Inclusive∑ ± production in\bar pp interactions at 12 GeV/c

Inclusive production of∑ ^±(1385) resonances is studied in \(\bar pp\) interactions at 12 GeV/c. The cross sections for∑ ⁺(1385)+cc and∑ ^? are determined to be 251±38 μb and 123±30 μb, respectively. The inclusive spectra are presented as a function of Feynman x, c.m. rapidity and the squared transverse momentump _T ² . Significant differences with the correspondingpp data are found in the longitudinal momentum distributions. The qualitative features of the production can be explained by simple quark ideas.     

Inclusive γ-production in\bar pp interactions at 0.76 and 2.0 GeV/c

The inclusive production of photons in \(\bar pp\) interactions has been studied at incident momenta of 0.76 and 2.0 GeV/c. The inclusive cross sections for γ-production and the average multiplicities of γ, «n _γ», are presented as a function of the charged prong topology. Results on the two particle correlation parametersf ⁰⁰ andf ^?0 are presented. The inclusive distributions of the Feynman variablex and of the transverse momentump _T of the photons are compared with the expectations from charged pion distributions on the basis of charge independence. A search has been made for direct γ-production in \(\bar pp\) interactions at 0.76 GeV/c by looking for events which fit uniquely the hypothesis \(\bar pp \to m\pi ^ + + m\pi ^ - + \gamma \) . An estimate of the ratio $$R = \frac{{\sigma (\bar pp \to m\pi ^ + + m\pi ^ - + \gamma )}}{{\sigma (\bar pp \to m\pi ^ + + m\pi ^ - + \pi ^0 )}}$$ is given.     

Study of inclusive production of π± and protons in\bar p p interactions at 32 GeV/c

Results are presented on the inclusive production of π^± mesons and protons in \(\bar p\) p interactions at an incident antiproton momentum of 32 GeV/c in the MIRABELLE bubble chamber, based on a sample of 55,000 inelastic events. The spectra of π⁺(π^?) andp( \(\bar p\) ) are separated in the whole kinematically admitted region of phase space by a statistical method. The semi-inclusive and inclusive cross sections and the main average characteristics of π andp production are calculated. The invariant differential cross sections are studied as functions of the Fevnman scaling variablex, the rapidity and the transverse momentum. Thex distribution of π^± mesons in the proton fragmentation region does not show any significant contribution from quark exchange or annihilation processes. A possible contribution of hard quark scattering on mesons or baryons is observed for large transverse momenta.     

Inclusive proton and antiproton production in π± hydrogen and π± nucleus interactions at 30 GeV/c

Data on fast protons and antiprotons produced byπ ^± incident on hydrogen and nuclear targets at 30 GeV/c are presented. The results covering the kinematic range 0.32 F <0.54 andp _T >0.2 GeV/c, complete our previous paper. We give results on inclusive cross-sections as a function ofx _F , ofp _T ² and on cross-section ratios. A search for effects of nuclear matter on the production of protons and antiprotons has yielded no major effects beyond final state absorption.     

Inclusive Λ production in\bar p p interactions at 3.0, 3.5, 4.0 and 4.5 GeV/c

Inclusive Λ production in \(\bar p\) p interactions at 3.0, 3.5, 4.0 and 4.5 GeV/c is studied. The inclusive cross sections for Λ and Λ \(\bar \Lambda \) production are measured. The differential cross sections as functions ofx, y, andP _T ² are given for each beam momentum. It is found that the contribution of indirect production of Λ from resonance decay is considerably enhanced in the region of higher missing mass against Λ. The negative polarization is observed for Λ with largerP _T and lower missing mass, and is found to be mainly from two body reactions. Inclusive cross sections for∑ ^±(1385) production and the fraction of indirect Λ from∑ ^±(1385) decay are measured. The ratio between the cross sections for∑ ⁺(1385) and∑ ^?(1385) productions is found to be almost constant for wide range of beam momenta.     

