References of "Ivanov, Igor"
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See detailForward Physics of Hadronic Colliders
Ivanov, Igor ULg

in Physics of Particles and Nuclei Letters (2013, December), 10(7), 739750

These lectures were given at the Baikal Summer School on Physics of Elementary Particles and Astrophysics in July 2012. They can be viewed as a concise introduction to hadronic diffraction, to the physics ... [more ▼]

These lectures were given at the Baikal Summer School on Physics of Elementary Particles and Astrophysics in July 2012. They can be viewed as a concise introduction to hadronic diffraction, to the physics of the Pomeron and related topics. [less ▲]

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See detailAbelian symmetries of the N-Higgs-doublet model with Yukawa interactions
Ivanov, Igor ULg; Nishi, Celso

in Journal of High Energy Physics [=JHEP] (2013), 2013(11), 069

We investigate finite abelian groups which can represent symmetries of the N-Higgs-doublet models with quarks. We build a general formalism based on the powerful method of the Smith normal form and obtain ... [more ▼]

We investigate finite abelian groups which can represent symmetries of the N-Higgs-doublet models with quarks. We build a general formalism based on the powerful method of the Smith normal form and obtain an analytic upper bound on the order of abelian symmetry groups for any N. We investigate in detail the case N = 2 and rederive known results in a more compact and intuitive fashion. We also study the NHDM with the maximal finite abelian symmetry for all small N cases up to N = 5, and show that in each case all Yukawa textures compatible with such symmetry originate from a unique basic structure. This work opens the way to a systematic exploration of phenomenology of the NHDM with a desired symmetry, and illustrates the power of the Smith normal form technique. [less ▲]

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See detailPolarization radiation of vortex electrons with large orbital angular momentum
Ivanov, Igor ULg; Karlovets, Dmitry

in Physical Review. A (2013), 88(4), 043840

Vortex electrons—freely propagating electrons whose wave functions have helical wave fronts—could become a novel tool in the physics of electromagnetic radiation. They carry a nonzero intrinsic orbital ... [more ▼]

Vortex electrons—freely propagating electrons whose wave functions have helical wave fronts—could become a novel tool in the physics of electromagnetic radiation. They carry a nonzero intrinsic orbital angular momentum (OAM) ℓ with respect to the propagation axis and, for ℓ≫1, a large OAM-induced magnetic moment μ≈ℓμB (μB is the Bohr magneton), which influences the radiation of electromagnetic waves. Here, we consider in detail the OAM-induced effects caused by such electrons in two forms of polarization radiation, namely, in Cherenkov radiation and transition radiation. Thanks to the large ℓ, we can neglect quantum or spin-induced effects, which are of the order of ℏω/Ee≪1, but retain the magnetic moment contribution ℓℏω/Ee≲1, which makes the quasiclassical approach to polarization radiation applicable. We discuss the magnetic moment contribution to polarization radiation, which has never been experimentally observed, and study how its visibility depends on the kinematical parameters and the medium permittivity. In particular, it is shown that this contribution can, in principle, be detected in azimuthally nonsymmetrical problems, for example when vortex electrons obliquely cross a metallic screen (transition radiation) or move near it (diffraction radiation). We predict a left-right angular asymmetry of the transition radiation (in the plane where the charge radiation distributions would stay symmetric), which appears due to an effective interference between the charge radiation field and the magnetic moment contribution. Numerical values of this asymmetry for vortex electrons with Ee=300 keV and ℓ=100–1000 are 0.1%–1%, and we argue that this effect could be detected with existing technology. The finite conductivity of the target and frequency dispersion play crucial roles in these predictions. [less ▲]

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See detailEvading death by vacuum
Barroso, Augusto; Ferreira, Pedro; Ivanov, Igor ULg et al

in European Physical Journal C -- Particles & Fields (2013), 73

In the Standard Model, the Higgs potential allows only one minimum at tree level. But the open possibility that there might be two scalar doublets enriches the vacuum structure, allowing for the risk that ... [more ▼]

In the Standard Model, the Higgs potential allows only one minimum at tree level. But the open possibility that there might be two scalar doublets enriches the vacuum structure, allowing for the risk that we might now be in a metastable state, which we dub the panic vacuum. Current experiments at the LHC are probing the Higgs particle predicted as a result of the spontaneous symmetry breaking. Remarkably, in the two Higgs model with a softly broken U(1) symmetry, the LHC experiments already allow to exclude many panic vacuum solutions. [less ▲]

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See detailDetecting transition radiation from a magnetic moment
Ivanov, Igor ULg; Karlovets, Dmitry

in Physical Review Letters (2013), 110(26), 2648015

Electromagnetic radiation can be emitted not only by particle charges but also by magnetic moments and higher electric and magnetic multipoles. However, experimental proofs of this fundamental fact are ... [more ▼]

