Production cross-sections of prompt charm mesons are measured with the first data from $pp$ collisions at the LHC at a centre-of-mass energy of $13\,\mathrm{TeV}$. The data sample corresponds to an integrated luminosity of $4.98 \pm 0.19\,\mathrm{pb}^{-1}$ collected by the LHCb experiment. The production cross-sections of $D^{0}$, $D^{+}$, $D_{s}^{+}$, and $D^{*+}$ mesons are measured in bins of charm meson transverse momentum, $p_{\mathrm{T}}$, and rapidity, $y$, and cover the range $0 < p_{\mathrm{T}} < 15\,\mathrm{GeV}/c$ and $2.0 < y < 4.5$. The inclusive cross-sections for the four mesons, including charge conjugation, within the range of $1 < p_{\mathrm{T}} < 8\,\mathrm{GeV}/c$ are found to be \begin{equation} \sigma(pp \to D^{0} X) = 2072 \pm 2 \pm 124\,\mu\mathrm{b}\\ \sigma(pp \to D^{+} X) = 834 \pm 2 \pm \phantom{1}78\,\mu\mathrm{b}\\ \sigma(pp \to D_{s}^{+} X) = 353 \pm 9 \pm \phantom{1}76\,\mu\mathrm{b}\\ \sigma(pp \to D^{*+} X) = 784 \pm 4 \pm \phantom{1}87\,\mu\mathrm{b} \end{equation} where the uncertainties are due to statistical and systematic uncertainties, respectively.
The inclusive production of π± andK± mesons and of protons and antiprotons ine+e− annihilation has been measured at c.m. energies ofW=14, 22 and 34GeV. Using time of flight measurements and Cerenkov counters the full momentum range has been covered. Differential cross sections and total particle yields are given. At particle momenta of 0.4 GeV/c more than 90% of the charged hadrons are pions. With increasing momentum the fraction of pions among the charged hadrons decreases. AtW=34 GeV and a momentum of 5 GeV/c the particle fractions are approximately π±:K±:p,\(\bar p = 0.55:0.3:0.15\). On average an event atW=34 GeV contains 10.3±0.4π±, 2.0±0.2K± and 0.8±0.1p,\(\bar p\). In addition, we present results on baryon correlations using a sample of events where two or more protons and/or antiprotons are observed in the final state.
We report on an analysis of the multiplicity distributions of charged particles produced ine+e− annihilation into hadrons at c.m. energies between 14 and 46.8 GeV. The charged multiplicity distributions of the whole event and single hemisphere deviate significantly from the Poisson distribution but follow approximate KNO scaling. We have also studied the multiplicity distributions in various rapidity intervals and found that they can be well described by the negative binomial distribution only for small central intervals. We have also analysed forward-backward multiplicity correlations for different energies and selections of particle charge and shown that they can be understood in terms of the fragmentation properties of the different quark flavours and by the production and decay of resonances. These correlations are well reproduced by the Lund string model.
The production cross sections for the Λ, Σ0, Ξ−, Σ0 (1385), Ξ0 (1530) and Ω− hyperons have been measured, both in the continuum and in direct ϒ decays. Baryon rates in direct ϒ decays are enhanced by a factor of 2.5 or more compared to the continuum. Such a large baryon enhancement cannot be explained by standard fragmentation models. The strangeness suppression for baryons and mesons turns out to be the same. A strong suppression of spin 3/2 states is observed.
The inclusive production of π± andK± mesons and of protons and antiprotons ine+e− annihilations has been measured at 34 GeV and 44 G
Results on inclusive K s 0 production in e + e − annihilation at mean center-of-mass energies of 9.4, 12.0 and 30 GeV are presented. The ratio R (K 0 ) = 2 σ (K s 0 )/ σ μμ rises from 3.10 ± 0.75 at √ s = 9.4 GeV to 5.6 ± 1.2 at √ s = 30 GeV, corresponding to an approximately constant K 0 /charged-particle ratio of 0.12 ± 0.02. A similar ratio for K 0 / charged particle is observed for direct hadronic decays of the ϒ.
Inclusive production of ifπ ± , K ± and p has been studied near charm threshold for c.m. energies between 3.6 and 5.2 GeV. Differential and scaling cross sections together with particle multiplicities have been determinated. By comparing data below and above charm threshold the charm contribution to if π ± and K ± production has been extracted. A comparison has been made between inclusice p production and inelastic electron-proton scattering. To study differences between three-gluon annihilation and two-quark production of the spectra from J/ decay and from non-resonant production at 3.6 GeV has been compared.
Data on p and Λ production by e + e − -annihilation at CM energies between 30 and 36 GeV are presented. Indication for an angular anticorrelation in events with baryon-antibaryon pairs is seen.
We report the first observation of an orbitally excited baryon, the Λ(1520), in quark and gluon fragmentation. The production rate is found to be (1.15±0.21±0.16)×10 −2 and (0.80±0.17 −0.13 +0.10 )×10 −2 Λ (1520) hyperons per event in direct ϒ decays and in the continuum, respectively. In contrast to the observed situation for ground state baryons, the production of the Λ(1520) in direct ϒ decays shows little or no enhancement with respect to continuum production.
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