Data are presented on inclusiveKs0 and Λ production inK+ and π+ collisions with Al and Au nuclei at 250 GeV/c. Results are given on total inclusive cross sections and theA dependence, as well as on distributions in Feynman-xF, rapidityy and transverse momentum. Ratios ofKS0 and of Λ to π+ production are presented. The data are compared with predictions of the quark-parton model FRITIOF.
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We report on a study of inclusiveπ0 and η meson production inπ+p andK+p interactions at 250 GeV/c beam momentum. The Feynman-x spectrum ofπ0 is very similar in shape and normalization to that of negatively charged particles produced in the same experiment. The results are compared with data at other energies and with FRITIOF model predictions. This model overestimates the η cross section by a factor of 2.5. It reproduces theπ0 cross section correctly, but predicts a too hardπ0x distribution.
'RAW' data sample.
'CLEAN' data sample found by further discarding gammas forming at pi0 with any other gamma in the event.
'CLEAN' data sample found by further discarding gammas forming at pi0 with any other gamma in the event.
Experimental data are presented on deuteron production in the target fragmentation region for 250 GeV/c π+ interactions with Al and Au nuclei, and compared with analogous data on proton production. Indications are observed for narrow structures in the (dπ-) effective mass system at ∼2.04 and ∼2.08 GeV.
Average numbers of ϱ 0 , K ∗0 (890) and K ∗0 (890) produced in peripheral collisions (with the number of “grey” protons n g ⩽2) of K + with Al and of π + with Al and Au nuclei at 250 GeV/ c are measured in the EHS(NA22) experiment at the CERN SPS. No evidence is found for suppression of vector meson production relative to K + p and π + collisions at the same energy.
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Cross-sections are obtained for coherent interactions of π+ and K+-mesons with Al and Au nuclei at 250 GeV/c, leading to three, five and seven charged mesons. The total coherent cross-section is (4.3 ± 0.5)% of the inelastic cross-section for each of the four meson-nucleus interactions. In 85% of the coherent events, the charged meson production is accompanied by neutral mesons. Effective mass distributions are presented for coherently produced particles, including charged mesons and photons, carrying total measured energy of more than 85% of the initial energy. Charged particle and γ spectra are analysed. No charge asymmetry is observed within the coherently produced cluster.
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An analysis of theA-dependence of the target-diffractive cross-section is presented. Data on thet-dependence of the cross section are fitted in the usual exponential form. The mean multiplicity of negative particles produced diffractively is found not to be sensitive to the nuclear mass. TheA-dependence of the emitted proton multiplicity and the angular distributions of the produced charged particles suggest re-scattering of the emitted particles on other nucleons of the nucleus. All these facts are compared with results obtained by Monte-Carlo simulation according to a two-component Dual Parton Model.
For target-diffractive cross-section.
For target-diffractive cross-section.
Multiplicities for the diffractive system.
Inclusive production of direct soft photons is studied inK+p andK+π interactions at 250 GeV/c. Total cross sections, Feynman-x and transverse momentum distributions of direct γ's are presented. The measured cross sections are several times larger than expected from QED inner bremsstrahlung, indicating the presence of an anomalous soft photon source. The model of Lichard and Van Hove, based on the “cold quark-gluon plasma” picture, agrees with the data.
Compensation of transverse momentum is studied in π+p interactions at 250 GeV/c. SignificantpT-transfer is found between c.m.s. hemispheres. With respect to the beam axis transverse momentum is compensated over the whole event, with respect to the sphericity axis mainly within one hemisphere. The highestpT in the event is mainly compensated by increased multiplicity. The QGSM and FRITIOF models qualitatively reproduce these effects, but important differences are observed.
A sample of 8000 interactions of 250 GeV/c π+ andK+ mesons on Al and Au nuclei, is used to search for intermittency effects by calculating the normalized factorial moments of order two to four. No significant effect is observed in the higher moments. Two-body rapidity correlations and Bose-Einstein correlations in these interactions are presented.
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