arXiv subjects

Tommy Ohlsson

Publications and source records attributed to Tommy Ohlsson.

115 records · Page 7Linked to original sources

arXiv2000

Matter Enhanced Neutrino Oscillations with a Realistic Earth Density Profile

We have investigated matter enhanced neutrino oscillations with a mantle-core-mantle step function and a realistic Earth matter density profile in both a two and a three neutrino scenario. We found that the realistic Earth matter density profile can be well approximated with the mantle-core-mantle step function and that there could be an influence on the oscillation channel $ν_μ\to ν_τ$ due to resonant enhancement of one of the mixing angles.

hep-ph↗

arXiv1999

Analysis of a three flavor neutrino oscillation fit to recent Super-Kamiokande data

We have analyzed the most recent available Super-Kamiokande data in a three flavor neutrino oscillation model. We have here neglected possible matter effects and performed a fit to atmospheric and solar Super-Kamiokande data. We have investigated a large parameter range, where the mixing angles were restricted to $0 \leq θ_i \leq π/2$, $ i=1,2,3$, and the mass squared differences were taken to be in the intervals $10^{-11} {\rm eV}^2 \leq Δm^2 \leq 10^{-2} {\rm eV}^2$ and $10^{-4} {\rm eV}^2 \leq ΔM^2 \leq 10 {\rm eV}^2$. This yielded a best solution characterized by the parameter values $θ_1 \simeq 45^\circ$, $θ_2 \simeq 10^\circ$, $θ_3 \simeq 45^\circ$, $Δm^2 \simeq 4.4 \times 10^{-10} {\rm eV}^2$, and $ΔM^2 \simeq 1.01 \times 10^{-3} {\rm eV}^2$, which shows that the analyzed experimental data speak in favor of a bimaximal mixing scenario with one of the mass squared differences in the ``just-so'' domain and the other one in the range capable of providing a solution to the atmospheric neutrino problem.

hep-ph↗

arXiv1999

Weak form factors for semileptonic octet baryon decays in the chiral quark model

We study the weak vector and axial-vector form factors of first- and second-class currents for the semileptonic octet baryon decays in the spirit of the chiral quark model. Our results for the weak magnetism form factors are consistent with the conserved vector current (CVC) results. The induced pseudotensor form factors, which are highly model dependent, are small. The overall performance of the chiral quark model is quite good and in general agreement with existing experimental data.

hep-ph↗

arXiv1999

Chiral quark model analysis of nucleon quark sea isospin asymmetry and spin polarization

We analyze recent measurements of the nucleon quark sea isospin asymmetry in terms of the chiral quark model. The new measurements indicate that the SU(3) model with modest symmetry breaking and no $η'$ Goldstone boson gives a satisfactory description of data. We also discuss the matching parameter for the axial-vector current. Finally, we analyze the nucleon quark spin polarization measurements directly in the chiral quark model without using any SU(3) symmetry assumption on the hyperon axial-vector form factors. The new data indicate that the chiral quark model gives a remarkably good and consistent description of all low energy baryon measurements.

hep-ph↗

arXiv1999

Neutrino oscillations and mixings with three flavors

Global fits to all data of candidates for neutrino oscillations are presented in the framework of a three-flavor model. The analysis excludes mass regions where the MSW effect is important for the solar neutrino problem. The best fit gives $θ_1 \approx 28.9^\circ, θ_2 \approx 4.2^\circ, θ_3 \approx 45.0^\circ, m_2^2 - m_1^2 \approx 2.87 \cdot 10^{-4} eV^2$, and $m_3^2 - m_2^2 \approx 1.11 eV^2$ indicating essentially maximal mixing between the two lightest neutrino mass eigenstates.

hep-ph↗

arXiv1998

Decuplet Baryon Magnetic Moments in the Chiral Quark Model

We present calculations of the decuplet baryon magnetic moments in the chiral quark model. As input we use parameters obtained in qualitatively accurate fits to the octet baryon magnetic moments studied previously. The values found for the magnetic moments of $Δ^{++}$ and $Ω^{-}$ are in good agreement with experiments. We finally calculate the total quark spin polarizations of the decuplet baryons and find that they are considerably smaller than what is expected from the non-relativistic quark model.

hep-ph↗

arXiv1997

Octet Baryon Magnetic Moments in the Chiral Quark Model with Configuration Mixing

The Coleman-Glashow sum-rule for magnetic moments is always fulfilled in the chiral quark model, independently of SU(3) symmetry breaking. This is due to the structure of the wave functions, coming from the non-relativistic quark model. Experimentally, the Coleman-Glashow sum-rule is violated by about ten standard deviations. To overcome this problem, two models of wave functions with configuration mixing are studied. One of these models violates the Coleman-Glashow sum-rule to the right degree and also reproduces the octet baryon magnetic moments rather accurately.

hep-ph↗