ZZ production at hadron colliders in NNLO QCD

We report on the first calculation of next-to-next-to-leading order (NNLO) QCD corrections to the inclusive production of Z -boson pairs at hadron colliders. Numerical results are presented for pp collisions with centre-of-mass energy ( <math altimg="si1.gif" xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mi>s</mi></msqrt></math> ) ranging from 7 to 14 TeV. The NNLO corrections increase the NLO result by an amount varying from 11% to 17% as <math altimg="si1.gif" xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mi>s</mi></msqrt></math> goes from 7 to 14 TeV. The loop-induced gluon fusion contribution provides about <math altimg="si2.gif" xmlns="http://www.w3.org/1998/Math/MathML"><mn>60</mn><mtext>%</mtext></math> of the total NNLO effect. When going from NLO to NNLO the scale uncertainties do not decrease and remain at the <math altimg="si3.gif" xmlns="http://www.w3.org/1998/Math/MathML"><mo>±</mo><mn>3</mn><mtext>%</mtext></math> level

Transverse-momentum resummation for vector-boson pair production at NNLL+NNLO

We consider the transverse-momentum ( p T ) distribution of ZZ and W + W − boson pairs produced in hadron collisions. At small p T , the logarithmically enhanced contributions due to multiple soft-gluon emission are resummed to all orders in QCD perturbation theory. At intermediate and large values of p T , we consistently combine resummation with the known fixed-order results. We exploit the most advanced perturbative information that is available at present: next-to-next-to-leading logarithmic resummation combined with the next-to-next-to-leading fixed-order calculation. After integration over p T , we recover the known next-to-next-to-leading order result for the inclusive cross section. We present numerical results at the LHC, together with an estimate of the corresponding uncertainties. We also study the rapidity dependence of the p T spectrum and we consider p T efficiencies at different orders of resummed and fixed-order perturbation theory