Top near threshold: all αS corrections are trivial

Melnikov, Kirill; Yakovlev, O. I.

doi:10.1016/0370-2693(94)90410-3

Cited by 94 publications

(134 citation statements)

References 2 publications

(2 reference statements)

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“…This result has also been re-established recently [14,15]. But this statement does not hold for the differential cross section or polarization, since these are affected through the diagrams shown in Figs.…”

Section: Introductory Remarkssupporting

confidence: 69%

Top quark polarization in polarized $e^+e^-$ annihilation near threshold

Harlander

Jeżabek²,

Kühn

et al. 1997

Zeitschrift f�r Physik C Particles and Fields

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Top quark polarization in e + e − annihilation into tt is calculated for linearly polarized beams. The Green function formalism is applied to this reaction near threshold. The Lippmann-Schwinger equations for the S-wave and P -wave Green functions are solved numerically for the QCD chromostatic potential given by the two-loop formula for large momentum transfer and Richardson's ansatz for intermediate and small momenta. S-P -wave interference contributes to all components of the top quark polarization vector. Rescattering of the decay products is considered. The mean values nℓ of the charged lepton fourmomentum projections on appropriately chosen directions n in semileptonic top decays are proposed as experimentally observable quantities sensitive to top quark polarization. The results for nℓ are obtained including S-P -wave interference and rescattering of the decay products. It is demonstrated that for the longitudinally polarized electron beam a highly polarized sample of top quarks can be produced.

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Section: Introductory Remarkssupporting

confidence: 69%

Top quark polarization in polarized $e^+e^-$ annihilation near threshold

Harlander

Jeżabek²,

Kühn

et al. 1997

Zeitschrift f�r Physik C Particles and Fields

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“…h V 4 (x, y) = − 3x 64π 2 (1 − x) 2 (2x + 1) 1 y dt 9 − t 1 − t − (t − x) t(2tx + t − 17x − 1) + 23x 6tx 2 + t 3 x + t 2 (2x 2 − 5x + 2) + t(x + 2) − x(86x + 13) 3 (9 − t)(1 − t) x 2 f − (t, x) + 1 2 t 3 − 5t 2 − 25t + 93 g (0) (t, x) + t 4 − 4t 3 − 106t 2 + 604t − 495 2 (9 − t)(1 − t) g (1) (t, x) + 1 2 −t 3 + 21t 2 − 119t + 99 g (2) (t, x) − 1 2 (9 − t)(1 − t) 3/2 g (3) (t, x) , (40) h A 4 (x, y) = 3x 64π 2 (1 − x) 2 (2x + 1) 1 y dt 9 − t 1 − t (t − x) t 2 x − 2t(4x + 1) − 7x 3tx 2 − t 3 x + t 2 (2x 2 − 5x + 2) + t(21x + 2) + (7 − 30x)x 3 (9 − t)(1 − t) x 2 f − (t, x) − 1 2 (t − 3)(t − 1) 2 g (0) (t, x) + −t 4 + 4t 3 + 74t 2 − 284t + 207 2 (9 − t)(1 − t) g (1) (t, x) + 1 2 t 3 − 21t 2 + 119t − 99 g (2) (t, x) + 1 2 (9 − t)(1 − t) 3/2 g (3) (t, x) , (41) with g (i) (t, x) = 1 2…”

Section: Discussionunclassified

“…• Corrections coming from gluon exchange involving the bottom quarks in the final state (QCD interference effects) appear at NLO but vanish at NLO for the total cross section [40]. We show in Section 4 that they are parametrically suppressed in the presence of invariant-mass cuts, provided the cuts are loose in the sense defined below (see also [37]).…”

Section: Nlo Corrections Related To the Top-quark Instability And Elementioning

confidence: 93%

Electroweak non-resonant NLO corrections to in the resonance region

2010

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We analyse subleading electroweak effects in the top anti-top resonance production region in e + e − collisions which arise due to the decay of the top and anti-top quarks into the W + W − bb final state. These are NLO corrections adopting the nonrelativistic power counting v ∼ α s ∼ √ α EW . In contrast to the QCD corrections which have been calculated (almost) up to NNNLO, the parametrically larger NLO electroweak contributions have not been completely known so far, but are mandatory for the required accuracy at a future linear collider. The missing parts of these NLO contributions arise from matching coefficients of non-resonant productiondecay operators in unstable-particle effective theory which correspond to off-shell top production and decay and other non-resonant irreducible background processes to tt production. We consider the total cross section of the e + e − → W + W − bb process and additionally implement cuts on the invariant masses of the W + b and W −b pairs.

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“…Note that (mm2) is not a double-counting of the Coulomb-exchange diagram in Figure 9, since the two diagrams refer to different loop momentum regions. It is well known that for the process e − e + → W − W + → f 1f2 f 3f4 the soft-photon corrections related to the final state cancel for the inclusive cross section [42,43]. The diagrams of type (im) in Figure 10 cancel pairwise when the sum over incoming positrons and electrons is performed.…”

Section: Soft-photon Correctionsmentioning

confidence: 96%

Four-fermion production near the W pair-production threshold

et al. 2008

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We perform a dedicated study of the four-fermion production process e − e + → µ −ν µ ud X near the W pair-production threshold in view of the importance of this process for a precise measurement of the W boson mass. Accurate theoretical predictions for this process require a systematic treatment of finite-width effects. We use unstable-particle effective field theory (EFT) to perform an expansion in the coupling constants, Γ W /M W , and the non-relativistic velocity v of the W boson up to next-to-leading order in Γ W /M W ∼ α ew ∼ v 2 . We find that the dominant theoretical uncertainty in M W is currently due to an incomplete treatment of initial-state radiation. The remaining uncertainty of the NLO EFT calculation translates into δM W ≈ 10 -15 MeV, and to about 5 MeV with additional input from the NLO four-fermion calculation in the full theory.

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Top near threshold: all αS corrections are trivial

Cited by 94 publications

References 2 publications

Top quark polarization in polarized $e^+e^-$ annihilation near threshold

Top quark polarization in polarized $e^+e^-$ annihilation near threshold

Electroweak non-resonant NLO corrections to in the resonance region

Four-fermion production near the W pair-production threshold

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