| 1. |
- Bessidskaia Bylund, Olga, et al.
(författare)
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Probing top quark neutral couplings in the Standard Model Effective Field Theory at NLO in QCD
- 2016
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :5
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Tidskriftsartikel (refereegranskat)abstract
- Top quark pair production in association with a Z-boson or a photon at the LHC directly probes neutral top-quark couplings. We present predictions for these two processes in the Standard Model (SM) Effective Field Theory (EFT) at next-to-leading order (NLO) in QCD. We include the full set of CP-even dimension-six operators that enter the top-quark interactions with the SM gauge bosons. For comparison, we also present predictions in the SMEFT for top loop-induced HZ production at the LHC and for t (t) over bar production at the ILC at NLO in QCD. Results for total cross sections and differential distributions are obtained and uncertainties coming from missing higher orders in the strong coupling and in the EFT expansions are discussed. NLO results matched to the parton shower are available, allowing for event generation to be directly employed in an experimental analyses. Our framework provides a solid basis for the interpretation of current and future measurements in the SMEFT, with improved accuracy and precision.
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| 2. |
- Broggio, Alessandro, et al.
(författare)
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Top-quark pair hadroproduction in association with a heavy boson at NLO+NNLL including EW corrections
- 2019
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2019:8
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Tidskriftsartikel (refereegranskat)abstract
- This work studies the associated production of a top-quark pair with a W, Z, or Higgs boson at the LHC. Predictions for the total cross sections as well as for several differential distributions of the massive particles in the final state are provided. These predictions, valid for the LHC operating at 13 TeV, include without any approximation all the NLO electroweak and QCD contributions of O (αsαj+1) with i + j = 2, 3. In addition, the predictions presented here improve upon the NLO QCD results by adding the effects of soft gluon emission corrections resummed to next-to-next-to-leading logarithmic accuracy. The residual dependence of the predictions on scale and PDF choices is analyzed.
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| 3. |
- Broggio, Alessandro, et al.
(författare)
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tt̄X Calculations and Modeling
- 2021
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Ingår i: The Ninth Annual Conference on Large Hadron Collider Physics : LHCP2021 - LHCP2021. - Trieste, Italy : Sissa Medialab. - 1824-8039. ; 397
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Konferensbidrag (refereegranskat)abstract
- In this talk, we review the status of calculations for the associated production of a top pair and a Higgs, W or Z boson at the Large Hadron Collider. In particular, we focus on the resummation of soft gluon emission effects and on their combination with the complete set of next-to-leading-order corrections of both QCD and electroweak origin, in calculations in which the final state top pair and massive boson are kept on shell. The impact of these corrections on the total cross section and several differential distributions is studied.
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| 4. |
- Czakon, Micha&lstrok, et al.
(författare)
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Top quark pair production at complete NLO accuracy with NNLO+NNLL′ corrections in QCD
- 2020
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Ingår i: Chinese Physics C. - : IOP Publishing. - 1674-1137 .- 2058-6132. ; 44:8
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Tidskriftsartikel (refereegranskat)abstract
- We describe predictions for top quark pair differential distributions at hadron colliders, by combining the next-to-next-to-leading order quantum chromodynamics calculations and next-to-leading order electroweak corrections with double resummation at the next-to-next-to-leading logarithmic accuracy of threshold logarithms and small-mass logarithms. To the best of our knowledge, this is the first study to present such a combination, which incorporates all known perturbative information. Numerical results are presented for the invariant-mass distribution, transverse-momentum distribution, and rapidity distributions.
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| 5. |
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| 6. |
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| 7. |
- Frederix, Rikkert, et al.
(författare)
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On improving NLO merging for t t ¯ W production
- 2021
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2021:11
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Tidskriftsartikel (refereegranskat)abstract
- We introduce an improvement to the FxFx matrix element merging procedure for pp →tt¯ W production at NLO in QCD with one and/or two additional jets. The main modification is an improved treatment of jets that are not logarithmically enhanced in the low transverse-momentum regime. We provide predictions for the inclusive cross section and the tt¯ W differential distributions including parton-shower effects. Taking also the NLO EW corrections into account, this results in the most-accurate predictions for this process to date. We further proceed to include the on-shell LO decays of the tt¯ W including the tree-level spin correlations within the narrow-width approximation, focusing on the multi-lepton signatures studied at the LHC. We find a ∼30% increase over the NLO QCD prediction and large non-flat K-factors to differential distributions.
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| 8. |
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| 9. |
- Frederix, Rikkert, et al.
(författare)
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Probing the spin correlations of tt¯ production at NLO QCD+EW
- 2021
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 81:9
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Tidskriftsartikel (refereegranskat)abstract
- In this work we investigate the NLO QCD+EW corrections to the top quark pair production and their effects on the spin correlation coefficients and asymmetries at fixed-order top quark pair production and LO decay in the dilepton channel, within the narrow-width approximation. The spin correlations are implicitly measured through the lepton kinematics. Moreover we study the EW effects to the leptonic differential distributions. We find that the EW corrections to the tt¯ production are within the NLO QCD theoretical uncertainties for the spin correlation coefficients and the leptonic asymmetries. On the other hand, for the differential distributions we find that the EW corrections exceed the NLO QCD scale uncertainty band in the high rapidity regimes and are of the order of the NLO QCD scale uncertainty in the case of invariant mass and transverse momentum distributions.
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| 10. |
- Frederix, Rikkert, et al.
(författare)
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Subleading EW corrections and spin-correlation effects in tt¯ W multi-lepton signatures
- 2020
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 80:9
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Tidskriftsartikel (refereegranskat)abstract
- Recently a slight tension between data and predictions has been reported in tt¯ W production by both the CMS and ATLAS collaborations. We revisit the theoretical predictions for this process, focussing on the following two effects. We disentangle various effects that lead to asymmetries among the leptonic decay products of the (anti-)top quarks and W bosons, for which we find that the spin correlations in the top-quark pair are the dominant source. We also discuss the impact of the large, formally subleading, electroweak corrections to tt¯ W production at the LHC. We find that this effect changes the tt¯ W cross section significantly in the signature phase-space regions, and should therefore be included differentially in the theory to data comparisons.
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