Search

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〉=6.16±0.09, 〈 n〉/ D=2.04±0.05 and f=2.97±0.03. The average number of Dalitz pairs per inelastic event is (3.12±0.09)×10. Assuming that these all arise from π decay the average π 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 = 4.42±0.41 mb and the moments of the annihilation multiplicty distribution are 〈 n〉=8.0±0.3, 〈 n〉/ D=2.5±0.2 and f=−1.4±0.3. An independent check of σ 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 = 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. [ABSTRACT FROM AUTHOR]

New experimental results are presented on inclusive production properties of $$\bar \Sigma ^{ * + } $$ (1385) and $$\bar \Sigma ^{ * + } $$ (1385) in K p interactions at 32 GeV/c. The analysis is based on significantly larger statistics than previously available. A comparison is also made of invariant x-distributions of K/ $$\bar K^0 $$ , $$\bar \Lambda $$ and $$\bar \Xi ^ + $$ and of $$\bar \Sigma ^{ * \pm } $$ (1385) and K(892). These spectra exhibit regularities expected from the quark-recombination picture when it is assumed that the strange mesons and antibaryons are produced off the strange $$\bar s$$ -valence-quark in the incident K meson. Transverse momentum distributions are also presented for K(892) and $$\bar \Sigma ^{ * \pm } $$ (1385) and found to be very similar. The results on strange antibaryon average multiplicities disagree strongly with a recent version of the additive quark model. [ABSTRACT FROM AUTHOR]

Results are presented on inclusive production of resonant and non-resonant particle systems produced in K p interactions at 32 GeV/c. We compare K(892), $$\bar \Sigma ^{ * - } $$ (1385), Σ(1385), and ϱ inclusive x-spectra with the ones of non-resonant Kπ, $$\bar \Lambda \pi ^ - $$ , Λπ and ππ pairs at the same effective mass. Resonance-particle pairs Kπ, Σπ, and $$\bar \Sigma ^{ * - } \pi ^ - $$ are also studied together with non-resonant triplets Kπ, Λππ, $$\bar \Lambda \pi ^ - \pi ^ - $$ . The invariant x-spectra of resonant particle pairs decrease less rapidly with x then the corresponding non-resonant pairs. Comparison with quark-recombination predictions indicates that the particles, resonances and multiparticle systems are probably created off a single valence quark or diquark instead of carrying all possible valence-quarks. [ABSTRACT FROM AUTHOR]

Results are presented on total and semiinclusive cross sections, longitudinal and transverse momentum distributions of the tensor mesons K(1430), K(1430), and f(1270) observed in K p interactions at 32 GeV/c. The data are compared with K(892). K(896) and ϱ vector meson production in the same experiment. The shapes of inclusive invariant x-spectra for the strange vector and tensor mesons are found to be rather similar, after removal of diffractive and quasi-two-body channels, in agreement with quark-recombination ideas. [ABSTRACT FROM AUTHOR]

The data obtained in an exposure of BEBC to an r.f. separated beam of antiprotons at 12 GeV/c are used to derive exclusive cross sections for reactions having one or more neutral strange particles in the final state. Particular attention is given to the estimation of the background. An upper limit of the cross section for the inclusive production of the charmed meson D is also given. [ABSTRACT FROM AUTHOR]

A search for directly produced electrons in 70 GeV/c pp interactions has been performed using BEBC equipped with a hydrogen filled track sensitive target surrounded by a hydrogen/neon blanket. No candidates for single electron production with momentum p>500 MeV/c were found in a sample of 66,000 primary interactions. This result places an upper limit of 2.5 μb on the cross section for single e production at the 90% confidence level. The corresponding upper limit on the charmed particle production cross section in 14 μb. From the observation of 7 events producing an ee pair with mass, $$m_{e^ + e^ - } > m_{\pi ^0 } $$ the e/π ratio from this source is estimated to be (0.7±0.2)×10. [ABSTRACT FROM AUTHOR]

The inclusive K, ¶, and $$\bar \Lambda$$ production has been studied in a $$\bar pp$$ experiment performed in the Mirabelle bubble chamber at an incident beam momentum of 32.1 GeV/c. Total, topological and differential cross sections are presented and compared with those obtained at other energies. The invariant structure functions have been parametrised in the fragmentation region by a power law and are consistent with the expectations based on quark counting rules. [ABSTRACT FROM AUTHOR]

