First results are reported on J ψ and Drell-Yan cross-sections in PbPb reactions at 158 GeV/ c per nucleon. The ratio of cross-sections σ J/ψ /σ DY is studied as a function of the impact parameter of the collision estimated from the measured transverse energy.
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The Drell-Yan cross sections are taken in the mass interval 2.9 to 4.5 GeV. SIG/SIG ratio are free from most systematic errors.
Inclusive and semi-inclusive ρ 0 production are studied in 205 GeV/ c pp interactions. The number of ρ 0 per inelastic event is 0.33 ± 0.06, so that (13 ± 2)% of the π − are products of ϱ 0 decay. The ρ 0 are found to be produced mainly near y = 0 and tend to have larger average transverse momentum than do pions.
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Using data from the Fermilab 15 ft hydrogen bubble chamber, we have studied inclusive ϱ 0 production in antineutrino-proton charged-current interactions. We measure (0.21 ± 0.03) ϱ 0 /event, corresponding to ϱ 0 / π − =0.12 ± 0.02. As a function of Q 2 and for hadronic masses above a threshold region, the ϱ 0 / π − ratio shows little variation. At least 50% of the ϱ 0 's are consistent with coming from the current fragmentation region. The results agree reasonably well with the predictions of the quark fragmentation model of Feynman and field.
AVERAGE BEAM ENERGY 31 GEV.
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The relative production yields and transverse mass spectra for Λ, Λ , Ξ − and Ξ + hyperons in proton-tungsten interactions are presented and compared with the WA85 results from central sulphur-tungsten interactions. A study of the negative particle yield has also been undertaken and the ratio of Λ hyperons to negative particles has been calculated.
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We report the first measurement of the ratio R=(σe+e−→hadrons)(σe+e−→μ+μ−) (with negligible τ-lepton contribution) at a center-of-mass energy s=13 GeV and s=17 GeV, from the just finished electron-positron colliding-beam facility PETRA. The detector, MARK-J, has an approximately 4π solid angle and measures γ, e, μ, and charged and neutral hadrons simultaneously. Our results yield R(s=17 GeV)=4.9±0.6 (statistical) ±0.7 (systematic error), and R(s=13 GeV)=4.6±0.5 (statistical) ±0.7 (systematic error). The ratio R(s=17 GeV)R(s=13 GeV) is 1.08±0.18.
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We report results from two new methods for measuring the total production of charmed particles in nonresonant e+e− annihilations at √s =10.5 GeV. The rate for detection of events containing two reconstructed charmed mesons relative to that for events containing one is used to extract information about total charm production independent of decay branching fractions. The value of ΔRcc¯, the total charm-pair cross section normalized to the pointlike μ-pair cross section, is found to be 1.13−0.13+0.17±0.09, under an assumption of limited particle correlations. In an independent analysis the inclusive cross section for e+e−→qq¯→e±X is measured to be 0.293±0.017±0.017 nb. Using measured relative production rates and semileptonic branching fractions of D0 and D+ mesons and estimates of these quantities for Ds and Λc, this is found to correspond to ΔRcc¯=2.07±0.12±0.26. These two measurements are discussed in the context of measurements made by reconstruction of exclusive hadronic decay modes and of theoretical expectations.
Charm quarks production cross section (C=CQCQBQR) evaluated from tagged events.
Results using method 1).
Results using method 2).
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The production of $\Upsilon$ mesons in $pp$ collisions at $\sqrt=7$ and $8\,\mathrm{TeV}$ is studied with the LHCb detector using data samples corresponding to an integrated luminosity of $1\,\mathrm{fb}^{-1}$ and $2\,\mathrm{fb}^{-1}$ respectively. The production cross-sections and ratios of cross-sections are measured as functions of the meson transverse momentum $p_T$ and rapidity $y$, for $p_T<30\,\mathrm{GeV}/c$} and $2.0<y<4.5$.
Double-differential cross-section $\mathrm{d}^2 \sigma ( pp \to ( \Upsilon \to \mu^+ \mu^- ) X ) / \mathrm{d} p_T/\mathrm{d}y$ [pb/(GeV/$c$)] for $2.0 < y < 2.5$.
Double-differential cross-section $\mathrm{d}^2 \sigma ( pp \to ( \Upsilon \to \mu^+ \mu^- ) X ) / \mathrm{d} p_T/\mathrm{d}y$ [pb/(GeV/$c$)] for $2.0 < y < 2.5$.
Double-differential cross-section $\mathrm{d}^2 \sigma ( pp \to ( \Upsilon \to \mu^+ \mu^- ) X ) / \mathrm{d} p_T/\mathrm{d}y$ [pb/(GeV/$c$)].
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