The spectra of strange hadrons are measured in proton-proton collisions, recorded by the CMS experiment at the CERN LHC, at centre-of-mass energies of 0.9 and 7 TeV. The K^0_s, Lambda, and Xi^- particles and their antiparticles are reconstructed from their decay topologies and the production rates are measured as functions of rapidity and transverse momentum. The results are compared to other experiments and to predictions of the PYTHIA Monte Carlo program. The transverse momentum distributions are found to differ substantially from the PYTHIA results and the production rates exceed the predictions by up to a factor of three.
The rapidity production spectra per NSD event spectra for KS mesons at 0.9 and 7 TeV.
The transverse momentum production spectra per NSD event spectra for KS mesons at 0.9 and 7 TeV.
The rapidity production spectra per NSD event spectra for LAMBDA mesons at 0.9 and 7 TeV.
The production of J/psi mesons is studied in pp collisions at sqrt(s)=7 TeV with the CMS experiment at the LHC. The measurement is based on a dimuon sample corresponding to an integrated luminosity of 314 inverse nanobarns. The J/psi differential cross section is determined, as a function of the J/psi transverse momentum, in three rapidity ranges. A fit to the decay length distribution is used to separate the prompt from the non-prompt (b hadron to J/psi) component. Integrated over J/psi transverse momentum from 6.5 to 30 GeV/c and over rapidity in the range |y| < 2.4, the measured cross sections, times the dimuon decay branching fraction, are 70.9 \pm 2.1 (stat.) \pm 3.0 (syst.) \pm 7.8(luminosity) nb for prompt J/psi mesons assuming unpolarized production and 26.0 \pm 1.4 (stat.) \pm 1.6 (syst.) \pm 2.9 (luminosity) nb for J/psi mesons from b-hadron decays.
Total cross section within the kinematic limits for prompt and non-prompt J/PSI production times branching ratio into MU+ MU-, assuming zero polarizartion. The second systematic error is the luminosity uncertainty.
Differential inclusive cross J/PSI section for the |rapidity| range 0 to 1.2 for each prompt J/PSI polarization scenario considered.
Differential inclusive cross J/PSI section for the |rapidity| range 1.2 to 1.6 for each prompt J/PSI polarization scenario considered.
The production dynamics of baryon-antibaryon pairs are investigated using hadronic Z 0 decays, recorded with the OPAL detector, which contain at least two identified Λ baryons. The rapidly difference for Λ Λ pairs shows the correlations expected from models with a chain-like production of baryon-antibaryon pairs. If the baryon number of a Λ is compensated by a Λ , the Λ is found with a probability of 53% in an interval of ±0.6 around the Λ rapidity. This correlation strength is weaker than predicted by the Herwig Monte Carlo and the Jetset Monte Carlo with a production chain of baryon-antibaryon, and stronger than predicted by the UCLA model. The observed rapidity correlations can be described by the Jetset Monte Carlo with a dominant production chain of baryon-meson-antibaryon, the popcorn mechanism. In addition to the short range correlations, one finds an indication of a correlation of Λ Λ pairs in opposite hemispheres if both the Λ and the Λ have large rapidities. Such long range correlations are expected if the primary quark flavours are compensated in opposite hemispheres and if these quarks are found in energetic baryons. Rates for simultaneous baryon and strangeness number compensation for Λ Λ , Ξ − Ξ + and Ξ − Λ ( Λ + Λ ) are measured and compared with different Monte Carlo models.
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Opposite and same baryon number invariant PI P mass distribuition for additional LAMBDA(LAMBDABAR) candidates in events with one identified LAMBDA(LAMBDABAR). CT.= Data read from plot.
Opposite and same baryon number invariant PI P mass distribuition for additional LAMBDA(LAMBDABAR) candidates in events with one identified XI-(XIBAR+). CT.= Data read from plot.
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