B.R. French

Observation of direct soft photon production in K+p interactions at 70 GeV/c

Abstract The inclusive γ cross section in K + p interactions at 70 GeV/ c shows an excess of (4.5 ± 0.9) mb over the contributions arising from hadron decays. The excess consists of soft γs with −0.001 x p T c . The shape of this soft γ spectrum is consistent with that expected from QED inner bremsstrahlung, but the measured total cross section exceeds the QED expectation, indicating the presence of other source(s) of soft photons.

A study of the ηπ+π− channel produced in central pp interactions at 450 GeV/c

The reaction pp ->pf (eta eta) ps has been studied at 450 GeV/c. For the first time a partial wave analysis of the centrally produced eta eta system has been performed. Signals for the f0(1500), f0(1710) and f2(2150) are observed and the decay branching fractions of these states are determined.

Λ and Λ production in sulphur-tungsten interactions at 200 GeV/c per nucleon

Abstract Results from the WA85 Experiment at the CERN Ω Spectrometer are presented. A 200 A GeV/ c beam of 32 S ions was used with a tungsten target. The apparatus is used to detect V 0, s and charged tracks in the range p T > 0.9 GeV/ c and 2.3 Y lab Λ and negative hadrons all show a linear increase with rapidity density in the range 70–140 as expected from models based on a superposition of independent NN collisions.

Observation of a narrow scalar meson at 1450 MeV in the reaction pp → pƒ(π+π−π+π−)ps at 450 GeV/c using the CERN Omega spectrometer

Abstract The reaction pp → pƒ(π + π − π + π − )p s has been studied at 450 GeV/c in an experiment designed to search for gluonic states. In addition to the well known ƒ 1 (1285) , the π+π−π+π− mass spectrum shows evidence for two states pre only observed by the WA76 experiment, the X(1450) and X(1900). An analysis of the X(1450) shows that it is a relatively narrow state (Γ = 56 ± 12 MeV) with I(JPC) = 0(0++) which decays to ϱ0π+π−. The X (1900) could either b single broad state (Γ = 370±70 MeV) with I(JPC) = 0(2++) or possibly separate states.

Study of D+ and D− Feynman's x distributions in π−-nucleus interactions at the SPS

Abstract Experiment WA82 studied charm production by a π− beam of 340 GeV/c at the CERN Ω′ spectrometer, using a silicon microstrip vertex detector and an impact parameter trigger. Results on the xF distributions of D+ and D− mesons are presented and discussed. A clear excess of D− over D+, increasing at high xF, is observed.

Measurements of charmed-meson production in interactions between 350 GeV/c π− particles and nuclei

Abstract Charmed-meson production by 350 GeV/c π − particles incident on copper and tungsten targets has been studied in the WA92 experiment, performed at the CERN Ω′ spectrometer. Results obtained are reported and discussed. Reconstruction of decays from the set D 0 → K − π + D 0 → K − π − π + π + , D s + → φπ + and charge conjugates has yielded a sample of 7280 ± 108 charmed mesons, produced with χ F > 0, ( χ F ) = 0.18 and〈 p T 2 〉 = 1.86 ( GeV / c ) 2 . Assuming a relationship σ = σ 0 A α between the cross section, σ, per nucleus of mass A and the nucleonic cross section, σ 0 the α value found for the detected charmed particles is 0.95 ± 0.06 ± 0.03. Taking α = 1, the measured cross sections per nucleon for χ F > 0 production are 7.78 ± 0.14 ± 0.52 μ b for D 0 / D 0 , 3.28 ± 0.08 ± 0.29 μ b for D + /D − and 1.29 ± 0.16 ± 0.33 μ b for D s + /D s − . Differential cross sections with respect to χ F and p T 2 have been determined for the various types of charmed meson, and particle-antiparticle asymmetries have been analysed.

Spin-parity analysis of the E meson centrally produced in the reactions π+ p → π+ (K01K±K±) p and pp → p(K01K±π ±)p at 85 GeV/c

Results are presented of a spin-parity analysis on a sample of ∼ 1000 E mesons centrally produced in the reactions (π+/p) p → (π+/p) (K01K±π∓) p at 85 GeV/c. The E quantum numbers are determined to be JPC = 1++. Its decay in this channel is consistent with being 100% into K∗K + c.c. and no evidenceis seen for a δ π decay mode where δ → KK. The mass and width were determined to be M = (1425 ± 2) MeV and Γ = (62 ± 5) MeV.

A partial wave analysis of the centrally produced

A partial wave analysis of the centrally produced K+K- and K0K0 channels has been performed in pp collisions using an incident beam momentum of 450 GeV/c. An unambiguous physical solution has been found in each channel. The striking feature is the observation of peaks in the S-wave corresponding to the f0(1500) and fJ(1710) with J = 0. The D-wave shows evidence for the f2(1270)/a2(1320), the f2(1525) and the f2(2150) but there is no evidence for a statistically significant contribution in the D-wave in the 1.7 GeV mass region.A partial wave analysis of the centrally produced K+K- and K0K0 channels has been performed in pp collisions using an incident beam momentum of 450 GeV/c. An unambiguous physical solution has been found in each channel. The striking feature is the observation of peaks in the S-wave corresponding to the f0(1500) and fJ(1710) with J = 0. The D-wave shows evidence for the f2(1270)/a2(1320), the f2(1525) and the f2(2150) but there is no evidence for a statistically significant contribution in the D-wave in the 1.7 GeV mass region.

K^{+}K^{-}

Abstract Production of Ξ − and Ξ − has been observed for the first time in heavy ion interactions by the WA85 Experiment. Multistrange baryon and antibaryon production is expected to be a useful probe in the search for quark-gluon plasma formation. We describe the procedure used to select these cascade candidates and show that Ξ − and Ξ − decays can be identified. The ratio of Ξ Ξ production, corrected for geometrical acceptances and reconstruction efficiencies, is 0.39 ± 0.07 for sulphur-tungsten interactions in the central rapidity interval 2.3 Y lab p T >1.1 GeV/ c .

and

Abstract A study of the f 1 (1285) and f 1 (1420) produced in central pp interactions has been performed. For the first time in a single experiment the branching fractions of both mesons in all major decay modes have been determined. Both the f 1 (1285) and f 1 (1420) are consistent with being produced by double Pomeron exchange.A study of the f1(1285) and f1(1420) produced in central pp interactions has been performed. For the first time in a single experiment the branching fractions of both mesons in all major decay modes have been determined. Both the f1(1285) and f1(1420) are consistent with being produced by double Pomeron exchange.