arXiv subjects

Per Osland

Publications and source records attributed to Per Osland.

At least 37 records · Page 2Linked to original sources

arXiv2007

Consistency of the Two Higgs Doublet Model and CP violation in top production at the LHC

It is important to provide guidance on whether CP violation may be measurable in top-quark production at the Large Hadron Collider. The present work extends an earlier analysis of the non-supersymmetric Two-Higgs-Doublet Model in this respect, by allowing a more general potential. Also, a more comprehensive study of theoretical and experimental constraints on the model is presented. Vacuum stability, unitarity, direct searches and electroweak precision measurements severely constrain the model. We explore, at low \tanβ, the allowed regions in the multidimensional parameter space that give a viable physical model. This exploration is focused on the parameter space of the neutral sector rotation matrix, which is closely related to the Yukawa couplings of interest. In most of the remaining allowed regions, the model violates CP. We present a quantitative discussion of a particular CP-violating observable. This would be measurable in semileptonically decaying top and antitop quarks produced at the LHC, provided the number of available events is of the order of a million.

hep-ph↗

arXiv2007

CP Violation, Stability and Unitarity of the Two Higgs Doublet Model

The Two-Higgs-Doublet Model is considered, in its CP-non-conserving version. It is shown quantitatively how vacuum stability and tree-level unitarity in the Higgs-Higgs-scattering sector constrain the parameter space of the model. In particular, at high values of tanbeta, the model violates unitarity, unless some of the Higgs bosons are heavy. In the regime of large CP violation in the neutral-Higgs-t-quark sector, which requires tanbeta lsim 1, the Yukawa coupling parameter space (determined by the neutral-Higgs-sector rotation matrix) is reasonably unconstrained. On the other hand, the corresponding neutral-Higgs-b-quark sector allows for large CP violation at tanbeta gg 1. However, here the model is more constrained: Significant CP violation is correlated with a considerable splitting among the two heavier Higgs bosons.

hep-ph↗

arXiv2004

Graviton-induced Bremsstrahlung at e^+e^- colliders

We consider graviton-induced Bremsstrahlung at future e^+e^- colliders in both the ADD and RS models, with emphasis on the photon perpendicular momentum and angular distribution. The photon spectrum is shown to be harder than in the Standard Model, and there is an enhancement for photons making large angles with respect to the beam. In the ADD scenario, the excess at large photon perpendicular momenta should be measurable for values of the cut-off up to about twice times the c.m. energy. In the RS scenario, radiative return to graviton resonances below the c.m. energy can lead to large enhancements of the cross section.

hep-ph↗

arXiv2003

Maximal CP nonconservation in the Two-Higgs-Doublet Model

We study the simplest Two-Higgs-Doublet Model that allows for CP nonconservation, where it can be parametrized by only one parameter in the Higgs potential. Different concepts of maximal CP-nonconservation in the gauge-Higgs and the quark-Higgs (Yukawa) sectors are compared. Maximal CP nonconservation in the gauge-Higgs sector does normally not lead to maximal CP nonconservation in the Yukawa sector, and vice versa.

hep-ph↗

arXiv2003

CP violation in top quark production at the LHC and Two-Higgs-Doublet Models

We discuss CP violation in top-antitop production at the LHC, induced by gluon fusion and final-state Higgs exchange. Results by Bernreuther and Brandenburg are confirmed and further reduced. The lepton energy asymmetry is studied in detail in explicit Two-Higgs-Doublet Models with near-maximal mixing in the neutral Higgs sector. Unless there is only one light Higgs particle, and unless (in Model II) tanbeta \lsim 1, the CP-violating effects are very small, possibly too small to be seen at the LHC.

hep-ph↗

arXiv2003

Graviton-induced Bremsstrahlung

We discuss photon Bremsstrahlung induced by virtual graviton exchange in proton-proton interactions at hadronic colliders, resulting from the exchange of Kaluza-Klein excitations of the graviton. The relevant subprocesses, gg to G to e^+e^-gamma and q barq to e^+e^-gamma are discussed in both the ADD and the RS scenarios. Although two-body final states (or real graviton emission) would presumably be the main discovery channels, a search for three-body final states could be worthwhile since such events have characteristic features that could provide additional confirmation. In particular, the k_perp-distribution of the photon is in both scenarios harder than that of the Standard-model background.

