Measurement of the dependence of transverse energy production at large pseudorapidity on the hard-scattering kinematics of proton-proton collisions at $\sqrt{s}=2.76$ TeV with ATLAS

Abstract

The relationship between jet production in the central region and the underlying-event activity in a pseudorapidity-separated region is studied in 4.0 pb${}^{-1}$ of $\sqrt{s}=2.76$ TeV $pp$ collision data recorded with the ATLAS detector at the LHC. The underlying event is characterised through measurements of the average value of the sum of the transverse energy at large pseudorapidity downstream of one of the protons, which are reported here as a function of hard-scattering kinematic variables. The hard scattering is characterised by the average transverse momentum and pseudorapidity of the two highest transverse momentum jets in the event. The dijet kinematics are used to estimate, on an event-by-event basis, the scaled longitudinal momenta of the hard-scattered partons in the target and projectile beam-protons moving toward and away from the region measuring transverse energy, respectively. Transverse energy production at large pseudorapidity is observed to decrease with a linear dependence on the longitudinal momentum fraction in the target proton and to depend only weakly on that in the projectile proton. The results are compared to the predictions of various Monte Carlo event generators, which qualitatively reproduce the trends observed in data but generally underpredict the overall level of transverse energy at forward pseudorapidity.

15 pages plus author list + cover pages (33 pages total), 5 figures, 1 table, submitted to Phys. Lett B, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2015-02/

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• Consequences of high-$x$ proton size fluctuations in small collision systems at RHIC
• Spin-isospin correlated configurations in complex nuclei and neutron skin effect in W${}^{\pm }$ production in high-energy proton-lead collisions
• Revealing minijet dynamics via centrality dependence of the double parton interactions in proton-nucleus interactions
• Mapping color fluctuations in the photon in ultraperipheral heavy ion collisions at the Large Hadron Collider
• Measurement of the centrality dependence of the dijet yield in $p$+Pb collisions at $\sqrt{s_{{}_{\text{NN}}}}$ = 8.16 TeV with the ATLAS detector
• Selection bias effects on high-$p_{\mathrm{T}}$ yield and correlation measurements in Oxygen+Oxygen collisions
• Study of very forward energy and its correlation with particle production at midrapidity in pp and p-Pb collisions at the LHC
• Hard processes in small systems
• Four-jet production via double parton scattering in $pA$ collisions at the LHC