Search

We study the production of meson resonance at pT≥2 GeV/c in π Be interactions at two beam energies (150 and 300 GeV/c). The motivation is to look for the higher twist (HT) production mechanism, expected to exist besides standard hadron production through the fragmentation process of scattered quarks and gluons, the so-called leading twist (LT) mechanism. We show that the φ, K* (892) and K* (892) are found free from HT effects with a good accuracy, as expected from HT estimates and QCD sum rules. The magnitudes of the f (1270) and ρ mesons signals are found larger than expected from the standard Lund (LT) Monte Carlo and from information provided by e e annihilation experiments. The possible connection of these excesses with HT physics is discussed. We also report the first evidence for the production of f (975) mesons in hadronic experiments at large p . [ABSTRACT FROM AUTHOR]

We present the analysis of data samples taken by the WA77 experiment for π interactions at 300 and 150 GeV/c. The trigger selects a pair of oppositely charged particles with p≥2 GeV/c balancing the transverse momentum of a third high- p track. The primary aim of this experiment was the search for higher-twist production, mainly that of vector mesons. Since there are definite predictions for the polarization of mesons produced in fragmentation and through the higher-twist mechanism, we study the polarization properties of clearly identified mesons, namely the Φ and f(1270) mesons. The results are compatible with no polarization. This can be interpreted as a production dominantly due to parton fragmentation. [ABSTRACT FROM AUTHOR]

We study the shape of the invariant mass spectra of several resonances produced at P≧2.0 GeV/c and observed through two-particle final states, namely the f(1270), K(892), $$\bar K*(892)$$ , K(1430), and $$\bar K*(1430)$$ mesons. The data sample comes from π Be interactions at P=150 GeV/c and 300 GeV/c which have been collected using the OMEGA spectrometer at CERN. We find that although these meson resonances have their masses and widths consistent with the corresponding world average values, their shapes are all subject to the same kind of distortion: their low-mass tail is enhanced while their high-mass tail is sharply cut. This observation indicates that meson resonances produced in the fragmentation of quarks and gluons are distorted by the same damping factor in a way which preserves their masses and lifetimes. [ABSTRACT FROM AUTHOR]

The transverse momentum distributions for $$\rho ^0 (770),f_2 (1270),K*^0 (892),\bar K*^0 (892)$$ and ϕ (1020) have been studied in the p region between 2 and 4 GeV/c and central rapidity. The data analysed come from the WA77 experiment at CERN with a 300 GeV/c π beam incident on a Be target. These distributions are well described by the function p with n∼8. A sample of simulated events from the Lund Monte Carlo in the same experimental conditions reproduces well the data. [ABSTRACT FROM AUTHOR]

We have performed a search for vector-vector final states centrally produced in proton proton interactions at 300 GeV/c using the CERN Ω spectrometer. Evidence is found for ωρ production in the reaction pp→ p(2π2π2π) p and for ωω production in the reaction pp→ p(2π2π2π) p. However no evidence is found for ωø production in the reaction pp→ p( K Kπππ) p. [ABSTRACT FROM AUTHOR]

We have studied the reactions $$({{\pi ^ + } \mathord{\left/ {\vphantom {{\pi ^ + } p}} \right. \kern-\nulldelimiterspace} p})p \to ({{\pi ^ + } \mathord{\left/ {\vphantom {{\pi ^ + } p}} \right. \kern-\nulldelimiterspace} p})(K\bar K\pi )p$$ where the $$K\bar K\pi $$ system is centrally produced, at 85 GeV/c and 300 GeV/c using the CERN Omega spectrometer. A spin-parity analysis of the K K π system shows the presence of a strong J=1 signal which we identify as the E/f (1420) meson. We also find evidence for the decay E/f(1420)→ K K π which determines the C-parity of this state to be positive. Alternative explanations of the data have been tested and ruled out. Hence we obtain the quantum numbers of the E/f (1420) to be I(J)=0(1). [ABSTRACT FROM AUTHOR]

Production of oppositely charged particle pairs at large p is studied, where both particles, are in the central rapidity region within one unit of rapidity and nearby in azimuth. The data sample, which comes from π Be interactions obtained using the CERN OMEGA spectrometer, contains events with a pair of oppositely charged particles having p≧2 GeV/c recoiling, against a third one with p≧1 GeV/c. Our data provide new information on short range correlations involving the production of the nine possible pairs made from ( π, K, p) and $$(\pi ^ - ,K^ - ,\bar p)$$ . Comparison with Lund Monte Carlo predictions is made. Apart from proton yields, the model reproduces correctly our data. The main discrepancies observed with protons can be attributed to hard scattering of diquarks from the target nucleons. [ABSTRACT FROM AUTHOR]

We have studied the ππ and K $$\bar K$$ systems centrally produced in proton proton collisions at 300 GeV/c and π/ p proton collisions at 85 GeV/c using the CERN Ω spectrometer. Clear evidence for S/ f(975) production is observed. An analysis performed on the π π mass spectrum in the 1.0 GeV region, using a coupled channel formalism, shows that it is possible to describe the S/ f(975) effect with one single resonance once interference of the S/ f(975) with the S-wave background is introduced. The resulting S/ f(975) parameters are m=979±4MeV, g=0.28±0.04, g=0.56±0.18 corresponding to a pole position on sheet II at (1001±2)− i(36±4) MeV. Evidence is also found for a structure having a mass of 1472±12 MeV and a width of 195±33 MeV. [ABSTRACT FROM AUTHOR]

The reaction pp→ p(πππ) p, where the πππ system is centrally produced, has been studied at 300 GeV/c. The πππ mass spectrum shows evidence for the η, ω and a (1320) as well as an enhancement in the a (1260) region. A Dalitz plot analysis of the πππ system has been performed. The a (1260) parameters coming from the fit of the 1 S wave are m=1208±15 MeV and Γ=430±50 MeV. No evidence is found for the h(1170) or h(1380). [ABSTRACT FROM AUTHOR]

The reaction pp→ p( K Kππ) p, where the K K ππ system is centrally produced, has been studied at 300 GeV/c. The K $$K^{*0} \bar K^{*0} $$ final state has been observed and the cross sections for its central production are found to be the same at 300 and 85 GeV/c. The K $$K^{*0} \bar K^{*0} $$ final state appears to be produced as a non-resonant threshold enhancement. [ABSTRACT FROM AUTHOR]