A set of top quark spin correlation and polarization observables for the LHC: Standard Model predictions and new physics contributions

Bernreuther, W.; Heisler, Dennis; Si, Zong-Guo

doi:10.1007/jhep12(2015)026

Cited by 78 publications

(164 citation statements)

References 114 publications

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“…(Since SM predictions are not available for the single lepton asymmetries, for consistency we always present our results in terms of the new physics contributions.) We collect the SM predictions [8,16,45,46] and experimental measurements used in Table 1. It has been shown [47] that the Tevatron tt asymmetry A FB , the lepton asymmetries A FB , A FB , and the top polarisation, are in general independent observables.…”

Section: Predictions For Ttmentioning

confidence: 99%

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: Predictions For Ttmentioning

confidence: 99%

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

Aguilar-Saavedra

2018

Eur. Phys. J. C

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“…Each of the 15 observables is sensitive to a different coefficient of the top quark pair's spin density matrix, probing different symmetries in the production mechanism [19]. Ten of these observables have not been measured until now.…”

Section: Jhep03(2017)113mentioning

confidence: 99%

Measurements of top quark spin observables in t t ¯ $$ t\overline{t} $$ events using dilepton final states in s = 8 $$ \sqrt{s}=8 $$ TeV pp collisions with the ATLAS detector

Aaboud¹,

Aad²,

Abbott³

et al. 2017

J. High Energ. Phys.

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Measurements of top quark spin observables in tt events are presented based on 20.2 fb −1 of √ s = 8 TeV proton-proton collisions recorded with the ATLAS detector at the LHC. The analysis is performed in the dilepton final state, characterised by the presence of two isolated leptons (electrons or muons). There are 15 observables, each sensitive to a different coefficient of the spin density matrix of tt production, which are measured independently. Ten of these observables are measured for the first time. All of them are corrected for detector resolution and acceptance effects back to the parton and stable-particle levels.The measured values of the observables at parton level are compared to Standard Model predictions at next-to-leading order in QCD. The corrected distributions at stable-particle level are presented and the means of the distributions are compared to Monte Carlo predictions. No significant deviation from the Standard Model is observed for any observable.

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“…Despite the vast literature on top-gluon [5][6][7][8][9][10][11][12][13][14][15][16], top-photon [17][18][19][20][21], top-W [22][23][24][25][26][27][28], top Yukawa [29][30][31][32][33][34][35][36] couplings, and global analyses [37][38][39][40][41][42], the impact of electric dipole moments (EDMs) has received comparatively little attention [17,29,37,43,44]. The central new element of our work is the systematic inclusion of EDM constraints.…”

mentioning

confidence: 99%

Is there room forCPviolation in the top-Higgs sector?

et al. 2016

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We discuss direct and indirect probes of chirality-flipping couplings of the top quark to Higgs and gauge bosons, considering both CP-conserving and CP-violating observables, in the framework of the Standard Model effective field theory. In our analysis we include current and prospective constraints from collider physics, precision electroweak tests, flavor physics, and electric dipole moments (EDMs). We find that low-energy indirect probes are very competitive, even after accounting for long-distance uncertainties. In particular, EDMs put constraints on the electroweak CP-violating dipole moments of the top that are two to three orders of magnitude stronger than existing limits. The new indirect constraint on the top EDM is given by |dt| < 5 · 10−20 e cm at 90% C.L. Introduction:The top quark might offer a first gateway to physics beyond the Standard Model (BSM), due to its large coupling to the Higgs and hence to the electroweak symmetry breaking sector. In several scenarios, ranging from partial compositeness [1] to supersymmetric models with light stops [2], enhanced deviations from the SM are expected in the top sector which can be relevant for electroweak baryogenesis [2,3]. Experiments at the Large Hadron Collider (LHC) offer a great opportunity to directly probe non-standard top quark couplings. On the other hand, these same couplings also affect via quantum corrections processes that do not involve a top quark. Such "indirect probes" give very valuable complementary information and in several cases constrain non-standard top couplings more strongly than direct searches.In this letter we discuss direct and indirect probes of chirality-flipping top-Higgs couplings, including both CP-conserving (CPC) and CP-violating (CPV) interactions, the latter being of great interest in light of Sakharov's conditions for baryogenesis [4]. Despite the vast literature on top-gluon [5][6][7][8][9][10][11][12][13][14][15][16] [37][38][39][40][41][42], the impact of electric dipole moments (EDMs) has received comparatively little attention [17,29,37,43,44]. The central new element of our work is the systematic inclusion of EDM constraints. Even after properly taking into account the hadronic and nuclear uncertainties [44], EDMs dominate the bounds on all the CPV top couplings. Our major finding is that bounds on the top EDM (weak EDM) are improved by three (two) orders of magnitude over the previous literature. As part of our analysis, we also update indirect constraints from Higgs production and decay.We work in the linear SM Effective Field Theory (SM-EFT) framework [45][46][47][48][49]. We assume that a gap exists between the scale of new physics Λ and the electroweak scale v = 246 GeV and keep only the leading terms in (v/Λ) 2 , corresponding to dimension-six operators. We assume that at the high-scale Λ the largest non-standard effects appear in the top sector, and hence set to zero all

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A set of top quark spin correlation and polarization observables for the LHC: Standard Model predictions and new physics contributions

Cited by 78 publications

References 114 publications

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

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

Measurements of top quark spin observables in t t ¯ $$ t\overline{t} $$ events using dilepton final states in s = 8 $$ \sqrt{s}=8 $$ TeV pp collisions with the ATLAS detector

Is there room forCPviolation in the top-Higgs sector?

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