Thex dependence of single pion and multi pion production is studied in the proton fragmentation region ofK−p interactions at 110 GeV/c. A recombination and a string fragmentation model have been tuned to describe the single particle distributions well and are then used to describe two and three pion production when one particle or particle system is selected in a given interval of longitudinal momentum. The string fragmentation model reproduces most of the observed distributions correctly, but fails in the case of multi π+ production.

Thex dependence of single pion and multi pion production is studied in the proton fragmentation region ofK−p interactions at 110 GeV/c. A recombination and a string fragmentation model have been tuned to describe the single particle distributions well and are then used to describe two and three pion production when one particle or particle system is selected in a given interval of longitudinal momentum. The string fragmentation model reproduces most of the observed distributions correctly, but fails in the case of multi π+ production.

The inclusive proton diffraction dissociation cross sections in 16, 32, and 110 GeV/cK−p interactions are determined from the spike nearx=1 in the inclusive negative particle spectra and are compared to those obtained inK−p interactions using other selection methods at various energies. The same procedure is applied to events containing aV0 in order to obtain the cross section for diffractive\(s\bar s\) production. While the total cross section for proton diffraction is found to be approximately constant in the energy range studied here, proton diffraction yielding an\(s\bar s - pair\) is found to increase significantly. In particular it is almost constant at 85 μb forΛ0 and Σ production but for\(NK\bar K\) it rises from zero at 16 GeV.c to about 200 μb at 110 GeV/c. From the result for\(s\bar s\) diffractive production an estimate for the\(c\bar c\) diffractive production cross section of approximately 1–10 μb at 110 GeV/c is obtained.

Fast secondary particles from interactions of K+ at 70 GeV/c and K− at 110 GeV/c in the BEBC hydrogen bubble chamber are identified by use of the relativistic rise of ionization in argon. The ionization is measured in a large multicell ionization counter system, the External Particle Identifier (EPI). The operation of this hybrid system, the calibration and the procedures of off-line analysis leading to particle identification are described. For a sample of 9283 secondary particles collected in the K+ p experiment, we present the measurements of ionization, and the determination of acceptance and identification efficiencies. The momentum-dependent populations of pions, kaons and protons have been obtained. Track by track identification procedures yielding samples of pions and kaons with a contamination ⪅ 12% are discussed. A study of the resolution of the EPI in these experimental conditions shows average values in a range of 7.6% to 11% depending on the number of ionization samples remaining after removal of background. These values extrapolate to a value consistent with the 6.6% fwhm measured over the whole device for single particles during calibration with a 50 GeV/cπ− beam.

The planar features of hadronic final states in K−p interactions at 4.5, 5.6 and 14.3 GeV c.m. energy are compared with data from e+e− annihilation and deep inelastic μp scattering. A strong energy variation of the distributions (1/σ)dσ/dpt2, 〈pt2〉in and Σp2t in is observed over this energy range. Striking agreement is found between the K−p data at 14.3 c.m. energy and the leptonic data at similar hadronic c.m. energies. The behaviour of these distributions from K−p data is not well described by the simple quark fragmentation model, but shows deviations similar to those attributed to hard gluon effects in leptonic interactions.

The production of φ(1020) mesons is studied in bubble chamber experiments on 10 and 16 GeV/c K−p and 16 GeV/cπ+p interactions. At 16 GeV/c, the inclusive φ-production cross section is 0.39±0.05 mb with incident kaons and 0.13±0.03 mb with incident pions. The differential cross sections dσ/dpT2 and dσ/dx are determined, as well as the φ-meson decay angular distribution. Comparison is made with ψ(3100) production. Evidence is presented for the dominant role of kaon fragmentation in φ-production in K−p interactions and for remarkable similarities in φ- and ψ-production in π+p interactions.

Total and differential cross sections ofK*−(890),K*−(890),\(\bar K^{ * 0} \)(890),K*0(890),\(\bar K^{ * 0} \)(1430) andϱ0(770) produced inK−p interactions at 110 GeV/c are presented. The cross sections of the neutral resonances show a smooth increase with energy from 10 to 110 GeV/c incident momentum. For theK*+(890) and theK*0(890), i.e. the resonances with strangenessS=+1, this rise is quite significant: their cross sections practically double between 32 GeV/c and 110 GeV/c incidentK− momentum. About 50% of the neutral kaons and 30% of charged pions produced inK−p interactions at our energy are found to be decay products of the resonances considered.

