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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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See detailColliding particles carrying nonzero orbital angular momentum
Ivanov, Igor ULg

in Physical Review. D : Particles and Fields (2011), 83(9), 093001

Photons carrying nonzero orbital angular momentum (twisted photons) are well-known in optics. Recently, using Compton backscattering to boost optical twisted photons to high energies was suggested ... [more ▼]

Photons carrying nonzero orbital angular momentum (twisted photons) are well-known in optics. Recently, using Compton backscattering to boost optical twisted photons to high energies was suggested. Twisted electrons in the intermediate energy range have also been produced recently. Thus, collisions involving energetic twisted particles seem to be feasible and represent a new tool in high-energy physics. Here we discuss some generic features of scattering processes involving twisted particles in the initial and/or final state. In order to avoid additional complications arising from nontrivial polarization states, we focus here on scalar fields only. We show that processes involving twisted particles allow one to perform a Fourier analysis of the plane-wave cross section with respect to the azimuthal angles of the initial particles. In addition, using twisted states, one can probe the autocorrelation function of the amplitude, which is inaccessible in the plane-wave collisions. Finally, we discuss prospects for experimental study of these effects. [less ▲]

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See detailFrustrated symmetries in multi-Higgs-doublet models
Ivanov, Igor ULg; Keus, Venus ULg

in Physics Letters B (2011), 695(5), 459-462

Within multi-Higgs-doublet models, one can impose symmetries on the Higgs potential, either discrete or continuous, that mix several doublets. In two-Higgs-doublet model any such symmetry can be conserved ... [more ▼]

Within multi-Higgs-doublet models, one can impose symmetries on the Higgs potential, either discrete or continuous, that mix several doublets. In two-Higgs-doublet model any such symmetry can be conserved or spontaneously violated after the electroweak symmetry breaking (EWSB), depending on the coefficients of the potential. With more than two doublets, there exist symmetries which are always spontaneously violated after EWSB. We discuss the origin of this phenomenon and show its similarity to frustration in condensed matter physics. [less ▲]

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See detailHigh-Energy Physics with Particles Carrying Non-Zero Orbital Angular Momentum
Ivanov, Igor ULg

in Few-Body Systems (2011)

Thanks to progress in optics in the past two decades, it is possible to create photons carrying well-defined non-zero orbital angular momentum (OAM). Boosting these photons into high-energy range ... [more ▼]

Thanks to progress in optics in the past two decades, it is possible to create photons carrying well-defined non-zero orbital angular momentum (OAM). Boosting these photons into high-energy range preserving their OAM seems feasible. Intermediate energy electrons with OAM have also been produced recently. One can, therefore, view OAM as a new degree of freedom in high-energy collisions and ask what novel insights it can bring. Here we discuss generic features of scattering processes involving twisted particles in the initial state. We show that they make it possible to perform a Fourier analysis of a plane wave cross section with respect to the azimuthal angles of the initial particles, and to probe the autocorrelation function of the amplitude, a quantity inaccessible in plane wave collisions. [less ▲]

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See detailPerturbative QCD
Ivanov, Igor ULg

in Naumov, Dmitry; Vall, Alexander (Eds.) Proceedings of the X Baikal Summer School On Physics Of Elementary Particles And Astrophysics (2011)

These lectures, intended mainly for undergraduates, contain a very short introduction into perturbative QCD. We introduce the QCD lagrangian, outline how QCD is quantized and renormalized, and as an ... [more ▼]

These lectures, intended mainly for undergraduates, contain a very short introduction into perturbative QCD. We introduce the QCD lagrangian, outline how QCD is quantized and renormalized, and as an example describe the calculation of the elastic two-gluon scattering. We then discuss the physics behind the parton model of hadron collisions, with the important issues of the infrared safety and factorization. We end with a short description of how different hadronic final states are searched for and studied at hadron colliders. [less ▲]

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See detailThe evolution of states and phase transitions under cooling of the early universe within the two-Higgs-doublet model
Ginzburg, I. F.; Ivanov, Igor ULg; Kanishev, K. A.

in Russian Physics Journal (2010, June), 53(6), 575-600

The two-Higgs-doublet model (2HDM) realizes ground states (vacuum) with different properties for different parameter values. The parameters of the effective potential change during cooling of the Universe ... [more ▼]

The two-Higgs-doublet model (2HDM) realizes ground states (vacuum) with different properties for different parameter values. The parameters of the effective potential change during cooling of the Universe after the Big Bang. In so doing, the properties of vacuum state can be affected, phase transitions take place. The evolution of phase states and the set of phase transitions can turn out to be much wider than those accounted for within the conventional Standard model (SM) with a single Higgs doublet. The phase history of the Universe is analyzed for any specified set of the 2HDM parameters. All possible variants of the history are considered. Sets of modern, observed, in principle, parameters corresponding to different sequences of thermal phase transitions are determined. Possible cosmological consequences are briefly discussed. [less ▲]

