Hamburg 2016 – scientific programme

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T: Fachverband Teilchenphysik

T 14: Starke Wechselwirkung (Experiment) I

T 14.4: Talk

Monday, February 29, 2016, 11:45–12:00, VMP8 SR 206

Determination of the total cross section in proton-proton collisions at the LHC at √s = 8 from elastic scattering using the ALFA sub-detector of ATLAS — •Christian Heinz, Hasko Stenzel, and Michael Düren — 2. Physikalisches Institut, Universität Gießen

The ALFA (Absolute Luminosity for ATLAS) Roman Pot detector system is part of the forward instrumentation of ATLAS located about 240 m away from the interaction point in the LHC tunnel in both directions. ALFA consists of a scintillating fibre tracker housed in vertical Roman Pots which enables the measurement of elastic proton-proton scattering at small scattering angles. In 2012 data were recorded at a centre-of-mass energy of √s = 8 TeV during a fill with special beam optics of the LHC with β^* = 90 m and parallel-to-point focusing.

The four-momentum transfer t is measured for elastically scattered protons and used to extract the differential elastic cross section. In this talk a preliminary determination of the total cross section and of the slope of the elastic cross section at small |t| obtained from a fit to the differential cross section using the optical theorem is reported. In addition a second run at √s = 8 TeV with a special beam optics of β^* = 1 km, providing access to the Coulomb-nuclear interference region, is being analysed. Preliminary analysis results from this run will be presented as well.