$t\bar{t}b\bar{b}$ at the LHC: On the size of off-shell effects and prompt $b$-jet identification

Abstract

We investigate full off-shell effects in $t\bar{t}b\bar{b}$ production in the dilepton channel at the LHC with the center-of-mass energy $\sqrt{s}=13$ TeV. Specifically, we compute NLO QCD corrections to the $pp\to e^{+}{\nu }_e{\mu }^{-}{\bar{\nu }}_{\mu }b\bar{b}b\bar{b}+X$ process and provide a prescription for $b$-jet identification to distinguish prompt $b$ jets from $b$ jets originating from the decay of the top quarks. As an important irreducible background to $pp\to t\bar{t}H(H\to b\bar{b})$, $t\bar{t}$ production in association with two prompt $b$ jets is a primary source of uncertainty in the measurement of $t\bar{t}H(H\to b\bar{b})$. In quantifying full off-shell effects, we perform comparisons between the state-of-the-art full off-shell computation and the calculation in the narrow width approximation. The former includes all double-, single- and non-resonant Feynman diagrams, interferences as well as finite-width effects of the top quarks and $W$ gauge bosons. The latter restricts the unstable top quarks and $W$ gauge bosons to on-shell states and includes for the first time NLO QCD corrections to both production and decays. We observe that full off-shell effects are subdominant compared to the scale uncertainties for the integrated fiducial cross section and for the majority of differential observables in the phase-space regions that we investigated. However, for a number of observables related to beyond the Standard Model searches, full off-shell effects are significant. Furthermore, with our $b$-jet labelling prescription, the prompt $b$ jets and the $b$ jets from top-quark decays can be successfully disentangled.

35 pages, 8 figures, 1 table, version to appear in PRD

References in corpus (27)

• Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
• Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC
• LHAPDF6: parton density access in the LHC precision era
• Reducing full one-loop amplitudes to scalar integrals at the integrand level
• A standard format for Les Houches Event Files
• OneLOop: for the evaluation of one-loop scalar functions
• Assault on the NLO Wishlist: pp -> tt bb
• Complete off-shell effects in top quark pair hadroproduction with leptonic decay at next-to-leading order
• The complex-mass scheme for perturbative calculations with unstable particles
• NLO QCD corrections to pp -> t anti-t b anti-b + X at the LHC
• Helac-Phegas: a generator for all parton level processes
• Polarizing the Dipoles
• NLO QCD corrections to off-shell top-antitop production with leptonic decays at hadron colliders
• Search for direct top-squark pair production in final states with two leptons in pp collisions at sqrt(s)=8TeV with the ATLAS detector
• Search for charged Higgs bosons decaying into a top quark and a bottom quark at $\sqrt{s}$=13 TeV with the ATLAS detector
• NNLO QCD corrections to leptonic observables in top-quark pair production and decay
• Matching the Nagy-Soper parton shower at next-to-leading order
• Determining the CP nature of spin-0 mediators in associated production of dark matter and $t\bar{t}$ pairs
• Measurement of Higgs boson decay into $b$-quarks in associated production with a top-quark pair in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• The simplest of them all: $t\bar{t}{W}^{\pm }$ at NLO accuracy in QCD
• Production and decay of the Higgs boson in association with top quarks
• $t\bar{t}b\bar{b}$ at the LHC: On the size of corrections and $b$-jet definitions
• Hadroproduction of $t\bar{t}b\bar{b}$ final states at LHC: predictions at NLO accuracy matched with Parton Shower
• Measurement of the cross section for $\text{t}\bar{\text{t}}$ production with additional jets and b jets in pp collisions at $\sqrt{s}=$ 13 TeV
• Modeling uncertainties of $t\bar{t}{W}^{\pm }$ multilepton signatures
• Full NLO QCD corrections to off-shell ttbb production
• The impact of top-quark modelling on the exclusion limits in $\mathbf{t}\bar{\mathbf{t}}+\text{DM}$ searches at the LHC

Cited by in corpus (8)

• High-energy QCD dynamics from bottom flavor fragmentation at the Hi-Lumi LHC
• Two-loop amplitudes for ttH production: the quark-initiated Nf-part
• A study of additional jet activity in top quark pair production and decay at the LHC
• Stairway to discovery: a report on the CMS programme of cross section measurements from millibarns to femtobarns
• Les Houches 2023 -- Physics at TeV Colliders: Report on the Standard Model Precision Wishlist
• Measurement of top-quark pair production in association with charm quarks in proton-proton collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Five-flavour scheme predictions for $t\bar{t}b\bar{b}$ at next-to-leading order accuracy
• $t\bar{t}jj$ -- NLO QCD corrections to top quark pair production and decays at the LHC