We have studied the hadronic production of charmed mesons in the NA 32 experiment at CERN. A special trigger together with a high resolution vertex detector consisting of charge coupled devices and silicon microstrip detectors allowed the selection of very clean samples of charmed mesons. We have collected 852 fully reconstructed decays: 60Ds+→K+K−π+, 543D°→K−π+ andK−π+π−π+ as well as 249D+→K−π+π+ (or charge conjugate). 147 mesons out of our\({{D^0 } \mathord{\left/ {\vphantom {{D^0 } {\bar D^0 }}} \right. \kern-\nulldelimiterspace} {\bar D^0 }}\) sample were produced via chargedD* state. For all charmed mesons we determine the total production cross-section and study thexF andpt2 distributions.
Data fitted with the form d2sig/dxdpt**2 alpha ((1-x)**N)* EXP(-B*PT**2) using combined maximum likelihood fit to the invariant mass spectrum and the x and pt**2 distributions. The values for N and B are given here. Additional systematic errors are 10 pct for N and 3 pct for B.
Data fitted with the form d2sig/dxdpt**2 alpha ((1-x)**N)* EXP(-B*PT**2) using combined maximum likelihood fit to the invariant mass spectrum and the x and pt**2 distributions. The values for N and B are given here. Additional systematic errors are 10 pct for N and 3 pct for B.
Data fitted with the form d2sig/dxdpt**2 alpha ((1-x)**N)* EXP(-B*PT**2) using combined maximum likelihood fit to the invariant mass spectrum and the x and pt**2 distributions. The values for N and B are given here. Additional systematic errors are 10 pct for N and 3 pct for B.
The production of the neutralK− (892) resonances by 200 GeVK− andπ− has been studied over the kinematic range 0.0<xf<1.0 andpt2<5.0 GeV2. Longitudinal and transverse momentum distributions are presented. In addition the decay angular distributions inK− fragmentation to\(\bar K^{0*} \) have been investigated.
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The inclusive spectra for p p collisions at 22.4 GeV/ c are investigated. We show that the transverse momentum distributions resemble those in high-energy pp interactions and discuss the influence of annihilation processes on the p T 2 distributions. The invariant inclusive cross section for pions in the central region is found to be 28 ± 1 mb. A charge asymmetry is indicated by the y ∗ spectrum in the central region, the asymmetry parameter having the value 0.15 ± 0.01. Finally, we estimate the upper limit of the diffraction dissociation of the beam particle to be 3.68 −0.15 +0.45 mb.
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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.
Inclusive and semi-inclusive cross sections and distributions of γ's and π0's inK+p interactions at 70 GeV/c are presented. The results are compared to other experiments and to the Lund model for low-pT hadron collisions.
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Inclusive φ production is studied in π − p collisions at 16 GeV/ c . The φ cross section for Feynman variable x φ > 0.2 is found to be (15.5 ± 3.6) μb. This leads to an extrapolated cross section of (29.9 ± 7.0) μb for x φ > 0.0. Fitting the momentum transfer squared distribution of the φ to the form e −bp 2 T gives an average slope of b = (2.4 ± 0.3) (GeV/ c −2 for x φ > 0.5.
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DATA OBTAINED FROM FIGURE BY A.A. LEBEDEV.
Inclusive K ∗0 production is studied in π − p interactions at 16 GeV/ c with x ϝ > 0.2. The K ∗0 is found to be pre-dominantly centrally produced with cross section σ( K ∗0 ) = (72 ± 12) μb for x ϝ > 0.2 and compares closely to data on K ∗0 production in π + p interactions at the same energy.
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A study of the inclusive production of π − , η , ϱ 0 , ω ad f mesons in p p annihilation at 0.7 GeV/ c is presented. Topological and channel cross sections are determined. Longitudinal and transversal momentum distributions of non-strange mesons are studied. It is deduced that nearly 48% of all negative pions arise from the decay of η , ϱ 0 , ω and f mesons.
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The inclusive production of ϱ 0 mesons in pp collisions has been measured at five c.m. energies from √ s = 23.6 to 63.0 GeV. The cross sections and the production spectra as a function of transverse momentum and rapidity are discussed.
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We present results on inclusive φ meson production in K + p interactions at 70 GeV/ c in the kaon fragmentation x >0.2 region. Comparison with other data on φ meson production in K ± and p induced reactions provides evidence that the strange valence-quark fragmentation or recombination processes play the dominant role in the K ± → φ transitions. Arguments are presented that the kaon valence strange s -quark carries a much higher momentum fraction than the u-quark. Evidence for the previously observed narrow φπ + state at mass ∼2.1 GeV is discussed.
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