hep-ph↗

arXiv2002

Two-Higgs-Doublet Models with CP violation

We consider the Two-Higgs-Doublet Model and determine the range of parameters for which CP violation and Flavor Changing Neutral Current effects are naturally small. It corresponds to small values of the mass parameter m_{12}^2, describing soft (ϕ_1,ϕ_2) mixing in the potential. We discuss how, in this approach, some Higgs bosons can be heavy, with mass of the order of 1 TeV. The possibility that at the Tevatron, LHC and an e^+e^- Linear Collider, only one Higgs boson will be found, with properties indistinguishable from those in the Standard Model (SM), we define as the SM-like scenario. While this scenario can be obtained with large μ^2 \sim \Re m_{12}^2 parameter, in which case there is decoupling, we here discuss the opposite case of small μ^2, without decoupling.

hep-ph↗

arXiv2002

Three-Neutrino MSW Effect and the Lehmann Mass Matrix

Recent work on analytical solutions to the MSW equations for three neutrino flavours is reviewed, with emphasis on the exponential density. Application to a particular mass matrix, proposed by Lehmann, Newton and Wu, is also discussed. Within this model, the experimental data allow a determination of the three neutrino masses. They are found to be 0.002-0.004, 0.01 and 0.05 eV.

hep-ph↗

arXiv2002

Neutrino masses from universal Fermion mixing

If three right-handed neutrinos are added to the Standard Model, then, for the three known generations, there are six quarks and six leptons. It is then natural to assume that the symmetry considerations that have been applied to the quark matrices are also valid for the lepton mass matrices. Under this assumption, the solar and atmospheric neutrino data can be used to determine the individual neutrino masses. Using the χ^2 fit, it is found that the mass of the lightest neutrino is (2-5)\times10^{-3} eV, that of the next heavier neutrino is (10-13)\times10^{-3} eV, while the mass of the heaviest neutrino is (52-54)\times10^{-3} eV.

hep-ph↗

arXiv2001

Neutrinoless double beta decay, solar neutrinos and mass scales

We obtain bounds for the neutrino masses by combining atmospheric and solar neutrino data with the phenomenology of neutrinoless double beta decay where hypothetical values of |< m>| are envisaged from future 0νββ-experiments. Different solutions for the solar neutrino data are considered. For the Large-Mixing-Angle solution, a bound |< m>| \leq 0.01 eV would strongly disfavour an inverted hierarchy of the neutrino masses.

hep-ph↗

arXiv2001

Characteristics of graviton-induced bremsstrahlung

We discuss Bremsstrahlung induced by graviton exchange in proton-proton interactions at hadronic colliders, resulting from gg\to G\to μ^+μ^-γ. Both the ADD and RS scenarios are discussed. Due to the coupling of the graviton to two photons, the cross section has a new kinematical singularity for hard photons. Thus, graviton-induced Bremsstrahlung tends to yield more hard photons than QED-based Bremsstrahlung. As compared with the corresponding two-body final state, μ^+μ^-, the cross section is, for realistic cuts, smaller by a factor \sim 0.02. At the LHC, and with a string scale of a few TeV (ADD scenario), or a graviton mass of a few TeV (RS scenario), a few events of high invariant mass are expected per year.

hep-ph↗

arXiv2001

Three-Neutrino MSW Effect and the LNW Mass Matrix

We review recent work on analytical solutions to the MSW equations for three neutrino flavours, for exponential and linear potentials. An application to a particular mass matrix is also discussed. The three neutrino masses are determined, respectively, to be 0.001--0.004, and roughly 0.01 and 0.05 eV.

hep-ph↗

arXiv2001

Perturbative Aspects of q-Deformed Dynamics

Within the framework of the q-deformed Heisenberg algebra a dynamical equation of q-deformed quantum mechanics is discussed. The perturbative aspects of the q-deformed Schrödinger equation are analyzed. General representations of the additional momentum-dependent interaction originating from the q-deformed effects are presented in two approaches. As examples, such additional interactions related to the harmonic-oscillator potential and the Morse potential are demonstrated.