Results are presented on two-particle inclusive production in K p interactions at 32 GeV/c. We study the x= x+ x dependence of invariant structure functions of (ππ)-pairs and compare them to single particle inclusive distributions in the fragmentation regions. Distributions of particles observed at Feynman x in association with various 'trigger' particles or systems at x in the same hemisphere are dicussed in terms of the reduced variable $$\tilde x_2 = x_2 /(1 - |x_1 |)$$ . We further present absolute production rates and production ratios of π's and π's associated with π, K, Λ, $$\bar \Lambda $$ , K (890), ( Kπ), and (π π)-triggers, and compare them with qualitative predictions of the quark recombination model. Forwardbackward correlations between ( Kπ), ( K, p), ( Λ, π), $$(\bar \Lambda \pi ^ \pm )$$ , and ( p, π) pairs are also discussed. [ABSTRACT FROM AUTHOR]

Total and semi-inclusive cross sections, longitudinal and transverse momentum distributions and spin density matrix elements of the K(892) and K(892) produced in the inclusive reactions K p→ K(892)+ X and K p→ K(892)+ X at 32 GeV/ c are studied in detail. The inclusive spectra of the K(892) and their decay products are compared with pion and neutral kaon production. The K(892) and K(892) are dominantly produced by kaon fragmentation processes. The dependence of average transverse momentum < p> vs. x for resonances has been investigated for the first time. [ABSTRACT FROM AUTHOR]

We study single and double inclusive diffractive production in a 32 GeV/ c K p experiment in MIRABELLE at the Serpukhov accelerator. From reactions K p→ K+ X and K p→ X+ p we determine the total proton and kaon single diffractive dissociation cross sections $$\sigma (p\xrightarrow{{K^ + }}p_D ) = 0.90 \pm 0.12 mb$$ and $$\sigma (K^ + \xrightarrow{p}K_D^ + ) = 0$$ . 90±0.17 mb, respectively. In either case the only notable contributions come from dissociations into 1 and 3 charged particles. Kaon dissociation exhibits a pronounced slope-mass correlation. The search for double diffractive production in reactions K p→( Kππ)+ X and K p→( pπ π)+ X leads in either case to an estimated total double diffractive cross section σ( Kp→Kp) of ≅220 μb. The double dissociation differential cross section exhibits a large slope of ≅10GeV in the nearthreshold mass region, rapidly decreasing to ≅4 GeV with increasing excitation mass. At our c.m. energy $$(\sqrt s \simeq 8 GeV)$$ the ratio σ/σ is 0.85±0.10, the total diffractive cross section σ≡σ+σ=4.41±0.24 mb and the fraction σ( K p)/σ( K p) is 25±2%. The K and K diffractive excitation mass spectra, differential cross sections and total diffractive cross sections are very similar for both single and double dissociations. [ABSTRACT FROM AUTHOR]

Final data on topological cross sections are presented. Inclusive single particle distributions for the reactions K p→ π X at 32 GeV/ c are discussed and compared with data at lower energies. Early scaling in the fragmentation regions is confirmed, while cross sections in th central region continue to rise with energy even faster than in pp interactions. The x-and p-dependence of the π/π ratio in K p interactions is discussed and a comparison of reactions K p→ π X and K p→ π X at 32 GeV/ c is made in the context of constituent models. We also present transverse momentum distributions, show prominent seagull effects and study how they are influenced by resonance production. [ABSTRACT FROM AUTHOR]

Results are presented on K p and K p elastic scattering at 32.1 GeV/ c in the | t| interval 0.06-1.4 GeV. The samples contain approximately 15,000 events each and are obtained in the MIRABELLE bubble chamber at the Serpukhov accelerator. The | t| distributions are parametrized by quadratic exponential forms dσ/ dt= A exp ( bt+ct). The total elastic cross sections, obtained by integrating the fitted distributions, are (2.39±0.07) mb and (2.57±0.10) mb in K p and K p interactions, respectively. A cross-over between the K p and K p differential cross sections is found at | t|=0.17±0.02 GeV. The hypothesis of geometric scaling becomes valid somewhere between 32 and 70 GeV/ c for K p interactions, and is trivially verified for K p scattering. Finally, an impact parameter analysis of the difference between K p and K p elastic amplitudes is presented. [ABSTRACT FROM AUTHOR]

