New NLOPS predictions for $$\varvec{t \bar{t} +b}$$ tt¯+b -jet production at the LHC
Abstract Measurements of $$t \bar{t} H$$ tt¯H production in the $$H\rightarrow b \bar{b} $$ H→bb¯ channel depend in a critical way on the theoretical uncertainty associated with the irreducible $$t \bar{t} +b$$ tt¯+b -jet background. In this paper, analysing the various topologies that account for b...
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| Format: | Article |
| Language: | English |
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SpringerOpen
2018-06-01
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| Series: | European Physical Journal C: Particles and Fields |
| Online Access: | http://link.springer.com/article/10.1140/epjc/s10052-018-5956-0 |
| _version_ | 1811270518434693120 |
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| author | Tomáš Ježo Jonas M. Lindert Niccolo Moretti Stefano Pozzorini |
| author_facet | Tomáš Ježo Jonas M. Lindert Niccolo Moretti Stefano Pozzorini |
| author_sort | Tomáš Ježo |
| collection | DOAJ |
| description | Abstract Measurements of $$t \bar{t} H$$ tt¯H production in the $$H\rightarrow b \bar{b} $$ H→bb¯ channel depend in a critical way on the theoretical uncertainty associated with the irreducible $$t \bar{t} +b$$ tt¯+b -jet background. In this paper, analysing the various topologies that account for b-jet production in association with a $$t \bar{t} $$ tt¯ pair, we demonstrate that the process at hand is largely driven by final-state $$g\rightarrow b \bar{b} $$ g→bb¯ splittings. We also show that in five-flavour simulations based on $$t \bar{t} +$$ tt¯+ multi-jet merging, b-jet production is mostly driven by the parton shower, while matrix elements play only a marginal role in the description of $$g\rightarrow b \bar{b} $$ g→bb¯ splittings. Based on these observations we advocate the use of NLOPS simulations of $$pp\rightarrow t \bar{t} b\bar{b} $$ pp→tt¯bb¯ in the four-flavour scheme, and we present a new Powheg generator of this kind. Predictions and uncertainties for $$t \bar{t} +b$$ tt¯+b -jet observables at the 13 TeV LHC are presented both for the case of stable top quarks and with spin-correlated top decays. Besides QCD scale variations we consider also theoretical uncertainties related to the Powheg matching method and to the parton shower modelling, with emphasis on $$g\rightarrow b \bar{b} $$ g→bb¯ splittings. In general, matching and shower uncertainties turn out to be remarkably small. This is confirmed also by a consistent comparison against Sherpa+OpenLoops. |
| first_indexed | 2024-04-12T22:03:25Z |
| format | Article |
| id | doaj.art-e6caa2dcd3a649928e1d3af36bcc491c |
| institution | Directory Open Access Journal |
| issn | 1434-6044 1434-6052 |
| language | English |
| last_indexed | 2024-04-12T22:03:25Z |
| publishDate | 2018-06-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | European Physical Journal C: Particles and Fields |
| spelling | doaj.art-e6caa2dcd3a649928e1d3af36bcc491c2022-12-22T03:15:02ZengSpringerOpenEuropean Physical Journal C: Particles and Fields1434-60441434-60522018-06-0178612910.1140/epjc/s10052-018-5956-0New NLOPS predictions for $$\varvec{t \bar{t} +b}$$ tt¯+b -jet production at the LHCTomáš Ježo0Jonas M. Lindert1Niccolo Moretti2Stefano Pozzorini3Physics Institute, Universität ZürichInstitute for Particle Physics Phenomenology, Durham UniversityPhysics Institute, Universität ZürichPhysics Institute, Universität ZürichAbstract Measurements of $$t \bar{t} H$$ tt¯H production in the $$H\rightarrow b \bar{b} $$ H→bb¯ channel depend in a critical way on the theoretical uncertainty associated with the irreducible $$t \bar{t} +b$$ tt¯+b -jet background. In this paper, analysing the various topologies that account for b-jet production in association with a $$t \bar{t} $$ tt¯ pair, we demonstrate that the process at hand is largely driven by final-state $$g\rightarrow b \bar{b} $$ g→bb¯ splittings. We also show that in five-flavour simulations based on $$t \bar{t} +$$ tt¯+ multi-jet merging, b-jet production is mostly driven by the parton shower, while matrix elements play only a marginal role in the description of $$g\rightarrow b \bar{b} $$ g→bb¯ splittings. Based on these observations we advocate the use of NLOPS simulations of $$pp\rightarrow t \bar{t} b\bar{b} $$ pp→tt¯bb¯ in the four-flavour scheme, and we present a new Powheg generator of this kind. Predictions and uncertainties for $$t \bar{t} +b$$ tt¯+b -jet observables at the 13 TeV LHC are presented both for the case of stable top quarks and with spin-correlated top decays. Besides QCD scale variations we consider also theoretical uncertainties related to the Powheg matching method and to the parton shower modelling, with emphasis on $$g\rightarrow b \bar{b} $$ g→bb¯ splittings. In general, matching and shower uncertainties turn out to be remarkably small. This is confirmed also by a consistent comparison against Sherpa+OpenLoops.http://link.springer.com/article/10.1140/epjc/s10052-018-5956-0 |
| spellingShingle | Tomáš Ježo Jonas M. Lindert Niccolo Moretti Stefano Pozzorini New NLOPS predictions for $$\varvec{t \bar{t} +b}$$ tt¯+b -jet production at the LHC European Physical Journal C: Particles and Fields |
| title | New NLOPS predictions for $$\varvec{t \bar{t} +b}$$ tt¯+b -jet production at the LHC |
| title_full | New NLOPS predictions for $$\varvec{t \bar{t} +b}$$ tt¯+b -jet production at the LHC |
| title_fullStr | New NLOPS predictions for $$\varvec{t \bar{t} +b}$$ tt¯+b -jet production at the LHC |
| title_full_unstemmed | New NLOPS predictions for $$\varvec{t \bar{t} +b}$$ tt¯+b -jet production at the LHC |
| title_short | New NLOPS predictions for $$\varvec{t \bar{t} +b}$$ tt¯+b -jet production at the LHC |
| title_sort | new nlops predictions for varvec t bar t b tt¯ b jet production at the lhc |
| url | http://link.springer.com/article/10.1140/epjc/s10052-018-5956-0 |
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