Search

Results are reported based on a study of π − p interactions at 147 GeV/ c in the FERMILAB 30-inch Proportional Wire Hybrid Bubble Chamber System. We have measured the topological cross sections and separated two-prong elastic and inelastic channels. In addition, we have extracted leading particle cross sections using the increased momentum resolution of the downstream proportional wire chambers. We have compared our results with experiments and predictions of a simple fragmentation hyphothesis.

We present data on inclusive and semi-inclusive ϱ 0 production in 147 GeV/ c π − p interactions. We find a total cross section of 7.3 ± 1.3 mb. Most of this cross section is found in the lower topology events (⩽ 10 prongs), and in the central and forward rapidity regions. The P T 2 dependence of ϱ 0 production, 〈: n > ϱ 0 per event, and the ϱ 0 / π + ratios are also discussed.

Results are presented from a study of inclusive neutral strange particle production by a 147 GeV/c tagged π+/K+/p beam in the Fermilab 30-inch hydrogen bubble chamber. The experiment made use of the proportional hybrid spectrometer system. Results are based on 995 KS0, 485 Λ, and 83 Λ found in a sample of 132 000 pictures. Cross sections are given for inclusive production of these particles by each of the three beam particles, and comparisons are made with measurements at other energies. Topological cross sections are also calculated, and KNO multiplicity scaling is investigated. Distributions are presented of invariant cross sections as functions of the Feynman scaling variable x and c.m. rapidity y. The transverse momentum-squared distributions with their fitted slopes are also given. Comparisons are made of the production characteristics for the three beam types.

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 Fermi's statistical model and by Landau's hydrodynamical model.

A study of charged particle production in 147 GeV/c π − p collisions yields no evidence for an electrically neutral central region or corresponding rapidity plateau. The results do indicate that electric charge and transverse momentum may be locally conserved over small intervals on the rapidity axis. These results support a picture in which the observed hadrons are emitted in clusters whose quantum numbers vary as a function of rapidity and reflect the incident channel quantum numbers at the extremes of the rapidity scale.

In this paper we present new data for the reactions π−p→pslow+X− and π−p→πfast− + X+ at 147 GeV/c. This is the first time that experimental information on these two processes has been obtained using the same apparatus at Fermilab energies. The triple-Regge formalism is applied to the differential cross sections dσ/dMx2 of both reactions using all the data at present available in the literature. A good description of the data is obtained when parameters from a triple-Regge fit of the reaction pp → p + X are used, together with the assumption of factorization of the pomeron and the reggeons. The equality of the dσ/dMx2 distributions of the two reactions may be explained in terms of an interesting assumption in the framework of the independent quark model and imposes an additional relation between the triple-Regge terms.

High energy neutrino interactions in a heavy liquid bubble chamber were classified by the presence or absence of dark tracks (stubs) at the interaction vertices. Quark distributions, σ ( x ), were compared in the two groups of data. Those with dark tracks, presumably indicative of an interaction with a deeply bound nucleon, show an enhanced nuclear effect.

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.

Nuclear scattering of K- mesons of an average energy of 21 MeV has been measured inG5 nuclear emulsion. An optical model calculation of the differential and total reaction cross-sections has been performed. Comparison of experiment and theory supports the conclusion reached at higher K- meson energies that the nuclear optical potential is attractive.

From a study of stopping K− meson interactions in a variety of elements located in a hydrogen bubble chamber, we find evidence for the existence of a substantial neutron halo in the periphery of heavy nuclei.

Examination of the available experimental evidence on mesic atoms suggests that the nuclear capture of K− mesons may well be less peripheral than is commonly supposed. This conclusion tends to vitiate recent results, obtained in a study of K− meson nuclear absorptions, that indicate a neutron halo on the surface of heavy nuclei.

A study of internally converted electron-positron pairs associated with K− neon absorption at rest reveals that 0.67 ± 0.15 γ-rays are emitted per nuclear absorption, indicating a large probability for residual nuclear excitation following K− absorption.

