Probing top-Z dipole moments at the LHC and ILC

Röntsch, Raoul; Schulze, Markus

doi:10.1007/jhep08(2015)044

Cited by 76 publications

(99 citation statements)

References 46 publications

(70 reference statements)

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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.…”

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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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confidence: 99%

Is there room forCPviolation in the top-Higgs sector?

et al. 2016

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“…The computation of NLO QCD corrections to top-quark processes involving anomalous couplings or higher-dimension operators has evolved in recent years [5,6,[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]. In particular automated calculations within MG5 aMC have been performed in [5,6,43,46,47], and…”

Section: Jhep10(2017)096mentioning

confidence: 99%

“…Such a calculation is an interesting one in itself: unlike the previous NLO EFT calculations in refs. [5,6,[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47], in this work the EFT is used in a top-down way, by starting from explicit BSM models, performing matching calculations at the same accuracy, employing RG equations down to the scale of the problem, and physical results are obtained by carrying out an NLO calculation there.…”

Section: Jhep10(2017)096mentioning

confidence: 99%

Scalar production and decay to top quarks including interference effects at NLO in QCD in an EFT approach

Franzosi

Vryonidou

Zhang

2017

J. High Energ. Phys.

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Scalar and pseudo-scalar resonances decaying to top quarks are common predictions in several scenarios beyond the standard model (SM) and are extensively searched for by LHC experiments. Challenges on the experimental side require optimising the strategy based on accurate predictions. Firstly, QCD corrections are known to be large both for the SM QCD background and for the pure signal scalar production. Secondly, leading order and approximate next-to-leading order (NLO) calculations indicate that the interference between signal and background is large and drastically changes the lineshape of the signal, from a simple peak to a peak-dip structure. Therefore, a robust prediction of this interference at NLO accuracy in QCD is necessary to ensure that higher-order corrections do not alter the lineshapes. We compute the exact NLO corrections, assuming a point-like coupling between the scalar and the gluons and consistently embedding the calculation in an effective field theory within an automated framework, and present results for a representative set of beyond the SM benchmarks. The results can be further matched to parton shower simulation, providing more realistic predictions. We find that NLO corrections are important and lead to a significant reduction of the uncertainties. We also discuss how our computation can be used to improve the predictions for physics scenarios where the gluon-scalar loop is resolved and the effective approach is less applicable.

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“…Fortunately, there is a simple way to solve the γ 5 problem in our case. Indeed, in the calculation of virtual corrections to the tW b weak vertex, γ 5 is taken to be anti-commuting [40][41][42][43]. This enforces the lefthanded polarization of the b-quark and removes the issue of γ 5 altogether.…”

Section: Pos(leptonphoton2015)026mentioning

confidence: 99%

“…Just to illustrate potential gains that one gets by extending the EFT analysis to NLO QCD, consider the case of ttZ anomalous couplings studied in Refs. [33,40]. Bounds on the weak anomalous magnetic moment defined as L ttZ = eC Z 2,Vū (p t ) iσ µν q ν M Z v(pt)Z µ are shown in Fig.…”

Section: Backgroundsmentioning

confidence: 99%