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We discuss theoretical and phenomenological aspects of two-Higgs-doublet extensions of the Standard Model. In general, these extensions have scalar mediated flavour changing neutral currents which are strongly constrained by experiment. Various strategies are discussed to control these flavour changing scalar currents and their phenomenological consequences are analysed. In particular, scenarios with natural flavour conservation are investigated, including the so-called type I and type * E-mail: gbranco@ist.utl.pt † E-mail: ferreira@cii.fc.ul.pt ‡ E-mail: balio@cftp.ist.utl.pt § E-mail: rebelo@ist.utl.pt ¶ E-mail: mtsher@wm.edu E-mail: jpsilva@cftp.ist.utl.pt 1 II models as well as lepton-specific and inert models. Type III models are then discussed, where scalar flavour changing neutral currents are present at tree level, but are suppressed by either specific ansatze for the Yukawa couplings or by the introduction of family symmetries leading to a natural suppression mechanism. We also consider the phenomenology of charged scalars in these models. Next we turn to the role of symmetries in the scalar sector. We discuss the six symmetry-constrained scalar potentials and their extension into the fermion sector. The vacuum structure of the scalar potential is analysed, including a study of the vacuum stability conditions on the potential and the renormalization-group improvement of these conditions is also presented. The stability of the tree level minimum of the scalar potential in connection with electric charge conservation and its behaviour under CP is analysed. The question of CP violation is addressed in detail, including the cases of explicit CP violation and spontaneous CP violation. We present a detailed study of weak basis invariants which are odd under CP. These invariants allow for the possibility of studying the CP properties of any two-Higgs-doublet model in an arbitrary Higgs basis. A careful study of spontaneous CP violation is presented, including an analysis of the conditions which have to be satisfied in order for a vacuum to violate CP. We present minimal models of CP violation where the vacuum phase is sufficient to generate a complex CKM matrix, which is at present a requirement for any realistic model of spontaneous CP violation.

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“…the vev of H 2 being zero and the vev of H 1 being real and positive, remain satisfied. The rotation (221) implies…”

Section: A Minimal Realistic Model With Spontaneous Cp Violationmentioning

confidence: 99%

“…Direct bounds on λ tc can be obtained from t → ch, which was first discussed by Hou [209] and much more recently in Refs. [219,220,221]. For a Higgs mass of 120 GeV, the branching ratio is roughly 0.005 λ 2 ct .…”

mentioning

confidence: 97%

Theory and phenomenology of two-Higgs-doublet models

et al. 2012

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“…Studies on the top quark FCNC in collider physics especially through anomalous top quark decays were performed in refs. [18][19][20][21][22]. There have been studies on the issue that large top quark FCNC coupling λ ct is needed [23,24] to explain the measurements of B(B d → D ( * ) τ ν) at BaBar [25], which were quite larger than the SM expectations.…”

Section: Jhep12(2015)038mentioning

confidence: 66%

Exploring top quark FCNC within 2HDM type III in association with flavor physics

Kim

Yoon

Yuan

2015

J. High Energ. Phys.

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Abstract:The top quark flavor changing neutral current (FCNC) process is an excellent probe to search for new physics in top sector since the Standard Model expectation is extremely suppressed. We explore Higgs-mediated top quark FCNC, focusing on H-tc Yukawa coupling λ ct within the general two Higgs doublet model. After electroweak symmetry breaking the top quark FCNC couplings are included in the charged Higgs Yukawa sector so that they contribute to various processes in flavor physics. To probe λ ct , we study anomalous single top production and the same sign top pair production at the LHC in association with flavor physics from the tree-level processes B → D ( * ) τ ν, B → τ ν as well as from the loop-level processes B d → X s γ, B d,s − B d,s mixing. We perform combined analysis of all the constraints regarding the fine-tuning argument to fit the data and discuss future prospect. The recently updated measurements on B → D ( * ) τ ν still prefer large λ ct , but we show that the current bound on the same sign top pair production at the LHC gives the most significant upper bound on λ ct to be less than 10 ∼ 30 depending on neutral heavy Higgs masses. We also find that for the given upper bound on λ ct , B → D ( * ) τ ν put significant lower bound on H-τ -τ Yukawa coupling, and the bound is proportional to the charged Higgs mass.

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“…Therefore an affirmative observation of the process t → qH, well above the SM rate, will be a conclusive indication of new physics beyond the SM. The probing of FCNC couplings in the quark sector, can be performed either at a high energy collider or indirect limits can be obtained from neutral meson oscillations (K 0 −K 0 , B 0 −B 0 and D 0 −D 0 ) [4][5][6]. The tqH coupling also affects the Z → cc decay at the loop level and is therefore constrained by the electroweak precision observables of the Z boson [7].…”

Section: Jhep01(2017)048mentioning

confidence: 99%

Exploring the top-Higgs FCNC couplings at polarized linear colliders with top spin observables

Melić¹,

Patra²

2017

J. High Energ. Phys.

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Abstract:We study the nature of flavor changing neutral couplings of the top quark with the Higgs boson and the up/charm quark in the tt production at linear colliders. There are previous bounds on such tqH couplings at both, linear and hadronic colliders, with the assumption that the top couples equally to the left and the right handed fermions. In this paper we examine chirality of the tqH coupling and construct different observables which will be sensitive to it. The kinematics of the emitted q from t → qH in tt production is discussed and it was found that the polar angle distribution of q is sensitive to the chiral nature of tqH couplings. The observables in the context of top-antitop spin correlations, which are sensitive to new physics in the top decay are considered using different spinquantization bases. It was found that in particular the off-diagonal basis can be useful to distinguish among the chiral tqH couplings. The sensitivity of the unpolarized ILC in probing the couplings at the 3σ level at √ s = 500 GeV and L = 500 fb −1 is also studied, resulting in predicted BR(t → qH) < 1.19 × 10 −3 . This limit is further improved to BR(t → qH) < 8.84 × 10 −4 with the inclusion of initial beam polarization of left handed electrons and right handed positrons.

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Higgs mediated flavor violating top quark decayst→uiH,uiγ,u

Cited by 24 publications

References 56 publications

Theory and phenomenology of two-Higgs-doublet models

Theory and phenomenology of two-Higgs-doublet models

Exploring top quark FCNC within 2HDM type III in association with flavor physics

Exploring the top-Higgs FCNC couplings at polarized linear colliders with top spin observables

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