Pavel Ruzicka (Acad. of Sciences of the Czech Rep. (CZ))
Transverse energy distributions and regions of low activity in proton-proton scattering events are sensitive to soft physics, low x and diffractive processes, and have been measured in inclusive "minimum bias" scatters as well as in dijet events at sqrt(s) = 7 TeV. In the inclusive analysis, cross sections are measured differentially in terms of Delta eta F, the larger of the pseudorapidity regions extending to the limits of the ATLAS sensitivity, in which no final state particles are produced above a transverse momentum threshold p_T Cut. The measurements span the region 0 < Delta eta F < 8 for 200 < p_T Cut < 800 MeV. The data are used to constrain the value of the pomeron intercept appropriate to triple Regge models of soft diffraction, and the cross section integrated over all gap sizes is compared with other LHC inelastic cross section measurements. The dijet measurements study jet activity in the rapidity interval bounded by a dijet system, as well as in the forward region. Differential distributions are compared to various QCD calculations including different approximations for gluon radiation.
Prof. Mark Oreglia (University of Chicago (US))