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

Bai, Y.; Han, Zhenyu

doi:10.1007/jhep02(2012)135

Cited by 15 publications

(16 citation statements)

References 82 publications

(102 reference statements)

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“…The inquiry to induce asymmetries at the LHC has begun since the conception of a symmetric machine [5,8] and has taken special force with the first measurements in the last years [9][10][11][12][13][14][15]. Most of the proposed induced asymmetries consist of a cut to enhance the quark-fusion fraction in the sample and an algorithm to attempt to recognize which proton put the quark, if is it the case that was quark fusion.…”

Section: Analysis Of Selecting Events Using T T Transverse Momentummentioning

confidence: 98%

“…However, as it has been studied in the last years [5,[8][9][10][11][12][13][14][15], it is possible to induce an asymmetry by setting an algorithm which indicates when an event should add to N þ and when to N À (see below). Usually, this algorithm is a function of the top and anti-top kinematic variables in each event.…”

Section: Significance Of An Induced Asymmetry At the Lhcmentioning

confidence: 98%

“…Moreover, some of the works have also proposed and explored new ideas to enhance the asymmetry, as for instance [13,14] using top polarization, spin correlation and relative rapidity and [9] using the transverse momentum of the t " t pair, which is the variable we study in the following paragraphs.…”

Section: Analysis Of Selecting Events Using T T Transverse Momentummentioning

confidence: 99%

“…However, although there is no preferred forward direction at the LHC, it is possible to induce an asymmetry by defining a forward direction event by event. This possibility has been studied since the 1990s [5,8] and it has been further explored in many different ways [9][10][11][12][13][14][15]. We use induced asymmetries to refer in general to all the different asymmetries defined in these works.…”

Section: Introductionmentioning

confidence: 98%

“…t " t, in many of the works which induce an asymmetry they attempt to isolate quark-fusion events over gluon-fusion events to enhance the asymmetry. In most of the cases [9][10][11][12][13][14][15] this enhancement is again sought by aiming at the fact that a valence quark is likely to carry more momentum than other partons. In some of these works they also use polarization, spin correlation, and relative rapidity of the tops [13,14] and the t " t transverse momentum, p T ðt " tÞ [9].…”

Section: Introductionmentioning

confidence: 99%

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Improving top quark induced charge asymmetries at the LHC usingtt¯transverse momentum

Álvarez

2012

Phys. Rev. D

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We study how the significance of top quark induced charge asymmetries at the LHC may be enhanced exploiting the t " t total transverse momentum to enrich the fraction of quark-fusion events in the sample. We combine this variable with previous variables related to the boost and the invariant mass of the t " t pair to find an optimum cut which maximizes the significance of the asymmetry when systematic and statistic errors are taken into account. We find that including the t " t transverse momentum in the analysis of the expected 2012 LHC data provides a considerable enhancement in the significance of the asymmetry.

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Section: Analysis Of Selecting Events Using T T Transverse Momentummentioning

confidence: 98%

Section: Significance Of An Induced Asymmetry At the Lhcmentioning

confidence: 98%

Section: Analysis Of Selecting Events Using T T Transverse Momentummentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Improving top quark induced charge asymmetries at the LHC usingtt¯transverse momentum

Álvarez

2012

Phys. Rev. D

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A new twist on top quark spin correlations

Baumgart

Tweedie

2013

J. High Energ. Phys.

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Top-antitop pairs produced at hadron colliders are largely unpolarized, but their spins are highly correlated. The structure of these correlations varies significantly over top production phase space, allowing very detailed tests of the Standard Model. Here, we explore top quark spin correlation measurement from a general perspective, highlighting the role of azimuthal decay angles. By taking differences and sums of these angles about the top-antitop production axis, the presence of spin correlations can be seen as sinusoidal modulations resulting from the interference of different helicity channels. At the LHC, these modulations exhibit nontrivial evolution from near-threshold production into the boosted regime, where they become sensitive to almost the entire QCD correlation effect for centrally produced tops. We demonstrate that this form of spin correlation measurement is very robust under full kinematic reconstruction, and should already be observable with high significance using the current LHC data set. We also illustrate some novel ways that new physics can alter the azimuthal distributions. In particular, we estimate the power of our proposed measurements in probing for anomalous color-dipole operators, as well as for broad resonances with parityviolating couplings. Using these methods, the 2012 run of the LHC may be capable of setting simultaneous limits on the top quark's anomalous chromomagnetic and chromoelectric dipole moments at the level of 3 × 10 −18 cm (0.03/m t ).

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Han

Katz

Krohn

et al. 2012

J. High Energ. Phys.

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Stop squarks with a mass just above the top's and which decay to a nearly massless LSP are difficult to probe because of the large SM di-top background. Here we discuss search strategies which could be used to set more stringent bounds in this difficult region. In particular, we note that both the rapidity difference ∆y(t,t) and spin correlations (inferred from, for example, ∆φ( + , − )) are sensitive to the presence of stops. We emphasize that systematic uncertainties in top quark production can confound analyses looking for stops, making theoretical and experimental progress on the understanding of Standard Model top production at high precision a very important task. We estimate that spin correlation alone, which is relatively robust against such systematic uncertainties, can exclude a 200 GeV stop at 95% confidence with 20 fb −1 at the 8 TeV LHC.

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

Cited by 15 publications

References 82 publications

Improving top quark induced charge asymmetries at the LHC usingtt¯transverse momentum

Improving top quark induced charge asymmetries at the LHC usingtt¯transverse momentum

A new twist on top quark spin correlations

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