Total proton-proton cross section at s1/2=30 TeV

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 λ = 72 ±9 g c m - 2 which implies that σ inel p-air = 530 ± 66 mb. Using Glauber theory and assuming that the elastic-scattering slope parameter b is proportional to σ tot pp, we infer a value of σ tot pp= 120 ± 15 mb which lies between a logs and a log2s extrapolation of the total /across section as measured at lower energies.