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Per Osland

Publications and source records attributed to Per Osland.

53 records · Page 3Linked to original sources
arXiv2000

Vacuum and MSW interpretations of solar neutrino data with the LNW mass matrix

The Lehmann-Newton-Wu mass matrix, which was recently applied to neutrinos, is further investigated. The analytic results presented earlier are confirmed numerically for the solar density profile of the Standard Solar Model. The combined analysis of atmospheric and solar neutrino data favors the MSW solution over the vacuum-oscillation solution. The total rates from the solar neutrino detectors and spectrum distortion reported by the Super-Kamiokande collaboration for solar neutrinos favors one heavy (m3\sim 0.05 eV) and two light (m1, m2\lsim 0.003 eV) neutrinos.

hep-ph↗
arXiv2000

Mikheyev-Smirnov-Wolfenstein Effect for Linear Electron Density

When the electron density is a linear function of distance, it is known that the MSW equations for two neutrino species can be solved in terms of known functions. It is shown here that more generally, for any number of neutrino species, these MSW equations can be solved exactly in terms of single integrals. While these integrals cannot be expressed in terms of known functions, some of their simple properties are obtained. Application to the solar neutrino problem is briefly discussed.

hep-ph↗
arXiv2000

Universal quark-lepton mixing and determination of neutrino masses

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. Three minima have been found, using the chi^2 fit, and, from these minima, it is determined that the mass of the lightest neutrino is 1.3\times10^-3 eV, that of the next heavier neutrino is 1.3\times10^-2 eV, while the mass of the heaviest neutrino is 3.4\times10^-2, 5.8\times10^-2 or 9.4\times10^-2 eV.

hep-ph↗
arXiv1999

Solar Mikheyev-Smirnov-Wolfenstein Effect with Three Generations of Neutrinos

Under the assumption that the density variation of the electrons can be approximated by an exponential function, the solar Mikheyev-Smirnov-Wolfenstein effect is treated for three generations of neutrinos. The generalized hypergeometric functions that result from the exact solution of this problem are studied in detail, and a method for their numerical evaluation is presented. This analysis plays a central role in the determination of neutrino masses, not only the differences of their squares, under the assumption of universal quark-lepton mixing.

hep-ph↗
arXiv1999

Distinguishing Higgs models at photon colliders

We consider the two effective couplings hZγand hγγinvolving a neutral scalar Higgs boson with a mass around 100 GeV in the Standard Model, in the Two Higgs Doublet Model, and in the Minimal Supersymmetric Standard Model. The couplings can be tested at Photon Colliders, and used to distinguish these models.

hep-ph↗
arXiv1999

More Series related to the Euler Series

We present results for 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. All these series can be expressed in terms of zeta(2) and zeta(3).

hep-th↗
arXiv1998

Summing one- and two-dimensional series related to the Euler series

We present results for some infinite series appearing in Feynman diagram calculations, many of which are similar to the Euler series. These include both one-dimensional and two-dimensional series. Most of these series can be expressed in terms of zeta(2), zeta(3), the Catalan constant G and Cl{2}(pi/3) where Cl{2}(theta) is Clausen's function.

hep-th↗
arXiv1996

Dyon mass bounds from electric dipole moments

Dyon loops give a contribution to the matrix element for light-by-light scattering that violates parity and time-reversal symmetry. This effect induces an electric dipole moment for the electron, of order $M^{-2}$, where $M$ is the dyon mass. The current limit on the electric dipole moment of the electron yields the lower mass bound $M>{\cal O}(1)~\mbox{TeV}$.

hep-ph↗
arXiv1995

CP Investigations in the Higgs Sector

In a more general electroweak theory, there could be Higgs particles that are odd under $CP$. When such particles decay via vector bosons to two fermion-antifermion pairs, the momenta of those will be correlated in a way which is determined by the $CP$ of the particle. Similarly, in the Bjorken process correlations among momenta of the initial electron and final-state fermions are sensitive to the $CP$ quantum number. Monte Carlo data on the expected efficiency demonstrate that it should be possible to verify the scalar character of an intermediate-mass Standard Model Higgs boson after three years of data taking at a future linear collider. This is most likely not possible at LEP2. Signals of possible presence of $CP$ violation in the Higgs sector are briefly discussed.

hep-ph↗
arXiv1995

Determining the CP of a Higgs Particle at a Future Linear Collider

In a more general electroweak theory, there could be Higgs particles that are odd under $CP$. Correlations among momenta of the initial electron and final-state fermions are in the Bjorken process sensitive to the $CP$ parity. Monte Carlo data on the expected efficiency demonstrate that it should be possible to verify the scalar character of an intermediate-mass Standard Model Higgs boson after three years of data taking at a future linear collider. This is most likely not possible at LEP2. Signals of possible presence of $CP$ violation in the Higgs sector are briefly discussed.

