$${t {{\bar{t}}}H}$$ production at NNLO: the flavour off-diagonal channels
Stefano Catani, Ignacio Fabre, Massimiliano Grazzini, Stefan Kallweit
Abstract
Abstract We consider QCD radiative corrections to the associated production of a heavy-quark pair ( $$Q{{\bar{Q}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Q</mml:mi> <mml:mover> <mml:mrow> <mml:mi>Q</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> </mml:math> ) with a generic colourless system F at hadron colliders. We discuss the resummation formalism for the production of the $$Q{{\bar{Q}}}F$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Q</mml:mi> <mml:mover> <mml:mrow> <mml:mi>Q</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> <mml:mi>F</mml:mi> </mml:mrow> </mml:math> system at small values of its total transverse momentum $$q_T$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>q</mml:mi> <mml:mi>T</mml:mi> </mml:msub> </mml:math> . We present the results of the corresponding resummation coefficients at next-to-leading and, partly, next-to-next-to-leading order. The perturbative expansion of the resummation formula leads to the explicit ingredients that can be used to apply the $$q_T$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>q</mml:mi> <mml:mi>T</mml:mi> </mml:msub> </mml:math> subtraction formalism to fixed-order calculations for this class of processes. We use the $$q_T$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>q</mml:mi> <mml:mi>T</mml:mi> </mml:msub> </mml:math> subtraction formalism to perform a fully differential perturbative computation for the production of a top-antitop quark pair and a Higgs boson. At next-to-leading order we compare our results with those obtained with established subtraction methods and we find complete agreement. We present, for the first time, the results for the flavour off-diagonal partonic channels at the next-to-next-to-leading order.