Inclusive production of vector mesons in π+ p interactions at 250 GeV/c

We report on a study of ρ⁰, ρ⁺, ω, \(\bar K^{*0} (892)\) andK ^*0 (892) inclusive production in π⁺ p interactions at 250 GeV/c, for ρ⁺, \(\bar K^{*0} (892)\) for the first time in a π⁺ p experiment. The data are compared withK ⁺ p data in the same experiment, with results of other experiments and with quark-parton models. Interesting differences are found between ρ^+,0 and ω production.     

\bar \Lambda Production inK − p interactions at 32 GeV/c

Antilambda production is studied inK ^? p interactions at 32 GeV/c. Both total and differential cross sections are presented. The inclusive \(\bar \Lambda \) production cross section amounts to 109±7 μb. A remarkable energy dependence is observed, σ( \(\bar \Lambda \) ) increasing by a factor of four between 14.3 and 32 GeV/c. Thep _⊥ ² distribution exhibits an exponential fall-off with a slope of 3.3±0.2 (GeV/c)^?2. Most of the \(\bar \Lambda \) 's are emitted in the forward hemisphere. The invariantx distribution increases between 14.3 and 32 GeV/c. Data are presented for \(\bar \Lambda \) production inK ^- p→Λ \(\bar \Lambda \) +X K ^- p→ \(\bar \Lambda \) K ⁿ +X, andK ^- p→ \(\bar \Lambda \) p+X.     

Λ and\bar \Lambda polarization inK ± P interactions at 32 GeV/c

Data on Λ and \(\bar \Lambda \) polarization inK ^± p interactions at 32 GeV/c are presented. A comparison is made between the results of these two experiments as well as with the data at lower energies. The contribution of the different production mechanisms to the Λ( \(\bar \Lambda \) ) polarization are discussed.     

Study of theA-dependence of inclusivep,\bar p,Λ and\bar \Lambda production in π±-Nucleus interactions at 30 GeV/c

We present the first results on the production of fast (p>10 GeV/c)p, \(\bar p\) , Λ and \(\bar \Lambda \) from π^± hydrogen and nucleus interactions at 30 GeV/c using the CERN Ω′ spectrometer. We have used five nuclear targets (C, Al, Cu, Sn, Pb) to study theA-dependence of the inclusive particle distributions in the region 0.3<x _F <0.6. The high statistical level of our experiment allows us to demonstrate the differentA-behaviour of baryon and antibaryon inclusive reactions. We relate this difference to the final state interaction inside a nucleus using the formation-zone model.     

Inclusive production of non-strange resonances inK − p interactions at 32 GeV/c

New data on the inclusive production of the non-strange resonances ?⁰(770), ω(783), ?(1020) andf(1270) inK ^? p interactions at 32 GeV/c are presented. The inclusive production cross sections are equal to (4.32±0.72) mb, (3.7±1.4) mb, (0.65±0.10) mb and (0.91±0.35) mb respectively. Estimates of the topological cross sections are also obtained. The invariant and non-invariantx-distributions for the vector mesons ?⁰ and ? indicate the prevalence of forward resonance production in the c.m. system. For the tensorf-meson the rapidity andx-distributions are presented. Thet′-distributions for ?⁰, ?, andf have exponential slopes of 0.6±0.1 GeV^?2, 1.2±0.2 GeV^?2, and 0.8±0.5 GeV^?2 respectively. The exponential slope ofp _T ² -distribution of thef-meson is equal to (2.3±0.5) GeV^?2.     

Inclusive production of neutral kaons inK − p interactions at 32 GeV/c

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 \(\sqrt s \simeq 8 GeV\) .     

