J. Malos

Observation of double ø-meson production in 100 and 175 GeV π−-Be interactions

Abstract Inclusive oo production has been studied in π−-Be interactions for 100 and 175 GeV incident momentum. An upper limit of 72 nb has been set for σ(π − Be → η c (2980) + X ) s BR (η c → oo) at 175 GeV . At both momenta the number of oo events is larger than expected for uncorrelated o pairs. A narrow width enhancement is observed at Moo≈2100 MeV with a 4 standard deviation significance.

DCS for π−p elastic scattering from 1.2 to 3.0 GeV/c and phase shift analysis

Abstract Differential cross sections have been measured for π − p elastic scattering at laboratory momenta in the range 1.2 to 3.0 GeV/ c for the c.m. range 0.97 > cos θ ∗ > −0.98 . The corresponding mass range is 1.78 to 2.56 GeV/ c 2 . The data was obtained from a counter experiment in which the scattered pions and protons were detected in coincidence by arrays of scintillation counters. The results are discussed and compared with the CERN phase-shift analyses. The results of a further restricted phase-shift analysis are presented which give support to the evidence for the P 13 (1860) resonance and suggest a possible F 17 /G 17 doublet with a mass near 2000 MeV.

Production and decay properties of D and D∗ mesons in π−Be interactions

Abstract D ∗± , D ± , D 0 , and D 0 production has been observed in π −Be interactions at 120, 175, and 200 GeV. The dependence of the D cross section on transverse and longitudinal momentum is presented. The ratio of D∗ to D and charged to neutral D production is determined. Leading particle effects in D production are investigated. Relative branching ratios for several D decay modes are evaluated. A limit on D 0 − D 0 mixing is given.

Observation of D∗± and production in high-energy π−Be interactions at the SPS

Abstract An experiment has been performed to search for associated hadronic production of charmed mesons, using a large-aperture forward magnetic spectrometer setup in a π− beam at the CERN SPS. A prompt electron trigger was used to select events containing a pair by charmed particles. D mesons have been identified by reconstruction of hadronic decay modes such as Kπ, Kππ. Data have been taken at 120, 175, and 200 GeV, The D D cross section measured at 175 200 GeV is σ( D D ) = (48 ± 15) μ b with a systematic uncertainty of ±50%. The energy dependence of the cross section is measured to be σ( D D ) [120 GeV )/σ( D D [175/200 GeV ] = 0.62 ± 0.34 .

Upper Limits for Charm Production in 150-{GeV}

Abstract A search has been made for the hadronic production of charmed baryons and mesons with a large aperture forward magnetic spectrometer using 150 GeV protons originating from the CERN-SPS. A prompt electron trigger was used as a signature for charm. Upper limits at 90% confidence level have been obtained for the production of Λ c + D 0 , D 0 D + and D − : σ(Λ c ) ⩽ 8 μ b , σ( D 0 ) ⩽ 64 μ b , σ( D 0 ) b , σ( D + ) ⩽ 51 μ b and σ( D − ) ⩽ 49 μ b per nucleon, assuming linear A dependence. Systematic errors due to uncertainties in branching ratios and to model dependence of the acceptance calculation are discussed.

p

Abstract A search for the S(1936) has been made in the invariant mass spectrum of pp-pairs produced inclusively in proton-beryllium interactions at 100 GeV incident momentum. No enhancement is observed, giving a 3 standard deviation upper limit on the cross section of 220 nb/nucleon for production of a narrow pp state around ≈ 1940 MeV in the x F range 0.18 x F

Be Interactions

Abstract A constrained phase shift analysis of new π − p elastic scattering data is compared with the CERN π N phases in the range 1.0 to 2.0 GeV.

A search for the S(1936) in 100 GeV pBe interactions

Differential cross sections for elastic K+p scattering have been measured at nineteen momenta between 0.7 and 1.9 GeV/c. The data represent between 10 thousand and 20 thousand elastic events at each momentum and cover a wide range of scattering angles (−0.98 ≲ cos θ ∗ ≲ 0.95). A computer controlled system of scintillation counters and acoustic spark chambers was used to detect the elastic events. Various internal consistency checks indicate that the absolute normalization of the data is accurate to within 2–3%. The cross sections show a smooth transition from an isotropic angular distribution to a dominant forward peak over the range covered by the experiment. Phase-shift analyses including these results show little evidence for a direct-channel resonance, and fitting the results by t- and u-channel exchange processes alone gives a good fit.

Further evidence for N∗12 nucleon resonances in the mass range 1800–2200 MeV

AbstractThe reactionpBe→Λ(1,520)X has been measured at 100 GeV incident momentum in the kinematic range 0.15<x<0.35n