22 research outputs found
Nuclear targets as a powerful tool in selecting resonant states
No full textIl comportamento delle onde 0-S e 1+S è stato analizzato, studiando la produzione coerente su nucleo di sistemiπ − π − π +. L’esperienza ha avuto luogo all’acceleratore di Serpukov, a 25 e 40 GeV di energia incidente, utilizzando nove diversi bersagli nucleari. L’assorbimento nella materia nucleare dei sistemi mesonici prodotti nel nucleo favorisce i contributi risonanti rispetto al fondo non risonante. In tal modo è stato possibile analizzare la risonanza A1 con un fondo risonante molto ridotto e ottenere evidenza di due nuovi stati risonanti 0-S, che possono essere interpretati come la prima e la seconda eccitazione radiale del pione.The 0-S and 1+S waves have been analysed studying the coherent production ofπ − π − π + states at 25 and 40 GeV/c with nine different nuclear targets. The absorption in nuclear matter of the meson systems, produced within the nucleus, helps in disentangling the resonant states from the nonresonant background. It was so possible to analyse the A1 resonance with a reduced Deck background and to obtain evidence of two new 0-S resonant states, which can be interpreted as the first and the second radial excitations of the pion
Evidence that absorption in the π+ π− π− system in nuclear matter is stronger in the JP = 0− than in the JP = 1+ state
No full textIn the reaction π- + A → π+ π- π- + A at 15.1 GeV/c the coherently produced 3π mass spectrum has a broad peak around 1.1 GeV which consists mainly of a JP = 1+ state and of a smaller fraction of 0-. Comparing the observed dependence of the production of these diffractive states on the atomic weight A of the target nuclei with the optical model, we have studied the absorption of the produced states in nuclear matter. We have found the following values of the absorption cross-sections: σ2(0-) = 49-7+9 mb and σ2(1+) = 15.8-1.3+1.5 mb
Evidence for new resonances in the systems
No full textPartial-wave analysis has been performed on 120 000 - -+ events coherently produced on nuclear targets in a - beam of 40 GeV/c. Evidence has been found for a 0- S resonance at 1.24 GeV with a width 0.36 GeV. The data also suggest the presence of another 0- S resonance of similar width near 1.8 GeV. These observations can be interpreted as radial excitations of the meson
Evidence for resonance behaviour of A1 and A3 mesons coherently produced on nuclei
No full textAn analysis of about 60 000 events produced in the reaction π-A → (π+π-π-)A on nine different nuclear targets A at 8.9, 12.9, and 15.1 GeV/c has been performed using the Illinois PWA program. In the A1 region our "coherent" sample of events (which contains about 11% of incoherently produced events) is described by only four partial waves: the 1+S and 1+P amplitudes, which both show a peak, and the O-S and O-P waves, which are rather constant. We observed variations of both 1+S and 1+P phases relative to the O-P phase by about 90° across the A1 peak. This observation suggests the presence of resonant 1+ waves in the A1 mass region (∼1.1 GeV). In the A3 region we observe that the 2- state shows resonance behaviour and that fπ and ρ{variant}π are two decays modes with amplitudes of opposite signs
A new 0-S meson and new results on the 1+S state in the system 3pi system coherently produced on nuclei; 5 pi coherent production on nuclei
No full textEvidence that absorption in the system in nuclear matter is stronger in the than in the state
No full textIn the reaction pi /sup -/+A to pi /sup +/ pi /sup -/ pi /sup -/+A at 15.1 GeV/c the coherently produced 3 pi mass spectrum has a broad peak around 1.1 GeV which consists mainly of a J/sup P/=1/sup +/ state and of a smaller fraction of 0/sup -/. Comparing the observed dependence of the production of these diffractive states on the atomic weight A of the target nuclei with the optical model, the authors have studied the absorption of the produced states in nuclear matter, and have found the following values of the absorption cross-sections: sigma /sub 2/(0/sup -/)=49/sub -7//sup +9/ mb and sigma /sub 2/(1/sup +/) =15.8/sub -1.3//sup +1.5/ mb. (12 refs)
A partial wave analysis of the system produced in at 10 GeV/c
No full textA partial wave analysis of the non-diffractively produced (K/sup 0/ pi /sup +/ pi /sup -/) system has been performed. The system was produced in the reaction K/sup -/p to K/sup 0/ pi /sup +/ pi /sup -/n at 10 GeV /c, measured in the CERN Omega spectrometer. Besides the well-known K* (1420) resonance, the authors find good evidence for the production of Q/sub 2/(1400) and some indication for Q/sub 1/(1290) production in J /sup P/=1/sup +/. In addition a bump in the 1800 MeV region is clearly observed, the properties of which are discussed
The (3π)-nucleon collision in coherent production on nuclei at 40 GeV/c
No full textCoherent 3π production on nine different nuclear targets has been studied using a 40 GeV/c π- beam at the Serpukhov accelerator (CERN-Serpukhov experiment no. 5). The absorption in nuclear matter of the produced system has been measured, analysing the data on the different nuclear targets. Identica results are obtained from the differential cross sections and from the coherent nuclear cross sections. The 1+ waves show a very weak absorption, definitely smaller than 0- and 2- waves. No influence on the absorption comes from the spin-flip amplitudes, which have been found to be negligible in the coherent region