InclusiveK s 0 , Λ and\bar \Lambda-production in\bar p p-interactions at 22.4 GeV/c

InclusiveK _s ⁰ , Λ and \(\bar \Lambda\) -production has been investigated in \(\bar p\) p-interactions at 22.4 GeV/c. Total and topological cross sections and multiplicity characteristics of neutral strange particles have been determined. DifferentialK _s ⁰ and Λ-cross sections and also characteristics of annihilation processes with neutral kaon production have been studied. It is shown that the difference of the shapes of the invariantx-distributions forK-mesons in the fragmentation region for annihilation and non-annihilation processes can be described in the framework of the “dual” valon model, but not by considering the current (undressed) quark recombination mechanisms only. The polarization of Λ and \(\bar \Lambda\) -hyperons has been measured.     

Charged particle and π0 multiplicity distributions and the annihilation properties of\bar p p interactions at 70 GeV/c

The elastic and inelastic \(\bar p\) p cross sections at 70 GeV/c have been determined in an experiment performed at CERN using BEBC equipped with a TST. The topological cross sections were measured and the moments of the inelastic multiplicity distribution are 〈n _c 〉=6.16±0.09, 〈n _c 〉/D=2.04±0.05 andf ₂ ^cc =2.97±0.03. The average number of Dalitz pairs per inelastic event is (3.12±0.09)×10^?2. Assuming that these all arise from π⁰ decay the average π⁰ multiplicity is \(\langle n_{\pi ^0 } \rangle = 2.71 \pm 0.14\) . The \(\bar p\) p?pp cross section differences lead to an annihilation cross section σ _A = 4.42±0.41 mb and the moments of the annihilation multiplicty distribution are 〈n _A 〉=8.0±0.3, 〈n _A 〉/D=2.5±0.2 andf ₂ ^A?? =?1.4±0.3. An independent check of σ _A was made by investigating fast forward charged and neutral secondary interactions in the TST and in the surrounding neon-hydrogen mixture, and gives a value σ _A = 5.0±1.6 mb. The ratio of fast \(\bar n\) to \(\bar p\) production in non-annihilation interactions at 70 GeV/c is found to be 0.45±0.11.     

Inclusive ϱ0,K *±(892) andf production in\bar p p Interactions at 12 GeV/c

Inclusive production of ?⁰,K ^*±(892), andf is studied in \(\bar p\) p interactions at 12 GeV/c. The inclusive cross sections for ?⁰,K ^*±(892), andf are found to be 6.7±0.3 mb, 1.0±0.2 mb, and 1.4±0.3 mb, respectively. The differential cross sections are presented as a function of c.m. rapidity, Feynmanx and square of the transverse momentump _T ² . Comparison with the correspondingpp data shows some interesting differences which can be attributed to the \(\bar p\) p annihilation. The results are compared with the predictions of the quark fusion model.     

Inclusive production ofK *(892) andΣ(1385) in\bar p p interactions at 3.6 GeV/c and a test of factorization hypothesis

We present a study of the inclusive production ofK ^*(892) and ∑^t+-(1385)+cc at 3.6 GeV/c from \(\bar p\) p interactions. The sensitivity of the exposure is 35.4 events/μb. Longitudinal and transverse momentum distributions are presented. The indirect production ofK _s ⁰ from parentK ^* and that of Λ's from parent Σ(1385) are studied. The shape of thex distribution of Λ's for \(p\xrightarrow{{\bar p}}\Lambda \) are calculated from \(p\xrightarrow{p}\Lambda \) and \(p\xrightarrow{{\pi ^ - }}\Lambda \) and compared with the experimental distributions. The difference of antiparticle production cross-section ofK _s ⁰ in the central region is compared with the expectation from Mueller-Regge formalism.     

