R. Steiner

The effective-energy dependence of the charged particle's multiplicity in p/π+/K+ interactions on protons at 147 GeV/c

Abstract The energy dependence of the average of the charged multiplicity and its dispersion in π + /K + /p interaction on protons at 147 GeV/ c is found to be the same as in e + e − annihilations if an “effective energy” variable is used instead of the total energy. The effective energy S eff is defined as the invariant mass of all secondaries left after the two leading particles have been removed. Fitting the expression aS eff b to the average charge multiplicity 〈 n ch 〉, we find the power b to be in good agreement with the value of 0.25 predicted by Fermis statistical model and by Landaus hydrodynamical model.

The reactionspp→ppπ+π-,K+p→K+pπ+π−π, π+p→ π+,pπ+π− and π−p →π+π− at 147 GeV/c

We have studied the reactionspp→ppπ+π-,K+p→K+pπ+π−π, π+p→ π+,pπ+π− and π−p →π+π− at 147 GeV/c using the 30-inch Fermilab hybrid system. All four reactions were detected with the same apparatus and analyzed in the same way. The energy dependence of the channel cross section was found to beAp−0.6+B for thepp reaction andAp−1+B for the other three. About 90% of the cross section at 147 GeV/c can be accounted for by either beam or target diffraction. Some of the remaining cross section may come from double Pomeron exchange reactions which we tried to isolate. We have tested the hypothesis of a factorizable Pomeron and our data indicates a violation of this hypothesis. We show that the 3π mass enhancement in the mass region 1.2–1.4 GeV is diffractively produced in the π± beam reactions. Fourprong, four-constraint and six-prong, four-constraint cross sections are reported.

Hadron production inπ+,K+p andpp collisions at 147 GeV/c and properties of jet-like multiparticle systems

The gross features of the data are reviewed and the momentum tensor components, 〈S〉, and 〈T〉 are studied. Evidence for coplanarity effects is observed. A probabilistic method to search for jets is proposed. The jets found by this method are seen to be similar to highpT jets frompp interactionse+e− annihilations andvp interactions. The effect of subtracting the leading particles and the effect of lowpT diffractive and non diffractive components are investigated.

Approach to scaling in inclusive π+/π− ratios at 147 GeV/c

The ratio of hadronic π+/π− production has been studied in the target fragmentation region of π+p, π−p,K+p andp p collisions at 147 GeV/c beam momentum. The difference between this ratio in the π+p and π−p data is less than at lower energies but still present. No difference exists anymore for the π+/π− ratio at this energy betweenK+p andpp collisions. Exclusion of diffraction dissociation and resonance production does not change the main conclusions. The energy dependence of the ratio for π+p and π−p collisions gives evidence for a universal asymptotic ratio for all beams. Thept-dependence at low-pt is in agreement with the expectation from geometrical correlation of the valence quarks.

Leading particle distributions in 200 GeV/c p+A interactions

Abstract Distributions of the leading positive particle have been measured in collisions of a 200 GeV/ c proton beam with hydrogen, Mg, Ag and Au targets using the FNAL Hybrid Spectrometer. Estimates of the rapidity loss of the projectile have been obtained as a function of the target mass, the multiplicity of negative particles and the number of recoil protons. We obtained a lower limit of the rapidity loss of 2.0±0.2 for central p+Au collisions. The impact parameter dependence of the momenta of the first few leading particles has also been investigated with important implications to estimates of energy densities obtained in central collisions.

Measurement of the multiplicities in the collision of hadrons with heavy nuclei at 200 GeV/c☆

We report on the interactions of an incident 200 GeV / c beam composed of 33% protons, 16% kaons, and 48% pions on targets of silver and gold mounted in the Fermilab 30″ bubble chamber. Within our limited statistics, we find the total cross sections and average multiplicities to agree with previously published data. We find the KNO scaling distribution curve to be broader for heavy nuclei than for hydrogen. We present the first data for V0 production on gold and silver. We also present, for the first time, evidence for a positive charge excess among the sample of relativistic tracks from interactions on gold and silver. We observe a trend where the positive charge excess increases with target atomic number and with increasing charged particle multiplicity. We find the charge excess to exist among the sample of particles having greater than 2 GeV / c momentum and to persist in the sample with momentum greater than 4 GeV / c.

Inclusive and Semiinclusive

In an experiment with the 30-inch Hybrid Spectrometer at Fermilab we have obtained the inclusive and semi-inclusive production cross sections of the ϱ0 meson using a conventional background subtraction technique. Production cross sections for the ϱ0 are derived as a function of the Feynman scaling variablex, and the transverse variablespt2 andEt=(pt2+M2)1/2. The longitudinal distributions are compared with the (1−x) dependence of the proton and meson valence quark structure functions, using various forms of recombination and fragmentation models. The transverse distributions are compared with thermodynamic models. We give density matrix elements for the ϱ0 production from pions in the extreme forward region.

\rho^0

We have searched for the production of long-lived R-..delta../sup + +/ hadrons, which contain a gluino in addition to three up quarks, in pp, ..pi../sup +/p, and K/sup +/p interactions at 147 GeV/c. For R-..delta../sup + +/s of lifetime greater than 10/sup -9/ sec, and laboratory momentum greater than 2 GeV/c, we place 90%-confidence-level upper limits of 6.1 ..mu..b in pp collisions, 4.4 ..mu..b in ..pi../sup +/p, and 29 ..mu..b in K/sup +/p.

Production in

An analysis is presented of the production of jets in low-ptπ±p,k+p,pp collisions at 147 GeV/c collected at Fermilab in the rapid cycling hydrogen bubble chamber hybrid spectrometer. It is shown that selected events are more planar than predicted by a cylindrical phase space, but that 3-jet and 4-jet like structures seen in the momentum flows are reasonably reproduced by the cylindrical phase space events subjected to the same mathematical manipulation required to build momentum flows.