hep-th↗

arXiv2001

Standard-Model-like scenarios in the 2HDM and Photon Collider potential

After operations at the LHC and e^+e^- Linear Colliders it may be found that a Standard-Model-like scenario is realized. In this scenario no new particle will be discovered, except a single Higgs boson having partial widths or coupling constants with fundamental particles, whose squares are close, within anticipated experimental uncertainty, to those of the SM. Experiments at a Photon Collider can resolve whether the SM or e.g. the Two-Higgs-Doublet Model is realized in Nature. For the SM-like realizations of the 2HDM (II) we study the loop couplings of the Higgs boson with γγand Z γ, and also with gluons. The deviation of the two-photon width from its SM value is generally higher than the expected inaccuracy in the measurement of Γ_{γγ} at a Photon Collider. The deviation is sensitive to the parameters of the Higgs self interaction.

hep-ph↗

arXiv2001

Potential of Photon Collider in resolving SM-like scenarios

After operations at the LHC and e^+e^- Linear Colliders it may be found that a Standard-Model-like scenario is realized. In this scenario no new particle will be discovered, except a single Higgs boson having partial widths or coupling constants squared with fundamental particles close, within anticipated experimental uncertainty, to those of the SM. Experiments at a Photon Collider can resolve whether the SM model or e.g. the Two Higgs Doublet Model is realized in Nature. For the SM-like version of the 2HDM (II) we study the loop couplings of the Higgs boson with γγand Z γ, and also with gluons. The deviation of the two-photon width from its SM value is generally higher than the expected inaccuracy in the measurement of Γ_{γγ} at a Photon Collider. The result is sensitive to the parameters of the Higgs self interaction.

hep-ph↗

arXiv2001

Resolving SM-like scenarios via Higgs boson production at a Photon Collider: I. 2HDM versus SM

We consider the possibility that after operations at the LHC and e^+e^- Linear Colliders a Higgs boson will be discovered, but no signal of New Physics will be found (Standard-Model-like scenario). This can occur in the Standard Model (SM) as well as in other models, including the Two-Higgs-Doublet Model (2HDM), the MSSM, etc. Experiments at a Photon Collider can resolve these cases. In this paper we compare the SM and the 2HDM~(II). In the analysis we use as independent quantities the ratios, to the SM values, of couplings of the observed Higgs boson to gauge bosons, and to up and down-type quarks (basic couplings). We derive a relation between these ratios within the 2HDM~(II), a pattern relation. With the aid of this relation, different possible realizations of an SM-like scenario are found. For these realizations, we calculate the loop couplings of the Higgs boson with γγand Z γ, and also with gluons, taking into account the expected accuracy in the measurements of the basic couplings. The obtained deviation of the two-photon width from its SM value is generally higher than the expected inaccuracy in the measurement of Γ_{γγ} at a Photon Collider. The result is sensitive to the parameters of the Higgs self interaction.

hep-ph↗

arXiv2000

Some infinite series related to Feynman diagrams

Results are presented for some infinite series appearing in Feynman diagram calculations, many of which are similar to the Euler series. These include both one-, two- and three-dimensional series. The sums of these series can be evaluated with the help of various integral representations for hypergeometric functions, and expressed in terms of $ζ(2)$, $ζ(3)$, the Catalan constant $G$ and ${\rm Cl}_2(π/3)$ where ${\rm Cl}_2(θ)$ is Clausen's function.

math-ph↗

arXiv2000

Critical Phenomenon of a Consistent q-Deformed Squeezed State

Within a self-consistent framework of q-deformed Heisenberg algebra and its equivalent framework of q-deformed boson commutation relations, which relate to the under-cutting phenomenon of Heisenberg's minimal uncertainty relation, special q-deformed squeezed states are constructed. Besides the similar local maximum squeezing as the one in the undeformed case, new strong squeezing appears when the amplitude of the related coherent state increases to large values. A critical phenomenon appears at a large value of the amplitude: the variance of one component of the quadrature of the light field approaches zero, but the variance of the corresponding conjugate quantity remains finite, which is a surprising deviation from Heisenberg's uncertainty relation. The qualitative character exposed by this q-squeezed state may provide some evidence about q-deformed effects in current experiments.

hep-th↗