In the first holographic bubble chamber experiment - the HOBC experiment - we have accumulated a total of 40000 holograms with particle interactions. We have determined the total charm pair cross section in pN collisions to be 23.3 μb and 3.6 μb for 360 and 200 GeV/c incident protons respectively. We have assumed a linear dependence of the cross section on the atomic number of the target. This experiment has demonstrated the feasibility of holographic recording in small bubble chambers. Assuming that the charm cross section can be described by the standard QCD factorized expression with gluon fusion and quark-antiquark annihilation, we have used our measured charm cross sections with other measurements to determine the effective charmed quark mass to be 1.8 GeV/c. The K factor, which describes the importance of the higher order corrections, is calculated to be 9.8 (See noted added in proof.) [ABSTRACT FROM AUTHOR]

Energy and charge flow distributions are studied for pp, K p and π p interactions at 147 GeV/c in the variable λ= x/p. The distribution dE/dλ and dQ/dλ scale from 32-147 GeV/c, and are the same for pp, K p and π p reactions. [ABSTRACT FROM AUTHOR]

Inclusive and semi-inclusive cross sections and distributions of γ's and π's in K p interactions at 70 GeV/c are presented. The results are compared to other experiments and to the Lund model for low- p hadron collisions. [ABSTRACT FROM AUTHOR]

Results are reported on a study of events with high- p in K p collisions at centre of mass energy of 11.5 GeV/c. Interesting similarities with ISR results are observed both in charge and rapidity correlations among particles with a p>1 GeV/c trigger. Properties of high- p jet fragmentation are found to be similar to the ones observed at the ISR and in e e annihilation. [ABSTRACT FROM AUTHOR]

Energy, charge and strangeness flow in K p interactions at 32 and 70 GeV/c, and π p interactions at 32 GeV/c are studied in terms of the angular variable λ=| x|/ p. The data on dQ/dλ and dE/dλ show only a weak indication of scale breaking between 32 and 70 GeV/c. For inclusive 'non-diffractive', inclusive 'diffractive' and exclusive 'non-diffractive' jets, the fraction of charge in any angular region ΔΩ away from the central region is found to be proportional to the energy fraction in the same interval. The data on dQ/dE versus λ are compatible with some versions of dual-sheet models and agree also with the LUND Monte-Carlo model. The data are also compared with $$v(\bar v)p$$ interactions in BEBC. In exclusive channels the average ratio dQ/dS=0.78±0.04 is consistent, in the framework of fragmentation models, with a larger probability for the fragmentation of the $$\bar s$$ -valence quark than the u-valence quark in the K-meson. [ABSTRACT FROM AUTHOR]

Results are presented on K p elastic scattering and on the reaction K p→ K pππ at 70 GeV/c. For the elastic channel, we measured the total ((2.29±0.04)mb) and differential dσ/dt cross sections. The reaction K p→ K pππ has a total cross section of (470±23) μb and is shown to be dominated by diffractive dissociation processes. The contributions of the quasi-two-body channels and and of the Double-Pomeron Exchange (DPE) processes are estimated. [ABSTRACT FROM AUTHOR]

The WA82 experiment has collected data with the Ω′ spectrometer at the CERN SPS. Its aim was a high-statistics study of charm hadroproduction, using a silicon microstrip vertex detector and a trigger on impact parameter. WA82 is also studying rare decay modes for charm. Latest results on non-leptonic charmed meson decay branching ratios are presented here, including the study of doubly Cabibbo-suppressed modes for D. This analysis, using the particle identification provided by a Ring Imaging CHerenkov detector (RICH), gives an indication for a new decay mode, D→KKK. An upper limit for the D→Kππ mode branching ratio is also obtained. [ABSTRACT FROM AUTHOR]

Copyright of Il Nuovo Cimento: A is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Il Nuovo Cimento: A is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Evidence is provided for a new resonance in the K Kππ system with a mass of 1.97±0.01 GeV and width 40±20 MeV. It is produced with an inclusive cross section of ∼6μb in the beam fragmentation process of 4-prong K p interactions with at least 2 associated V's at 32 GeV/ c and decays dominantly into the K (892) Kπ mode. [ABSTRACT FROM AUTHOR]