The inclusive production of neutral kaons inK-p interactions at 32 GeV/c is studied in final states with one, two and three strange particles (Kn or ?). Inclusive and topological cross sections are obtained and their energy dependence discussed by comparison with lower energy data. The invariant differential cross sections of neutral kaons are studied as a function of Feynmanx, the c.m. rapidity and the transverse momentum, and a comparison is made with data at 14.3 GeV/c. Invariantx-distributions are obtained separately for “indirect” neutral kaons from <img src="/fulltext-image.asp?format=htmlnonpaginated&src=MM3882136G687T73_html\10052_2005_Article_BF01555752_TeX2GIFIE1.gif" border="0" alt=" $$\bar K*(890)$$ " /> decays and for “prompt” kaons. We also discuss the possibility of connecting quark structure functions with hadron fragmentation spectra at this c.m. energy <img src="/fulltext-image.asp?format=htmlnonpaginated&src=MM3882136G687T73_html\10052_2005_Article_BF01555752_TeX2GIFIE2.gif" border="0" alt=" $$\sqrt s \simeq 8 GeV$$ " />.

Multiplicity distributions and correlations between charged particles in the forward and back-ward c.m. hemispheres are studied inK−p interactions at 110 GeV/c and compared with other data on mesonnucleon scattering. The interpretation in terms of a simple quark-parton picture assuming that the forward multiplicity is dominated by quark fragmentation and the backward multiplicity by diquark fragmentation is supported by the experimental fact that the forward and the backward mean multiplicities are approximately equal to half of thee+e− andpp multiplicities, respectively. The 110 GeV/cK−p data show significant correlations between the numbers of slow forward and slow backward particles, whereas the multiplicities of fast forward and fast backward particles are independent.

The charge transfer distribution, its average, dispersion and skewness are studied in K−p interactions at 110 GeV/c and lower energies. The ratio of dispersion squared to rapidity plateau height is found to be energy independent as suggested by the neutral cluster models. The short-range charge correlations in rapidity are observed at all energies; at 110 GeV/c there is also evidence for a long-range component.

The inclusive production of neutral kaons inK−p interactions at 32 GeV/c is studied in final states with one, two and three strange particles (K n or Λ). Inclusive and topological cross sections are obtained and their energy dependence discussed by comparison with lower energy data. The invariant differential cross sections of neutral kaons are studied as a function of Feynmanx, the c.m. rapidity and the transverse momentum, and a comparison is made with data at 14.3 GeV/c. Invariantx-distributions are obtained separately for “indirect” neutral kaons from\(\bar K*(890)\) decays and for “prompt” kaons. We also discuss the possibility of connecting quark structure functions with hadron fragmentation spectra at this c.m. energy\(\sqrt s \simeq 8 GeV\).

Results on inclusive production of γ,Kn, Λ0 and Λ0 in K−p interactions at 110 GeV/c are presented. Total cross sections, and differential cross sections in terms of Feynman x, rapidity and pT2 are given. It is found that about 40% of Kn's are produced together with a strange particle pair, and that 80% of Λ0's are produced together with a KK pair. These Λ0,'s are produced predominantly in the backward direction. Fits to the form (1−|x|)n to the xF distributions of Kn and Λ0 in the fragmentation regions are found to be in general agreement with quark counting rule predictions.

The longitudinal momentum spectra of mesons produced in the projectile fragmentation region ofK−p interactions at 110 GeV/c, measured in a bubble chamber experiment, are compared to two fragmentation models related to hadron production by incident leptons. The models give a qualitative description of the data. However, it is found that the mesons having a valence quark in common with the projectile tend to have higher momenta than predicted.

The distribution with c.m. rapidity,y, of the net charge of hadrons produced inK−p interactions at 110 GeV/c is presented and compared withK−p and π-p data at several energies from 10 to 360 GeV/c. In both reactions and at all energies the net charge changes sign from positive to negative aty∼0. The total net charge in the forward direction is −0.70±0.02 at 110 GeV/c. It decreases with increasing energy and the results are consistent with a total net forward charge of −1.0 at infinite energies. These results imply that the fragments of the beam and target particles are far from being completely separated even at the highest energies available at present accelerators.

The charged multiplicity distribution is presented for K−p interactions produced in the hydrogen bubble chamber, BEBC, using an r.f. separated, tagged K− beam of 110 GeV/c momentum. A comparison with K+p, πp and pp data at lower energies shows that the main features of the multiplicity distributions depend on energy and charge of the incident particles, but not on their strangeness. At high energies, only the energy is important.