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Abstract: The measurement of top quark spin correlation is an important tool for precise studies of top quark interactions. In this Letter I construct a quantization axis maximizing the spin correlation at the LHC within the Standard Model. Using this axis a spin correlation of 48% or even more, on applying additional cuts, can be reached. This represents a significant improvement compared to the helicity bases studied thus far. [Copyright &y& Elsevier]

We recalculate the next-to-leading order Altarelli–Parisi kernel using a method which relates it to the splitting amplitudes describing the collinear factorization properties of scattering amplitudes. The method breaks up the calculation of the kernel into individual pieces which have an independent physical interpretation. [Copyright &y& Elsevier]

Abstract: We study three and four jet production in hadronic collisions at next-to-leading order accuracy in massless QCD. We cross check results previously obtained by the BlackHat Collaboration for the LHC with a centre-of-mass energy of TeV and present new results for the LHC operating at 8 TeV. We find large negative NLO corrections reducing the leading order cross sections by about 40–50%. Furthermore we observe an important reduction of the scale uncertainty. In addition to the cross sections we also present results for differential distributions. The dynamical renormalization/factorization scale used in the calculation leads to a remarkably stable K-factor. The results presented here were obtained with the NJet package (Badger et al., 2012) [1], a publicly available library for the evaluation of one-loop amplitudes in massless QCD. [Copyright &y& Elsevier]