First measurement of the total proton-proton cross-section at the LHC energy of sqrt(s) =7 TeV

TOTEM has measured the differential cross-section for elastic proton-proton scattering at the LHC energy of root s = 7 TeV analysing data from a short run with dedicated large-beta* optics. A single exponential fit with a slope B = (20.1 +/- 0.2(stat) +/- 0.3(syst)) GeV-2 describes the range of the four-momentum transfer squared vertical bar t vertical bar from 0.02 to 0.33 GeV2. After the extrapolation to vertical bar t vertical bar = 0, a total elastic scattering cross-section of (24.8 +/- 0.2(stat) +/- 1.2(syst)) mb was obtained. Applying the optical theorem and using the luminosity measurement from CMS, a total proton-proton cross-section of (98.3 +/- 0.2(stat) +/- 2.8(syst)) mb was deduced which is in good agreement with the expectation from the overall fit of previously measured data over a large range of center-of-mass energies. From the total and elastic pp cross-section measurements, an inelastic pp cross-section of (73.5 +/- 0.6(stat) (+1.8)(-1.3) (syst)) mb was inferred.