From the interaction of 3.29 GeV/cπ+ mesons with deuterium the production and decay of the f0 meson has been studied. The production is highly collimated in the forward direction. Under the assumption that the f0 is a spin 2 meson, measurement of the decay angular distributions yield values for the f0 spin density matrix elements. Only qualitative agreement with the one-pion exchange model is observed, the implication being that absorptive corrections and interference effects are required.

From 2267 measured events in a hydrogen-neon mixture we have isolated 1549 interactions of stopping K − mesons with neon. Results are presented on momentum spectra, hyperfragment production, Σ - Λ conversion, non-mesic absorption, relative neutron-proton interaction rates and Σ - π angular correlation.

The four- and five-pion systems from π + + n reactions at 3.29 GeV/ c , are studied. In the 4π system strong resonant production is confined to the N ∗++ (1238) and ϱ o meson, while weaker production of N ∗o (1238) is also observed. The interaction is suggestive of exchange mechanisms other than single charged meson exchange. No evidence is found for the isobars to be the decay products of higher resonances. The ϱ o produiced in association with N ∗++ does not exhibit the usual large forward-backward asymmetry. For the five pion final state strong ω o production is observed.

Cross sections for N∗(1238) production arising from various inelastic reactions of 3.7 GeV/c protons with deuterons are presented. We find that N∗ production in the reaction pn → pnπ+π− is considerably smaller than in the pp and pp analogue reactions. An upper limit of 350 μb is found for the N∗(1400) production cross section.

The neutral three pion system (π+π−π0) from the reaction π++n→p+π++π−+π0 at 3.29 GeV/c, is examined in the mass region of the A-mesons. It is shown that the enhancement at 1310 MeV can be identified with the neutral component of the A2 meson. However, no compulsive evidence is found for the neutral component of the A1 meson even though the unrestricted three-pion mass spectrum demonstrates an enhancement in the region from 900–1200 MeV. There is also an indication that the H-meson is present in this reaction.

Low energy antiproton absorptions in complex nuclei were found to produce ..lambda../sup 0/ hyperons with a frequency of 1.9 +- 0.4%.

From a sample of 80 000 antiproton annihilations in complex nuclei, a search has been made for those multinucleon reactions which would result in the production of two units of strangeness. No example of such processes has been found, leading to upper limits for the frequencies of production of final states containing 2Λ 0 , 2K + , K − Λ 0 , or the H dibaryon of (1−5)×10 −4 per p annihilation.

In the reaction p + n + π+ + π− we have observed copious Δ++ and Δ− production at four-momentum transfers greater than 100 mπ2 even when restriction was made to the double isobar overlap region. Such behavior is not observed in the analogue p p and p p reactions and strongly the importance of a mechanism in addition to one pion exchange.

The Λ° trapping probability following Σ − capture in neon has been determined to be 26 ± 5%. A comparable value for K − absorption is 12 ± 4%. These observations are in contrast to calculations that suggest that Λ° trapping following K − absorption should occur more often than after Σ − capture. They also are at variance with nuclear emulsion results.

In a bubble chamber study of stopping K − neon interactions, we have measured the hyperfragment production probability (trapped Λ events) following K − absorption to be 9.5 ± 3%. The mesic decay probability for these hyperfragments was less than 9% and the multi-nucleon or non-mesic K − absorption probability was 22 ± 4%.

The πϱ system in the A 1 region is shown to have similar characteristics when produced in π-nucleon or coherent π − D interactions. The πϱ mass spectrum, which shows no evidence for narrow A 1 or A 1.5 production, agrees well with that predicted by the Reggeized Deck model.

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.

A comparison of two recent kaonic X-ray experiments indicates that the initial distribution of K − in the vicinity of the electronic K shell in kaonic atoms has a substantial low angular momentum excess which cannot be accomodated by the conventional parametrization, (2 l + 1) exp ( αl ).

Measurements of the reaction cross sections for approx.70 MeV (laboratory kinetic energy) antiprotons on lead and carbon are presented. Although lacking great statistical authority, the large observed cross sections suggest that the low energy reaction cross sections increase rapidly at lower energies above the Coulomb barrier.