N. Armenise

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

Abstract We have studied the I =2, ππ scattering using the classical Chew-Low extrapolation method. Results are given on the cross sections and the phase shifts δ 0 2 , δ 2 2 and δ 4 2 up to 2.2. GeV. δ 0 2 values are -7.8 ∓ 3.0° at the K o mass, -15. ∓ 1.5° at the ϱ mass and -29. ∓ 2.2° of the f o mass. Above the f o mass | δ 0 2 | decreases.

Analysis of the reaction π±d → dπ±π+π− at 5 GeV/c interpretation with a reggeised π-exchange model

With a simple of 1304 events that fit the reaction π±d → dπ±π+π− at 5 GeV/c, we find a total cross section of 342 ± 25 μb and that the final state has 31% d∗ϱ0, 6% d∗f0, 14% d∗(ππ)IZ=2 and 43% of dπϱ. We are able to interpret the production cross sections and differential distributions in terms of a reggeised π-exchange mechanism and we show that for the ϱπ system the model predicts distributions indistinguishable from the ones obtained from the A1(1+) hypothesis. The experimental width of the ϱ0 and f0 are smaller than usually observed in strong interaction experiments.

Λ, Ξ and Ω production in PbPb collisions at 158 A GeV/c

Abstract Enhanced production of strange baryons and anti-baryons at central rapidity in S-W and S-z.sbnd;S with respect to p-A reactions has been reported by the CERN experiments WA85 and WA94. The WA97 experiment is extending such a study to Pb Pb collisions making use of the newly developed silicon pixel detectors. Results on Λ, Ξ − and Ω − production in Pb Pb collisions at 158 A GeV/ c at central rapidity are presented. Transverse mass spectra and particle ratios are presented. Hyperon yields are given as a function of the collision centrality and compared with those obtained from p-Pb collisions using the same experimental setup.

Study of neutron diffraction dissociation in the reaction π−n→π−π−p at GeV/c

Abstract In the reaction π−d→π−π−ppS at 9 GeV/c the pπ− mass spectrum exhibits, beyond a broad enhancement near the threshold, a production of N∗ 1520 and N∗ 1690. The production mechanism is studied and the difference in dσ/dt between the threshold enhancement and the isobars seems to be well accounted by the variation of the slope versus mass.

Production and decay of the π−π−π+ system in the reaction π−d → dπ−π−π+ at 9 GeV/c

Abstract In this paper we present a study of the reaction π − d → π − π − π + d at 9 GeV/ c . The mass spectra are in fair agreement with the predictions of a reggeized pion-exchange Deck model. However, the s -channel azimuthal angular distribution indicates a ϱ-exchange Deck contribution. The results of the partial-wave analysis of the (3 π ) − system are compared with those obtained in a hydrogen target: the J P = 2 + contribution is very small (at most 1.5 ± 1.2)% in our data, which are dominated by J P = 1 + for low mass, whereas the J P = 0 − , 1 + , 2 − have comparable importance in the higher mass region.

Lambda, Xi and Omega production at mid-rapidity in Pb Pb and p Pb collisions at 158-A-GeV/c

Λ, Ξ and Ω yields and transverse mass spectra measured at central rapidity in Pb-Pb and p-Pb collisions at 158 A GeV/c are presented. The yields in Pb-Pb interactions are given as a function of the collision centrality and compared with those obtained from p-Pb collisions. The dependence of hyperon yields on the centrality of the impact and on the strangeness content of the hyperon are discussed.

A hybrid set-up to study charmed particle production in 32S-nucleus central interactions

Abstract An emulsion-counter hybrid set-up to detect charmed particle decays in samples of triggered 32 S-nucleus central interactions is described. A new tracking technique with two emulsion tapes was developed and used successfully.