Electromagnetic radiation can be emitted not only by particle charges but also by magnetic moments and higher electric and magnetic multipoles. However, experimental proofs of this fundamental fact are extremely scarce. In particular, the magnetic moment contribution has never been observed in any form of polarization radiation. Here, we propose to detect it using vortex electrons carrying large orbital angular momentum ℓ. The relative contribution of the orbital angular momentum-induced magnetic moment, ℓℏω/Ee, becomes much larger than the spin-induced contribution ℏω/Ee, and it can be observed experimentally. As a particular example, we consider transition radiation from vortex electrons obliquely incident on an interface between a vacuum and a dispersive medium, in which the magnetic moment contribution manifests itself via a left-right angular asymmetry. For electrons with Ee=300  keV and ℓ=100–1000, we predict an asymmetry of the order of 0.1%–1%, which could be measured with existing technology. Thus, vortex electrons emerge as a new tool in the physics of electromagnetic radiation. [less ▲]

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See detailMetastability bounds on the two Higgs doublet model
Barroso, Augusto; Ferreira, Pedro; Ivanov, Igor ULg et al

in Journal of High Energy Physics [=JHEP] (2013), 1306

In the two Higgs doublet model, there is the possibility that the vacuum where the universe resides in is metastable. We present the tree-level bounds on the scalar potential parameters which have to be ... [more ▼]

In the two Higgs doublet model, there is the possibility that the vacuum where the universe resides in is metastable. We present the tree-level bounds on the scalar potential parameters which have to be obeyed to prevent that situation. Analytical expressions for those bounds are shown for the most used potential, that with a softly broken Z 2 symmetry. The impact of those bounds on the model’s phenomenology is discussed in detail, as well as the importance of the current LHC results in determining whether the vacuum we live in is or is not stable. We demonstrate how the vacuum stability bounds can be obtained for the most generic CP-conserving potential, and provide a simple method to implement them. [less ▲]

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See detailGeometrical CP violation in the N-Higgs-doublet model
Ivanov, Igor ULg; Lavoura, Luis

in European Physical Journal C -- Particles & Fields (2013), 73

Geometrical CP violation is a particular type of spontaneous CP violation in which the vacuum expectation values have phases which are calculable, i.e. stable against the variation of the free parameters ... [more ▼]

Geometrical CP violation is a particular type of spontaneous CP violation in which the vacuum expectation values have phases which are calculable, i.e. stable against the variation of the free parameters of the scalar potential. Although originally suggested within a specific version of the three-Higgs-doublet model, it is a generic phenomenon. We investigate its viability and characteristic features in models with several Higgs doublets. Our work contains both general results and illustrative examples. [less ▲]

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See detailClassification of finite reparametrization symmetry groups in the three-Higgs-doublet model
Ivanov, Igor ULg; Vdovin, Evgeny

in European Physical Journal C -- Particles & Fields (2013), 73

Symmetries play a crucial role in electroweak symmetry breaking models with non-minimal Higgs content. Within each class of these models, it is desirable to know which symmetry groups can be implemented ... [more ▼]

Symmetries play a crucial role in electroweak symmetry breaking models with non-minimal Higgs content. Within each class of these models, it is desirable to know which symmetry groups can be implemented via the scalar sector. In N-Higgs-doublet models, this classification problem was solved only for N=2 doublets. Very recently, we suggested a method to classify all realizable finite symmetry groups of Higgs-family transformations in the three-Higgs-doublet model (3HDM). Here, we present this classification in all detail together with an introduction to the theory of solvable groups, which play the key role in our derivation. We also consider generalized-CP symmetries, and discuss the interplay between Higgs-family symmetries and CP-conservation. In particular, we prove that presence of the $Z_4$ symmetry guarantees the explicit CP-conservation of the potential. This work completes classification of finite reparametrization symmetry groups in 3HDM. [less ▲]

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See detailGeometric minimization of highly symmetric potentials
Degée, Audrey ULg; Ivanov, Igor ULg; Keus, Venus ULg

in Journal of High Energy Physics [=JHEP] (2013), 2013

In non-minimal Higgs mechanisms, one often needs to minimize highly symmetric Higgs potentials. Here we propose a geometric way of doing it, which, surprisingly, is often much more efficient than the ... [more ▼]

In non-minimal Higgs mechanisms, one often needs to minimize highly symmetric Higgs potentials. Here we propose a geometric way of doing it, which, surprisingly, is often much more efficient than the usual method. By construction, it gives the global minimum for any set of free parameters of the potential, thus offering an intuitive understanding of how they affect the vacuum expectation values. For illustration, we apply this method to the S_4 and A_4-symmetric three-Higgs-doublet models. We find that at least three recent phenomenological analyses of the A_4-symmetric model used a local, not the global minimum. We discuss coexistence of minima of different types, and comment on the mathematical origin of geometrical CP-violation and on a new symmetry linking different minima. [less ▲]

