First estimate of the NNLO nonresonant corrections to top-antitop threshold production at lepton colliders

Ruiz-Femenía, Pedro

doi:10.1103/physrevd.89.097501

Cited by 9 publications

(21 citation statements)

References 16 publications

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“…Our result for this diagram including its resonant counterpart indeed agrees with the above except for the constant term +1 (see (C.4), (C.5) in Appendix C). However, as was already mentioned in [27,30], contrary to the statement made in [31] there is a nonvanishing contribution from h 1b at the same order. We computed the O(α s /ρ) from this diagram explicitly, and find that the complete O(α s /ρ) contribution to the total cross section reads…”

Section: Comparison To [31]mentioning

confidence: 52%

“…It is instructive to construct the O(α s /ρ) terms from the results in [30] and in the present paper. We find that they arise only from…”

Section: Comparison To [31]mentioning

confidence: 98%

“…We note the absence of phase-space suppression and Coulomb resummation for the non-resonant part. The non-resonant contribution is known at NLO [26], but only partial results are available at NNLO [27,30,31]. On the resonant side, the (α em /v) k terms arise from the QED Coulomb potential.…”

Section: Introductionmentioning

confidence: 99%

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Non-resonant and electroweak NNLO correction to the e+e− top anti-top threshold

Beneke

Maier

Rauh

et al. 2018

J. High Energ. Phys.

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Abstract:We determine the NNLO electroweak correction to the e + e − → bbW + W − X production cross section near the top-pair production threshold. The calculation includes non-resonant production of the final state as well as electroweak effects in resonant top anti-top pair production with non-relativistic resummation, and elevates the theoretical prediction to NNNLO QCD plus NNLO electroweak accuracy. We then study the impact of the new contributions on the top-pair threshold scan at a future lepton collider.

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Section: Comparison To [31]mentioning

confidence: 52%

“…It is instructive to construct the O(α s /ρ) terms from the results in [30] and in the present paper. We find that they arise only from…”

Section: Comparison To [31]mentioning

confidence: 98%

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Non-resonant and electroweak NNLO correction to the e+e− top anti-top threshold

Beneke

Maier

Rauh

et al. 2018

J. High Energ. Phys.

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“…For the same reason, it will be mandatory to consider the process e + e − → W + W − bb including the non-resonant contributions. Non-resonant effects have been computed to NLO and partially to NNLO accuracy [33][34][35][36], and can be naturally separated in the framework of unstable particle EFT [37,38]. d) Electromagnetic initial-state radiation generates large logarithms ln(4m 2 t /m 2 e ), where m e is the electron mass, which must be summed.…”

mentioning

confidence: 99%

Next-to-Next-to-Next-to-Leading Order QCD Prediction for the Top AntitopS-Wave Pair Production Cross Section Near Threshold ine+e−Annihilation

et al. 2015

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We present the third-order QCD prediction for the production of top-anti-top quark pairs in electronpositron collisions close to the threshold in the dominant S-wave state. We observe a significant reduction of the theoretical uncertainty and discuss the sensitivity to the top quark mass and width.PACS numbers: 14.65. Ha, 12.38.Bx, 13.66.Bc Among the main motivations for building a future highenergy electron-positron collider in steps of increasing center-of-mass energy are precise measurements at √ s ≈ 345 GeV close to the production threshold of top antitop quark pairs. The peculiar behaviour of the cross section allows for the precise determination of a number of Standard Model parameters, most prominently the top quark mass. To date the most precise measurement of m t = 173.34±0.27(stat)±0.71(syst) GeV comes from the hadron colliders Fermilab Tevatron and CERN LHC [1] and is based on the reconstruction of the top and antitop quarks through their decay products. This approach and the value quoted above are plagued by unknown relations of the extracted mass value m t to top quark masses in the pole or MS renormalization scheme, which may well exceed 1 GeV. At hadron colliders there are also methods to determine directly a well-defined top quark mass, such as the extraction of m t from top quark cross section measurements. However, the final precision is of the order of a few GeV and thus significantly worse. At an electron-positron collider, on the other hand, scans of the top anti-top pair production threshold can lead to very precise measurements of well-defined mass values with a statistical accuracy of only 20-30 MeV [2,3]. Besides the top quark mass also its decay width and the strong coupling constant can be extracted with an accuracy of 21 MeV [3] and 0.0009 [2], respectively. A recent study has shown that for a Higgs boson with a mass of about 125 GeV the top quark Yukawa coupling can be obtained with a statistical uncertainty of only 4.2% [3]. These numbers pose several challenges to theory.A crucial input to reach the aimed precision is a precise calculation of the top anti-top pair production cross section in the threshold region. While the fundamental theory of quantum chromodyanmics (QCD) is wellestablished, performing calculations of quantum corrections to the very high accuracies demanded here is very difficult indeed. The problem is further complicated by the fact that in the threshold region the colour Coulomb potential ∝ α s /r, where α s denotes the strong coupling, can no longer be treated as a perturbation even though α s ≪ 1. Standard perturbation theory in α s breaks down and resummation is required.The relevant techniques have been developed in the 1990s in the framework of effective field theory (EFT), which accounts for the different dynamical scales in the problem. For a heavy quark anti-quark system at threshold there are three relevant scales, the hard scale m, the potential and soft scale mv, and the ultrasoft scale mv 2 , where m denotes the mass of the quark and v its velocit...

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“…We thus omit the contributions related to non-ttresonant W + bW −b production discussed in Refs. [19,20,114], but note that they are included in our final matched predictions through the full QCD-LO and QCD-NLO W + bW −b cross section calculations, as described in Section 5. Furthermore, in this validation section we use the EHA in Whizard and consistently treat the top decay at LO in all analytic and MC results.…”

Section: Validation For the Inclusive Cross Sectionmentioning

confidence: 99%

Fully-differential top-pair production at a lepton collider: from threshold to continuum

Bach

Nejad²,

Hoang

et al. 2018

J. High Energ. Phys.

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We present an approach to predict exclusive W + bW −b production at lepton colliders that correctly describes the top-anti-top threshold as well as the continuum region. We incorporate tt form factors for the NLL threshold resummation derived in NRQCD into a factorized relativistic cross section using an extended double-pole approximation, which accounts for fixed-order QCD corrections to the top decays at NLO. This is combined with the full fixed-order QCD result at NLO for W + bW −b production to obtain predictions that are not only valid at threshold but smoothly transition to the continuum region. Our implementation is based on the Monte Carlo event generator Whizard and the code Toppik and allows to compute fully-differential threshold-resummed cross sections including the interference with non-resonant background processes. For the first time it is now possible to systematically study general differential observables at future lepton colliders involving the decay products of the top quarks at energies close to the pair production threshold and beyond.

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First estimate of the NNLO nonresonant corrections to top-antitop threshold production at lepton colliders

Cited by 9 publications

References 16 publications

Non-resonant and electroweak NNLO correction to the e+e− top anti-top threshold

Non-resonant and electroweak NNLO correction to the e+e− top anti-top threshold

Next-to-Next-to-Next-to-Leading Order QCD Prediction for the Top AntitopS-Wave Pair Production Cross Section Near Threshold ine+e−Annihilation

Fully-differential top-pair production at a lepton collider: from threshold to continuum

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