Measurements of Proton-Proton Elastic Scattering and Total Cross-Section at the LHC by TOTEM

The TOTEM experiment at the LHC has extended the measurement of the differential cross-section for elastic proton-proton scattering at root s = 7 TeV to four-momentum transfers vertical bar t vertical bar as low as 5 x 10(-3) GeV2. The new data were collected in different dedicated runs with a special beam optics (beta* = 90m) and Roman Pot detectors placed as close as 4.8 times the transverse beam size from the outgoing beams. In addition, the accompanying inelastic rates were recorded with the forward telescopes T1 and T2 for 3.1 < vertical bar eta vertical bar < 6.5. Thus the first measurement of the total proton-proton cross-section with the luminosity-independent method based on the optical theorem could be performed. Alternatively, using the CMS luminosity measurement as an input, two additional total cross-section determinations with different systematic dependences were obtained: (a) as the direct sum of the elastic and inelastic cross-sections, and (b) calculated from only the elastic cross-section extrapolated to t = 0, as published previously [1] for an earlier data set. The results from all methods and data sets agree very well within their uncertainties.