We have measured the proton-air inelastic cross section at s 1/2 =30 TeV by observing the distribution of extensive-air-shower maxima as a function of atmospheric depth. This distribution has an exponential tail whose slope is ë = 72 ± 9 g cm-2 which implies that ó tot p-air= 530 ± 66 mb. Using Glauber theory and assuming that the elastic-scattering slope parameter b is proportional to ó tot pp , we infer a value of ó tot pp =120 ± 15 mb which lies between a log 2 s and a loges extrapolation of the total pp cross section as measured at lower energies.

No abstract

We report on a search fordeeply penetrating particles in the >1017 eV cosmic ray flux. No such events have been found in 8.2x106 sec of running time. We consequently set limits onthe following: quark-matter in the primary cosmic ray flux; long-lived, weakly interacting particles produced in p-air collisions; the astrophysical neutrino flux. In particular, the neutrino flux limit at 1017 eV implies that 3, the red shift of maximum activity is <10 in the model of Hill and Schramm6.

A new technique is applied to data collected at the 0(3770) resonance to derive charmed-Dmeson branching fractions without relying on the measurement of D-production cross sections. Measurements are presented for three decay modes of the D° (K~TT + , D~ * and K-TT + TT 0 ) and four decay modes of the D + (K~7r + 7r + , K-TT + TT + TT 0 , K$<7T + , and tf 5°i r + ir 0 ). The resulting branching fractions are significantly larger than previous measurements.

Direct 2-D numerical simulation of the fluid instability of a shock-accelerated thin gas layer shows flow patterns in agreement with experimental images. The Eulerian-based hydrodynamics code features Adaptive Mesh Refinement that allows the code to follow the vorticity generation and the complex flow resulting from the measured initial perturbations. These experiments and simulations are the first to address in quantitative detail the evolution of the Richtmyer-Meshkov instability in a thin fluid layer, and to show how interfluid mixing and vorticity production depend sensitively on initial perturbations in the layer.