A new twist on top quark spin correlations

Baumgart, Matthew; Tweedie, Brock

doi:10.1007/jhep03(2013)117

Cited by 37 publications

(63 citation statements)

References 54 publications

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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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Is there room forCPviolation in the top-Higgs sector?

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“…These operators involve at least one third-generation quark (from the O γ,g,W t,W b vertex). While there are no strong phenomenological handles on these four-fermion operators 2 , the semileptonic and four-quark operators Q (3) lequ and Q (1), (8) quqd mix back into the lepton and quark dipoles, respectively 3 . Thus, Q (3) lequ and Q (1), (8) quqd feed into the electron, mercury, and neutron EDMs, and we therefore include them in our extended basis.…”

Section: Mixing Structurementioning

confidence: 99%

“…quqd , C (8) quqd ) T , which in turn contribute to C EDM . Including the selfrenormalization of the operators in Eq.…”

Section: Rg Equations For Edmsmentioning

confidence: 99%

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Constraining the top-Higgs sector of the standard model effective field theory

et al. 2016

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Working in the framework of the Standard Model Effective Field Theory, we study chirality-flipping couplings of the top quark to Higgs and gauge bosons. We discuss in detail the renormalization group evolution to lower energies and investigate direct and indirect contributions to high-and low-energy CP-conserving and CP-violating observables. Our analysis includes constraints from collider observables, precision electroweak tests, flavor physics, and electric dipole moments. We find that indirect probes are competitive or dominant for both CP-even and CP-odd observables, even after accounting for uncertainties associated with hadronic and nuclear matrix elements, illustrating the importance of including operator mixing in constraining the Standard Model Effective Field Theory. We also study scenarios where multiple anomalous top couplings are generated at the high scale, showing that while the bounds on individual couplings relax, strong correlations among couplings survive. Finally, we find that enforcing minimal flavor violation does not significantly affect the bounds on the top couplings.

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“…This idea has been discussed in different scenarios for axigluons with masses in the range of 50 − 1000 GeV [45][46][47][48][49], and usually with a large axigluon decay width to prevent strong bounds from measurements of tt invariant mass spectra. Extensive studies of the phenomenology of light axigluons have been performed, including [50][51][52][53][54][55][56][57][58][59]. In particular, in ref.…”

Section: Jhep09(2014)084mentioning

confidence: 99%

Top quark charge asymmetry: searching for light axigluons in t t ¯ $$ t\overline{t} $$ + jet production at the LHC

Alte

Berge

Spiesberger

2014

J. High Energ. Phys.

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Abstract:We investigate the discovery potential of light color-octet bosons in the mass range of 100-400 GeV in exclusive top-pair plus jet production at the LHC, pp → tt + jet. We study the impact of such bosons on the incline, the energy and the rapidity asymmetries. We show that light axigluons with large couplings to quarks can be discovered at the LHC with a luminosity of a few fb −1 . Almost all of the considered axigluon parameter space can be probed using the already available 2011/2012 LHC data. In a small-coupling scenario, axigluons could be discovered using the charge asymmetry with 65 fb −1 at the LHC and a center of mass energy of 14 TeV. We furthermore show that tt + jet production could reveal the existence of scenarios where axigluons couple with a different strength to upand down-type quarks.

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A new twist on top quark spin correlations

Cited by 37 publications

References 54 publications

Is there room forCPviolation in the top-Higgs sector?

Is there room forCPviolation in the top-Higgs sector?

Constraining the top-Higgs sector of the standard model effective field theory

Top quark charge asymmetry: searching for light axigluons in t t ¯ $$ t\overline{t} $$ + jet production at the LHC

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