Infrared QCD resummations at hadron colliders

  • Rosa Duran Delgado

Student thesis: Phd


In this thesis we study two different processes at hadron colliders: Z-boson production and dijet production with a jet veto. Our calculations focus on the resummation of logarithmically enhanced contributions coming from soft and/or collinear gluon emission. For Z-boson production, we calculate the cross-section distribution in aT , a novel variable proposed by Vesterinen and Wyatt as a more accurate probe of the Z at low transverse momentum pT . The observable aT is defined as the component of pT perpendicular to an experimentally convenient axis: the axis with respect to which the two final-state leptons (from a Z leptonic decay) have equal transverse momenta. Our study involves the resummation of large logarithms in aT /pT up to next-to-leading accuracy. We then compare the resulting distributions in aT to the well-known pT distribution, identifying important physical differences between the two cases. We also test our resummed result at the two-loop level by comparing its expansion with a fixed-order calculation and find agreement with our expectations. Besides, we study dijet production with a veto in the inter-jet rapidity region in proton-proton collisions. We resum the leading logarithms in the ratio of the transverse momentum of the leading jets and the veto scale and we match this result to leading-order QCD matrix elements, taking into account energy-momentum conservation effects. We compare our theoretical predictions to experimental data measured by the ATLAS collaboration and find good agreement, although our results are affected by large theoretical uncertainties.
Date of Award31 Dec 2011
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorJeffrey Forshaw (Supervisor) & Mrinal Dasgupta (Supervisor)

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