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See detailSymmetries in multi-Higgs-doublet models
Ivanov, Igor ULg; Vdovin, Evgeny

in AIP Conference Proceedings (2013)

We report the recent progress in understanding of symmetries which can be implemented in the scalar sector of electroweak symmetry breaking models with several Higgs doublets. In particular we present the ... [more ▼]

We report the recent progress in understanding of symmetries which can be implemented in the scalar sector of electroweak symmetry breaking models with several Higgs doublets. In particular we present the list of finite reparametrization symmetry groups which can appear in the three-Higgs-doublet models. [less ▲]

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See detailProbing the phase of the elastic $pp$ scattering amplitude with vortex proton beams
Ivanov, Igor ULg

in AIP Conference Proceedings (2013)

We show that colliding vortex proton beams instead of (approximate) plane waves can lead to a direct measurement of how the overall phase of the scattering amplitude changes with the scattering angle. In ... [more ▼]

We show that colliding vortex proton beams instead of (approximate) plane waves can lead to a direct measurement of how the overall phase of the scattering amplitude changes with the scattering angle. In elastic $pp$ scattering, this will open a novel way to measure the parameter $\rho(t)$ and probe the real part of the Pomeron. [less ▲]

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See detailDiscrete symmetries in the three-Higgs-doublet model
Ivanov, Igor ULg; Vdovin, Evgeny

in Physical Review. D : Particles and Fields (2012), 86(9), 0950305

N-Higgs-doublet models (NHDM) are among the most popular examples of electroweak symmetry breaking mechanisms beyond the Standard Model. Discrete symmetries imposed on the NHDM scalar potential play a ... [more ▼]

N-Higgs-doublet models (NHDM) are among the most popular examples of electroweak symmetry breaking mechanisms beyond the Standard Model. Discrete symmetries imposed on the NHDM scalar potential play a pivotal role in shaping the phenomenology of the model, and various symmetry groups have been studied so far. However, in spite of all efforts, the classification of finite Higgs-family symmetry groups realizable in NHDM for any N>2 is still missing. Here, we solve this problem for the three-Higgs-doublet model by making use of Burnside’s theorem and other results from pure finite group theory which are rarely exploited in physics. Our method and results can also be used beyond high-energy physics, for example, in the study of possible symmetries in three-band superconductors. [less ▲]

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See detailSymmetries in the three-Higgs-doublet model
Ivanov, Igor ULg

Conference (2012, August 31)

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See detailZ_p scalar dark matter from multi-Higgs-doublet models
Ivanov, Igor ULg; Keus, Venus ULg

in Physical Review. D : Particles and Fields (2012), 86(1), 0160047

In many models, stability of dark matter particles is protected by a conserved Z_2 quantum number. However dark matter can be stabilized by other discrete symmetry groups, and examples of such models with ... [more ▼]

In many models, stability of dark matter particles is protected by a conserved Z_2 quantum number. However dark matter can be stabilized by other discrete symmetry groups, and examples of such models with custom-tailored field content have been proposed. Here we show that electroweak symmetry breaking models with N Higgs doublets can readily accommodate scalar dark matter candidates stabilized by groups Z_p with any $p \le 2^{N-1}$, leading to a variety of kinds of microscopic dynamics in the dark sector. We give examples in which semi-annihilation or multiple semi-annihilation processes are allowed or forbidden, which can be especially interesting in the case of asymmetric dark matter. [less ▲]

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See detailMeasuring the phase of the scattering amplitude with vortex beams
Ivanov, Igor ULg

in Physical Review. D : Particles and Fields (2012), 85(7), 07600110

We show that colliding vortex beams instead of (approximate) plane waves can lead to a direct measurement of how the overall phase of the plane wave scattering amplitude changes with the scattering angle ... [more ▼]

We show that colliding vortex beams instead of (approximate) plane waves can lead to a direct measurement of how the overall phase of the plane wave scattering amplitude changes with the scattering angle. Since vortex beams are coherent superpositions of plane waves with different momenta, their scattering amplitude receives contributions from plane wave amplitudes with distinct kinematics. These contributions interfere, leading to the measurement of their phase difference. Although interference exists for any generic wave packet collision, we show that using vortex beams dramatically enhances sensitivity to the phase in comparison with nonvortex beams. Since the overall phase is inaccessible in a plane wave collision, this measurement would be of great importance for a number of topics in hadronic physics, for example, meson production in the resonance region, physics of nucleon resonances, and small angle elastic hadron scattering. [less ▲]

