Hadroproduction of W + W − b b ¯ $$ \overline{\mathrm{b}} $$ at NLO accuracy matched with shower Monte Carlo programs
Maria Vittoria Garzelli (Institute of Physics and MTA-DE Particle Physics Research Group, University of Debrecen, H-4010 Debrecen P.O.Box 105, Hungary); Adam Kardos (Institute of Physics and MTA-DE Particle Physics Research Group, University of Debrecen, H-4010 Debrecen P.O.Box 105, Hungary); Zoltán Trócsányi (Institute of Physics and MTA-DE Particle Physics Research Group, University of Debrecen, H-4010 Debrecen P.O.Box 105, Hungary)
We present the computation of the differential cross section for the process p p ( p ¯ $$ \overline{p} $$ ) → (W + W − b b ¯ $$ \overline{\mathrm{b}} $$ →) e + ν e μ − ν ¯ $$ \overline{\nu} $$ μ b b ¯ $$ \overline{\mathrm{b}} $$ + X at NLO QCD accuracy matched to Shower Monte Carlo (SMC) simulations using PowHel, on the basis of the interface between HELAC-NLO and POWHEG-BOX. We include all resonant and non-resonant contributions. This is achieved by fully taking into account the effect of off-shell t-quarks and off-shell W-bosons in the complex mass scheme. We also present a program called DECAYER that can be used to let the t-quarks present in the event files for p p ( p ¯ $$ \overline{p} $$ ) → t t ¯ $$ \overline{\mathrm{t}} $$ X processes decay including both the finite width of the t-quarks and spin correlations. We present predictions for both the Tevatron and the LHC, with emphasis on differences emerging from three different W + W − b b ¯ $$ \overline{\mathrm{b}} $$ hadroproduction computations: (i) full implementation of the p p ( p ¯ $$ \overline{p} $$ ) → W + W − b b ¯ $$ \overline{\mathrm{b}} $$ process, (ii) generating on-shell t-quarks pushed off-shell with a Breit-Wigner finite width and decayed by Decayer, and (iii) on-shell t-quark production followed by decay in the narrow width approximation, as described by the SMC.
