Search

With the production rates, 〈 n part 〉, of the K 0 , K + , p and Λ and average charged particle multiplicities, 〈 n ch 〉, recently measured at LEP1.5–LEP2, scaling of the relative particle production rates 〈 n part 〉/〈 n ch 〉 is seen in a broad center of mass energy range from s = 29–35 to 183 GeV. The quantity ξ 0 /〈 n ch 〉 1/2 , where ξ 0 is the position of the maximum of the ξ=− ln (2p/ s ) distribution and p is the particle momentum, also scales from 14 to 183 GeV. It is shown that the gaussian shape of the ξ distribution is a simple consequence of longitudinal phase space. The slope parameter in the logarithmic increase of ξ 0 with the center of mass energy must be smaller than 1, as observed experimentally, but this does not necessary imply a manifestation of coherence.

By redefining, for p ± p collisions, the energy available for particle production, we show that the energy dependence of the average charged particle multiplicity in e + e − and p ± p collisions in the presently available energy range is strikingly similar.

The average charged particle multiplicity, 〈 n ch ( M X 2 )〉, in the reaction K + p→K o X ++ is studied as a function of the mass squared, M X 2 , of the recoil system X and also as a function of the K o transverse momentum, p T , at incident momenta of 5.0, 8.2 and 16.0 GeV/ c . The complete data samples yield distributions which are not independent of c.m. energy squared, s , They exhibit a linear dependence on log ( M X 2 X / M o 2 )[ M o 2 =1 GeV 2 ] with a change in slope occurring for M X 2 ≈ s /2, and do not agree with the corresponding distributions of 〈 n ch 〉 as a function of s for K + p inelastic scattering. Sub-samples of the data for which K o production via beam fragmentation, central production and target fragmentation are expected to be the dominant mechanisms show that, within error, the distribution of 〈 n ch ( M X 2 )〉 versus M X 2 is independent of incident momentum for each sub-sample separately. In particular in the beam fragmentation region the 〈 n ch ( M X 2 )〉 versus M X 2 distribution agrees rather well with that of 〈 n ch 〉 versus s for inelastic K + p interactions. The latter result agrees with recent results on the reactions pp → pX and π − p → pX in the NAL energy range. Evidence is presented for the presence of different production mechanisms in these separate regions.

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

We present results on the inclusive polarization of Λ hyperons produced in K + p interactions at 32 and 70 GeV/ c . A large positive Λ polarization is observed in the kaon fragmentation region. The polarization is energy independent, increases strongly with increasing x , but shows essentially no p T -dependence.

The reaction K + p→ Δ ++ (1236)+ anything is studied at beam momenta 8.2 and 16 GeV/ c and compared with other Δ ++ producing reactions. We find that the low-mass Δ ++ π − enhancement affects the shapes of Δ ++ inclusive distributions. The triple-Regge formula is found to be consistent with the data. Dual properties of this formula are successfully tested.

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.

The inclusive reactions K + p → K 0 + X ++ at 5.0 and 8.2 GeV/ c and K + p → K 0 + π + + X + at 8.2 GeV/ c are analysed in terms of angular variables θ and o. The data are compared and found consistent with various theoretical bounds on the s -dependence of the inclusive reaction cross sections. Experimental evidence is presented that d σ /dcos θ = a exp (− b sin θ ) with b ∼ √ s and a increasing with energy. Correlations between the angular variables and between the variable o and the K 0 and π + momenta in the c.m.s. are observed and discussed.

We present an analysis of the reaction K + p → K 0 + anything at incident momenta of 5, 8.2 and 16 GeV/ c in terms of the Bjorken variables gw and x . Assuming dominance of ϱ exchange, we derive the structure function F 2 ( x , y ) which is found similar to the one obtained in deep inelastic electroproduction.