NLO matching for ttbb production with massive b-quarks

Abstract

Theoretical uncertainties in the simulation of ttbb production represent one of the main obstacles that still hamper the observation of Higgs-boson production in association with top-quark pairs in the H->bb channel. In this letter we present a next-to-leading order (NLO) simulation of ttbb production with massive b-quarks matched to the Sherpa parton shower. This allows one to extend NLO predictions to arbitrary ttbb kinematics, including the case where one or both b-jets arise from collinear g->bb splittings. We find that this splitting mechanism plays an important role for the ttH(bb) analysis.

Figures (3)

• Figure 1: Tree topologies corresponding to $\mathrm{t}$t$\bar{\mathrm{t}$t$}\mathrm{b}$b$\bar{\mathrm{b}$b$}$ production via single hard (left) or double collinear (right) $\mathrm{g}$g$\to\mathrm{b}$b$\bar{\mathrm{b}$b$}$ splitting.
• Figure 2: Transverse momentum of the first light jet and invariant mass of the first two b-jets with standard ttbb cuts. The MC@NLO bands display the combination in quadrature of $\mu_{\mathrm{R}}$, $\mu_{\mathrm{F}}$ and $\mu_{Q}$ scale variations. The MC@NLO$_{2b}$ curve is obtained by switching off $\mathrm{g}$g$\to\mathrm{b}$b$\bar{\mathrm{b}$b$}$ splittings in the parton shower.
• Figure 3: Transverse momentum of the first b-jet and $\Delta R$ separation of the first two b-jets with standard ttbb cuts and $M_{\mathrm{b}$b$\mathrm{b}$b$}>100~\mathrm{GeV}$. The MC@NLO bands display the combination in quadrature of $\mu_{\mathrm{R}}$, $\mu_{\mathrm{F}}$ and $\mu_{Q}$ scale variations. The MC@NLO$_{2b}$ curve is obtained by switching off $\mathrm{g}$g$\to\mathrm{b}$b$\bar{\mathrm{b}$b$}$ splittings in the parton shower.