J. Tuominiemi

Longitudinal phase space analysis of three-body final states in meson-nucleon collisions

Abstract The longitudinal phase-space analysis is applied to various three-body final states of meson-nucleon collisions at 5–16 GeV/ c primary momentum. The distributions of the angle ω along the hexagonal phase space plot and the dependence of average transverse momenta on ω are investigated in some detail. From the very rich structure of the ω distributions it is possible to conclude that, whenever allowed, the diffraction mechanism (single Pomeranchuk exchange) dominates the three-body reactions at high energy. The study of the transverse momentum distributions reveals the existence of strong correlations between longitudinal and transverse momenta which cannot be explained by phase-space effects. Some consequences of our analysis for the Regge-exchange models are briefly mentioned.

The reactions K+ m̊p → ΛX++ and K+ p → ΛX++ at incident momenta of 8.2 and 16.0 GeV/c

Inclusive production of Λ and Λ in K+ p interactions is studied at incident momenta of 8.2 and 16.0 GeV/c. Cross sections and single-particle distributions are presented, the correlation between longitudinal and transverse momentum is investigated, and the dependence of average charge multiplicity on missing mass measured. For Λ production, early scaling is observed in the target fragmentation region when the data are presented in terms of (M2-Mth2)/s and t, where Mth is the threshold value of the missing mass M. Furthermore, a triple-Regge analysis in these variable yields an effective exchange trajectory which passes through the K, Q and L mesons. There is evidence for beam fragmentation in Λ and Λ production, but the contributions seem not to be dominant in the fragmentation region. Nevertheless, the parameter values in a triple-Regge description are estimated, and together with those for target fragmentation in Λ production, provide a complete description of the fragmentation contributions to the two reactions. Integration of the resultant distribution functions over the complete Chew-Low plot yields fragmentation cross sections increasing approximately as log s; in addition the observed features of the x, pL and pT2 projections and of the pL-pT correlation are well-described in the fragmentation regions. Central production contributions are isolated by subtracting the calculated fragmentation distributions

Production of K∗(892) in K+N interactions at 3 GeV/c

We have studied the reactions K+d→K+π−pp,K+d→Koπopp,K+d→Koπ+pp, obtained from an exposure of the Saclay 81-cm bubble chamber filled with deuterium and exposed at CERN to a separated 3 GeV/c K+ beam. In reactions (1) and (2) there is abundant production of K∗0(892) and some production of K∗(1420). From the density matrix elements, it is found that K∗0(892) is produced mainly by pion exchange. The K∗(892) four-momentum-transfer distribution in reaction (1) agrees with the predictions of the OPE model, as modified by Durr and Pilkuhn. A marked asymmetry of the decay distribution of the K+π− system is observed and discussed in the framework of a unitarized Veneziano model. In reaction (3), on the other hand, the production of K∗+(892) and N∗+(1236) is found to proceed mainly by vector exchange.

A triple-Regge analysis of the inclusive reaction pp → Λ + X++ at 19 GeV/c

Abstract The inclusive reaction pp → Λ + X ++ at 19 GeV/ c beam momentum has been analyzed in terms of the triple-Regge formalism. A good description of the structure function is achieved for events with | t | c ) 2 . The effective trajectory obtained from fits to the M 2 / s distribution in different t bins is α R ( t ) = −(0.38 ± 0.11) + (1.15 ± 0.07) t , which holds up to a | t | value of 4 (GeV/ c ) 2 . This is consistent with the K trajectory rather than the K ∗ trajectory which has been reported from other experiments.

Study of the inclusive reaction K+p → K0 + anthing at 5, 8.2 and 16 GeV/c in the proton fragmentation region

Abstract The inclusive reaction K+p → K0X is studied at 5, 8.2 and 16 GeV/c. The inclusive cross sections as well as the inclusive transverse and longitudinal distributions are given. The energy dependence of the structure function in the proton fragmentation region is found to be consistent with s−1-behaviour indicating the presence of f′ - ϕ exchange in the missing mass channel, with a relative contribution of 50–70%.

Kπ elastic scattering studied by the Chew-Low extrapolation method

We have determined the cross section for elastic K+π−→K+π−, and charge exchange, K+π−→K0π0, scattering using the Chew-Low extrapolation method, for Kπ masses up to 1.35 GeV. This has been achieved by using 3026 events of the type K+p→K+π−N∗ (1236) and 1246events of the type K+p→K0π0N∗ (1236) obtained in bubble chamber exposures at CERN. The cross section exhibits the known K∗ (892) resonance shape. A similar study for the K+π+→K+π+ elastic scattering has been attempted. The partial wave expansion coefficients up to 〈Y40〉 (without off-shell correction) have been studied as a function of the Kπ masses.

Multifractal analysis of minimum bias events in\(\sqrt s \) = 630 GeV\(\bar p\)p collisions

A search for multifractal structures, in analogy with multifractal theories, is performed on UA1 minimum bias events. A downward concave multifractal spectral function,f(α) (where α is the Lipschitz-Hölder exponent), indicates that there are self-similar cascading processes, governing the evolution from the quark to the hadron level, in the final states of hadronic interactions.f(α) is an accurate measure of the bin to bin fluctuations of any observable. It is shown that the most sensitive comparison between data and the Monte Carlo models, GENCL and PYTHIA 4.8 can be made usingf(α). It is found that these models do not fully reproduce the behaviour of the data.

Measurement of Hadron Shower Punchthrough In Iron

The total punchthrough probability of showers produced by negatively charged pions of momenta 30, 40, 50, 75, 100, 200 and 300 GeV/c, has been measured in the RD5 experiment at CERN using a toroidal spectrometer. The range of the measurement extends to 5.3 m of equivalent iron. Our results have been obtained by two different analysis methods and are compared with the resutls of a previous experiment.

Inclusive K0, K∗+(892) and π± production in K+p interactions at 8.2 and 16 GeV/c and quark models in the central and fragmentation regions

Abstract Results are presented on the production of K0, K∗+(892) and π± in the interaction K+p → K0 + π± + anything at 8.2 and 16 GeV/c. The π± forward and backward d σ d x distributions are of the form exp (−Ax). It is shown that the forward and backward values of A in a quark-quark rest frame change after subtraction of the contributions due to the resonances produced. A comparison is made of d σ d x inclusive cross sections for K0s and K∗+(892) with the predictions of a quark model in the fragmentation region. The experimental cross section matches the theoretical predictions for K0s but disagree with those for K∗+(892).

Determination of the K+π- total cross section for c.m. energy up to 1.8 GeV

Abstract The reaction K + p → Δ ++ (1236) + anything is studied at beam momentum 8.2 GeV/ c . The spin density matrix of the Δ ++ shows than one-pion exchange is dominant at low-momentum transfer. The total and topological K + π − cross sections have been determined by a Chew-Low extrapolation in the cm energy range from threshold to 1.8 GeV, using three different methods of extrapolation.