Edge charge asymmetry in top pair production at the LHC

Xiao, Bo-Wen; Wang, You-Kai; Zhou, Zhihuan; Zhu, Shou-hua

doi:10.1103/physrevd.83.057503

Cited by 24 publications

(17 citation statements)

References 67 publications

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“…Here, this notation refers to the computation of the numerators of the asymmetries to order 3 s in the QCD coupling including the mixed QCD-QED and mixed QCD-weak interaction corrections. For some of these observables, respective results were recently obtained in the literature [11,[16][17][18] with which we compare; some of our results are new. So far, most of the predictions were made at the t " t production level, while the experimental measurements of the charge asymmetries at the ''reconstruction level'' were unfolded, i.e., corrected for detector acceptance and resolution, to obtain the corresponding t " t ''production level'' asymmetries.…”

Section: Introductionmentioning

confidence: 62%

“…frame is highly boosted along the beam axis with respect to the laboratory frame, or to put a cut on the transverse momentum of the t " t system. These observations have led to a number of suggestions for LHC observables [4,6,13,[15][16][17][18][19][20][21][22][23] that exhibit small, but nonzero SM-induced charge asymmetries and are useful in discriminating between various new physics models which were proposed to explain the Tevatron asymmetry. In the following analysis of various LHC charge asymmetries, we have taken into account in the computation of the respective numerators the Oð 3 s Þ QCD and the Oð 2 Þ and Oð 2 s Þ electroweak contributions as outlined in Sec.…”

Section: B Lhcmentioning

confidence: 99%

“…Choosing a cut y c on the rapidities of the t and " t quarks, one may define central and edge (or forward) charge asymmetries A C , A E [6,18,19]:…”

Section: Central and Edge Charge Asymmetrymentioning

confidence: 99%

“…[6,[16][17][18][19][20][21][22][23], that enhance the (predominantly QCD induced) effect and serve to discriminate between the SM and various new physics models. 1 In this paper we compute some of these asymmetries at next-to-leading order (NLO) in the SM gauge couplings.…”

Section: Introductionmentioning

confidence: 99%

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Top quark and leptonic charge asymmetries for the Tevatron and LHC

2012

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We compute, for $t \bar t$ production at the LHC and at the Tevatron, several charge asymmetries to NLO QCD, including also the electromagnetic and weak-interaction corrections. We calculate these asymmetries both inclusively and with additional kinematic cuts and compare our results, where possible, with recent experimental results and with SM predictions. The $t \bar t$ asymmetries induce also corresponding asymmetries for the charged leptons from semileptonic top-quark decay. Although these asymmetries are, in the SM, smaller than the corresponding ones for top quarks, they are expected to be measurable quite precisely. In fact, measurement of a lepton asymmetry in $\ell$ + jets events was reported by the D$\emptyset$ and CDF experiments. We analyze and compute to NLO in the gauge couplings leptonic charge asymmetries for dileptonic and semileptonic $\ttbar$ events, with and without acceptance cuts, at the Tevatron and the LHC.Comment: Some references and a note added on comparisons with recent experimental results. Published in Phys. Rev. D 86, 034026 (2012

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Section: Introductionmentioning

confidence: 62%

Section: B Lhcmentioning

confidence: 99%

“…Choosing a cut y c on the rapidities of the t and " t quarks, one may define central and edge (or forward) charge asymmetries A C , A E [6,18,19]:…”

Section: Central and Edge Charge Asymmetrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Top quark and leptonic charge asymmetries for the Tevatron and LHC

2012

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“…This obstacle can be overcome by observing that the valence quarks (u or d quarks) are statistically more energetic than the sea quarks (ū ord quarks). So, event by event one can still define the forward direction, making it posstible to measure the forward-backward asymmetry [23,24] (see [25][26][27][28][29] for studies for the LHC).…”

Section: Introductionmentioning

confidence: 99%

Improving the top quark forward-backward asymmetry measurement at the LHC

Bai

Han

2012

J. High Energ. Phys.

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At the LHC, top quark pairs are dominantly produced from gluons, making it difficult to measure the top quark forward-backward asymmetry. To improve the asymmetry measurement, we study variables that can distinguish between top quarks produced from gluons and those from quarks: the invariant mass of the top pair, the rapity of the top-antitop system in the lab frame, the rapity of the top quark in the top quark polarization and the top-antitop spin correlation. We combine all the variables in a likelihood discriminant method to separate gluon-initiated events from quark-initiated events. We apply our method on models including G-prime's and W-prime's motivated by the recent observation of a large top quark forward-backward asymmetry at the Tevatron. We have found that the significance of the asymmetry measurement can be enhanced by 10% to 30%. At the same time, the central values of the asymmetry increase by 40% to 100%. We have also obtained the best spin quantization axes for studying top quark polarization as well as spin-correlation for the new physics models.

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Discriminating top-antitop resonances using azimuthal decay correlations

Baumgart

Tweedie

2011

J. High Energ. Phys.

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Top-antitop pairs produced in the decay of a new heavy resonance will exhibit spin correlations that contain valuable coupling information. When the tops decay, these correlations imprint themselves on the angular patterns of the final quarks and leptons. While many approaches to the measurement of top spin correlations are known, the most common ones require detailed kinematic reconstructions and are insensitive to some important spin interference effects. In particular, spin-1 resonances with mostly-vector or mostly-axial couplings to top cannot be easily discriminated from one another without appealing to mass-suppressed effects or to more model-dependent interference with continuum Standard Model production. Here, we propose to probe the structure of a resonance's couplings to tops by measuring the azimuthal angles of the tops' decay products about the production axis. These angles exhibit modulations which are typically O(0.1-1), and which by themselves allow for discrimination of spin-0 from higher spins, measurement of the CP-phase for spin-0, and measurement of the vector/axial composition for spins 1 and 2. For relativistic tops, the azimuthal decay angles can be well-approximated without detailed knowledge of the tops' velocities, and appear to be robust against imperfect energy measurements and neutrino reconstructions. We illustrate this point in the highly challenging dileptonic decay mode, which also exhibits the largest modulations. We comment on the relevance of these observables for testing axigluon-like models that explain the top quark A F B anomaly at the Tevatron, through direct production at the LHC.

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Edge charge asymmetry in top pair production at the LHC

Cited by 24 publications

References 67 publications

Top quark and leptonic charge asymmetries for the Tevatron and LHC

Top quark and leptonic charge asymmetries for the Tevatron and LHC

Improving the top quark forward-backward asymmetry measurement at the LHC

Discriminating top-antitop resonances using azimuthal decay correlations

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