Inclusive production ofK s 0 , K s 0 K s 0 andK *±(892) in\bar pp interactions at 3.0, 3.5, 4.0 and 4.5 GeV/c

InclusiveK _s ⁰ andK _s ⁰ K _s ⁰ production in \(\bar pp\) interactions at 3.0, 3.5, 4.0 and 4.5 GeV/c are studied. Cross sections ofK _s ⁰ , K _s ⁰ K _s ⁰ andK ^*±(892) are presented for each incident momentum. The production ofK _s ⁰ andK ^*±(892) through annihilation process is investigated. It is found that the annihilation process is dominant but decreases with incident momentum. The annihilation process is compared withe ⁺ e ^? interactions. Remarkable similarity between them is found in the \({{x_0 = 2E(K_s^0 )} \mathord{\left/ {\vphantom {{x_0 = 2E(K_s^0 )} {\sqrt s }}} \right. \kern-0em} {\sqrt s }}\) distribution. Events with two detectedK _s ⁰ 's are analyzed. The result shows theK _s ⁰ K _s ⁰ pairs are produced in the central region of c.m. system and there is a clearS ^* signal in theK _s ⁰ K _s ⁰ effective mass distribution.     

Inclusive production of meson resonances inK − p interactions at 110GeV/c

Total and differential cross sections ofK ^*?(890),K ^*?(890), \(\bar K^{ * 0} \) (890),K ^*0(890), \(\bar K^{ * 0} \) (1430) and? ⁰(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.     

Inclusive ϕ production inK − p interactions at 110 GeV/c and search for structure in φ π−

Results on inclusive ? production inK ^? p interactions at 110 GeV/c are presented. The production cross section is found to be larger than in πp andpp interactions at similar energies, suggesting OZI allowed \(s\bar s\) fusion to be the dominant mechanism in ? production. Thex distributions of ? and \(\bar K^{*0} \) are found to be similar to each other over the entirex range suggesting an overall strangeness suppression factor of 0.20±0.04 in the sea to be the dominant source of the difference in the cross section for ? and \(\bar K^{*0} \) . There is no evidence of a narrowφπ ^? state around 2.1 GeV/c² as suggested byK ⁺ experiments, but there is some excess of events in the region 1.94?1.98 GeV/c² consistent with theF-meson mass as observed ine ⁺ e ^? experiments.     

Strange and non-strange baryon production in π+ p andK + p interactions at 250 GeV/c

We present data on the production of the baryons Λ, \(\bar \Lambda \) ,p and of the baryon resonances Σ^*+ (1385) and Δ⁺⁺ (1232) inK ⁺ p and π⁺ p interactions at 250 GeV/c. Results are given on total and semi-inclusive cross sections, Feynman-x spectra, transverse momentum distributions and Λ polarization. The data are compared with measurements at lower energies, with deep inclastic lepton nucleon data and with predictions of quark-parton models. The models underestimate Λ production in the central c.m. region, a feature also seen in recent heavy-ion data. This failure can be cured in JETSET 6.3 by adjustment of the di-quark break-up probability.     

Charged-particle multiplicity distribution in 100-GeV/c \bar pd and π− interactions

We present data on \(\bar pn\) and π^? n collisions obtained from an exposure of the 30′' FNAL deuterium filled bubble chamber to a mixed \({{\bar p} \mathord{\left/ {\vphantom {{\bar p} {\pi ^ - }}} \right. \kern-0em} {\pi ^ - }}\) beam with a momentum of 100 GeV/c. We find that in 17±2% of the collisions with the antiproton there is an interaction on the spectator while for the collisions with π^? mesons the corresponding number is 15±2%. The \(\bar pn\) and π^? n multiplicity distributions have average charged multiplicities of 6.46±0.07 and 6.53±0.08 respectively. The average multiplicities for both types of interactions are slightly smaller than those for the corresponding reactions on hydrogen by an amount that is the same as observed at other energies. As an estimate of \(\bar pn\) annihilation we have calculated the difference \(\sigma _n (\bar pn) - \sigma _n (pn)\) for each prong numbern. We find an average multiplicity of 9±1, a value close to that for \(\bar pp\) annihilation at the same energy. combining our data with lower energy \(\bar pn\) annihilation data, we observe that the average negative multiplicity is systematically larger than that for \(\bar pp\) annihilation similar to the difference between neutron and proton target data with other beam projectiles.