D. Websdale

K−p charge exchange at 5, 7 and 12 GeV/c☆

Abstract In this letter we present the results obtained from a magnet spark chamber experiment on K − −p charge exchange from 5 to 12 GeV/ c . We also compare our results with the prediction of a Regge pole model.

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

Abstract Measurements of the differential cross section and of the effective mass distribution of three- and five-pion coherent production on nuclei from Be to Pb are presented. The data are interpreted with an optical model and the total cross section of the unstable multipion system with nucleons is derived as a function of the effective mass.

A study of ππ → KK using an experiment on π−p → KS0KS0n at 8.9 GeV/c

We present an analysis of the KS0KS0 system, based on 6380 events, produced in the reactions π−p → KS0KS0n. Using a one-pion exchange model with absorption we determine the S- and D-wave amplitudes of ππ → KK. Several A2 production amplitudes were also included in the fits and we conclude that an unnatural parity exchange amplitudes which does not interfere with pion exchange, seems to present. A branching ratio Γ(f → KK/ Γ(f → ππ) = 0.029 ± 0.006 is determined. With this and other new values of branching ratios we have fitted the 2+ → 0−0− decay rates of the SU(3) relations resulting in (36.2 ± 1)° for the tensor nonet mixing angle.

Observation of resonance in the KO1KO1 system

Abstract We have analyzed 2560 events in the final-state K O 1 K O 1 n produced in π − p interactions at 5, 7 and 12 GeV/ c . We observe the S ∗ (1070), f O and A 2 decaying into K O 1 K O 1 . Resonance parameters, cross sections, and branching ratios are given.

Energy dependence of coherent production of three pions on nuclei between 9 and 15 GeV and comparison with diffractive three-pion production on hydrogen

A total of 34 000 coherent events, produced on different target nuclei and at incident pion momenta from 9 to 15 GeV/c, allows us to discuss the energy dependence of the differential cross section and of the three-pion mass spectrum. The comparison with the optical model is satisfactory. This model is then used to determine the total cross section of the unstable three-pion system on nucleons; the result is a value of about 25 mb. The value of the forward differential cross section on nucleons obtained by application of the optical model shows a tendency to increase with incident energy. A similar increase with energy is found for the forward diffractive cross section of three-pion production on hydrogen; the absolute value of this cross section is somewhat higher than the cross section determined from nuclear targets. Also the mass spectrum on nucleons derived from the present experiment is compatible with that produced on hydrogen. Furthermore, there is no evidence for abundant coherent production of A2 and A3. On the other hand, these two resonances seem to be present in the incoherent background.

Further results on the charge exchange pp →nn at 5, 6, 7 and 9 GeV/c☆

Data are presented on the total and differential cross sections at 5, 6, 7 and 9 GeV/c for the reaction pp →nn. The results are compared with the Regge-pole and the coherent droplet models.

Measurement of the polarization in K−p→K0n charge exchange at 8 GeV/c

Abstract The K−p → K 0n polarization has been measured at 8 GeV/c and for −t values ranging from 0 up tp 1.2 (GeV/c)2. A negative polarization has been found.

Differential cross section for coherent production of three-pion systems on nuclei at 15.1 GeV/c☆

Abstract The measured differential cross sections d 2 σ /d t ′ d m 3 π of three-pion production on nine different nuclei (based on 40 000 events) are presented. The corrections due to the background of incoherent reactions and due to the limited angular resolution of the experiment are discussed. The comparison of the differential cross sections of coherent three-pion production with the optical model is satisfactory.

A study of the final states K0n, Λπ0 and K0Δ0 in K−p interactions at 5 and 8 GeV/c☆

Abstract We present results on three reactions involving neutral final states which were studied in a magnet spark chamber system. These results are: (a) differential cross section with high statistics for K − p → K 0 n at 5 GeV /c (24 000 events) and at 8 GeV/c (11 000 events) for t′ K − p → K 0 Δ 0 (1232) at 5 GeV /c for t′ GeV /c) 2 . We compare our results with existing data and draw some phenomenological conclusions.

Performance of a large magnet spark chamber

Abstract The description of a 60 × 67 × 160 cm3 spark chamber in a 10.5 kG magnetic field and a report on its performance are given. This instrument was used at the CERN Proton Synchrotron for the detection of the neutral (and non-π0) reaction products of π−, K− and p on hydrogen. The sources of the systematic deviations in spark position have been investigated and corrections have been devised to compensate for them. The residual random errors are: 1. 1. the rms deviation of individual sparks from the fitted trajectory σy = 0.18 mm in space. 2. 2. the rms measurement error σy meas = 0.09 mm in space. The MDM of the instrument is 1000 GeV/c and the rms error in the mass of K10 mesons of 7 GeV/c momentum is Δm = 7.3 MeV/c2.