Asymmetries in top quark pair production at hadron colliders

Aguilar-Saavedra, J. A.; Amidei, D.; Rozas, A. Juste; Pérez-Victoria, M.

doi:10.1103/revmodphys.87.421

Cited by 58 publications

(61 citation statements)

References 147 publications

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“…Charge asymmetries in tt production at hadron colliders [1] arouse wide interest after measurements by the CDF and D0 Collaborations of the forward-backward (FB) asymmetry A FB in tt production at the Tevatron [2,3] showed some deviations from the existing standard model (SM) predictions [4]. These anomalies boosted the already extensive program to measure the top quark properties, and in particular they provided a strong motivation for the measurement of a charge asymmetry A C in tt production at the Large Hadron Collider (LHC).…”

Section: Introductionmentioning

confidence: 99%

“…1 (left). LHC measurements at centre of mass (CM) energies of 7 TeV [5,6,25,26] and 8 TeV [27-31] 1 do not exhibit a clear trend (see the right panel) but there is some shift towards measurements below the SM prediction. In particular, among the naive combination of A C measurements at 7 TeV, the naive combination at 8 TeV, and the two A C official combinations at 7 and 8 TeV, three of these four measurements are found below the SM.…”

Section: Introductionmentioning

confidence: 99%

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Single lepton charge asymmetries in $$t {\bar{t}}$$ t t ¯ and

Aguilar-Saavedra

2018

Eur. Phys. J. C

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We discuss lepton charge asymmetries in tt and ttγ production at the LHC, which can be measured in the semileptonic decay channel tt → W + b W −b → + νb qq b (or the charge conjugate). Considering several variants of a new physics scenario with a light colour octet, it is seen that for tt these asymmetries may have a sensitivity competitive with the dilepton asymmetry already measured. For ttγ the new leptonic asymmetries, as well as the tt charge asymmetry, will reach their full potential with the high luminosity LHC upgrade. These asymmetries can pinpoint deviations at the 3σ −4σ level for new physics scenarios where the charge asymmetries already measured in tt production agree within 1σ .

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Single lepton charge asymmetries in $$t {\bar{t}}$$ t t ¯ and

Aguilar-Saavedra

2018

Eur. Phys. J. C

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“…Among many measurements performed only one of them, namely the tt forward-backward (FB) asymmetry (see [1] for a recent review), showed a significant disagreement with respect to the Standard Model (SM) predictions [2][3][4][5][6]. This asymmetry can be defined as with ∆y = y t − yt the difference between the rapidities of the top quark and antiquark in the laboratory frame.…”

Section: Introductionmentioning

confidence: 99%

Portrait of a colour octet

Aguilar-Saavedra

2014

J. High Energ. Phys.

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New colour octets stand out among the new physics proposals to explain the anomalous forward-backward asymmetry measured in tt production by the CDF experiment at the Tevatron. We perform a fit to tt observables at the Tevatron and the LHC, including total cross sections, various asymmetries and the top polarisation and spin correlations, to find the most likely parameters of a light colour octet to be consistent with data. In particular, an octet coupling only to right-handed quarks gives a good fit to all measurements. The implications from the general fit are drawn in terms of predictions for top polarisation observables whose measurements are yet not very precise, and observables which simply have not been measured.

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“…A comprehensive review of asymmetry measurements performed at the Tevatron can be found in Ref. [16].…”

Section: Introductionmentioning

confidence: 99%

Simultaneous measurement of forward-backward asymmetry and top polarization in dilepton final states fromtt¯production at the Tevatron

Abazov¹,

Abbott²,

Acharya³

et al. 2015

Phys. Rev. D

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We present a simultaneous measurement of the forward-backward asymmetry and the top-quark polarization in tt production in dilepton final states using 9.7 fb −1 of proton-antiproton collisions at √ s = 1.96 TeV with the D0 detector. To reconstruct the distributions of kinematic observables we employ a matrix element technique that calculates the likelihood of the possible tt kinematic configurations. After accounting for the presence of background events and for calibration effects, we obtain a forward-backward asymmetry of A tt = (15.0 ± 6.4 (stat) ± 4.9 (syst))% and a top-quark polarization times spin analyzing power in the beam basis of κP = (7.2 ± 10.5 (stat) ± 4.2 (syst))%, with a correlation of −56% between the measurements. If we constrain the forward-backward asymmetry to its expected standard model value, we obtain a measurement of the top polarization of κP = (11.3±9.1 (stat)±1.9 (syst))%. If we constrain the top polarization to its expected standard model value, we measure a forward-backward asymmetry of A tt = (17.5 ± 5.6 (stat) ± 3.1 (syst))%. A combination with the D0 A tt measurement in the lepton+jets final state yields an asymmetry of A tt = (11.8 ± 2.5 (stat) ± 1.3 (syst))%. Within their respective uncertainties, all these results are consistent with the standard model expectations.

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Asymmetries in top quark pair production at hadron colliders

Cited by 58 publications

References 147 publications

Single lepton charge asymmetries in $$t {\bar{t}}$$ t t ¯ and

Single lepton charge asymmetries in $$t {\bar{t}}$$ t t ¯ and

Portrait of a colour octet

Simultaneous measurement of forward-backward asymmetry and top polarization in dilepton final states fromtt¯production at the Tevatron

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