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See detailCreation of two vortex-entangled beams in a vortex-beam collision with a plane wave
Ivanov, Igor ULg

in Physical Review. A : General Physics (2012), 85(3), 0338131-4

The physics of photons and electrons carrying orbital angular momentum (OAM) is an exciting field of research in quantum optics and electron microscopy. Usually, one considers propagation of these vortex ... [more ▼]

The physics of photons and electrons carrying orbital angular momentum (OAM) is an exciting field of research in quantum optics and electron microscopy. Usually, one considers propagation of these vortex beams in a medium or an external field and their absorption or scattering on fixed targets. Here we consider instead a beam-beam collision. We show that elastic scattering of a Bessel vortex beam with a counterpropagating plane wave naturally leads to two vortex-entangled outgoing beams. The vortex entanglement implies that the two final particles are entangled not only in their orbital helicities but also in the opening angles of their momentum cones. Our results are driven by kinematics of vortex-beam scattering and apply to particle pairs of any nature: eγ, e+e−, ep, etc. This collisional vortex entanglement can be used to create pairs of OAM-entangled particles of different nature and to transfer a phase vortex, for example, from low-energy electrons to high-energy protons. [less ▲]

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See detailAbelian symmetryies in NHDM
Keus, Venus ULg; Ivanov, Igor ULg; Vdovin, Evgeny

Diverse speeche and writing (2012)

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See detailAbelian symmetries in multi-Higgs-doublet models
Ivanov, Igor ULg; Keus, Venus ULg; Vdovin, Evgeny

in Journal of Mathematical Physics (2012)

N-Higgs-doublet models (NHDM) are a popular framework to construct electroweak symmetry breaking mechanisms beyond the Standard model. Usually, one builds an NHDM scalar sector which is invariant under a ... [more ▼]

N-Higgs-doublet models (NHDM) are a popular framework to construct electroweak symmetry breaking mechanisms beyond the Standard model. Usually, one builds an NHDM scalar sector which is invariant under a certain symmetry group. Although several such groups have been used, no general analysis of symmetries possible in the NHDM scalar sector exists. Here, we describe a strategy that identifies all abelian groups which are realizable as symmetry groups of the NHDM Higgs potential. We consider both the groups of Higgs-family transformations only and the groups which also contain generalized CP transformations. We illustrate this strategy with the examples of 3HDM and 4HDM and prove several statements for arbitrary N. [less ▲]

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See detailAddendum to “Scattering of twisted particles: Extension to wave packets and orbital helicity”
Ivanov, Igor ULg; Serbo, Valery

in Physical Review. A (2011), 84(6), 065802

In a recent work [ Phys. Rev. A 84 033804 (2011)] we considered elastic scattering of a twisted particle from a plane wave and studied how the orbital helicity of the twisted particle changes after ... [more ▼]

In a recent work [ Phys. Rev. A 84 033804 (2011)] we considered elastic scattering of a twisted particle from a plane wave and studied how the orbital helicity of the twisted particle changes after scattering. We showed that for realistic beams the relative change can be small, |m′−m|/m≪1, thus resolving a controversy which existed in the literature. In this Addendum, using a more accurate analysis, we argue that in the kinematics of Compton backscattering a stronger statement is true: in fact m′≈m, and the difference |m′−m| even by a single unit is already suppressed. [less ▲]

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See detailScattering of twisted particles: Extension to wave packets and orbital helicity
Ivanov, Igor ULg; Serbo, Valery

in Physical Review. A (2011), 84(3), 033804

High-energy photons and other particles carrying nonzero orbital angular momentum (OAM) emerge as a new tool in high-energy physics. Recently, it was suggested to generate high-energy photons with nonzero ... [more ▼]

High-energy photons and other particles carrying nonzero orbital angular momentum (OAM) emerge as a new tool in high-energy physics. Recently, it was suggested to generate high-energy photons with nonzero OAM (twisted photons) by the Compton backscattering of twisted optical photons on relativistic electron beams. Twisted electrons in the intermediate energy range have also been demonstrated experimentally; twisted protons and other particles can, in principle, be created in a similar way. Collisions of energetic twisted states can offer a new look at particle properties and interactions. A theoretical description of twisted particle scattering developed previously treated them as pure Bessel states and ran into difficulty when describing the OAM of the final twisted particle at nonzero scattering angles. Here we develop further this formalism by incorporating two additional important features. First, we treat the initial OAM state as a wave packet of a finite transverse size rather than a pure Bessel state. This realistic assumption allows us to resolve the existing controversy between two theoretical analyses for nonforward scattering. Second, we describe the final twisted particle in terms of the orbital helicity: the OAM projection on its average direction of propagation rather than on the fixed reaction axis. Using this formalism, we determine to what extent the twisted state is transferred from the initial to final OAM particle in a generic scattering kinematics. As a particular application, we prove that in the Compton backscattering the orbital helicity of the final photon stays close to the OAM projection of the initial photon. [less ▲]

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