hep-ph↗
arXiv1995

Testing $CP$ in the Bjorken process

In a more general electroweak theory, there could be Higgs particles that are odd under $CP$, and also Higgs-like particles which are not eigenstates of $CP$. We discuss distributions which for the Bjorken process are sensitive to the $CP$ parity. Correlations among momenta of the initial electron and final-state fermions yield this kind of information. We discuss also observables which may demonstrate presence of $CP$ violation and identify a phase shift $δ$ which is a measure of the strength of $CP$ violation in the Higgs-vector-vector coupling, and which can be measured directly in the decay distribution. We present Monte Carlo data on the expected efficiency, and conclude that it is relatively easy to determine whether the produced particle is even or odd under $CP$. However, observation of any $CP$ violation would require a very large amount of data.

hep-ph↗
arXiv1994

Light-Gluino Production at LEP

If gluinos are light, they will be produced in electron-positron annihilation at LEP, not only by radiation in pairs off quarks and antiquarks, but also without accompanying quark and antiquark jets. We here discuss the latter process, pair production of gluinos, in a model with soft supersymmetry breaking, allowing for mixing between the squarks. In much of the parameter space of the Minimal Supersymmetric Model (MSSM) the cross section corresponds to a $Z$ branching ratio above $10^{-5}$, even up to $10^{-4}$. A non-observation of gluinos at this level restricts the allowed MSSM parameter space.

hep-ph↗
arXiv1994

Gluino Production in Electron-Positron Annihilation

We discuss the pair production of gluinos in electron-positron annihilation at LEP, in a model with soft supersymmetry breaking, allowing for mixing between the squarks. In much of the parameter space of the Minimal Supersymmetric Model (MSSM) the cross section corresponds to a $Z$ branching ratio above $10^{-5}$, even up to $10^{-4}$. A non-observation of gluinos at this level restricts the allowed MSSM parameter space. In particular, it leads to lower bounds on the soft mass parameters in the squark sector.

hep-ph↗
arXiv1994

Signals of $CP$ violation in Higgs decay

We consider an extension of the Standard Model where some Higgs particle is not an eigenstate of $CP$, and discuss the possibility of extracting signals of the resulting $CP$ violation. In the case of Higgs decay to four fermions we study correlations among momenta of the final-state fermions. We discuss observables which may demonstrate presence of $CP$ violation and identify a phase shift $δ$, which is a measure of the strength of $CP$ violation in the Higgs-vector-vector coupling, and which can be measured directly in the decay distribution. In addition to these angular correlations, we consider correlations between energy differences. The former correlations include some recently reported results, whereas the latter ones appear to provide a much better probe for revealing $CP$ violation.

hep-ph↗
arXiv1993

Decorated-box-diagram-contributions to Bhabha scattering. (II)

We evaluate, in the high-energy limit, $s\gg|t|\gg m^2\ggλ^2$, the sum of amplitudes corresponding to a class of Feynman diagrams describing two-loop virtual photonic corrections to Bhabha scattering. The diagrams considered are box and crossed box diagrams with a vacuum polarization insertion in one of the photon lines.

hep-ph↗
arXiv1993

Decorated-box-diagram-contributions to Bhabha scattering. (I)

We evaluate, in the high-energy limit, $s\gg|t|\gg m^2\ggλ^2$, the sum of amplitudes corresponding to a class of Feynman diagrams describing two-loop virtual photonic corrections to Bhabha scattering. The diagrams considered are box and crossed box diagrams with an extra photon decorating one of the fermion lines. The mathematical method employed is that of Mellin transforms. In the eikonal approximation, this sum of two-loop amplitudes has previously been evaluated, and found to be equal to the sum of the box and crossed box amplitudes, multiplied by the electric form factor of the electron. We obtain a similar factorization, but with the form factor replaced by another expression involving the logarithms $\log(λ^2/m^2)$ and $\log(λ^2/|t|)$.

hep-ph↗
arXiv1993

Angular and energy correlations in Higgs decay

We discuss how correlations among momenta of the decay products may yield information about the CP-parity of the Higgs particle. These are correlations of decay planes defined by the momenta of pairs of particles as well as correlations between energy differences. Our study includes finite-width effects. In the narrow-width approximation the angular correlations coincide with previously reported results. The correlations between energy differences turn out to be a much better probe for CP determination than the previously suggested angular correlations, especially for massive Higgs bosons.

hep-ph↗