We discuss how the spatial intermittency of energy dissipation in 3D fully developed turbulence affects the small-scale statistics of passive scalars. We relate the passive-scalar behaviour to the diffusion properties of particle pairs in turbulent fluids. We thus find the intermittency correction to the -5/3 Obukhov-Corrsin law for the power spectrum of a passive scalar at wavenumber k where molecular diffusion and viscosity play a negligible role (inertial convective subrange). This correction is positive at difference with the negative correction to the -5/3 Kolmogorov law for the energy spectrum. We finally show that the structure functions of passive scalars have scaling exponents linear in the moment order, even in the framework of multifractal models.
'2'.
About 3700 two-prong and 5600 four-prong events of 10-GeV/c pp interactions in the Saclay 81-cm hydrogen bubble chamber have been measured and analyzed. The reliability of the identification of the different final states has been checked using Monte Carlo-generated events. For the channels accessible to analysis, cross sections and invariant-mass distributions are given. The c.m. angular distributions and the mean values of the transverse momentum for all final-state particles are shown and discussed. Production of Δ++(1236) accounts for about 30% of the cross section σ(pp→pnπ+)=4.1±0.4 mb. About 50% of the cross section σ(pp→ppπ+π−)=2.4±0.2 mb can be accounted for by Δ++ production. Production of nucleon isobars at 1450, 1520, and 1730 MeV and their subsequent decay into pπ+π− are investigated. Their cross sections, t dependences, and branching ratios are determined, using a one-pion-exchange model (OPEM) for calculating the background distributions. The production of resonances decaying into pπ− at 1236, 1500, and 1690 MeV is seen, and cross sections are given. Resonance production in the ppπ+π−π0 and pnπ+π+π− reactions is studied using background curves calculated with a model based on simple parametrizations of the c.m. momentum distributions. The production of nucleon isobars accounts for nearly 100% of these reactions. For the reactions pp→ppω, ppη, and ppf0, the cross sections found are 0.16±0.03, 0.16±0.07, and 0.10±0.04 mb, respectively, corrected for unobserved decay modes. It is shown that most of the gross features of the pion-production reactions can be explained by the OPEM with the form factors of Ferrari and Selleri.
No description provided.
Elastic scattering, single-pion and deuteron production have been investigated. The cross-section for elastic scattering is σelastic = (13.5±0.3) mb. The angular distribution has been fitted to dσ/d|t|=(dσ/d|t|)0 e −bt in the region of low values oft. The best fit givesb=(6.7±0.5) (GeV/c)−2 and (dσ/d|t|)0=(91±5) mb(GeV/c)−2. The cross-sections for ppπ0, pnπ+ reactions are respectively (2.6±0.3) mb and (9.7±0.4) mb. These reactions are dominated by the (3/2, 3/2) nucleonpion isobar production and by forward backward collimation of the nucleons. The production rates for the isobars ++1238 , +1238 , +1500 have been estimated, taking into account the experimental peripheral behaviour of the interaction. In the pnπ+ reaction they are (50±2)%; (10±3)%; (4±3)%. In the ppπ+ reaction the production of ++1238 is estimated to be (45±10)%. The dπ+ and dπ+π+π- reaction cross-sections are respectively (0.03±0.01) mb, and (0.04±0.01) mb.
No description provided.
No description provided.
Forum