Weak interaction corrections to hadronic top quark pair production: contributions from quark-gluon and bbˉb \bar b induced reactions

As an addendum to our previous evaluation of the weak-interaction corrections to hadronic top-quark pair production we determine the leading weak-interaction contributions due to the subprocesses $b {\bar b} \to t {\bar t}$ and $g q ({\bar q}) \to t {\bar t} q ({\bar q})$. For several distributions in $t {\bar t}$ production at the LHC we find that these contributions are non-negligible as compared to the weak corrections from the other partonic subprocesses.Comment: Latex, 9 pages, 4 figure

Hole dynamics in an antiferromagnet across a deconfined quantum critical point

We study the effects of a small density of holes, delta, on a square lattice antiferromagnet undergoing a continuous transition from a Neel state to a valence bond solid at a deconfined quantum critical point. We argue that at non-zero delta, it is likely that the critical point broadens into a non-Fermi liquid `holon metal' phase with fractionalized excitations. The holon metal phase is flanked on both sides by Fermi liquid states with Fermi surfaces enclosing the usual Luttinger area. However the electronic quasiparticles carry distinct quantum numbers in the two Fermi liquid phases, and consequently the limit of the ratio A_F/delta, as delta tends to zero (where A_F is the area of a hole pocket) has a factor of 2 discontinuity across the quantum critical point of the insulator. We demonstrate that the electronic spectrum at this transition is described by the `boundary' critical theory of an impurity coupled to a 2+1 dimensional conformal field theory. We compute the finite temperature quantum-critical electronic spectra and show that they resemble "Fermi arc" spectra seen in recent photoemission experiments on the pseudogap phase of the cuprates.Comment: 33 pages, 8 figures, Longer version of cond-mat/0611536, with additional results for electron spectrum at non-zero temperatur

Electroweak corrections to ttˉt\bar{t} production at hadron colliders

We report on our recent work on electroweak corrections to $t\bar{t}$ production at hadron colliders. Specifically, we discuss the weak-interaction contributions to the top quark transverse momentum and $t \bar{t}$ invariant mass distributions and an induced parity-violating top-spin asymmetry.Comment: Invited Talk given at International Workshop on Top Quark Physics, La Biodola, Elba, Italy, 18-24 May 200