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See detailProperties of the general NHDM. II. Higgs potential and its symmetries
Ivanov, Igor ULg

in Journal of High Energy Physics [=JHEP] (2010), 2010(7), 1-31

We continue our analysis of the general N-Higgs-doublet model and focus of the Higgs potential description in the space of gauge orbits. We develop a geometric technique that allows us to study the global ... [more ▼]

We continue our analysis of the general N-Higgs-doublet model and focus of the Higgs potential description in the space of gauge orbits. We develop a geometric technique that allows us to study the global minimum of the potential without explicitly finding its position. We discuss symmetry patterns of the NHDM potential, and illustrate the general discussion with various specific variants of the three-Higgs-doublet model. [less ▲]

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See detailEvolution of vacuum states and phase transitions in the two Higgs doublet model during cooling of the Universe
Ginzburg, Ilya; Ivanov, Igor ULg; Kanishev, Konstantin

in Physical Review. D : Particles and Fields (2010), 81

We consider the evolution of the ground state in the two Higgs doublet model during cooling down of the Universe after the big bang. Different regions in the space of free parameters of this model ... [more ▼]

We consider the evolution of the ground state in the two Higgs doublet model during cooling down of the Universe after the big bang. Different regions in the space of free parameters of this model correspond to different sequences of thermal phase transitions. We discuss different paths of thermal evolution and corresponding evolution of physical properties of the system for different modern values of the parameters. [less ▲]

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See detailHiggs boson masses of the general two-Higgs-doublet model in the Minkowski-space formalism
Degée, Audrey ULg; Ivanov, Igor ULg

in Physical Review. D : Particles and Fields (2010), 81

We study the masses of the Higgs bosons in the most general two-Higgs-doublet model in a basis-independent approach. We adapt the recently developed Minkowski-space formalism to this problem and calculate ... [more ▼]

We study the masses of the Higgs bosons in the most general two-Higgs-doublet model in a basis-independent approach. We adapt the recently developed Minkowski-space formalism to this problem and calculate traces of any power of the mass matrix in a compact and reparametrization-invariant form. Our results can be used to gain insight into the dynamics of the scalar sector of the general two-Higgs-doublet model. [less ▲]

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See detailProperties of the general N-Higgs-doublet model. I. The orbit space
Ivanov, Igor ULg; Nishi, Celso

in Physical Review. D : Particles and Fields (2010), 82(1), 0150141-16

We study the scalar sector of the general N-Higgs-doublet model via geometric constructions in the space of gauge orbits. We give a detailed description of the shape of the orbit space both for general N ... [more ▼]

We study the scalar sector of the general N-Higgs-doublet model via geometric constructions in the space of gauge orbits. We give a detailed description of the shape of the orbit space both for general N and, in more detail, for N=3. We also comment on remarkable analogies between the N-Higgs-doublet model and quantum information theory. [less ▲]

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See detailCentral exclusive production of dijets at hadronic colliders
Cudell, Jean-René ULg; Dechambre, Alice ULg; Hernandez, O. F. et al

in European Physical Journal C -- Particles & Fields (2009), 61(3), 369

In view of the recent diffractive dijet data from CDF run II, we critically re-evaluate the standard approach to the calculation of central production of dijets in quasi-elastic hadronic collisions. We ... [more ▼]

In view of the recent diffractive dijet data from CDF run II, we critically re-evaluate the standard approach to the calculation of central production of dijets in quasi-elastic hadronic collisions. We find that the process is dominated by the non-perturbative region, and that even perturbative ingredients, such as the Sudakov form factor, are not under theoretical control. Comparison with data allows us to fix some of the uncertainties. Although we focus on dijets, our arguments apply to other high-mass central systems, such as the Higgs boson. [less ▲]

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See detailExclusive central production of dijets at hadronic colliders
Ivanov, Igor ULg; Cudell, Jean-René ULg; Dechambre, Alice et al

in AIP Conference Proceedings (2009), 1105

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See detailTowards Thermal Evolution of the Most General 2HDM
Ivanov, Igor ULg

in Acta Physica Polonica B (2009), 40(10), 2789

We consider the scalar sector of the most general renormalizable two-Higgs-doublet model at non-zero temperature. We calculate the largest finite temperature corrections to the free-energy density and ... [more ▼]

We consider the scalar sector of the most general renormalizable two-Higgs-doublet model at non-zero temperature. We calculate the largest finite temperature corrections to the free-energy density and study thermal evolution of the ground state. Within the approximation chosen, we establish all possible sequences of thermal phase transitions and study their relation with the symmetries of the model. We show, in particular, that a charge-breaking or a CP-violating vacuum can arise at intermediate stages of thermal evolution, and that the first-order phase transition is associated with a discrete symmetry of the potential, but not of the entire scalar Lagrangian. [less ▲]

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