Measurement of the dependence of transverse energy production at large rapidity on the hard scattering kinematics of proton–proton collisions at √s = 2.76 TeV

Measurements of hard processes in proton-lead (pPb) collisions provide the means to char- acterize the partonic structure of large nuclei. In centrality-selected pPb events, hard process rates probe the interplay between hard and soft processes, give insight into the geometric de- scription of these collisions, and may even reveal novel features of the proton wavefunction. We present measurements of jet production in 5.02 TeV pPb and 2.76 TeV pp collisions with the ATLAS detector at the LHC. The nuclear modification factor RpPb is presented for jets over broad rapidity (−2.1 < y∗ < +4.4) and transverse momentum ranges (40-1000 GeV) in centrality- inclusive collisions and in centrality-selected ones. The centrality-dependence of jets at mid- and forward rapidities is found to vary strongly with the total energy of the jet, implying a dependence on the underlying parton-parton kinematics. A new control measurement of the hard scatter- ing kinematics-dependence of the mean transverse energy at large rapidities in dijet-producing pp collisions at 2.76 TeV is presented, as a function of the dijet system pseudorapidity and mean transverse energy and also the phenomenologically reconstructed Bjorken x1 and x2. The resulting implications for the interpretation of the pPb jet results are discussed.