Total Proton-Proton Cross Section ats12=30TeV

We have measured the proton-air inelastic cross section at $s^{\frac{1}{2}}=30\mathrm{}$ 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 $\lambda =72\mathrm{}\pm 9$ g ${\mathrm{cm}}^{-2\mathrm{}}$ which implies that ${\sigma }_{p-\mathrm{air}}^{\mathrm{inel}}=530\mathrm{}\pm 66$ mb. Using Glauber theory and assuming that the elastic-scattering slope parameter $b$ is proportional to ${\sigma }_{\mathrm{pp}}^{\mathrm{tot}}$, we infer a value of ${\sigma }_{\mathrm{pp}}^{\mathrm{tot}}=120\mathrm{}\pm 15$ mb which lies between a $logs$ and a ${log}^{2}s$ extrapolation of the total $\mathrm{pp}$ cross section as measured at lower energies.