π-π- mass distribution of the reaction π-p → π-pπ+π-. Comparison of this mass distribution and in general of this reaction with OPEM calculations shows that the enhancement in the A1 mass region is most likely a resonance and cannot be interpreted as a kinematical effect. The production cross-section in the reaction π-p → π-pπ+π- is for the A1-meson (83±18) μb and for the A2-meson (51±16) μb. An attempt to determine the quantum numbers of the A-mesons was made, but no unique assignments were found due to the large background under the A1 and A2 peaks. The decay modes A1-→π-+ neutrals and A2-→π-+ neutrals were observed in the reaction π-p→π-p+neutrals. If these decay modes are interpreted as A1,2→π0p-, we get a decay branching ratio (A1,2→π0p-)/A1,2→π-p0≈1, as expected if the A-mesons have isospinI=1. The decay mode A2-→ηπ- is observed, but not the decay A1-→ηπ-. We find a branching ratioR(A2→ηπ-)/[(A2→p0π-)+(A2→p-π0)=0.22±0.09].

G. Vegni

Papers

Application of a Reggeized multiperipheral model to π − p interactions at 11 GeV/c

Some aspects of the reaction π−p → nπ+π− at 11 GeV/c

Experimental investigation on helicity conservation

Cross-sections for $eta ^ - p$ reactions at 11 GeV/c and theirt-dependencereactions at 11 GeV/c and theirt-dependence

Analysis of A1 and A2 production in π-p collisions at 11 GeV/ccollisions at 11 GeV/c