Inclusive cross sections for Ξ- hyperon production in high-energy Σ-, π- and neutron induced interactions were measured by the experiment WA89 at CERN. Secondary Σ- and π- beams with average momenta of 345 GeV/c and a neutron beam of 260 GeV/c were produced by primary protons of 450 GeV/c from the CERN SPS. The influence of the target mass on the Ξ- cross section is explored by comparing reactions on copper and carbon nuclei. Both single and double differential cross sections are presented as a function of the transverse momentum and the Feynman variable xF. A strong leading effect for Σ- produced by Σ- is observed.
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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.
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Nuclear dependence is fitted by SIG=CONST*A**POWER for CU and WT nuclei.
We measure the differential cross sections with respect to Feynman x ( xF) and transverse momentum ( pT) for π, K, and p-induced charm meson production using fully reconstructed D+, D0, and Ds decays. The shapes of these cross sections are compared to the theoretical predictions for charm quark production of next-to-leading order perturbative QCD using modern parametrizations of the pion and nucleon parton distributions. We observe the differences expected in production induced by projectiles with different gluon distributions, harder distributions being indicated for mesons than for protons.
Additional systematic errors of 6 pct, 6 pct and 9 pct respectively for pi, K and p beams.
Additional systematic errors of 6 pct, 6 pct and 9 pct respectively for pi, K and p beams.
Result of fitting DSIG/dXL spectra with form (1-XL)**POWER.
Results on \jpsi\ production in $e p$ interactionsin the H1 experiment at HERA are presented. The \jpsi\ mesons are produced by almost real photons ($Q~2\approx 0$) and detected via their leptonic decays. The data have been taken in 1994 and correspond to an integrated luminosity of $2.7\,\mbox{pb}~{-1}$. The $\gamma p$ cross section for elastic \jpsi\ production is observed to increase strongly with the \cm\ energy. The cross section for diffractive $J/\psi$ production with proton dissociation is found to be of similar magnitude as the elastic cross section. Distributions of transverse momentum and decay angle are studied and found to be in accord with a diffractive production mechanism. For inelastic \jpsi\ production the total $\gamma p$ cross section, the distribution of transverse momenta, and the elasticity of the \jpsi\ are compared to NLO QCD calculations in a colour singlet model and agreement is found. Diffractive \psiprime\ production has been observed and a first estimate of the ratio to \jpsi\ production in the HERA energy regime is given.
J/PSI reconstructed via MU+ MU- decay mode.
J/PSI reconstructed via E+ E- decay mode.
J/PSI reconstructed via MU+ MU- decay mode.
We have studied the production of J/ψ and ψ(2S) charmonium mesons in 515 GeV/c π−Be collisions in the Feynman-x range 0.1
Statistical errors only. Normalization uncertainty is 12%.
Statistical errors only. Normalization uncertainty is 12%.
Statistical errors only. Normalization uncertainty is 12%.. Theta is the angle between the MU+ and the beam axis in the J/PSI restframe (Gottfried-Jackson decay angle).
Exclusive ϱ 0 and φ muoproduction on deuterium, carbon and calcium has been studied in the kinematic range 2< Q 2 < 25 GeV 2 and 40 < ν < 180GeV. We discuss the Q 2 dependence of the cross sections, the transverse momentum distributions for the vector mesons, the decay angular distributions and, in the case of the ϱ 0 , nuclear effects. The data for 0 production are compatible with a diffractive mechanism. The distinct features of φ production are a smaller cross section and less steep p t 2 distributions than those for the 0 mesons.
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We present a study of J ψ meson production in collisions of 26.7 GeV electrons with 820 GeV protons, performed with the H1-detector at the HERA collider at DESY. The J ψ mesons are detected via their leptonic decays both to electrons and muons. Requiring exactly two particles in the detector, a cross section of σ(ep → J ψ X) = (8.8±2.0±2.2) nb is determined for 30 GeV ≤ W γp ≤ 180 GeV and Q 2 ≲ 4 GeV 2 . Using the flux of quasi-real photons with Q 2 ≲ 4 GeV 2 , a total production cross section of σ ( γp → J / ψX ) = (56±13±14) nb is derived at an average W γp =90 GeV. The distribution of the squared momentum transfer t from the proton to the J ψ can be fitted using an exponential exp(− b ∥ t ∥) below a ∥ t ∥ of 0.75 GeV 2 yielding a slope parameter of b = (4.7±1.9) GeV −2 .
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QED background subtracted.
We report results from Fermilab experiment E769 on the differential cross sections of D*± charm vector mesons with respect to Feynman-x (xF) and transverse momentum (PT), and on the atomic mass dependence of the production. The D* mesons were produced by a 250 GeV π beam on a target of Be, Al, Cu, and W foils. The dσdxF distribution is fit by the form ((1−xF)n) with n=3.5±0.3±0.1, the dσdPT2 distribution by exp(−b×PT2) with b=0.70±0.07±0.04 GeV−2, and the cross section A dependence by Aα with α=1.00±0.07±0.02. These results are compared to the equivalent parameters for the production of pseudoscalar D0 and D± charm mesons.
Data are in arbitrary units and are the weighted averages bin-by-bin for the 3 D0 modes KPI, K3PI and KPIPI0.
Data are in arbitrary units and are the weighted averages bin-by-bin for the 3 modes KPI, K3PI and KPIPI0.
Results of fit to DSIG/DXL distribution of the form (1-XL)**POWER in the XL range 0.1 to 0.6.
We measure the differential cross section with respect to Feynman-x (xF) and transverse momentum (PT) for charm meson production using targets of Be, Al, Cu, and W. In the range 0.1
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Results of fit to DSIG/DXL distribution of the form (1-XL)**POWER in the XL range 0.1 to 0.7. Statistical errors only. Systematic errors are small in comparison.
Results of fit to DSIG/DPT**2 distribution of the form exp(-POWER*PT**2) in the PT**2 range 0.0 to 4.0 GeV**2.
Meson production in proton, oxygen and sulphur interactions with uranium targets at 200 GeV/nucleon is studied. We measure the inclusive meson cross-section d σ/dPT2 and its evolution fromp+U to S+U. The cross-section fitted with an exponential gives an inverse slopePT0 of the order of 210 MeV/c. As a function of the neutral transverse energy,PT0 values show a slight rise followed by a plateau. The normalized difference (σ+−σ−)/σ− between positive and negative meson cross-sections is found to increase withET.
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