A large multi-cell threshold gas Cherenkov counter

A large multi-cell threshold gas Cherenkov counter consisting of 78 cells has been built for use in a high energy muon scattering experiment at CERN (European muon collaboration). It is used with neon, nitrogen or a mixture of these two gases, allowing the pion threshold to be varied between 6 and 20 GeV/c. The sensitive region of the counter has a length of 4.0 m and entrance and exit windows of 1.1*2.4 m/sup 2/ and 2.4*5.0 m/sup 2/, respectively. (8 refs)

A high resolution beam hodoscope counter for use in very intense beams

The authors describe a set of multi-element beam hodoscope counters with a 0.6 mm spatial resolution, very high efficiency and the capability of handling the high intensity beams of the SPS. (7 refs)

Backward rho /sup -/ production in the reaction pi /sup -/p to p pi /sup -/ pi /sup 0/ at 9 GeV/c and 12 GeV/c

The backward production of mesons is studied in the reaction pi /sup - /p to p rho /sup -/. The differential cross section and the rho /sup - / density matrix are obtained using a Monte Carlo analysis of high statistics CERN experimental data on pi /sup -/p to p pi /sup -/ pi /sup 0/ reactions at 9 and 12 GeV/c. (10 refs)

π−p\pi^{-}p and K−pK^{-}p elastic scattering at 6.2 GeV/c

Data on 6.2 GeV/c pi /sup -/p and K/sup -/p elastic scattering cross sections are presented in the range 0.3<-t<10.7 (GeV/c)/sup 2/. Large- angle pi /sup -/p scattering differential cross sections oscillate around an average differential cross section of 50 nb/(GeV/c)/sup 2/, with minima at cos theta /sub cm/ approximately=0 and -0.4. The well- known dip at -t=2.8 (GeV/c)/sup 2/ remains constant in t. In the backward direction there is a dip at -u approximately=1 (GeV/c)/sup 2 /. K/sup -/p elastic scattering has a diffraction peak with a slope of 7.30+or-0.08 (GeV/c)/sup -2/ in the region 0.3<-t<0.6 (GeV/c)/sup 2/. The structure at about -t=1 (GeV/c)/sup 2/ is less pronounced than at 5 GeV/c. The large-angle region is characterized by a very fast decrease of the differential cross section with increasing energy. (67 refs)

Antiproton-proton annihilation into π+π−\pi^{+}\pi^{-} and K+K−K^{+}K^{-} at 6.2 GeV/c

The angular distribution for the two annihilation channels pp to pi /sup +/ pi /sup -/ and pp to K/sup +/K/sup -/ have been measured at 6.2 GeV/c. The two-pion channel shows peripheral peaks for pi /sup +/ and pi /sup -/ going forward, and the two-kaon channel shows a peripheral peak for the K/sup -/ going forward. The results have been compared with the line-reversed elastic backward scattering reactions and also with a constituent interchange model. (20 refs)

Evidence for two narrow pp resonances at 2020 MeV and 2200 MeV

From the study of the reaction pi /sup -/p to p/sub F/pp pi /sup -/ using a fast proton (p/sub F/) trigger device in the CERN Omega spectrometer, the authors find evidence for two narrow pp states produced mainly in association with a Delta degrees (1232) and a N degrees (1520). The statistical significance of each peak is greater than 6 standard deviations. Masses and natural widths of these resonances are respectively M/sub 1/=2020+or-3 MeV, Gamma /sub 1 /=24+or-12 MeV and M/sub 2/=2204+or-5 MeV, Gamma /sub 2/=16/sub -16 //sup +20/ MeV. The data are consistent with a small production of the narrow approximately 1935 MeV resonance already reported. Production cross sections for these new pp resonances are given. (8 refs)