References of "Ivanov, Igor"
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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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See detailGeneral two-order-parameter Ginzburg-Landau model with quadratic and quartic interactions
Ivanov, Igor ULg

in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2009), 79

The Ginzburg-Landau model with two-order parameters appears in many condensed-matter problems. However, even for scalar order parameters, the most general U(1)-symmetric Landau potential with all ... [more ▼]

The Ginzburg-Landau model with two-order parameters appears in many condensed-matter problems. However, even for scalar order parameters, the most general U(1)-symmetric Landau potential with all quadratic and quartic terms contains 13 independent coefficients and cannot be minimized with straightforward algebra. Here, we develop a geometric approach that circumvents this computational difficulty and allows one to study properties of the model without knowing the exact position of the minimum. In particular, we find the number of minima of the potential, classify explicit symmetries possible in this model, establish conditions when and how these symmetries are spontaneously broken, and explicitly describe the phase diagram. [less ▲]

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See detailCentral Exclusive Dijet Production
Dechambre, Alice ULg; Cudell, Jean-René ULg; Ivanov, Igor ULg et al

in AIP Conference Proceedings (2008), 1038

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See detailCorrections to the generalized vector dominance due to diffractive ρ3 production
Ivanov, Igor ULg; Pacetti, Simone

in European Physical Journal C -- Particles & Fields (2008), 53

The idea of the vector dominance is still in use in various analyses of the experimental data of photon–hadron reactions. It makes sense, therefore, to recast results of microscopic calculations of such ... [more ▼]

The idea of the vector dominance is still in use in various analyses of the experimental data of photon–hadron reactions. It makes sense, therefore, to recast results of microscopic calculations of such reactions in this language. Here we present the diffractive DIS ρ3 production as a specific correction to generalized vector dominance. We perform a coupled channel analysis of spin–orbital excitations in diffractive photoproduction and reiterate the point that ρ3 in diffractive DIS will be sensitive to a novel aspect of diffraction. [less ▲]

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See detailMinkowski space structure of the Higgs potential in the two-Higgs-doublet model. II. Minima, symmetries, and topology
Ivanov, Igor ULg

in Physical Review. D : Particles and Fields (2008), 77

We continue to explore the consequences of the recently discovered Minkowski space structure of the Higgs potential in the two-Higgs-doublet model. Here, we focus on the vacuum properties. The search for ... [more ▼]

We continue to explore the consequences of the recently discovered Minkowski space structure of the Higgs potential in the two-Higgs-doublet model. Here, we focus on the vacuum properties. The search for extrema of the Higgs potential is reformulated in terms of 3-quadrics in the 3+1-dimensional Minkowski space. We prove that 2HDM cannot have more than two local minima in the orbit space and that a twice-degenerate minimum can arise only via spontaneous violation of a discrete symmetry of the Higgs potential. Investigating topology of the 3-quadrics, we give concise criteria for existence of noncontractible paths in the Higgs orbit space. We also study explicit symmetries of the Higgs potential/Lagrangian and their spontaneous violation from a wider perspective than usual. [less ▲]

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See detailMinkowski space structure of the Higgs potential in 2HDM
Ivanov, Igor ULg

in Physical Review. D : Particles and Fields (2007), 75

The Higgs potential of 2HDM keeps its generic form under the group of transformation GL(2,C), which is larger than the usually considered reparametrization group SU(2). This reparametrization symmetry ... [more ▼]

The Higgs potential of 2HDM keeps its generic form under the group of transformation GL(2,C), which is larger than the usually considered reparametrization group SU(2). This reparametrization symmetry induces the Minkowski space structure in the orbit space of 2HDM. Exploiting this property, we present a geometric analysis of the number and properties of stationary points of the most general 2HDM potential. In particular, we prove that charge-breaking and neutral vacua never coexist in 2HDM and establish conditions when the most general explicitly CP-conserving Higgs potential has spontaneously CP-violating minima. We also define the prototypical model of a given 2HDM, which has six free parameters less than the original one but still contains all the essential physics. Our analysis avoids manipulation with high-order algebraic equations. [less ▲]

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See detailHow to measure Pomeron phase and discover odderon at HERA and RHIC
Ginzburg, Ilya; Ivanov, Igor ULg

in Acta Physica Polonica B (2006), 37

We suggest to measure the Pomeron phase and discover odderon via the measurement of charge asymmetry of pions in the diffractive processes ep\to e\pi +\pi - p, eA\to e\pi +\pi - A and in the processes AA ... [more ▼]

We suggest to measure the Pomeron phase and discover odderon via the measurement of charge asymmetry of pions in the diffractive processes ep\to e\pi +\pi - p, eA\to e\pi +\pi - A and in the processes AA\to AA\pi +\pi - with two rapidity gaps. [less ▲]

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See detailTwo-Higgs-doublet model from the group-theoretic perspective
Ivanov, Igor ULg

in Physics Letters B (2006), 632(2-3), 360-365

In the two-Higgs-doublet model, different Higgs doublets can be viewed as components of a generic “hyperspinor”. We decompose the Higgs potential of this model into irreducible representations of the SU(2 ... [more ▼]

In the two-Higgs-doublet model, different Higgs doublets can be viewed as components of a generic “hyperspinor”. We decompose the Higgs potential of this model into irreducible representations of the SU(2) group of transformations of this hyperspinor. We discuss invariant combinations of Higgs potential parameters λi that arise in this decomposition and provide simple and concise sets of conditions for the hidden Z2-symmetry, Peccei–Quinn symmetry, and explicit CP-conservation in 2HDM. We show that some results obtained previously by brute-force calculations are reduced to simple linear algebraic statements in our approach. [less ▲]

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See detailProduction of orbitally excited vector mesons in diffractive DIS
Caporale, Francesco; Ivanov, Igor ULg

in Physics Letters B (2005), 622(1-2), 55-62

Within the kt-factorization framework, we study diffractive production of orbitally excited vector mesons and compare it with the production of radial excitations, focusing on the ρ(1450)/ρ(1700) case. At ... [more ▼]

Within the kt-factorization framework, we study diffractive production of orbitally excited vector mesons and compare it with the production of radial excitations, focusing on the ρ(1450)/ρ(1700) case. At small Q2, orbital excitation of light quarkonia is found to dominate over radial excitations in diffractive production. We predict strong suppression of the production of orbital excitations by longitudinal photons, which leads to very small σL/σT ratio. At small Q2, the s-channel helicity violating transitions contribute not, vert, similar10–15% of the transverse cross section and not, vert, similar50% of the longitudinal cross section. We also study mixing between radial and orbital excitations and determine strategies towards clarification of S-wave/D-wave assignment to ρ(1450) and ρ(1700) mesons. The results are compared with the experimental data available, and predictions for future experiments are given. [less ▲]

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