Maximizing spin correlations in top quark pair production at the Tevatron

Mahlon, Gregory; Parke, Stephen J.

doi:10.1016/s0370-2693(97)00987-8

Cited by 168 publications

(168 citation statements)

References 17 publications

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“…A spin-quantization axis was constructed in [24,10] with respect to which the t andt spins are 100% correlated to leading order in the QCD coupling, for all energies and scattering angles. In terms of the structure functions of (6) this means that the 'optimal' spin axisd fulfills the condition…”

Section: Pacs Number(s)mentioning

confidence: 99%

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Next-to-leading order QCD corrections to top quark spin correlations at hadron colliders: the reactions

Bernreuther

Brandenburg²,

2000

Physics Letters B

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Abstract:Future hadron collider experiments are expected to record large to huge samples of tt events. The analysis of these data with respect to tt spin-spin correlations requires precise predictions of the production of these quark pairs in a general spin configuration. Therefore we have computed, at next-to-leading order (NLO) in the QCD coupling, the spin density matrices describing tt production by quark antiquark annihilation, which is the dominant production process at the Tevatron. Moreover we have computed the strength of the tt spin correlation at NLO, using various spin quantization axes. Pairs of top and antitop quarks will be produced copiously with the upgraded Fermilab Tevatron collider and in even larger numbers with the Large Hadron Collider (LHC) at CERN, allowing for detailed investigations of the properties of these quarks in the future. For this aim the study of top spin phenomena will play an important role. This is because the top quark, as compared with lighter quarks, is unique in that it is sufficiently short-lived to prevent hadronization effects from diluting the spin-polarisations and spin-spin correlations that were imprinted upon the t andt quarks by their production mechanism. Hence spin-polarization and spin-correlation phenomena will provide valuable information about the interactions of top quarks. An attempt to detect these spin correlations in a small tt dilepton sample collected at the Tevatron was recently reported by the D0 collaboration [1]. Needless to say, in order to interpret future data, the predictions of these spin phenomena should be as precise as possible. Within the Standard Model (SM) top antitop pair production at hadron colliders is determined by QCD. So far the nextto-leading order (NLO) QCD corrections are known for the spin-averaged differential tt cross section [2,3,4,5], while spin correlations were analysed only to leadingorder [6,7,8,9,10,11] in α s . In this letter we report on progress in providing a complete description of these spin effects within QCD at NLO: We have computed, as a first step in this direction, the tt spin density matrices for the parton reactions qq → tt, ttg to order α 3 s . We have also calculated, for these reactions, the degree of the tt spin correlation at NLO for different t andt spin quantization axes. PACS number(s):At the Tevatron qq annihilation is the dominant process for producing top quark pairs while at the LHC tt production is mainly due to gluon gluon fusion. The tt spin correlations and spin polarisations can be inferred from appropriate angular correlations and distributions of the t andt decay products. In the SM the main top decay modes are t → bW → bqq ′ , bℓν ℓ . Among these final states the charged leptons, or the jets from quarks of weak isospin -1/2 originating from W decay, are most sensitive to the polarisation of the top quarks. Hence to leading order in the QCD coupling one has to treat the two parton reactionswhere f = q, ℓ, ν ℓ . The amplitudes for these two-to six-body processes, with intermediate t...

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Section: Pacs Number(s)mentioning

confidence: 99%

“…(14) is a special property of the leading order spin density matrix for the reaction qq → tt. One finds [24,10]:4 where γ 1 = E 1 /m t . The construction of this axis explicitly uses the leading order result for the spin density matrix, and different generalizations to higher orders are possible.…”

mentioning

confidence: 99%

Next-to-leading order QCD corrections to top quark spin correlations at hadron colliders: the reactions

Bernreuther

Brandenburg²,

2000

Physics Letters B

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“…In the SM, tt pairs are produced essentially unpolarized at hadron colliders [3], as has been tested in recent measurements by the D0 Collaboration [4] and the ATLAS and CMS Collaborations [5,6]. Nonetheless, the correlation of the spin orientation of the top quark and the top antiquark can be studied, and is predicted to be nonzero [3,[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Measurements of spin correlation in top-antitop quark events from proton-proton collisions ats=7 TeVusing the ATLAS detector

Aad¹,

Abbott²,

Abdallah³

et al. 2014

Phys. Rev. D

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Measurements of spin correlation in top quark pair production are presented using data collected with the ATLAS detector at the LHC with proton-proton collisions at a center-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 4.6 fb −1 . Events are selected in final states with two charged leptons and at least two jets and in final states with one charged lepton and at least four jets. Four different observables sensitive to different properties of the top quark pair production mechanism are used to extract the correlation between the top and antitop quark spins. Some of these observables are measured for the first time. The measurements are in good agreement with the Standard Model prediction at next-to-leadingorder accuracy.

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“…[23,24] for the process qq → tt → bℓ + ν ℓ bℓ ′− ν ℓ ′ [25]. The term 1/N is defined such that the probability density satisfies the normalization condition, dx P s (x|M t ) = 1.…”

mentioning

confidence: 99%

Precision measurement of the top-quark mass from dilepton events at CDF II

Abulencia¹,

Adelman²,

Affolder³

et al. 2007

Phys. Rev. D

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We report a measurement of the top-quark mass, Mt, in the dilepton decay channel of tt→bℓ'+νℓ′b¯ℓ−ν¯ℓ using an integrated luminosity of 1.0 fb−1 of pp collisions collected with the CDF II detector. We apply a method that convolutes a leading-order matrix element with detector resolution functions to form event-by-event likelihoods; we have enhanced the leading-order description to describe the effects of initial-state radiation. The joint likelihood is the product of the likelihoods from 78 candidate events in this sample, which yields a measurement of Mt=164.5±3.9(stat.)±3.9(syst.) GeV/c2, the most precise measurement of Mt in the dilepton channel

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Maximizing spin correlations in top quark pair production at the Tevatron

Cited by 168 publications

References 17 publications

Next-to-leading order QCD corrections to top quark spin correlations at hadron colliders: the reactions

Next-to-leading order QCD corrections to top quark spin correlations at hadron colliders: the reactions

Measurements of spin correlation in top-antitop quark events from proton-proton collisions ats=7 TeVusing the ATLAS detector

Precision measurement of the top-quark mass from dilepton events at CDF II

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