Searcharxiv⌕ Search

arXiv subjects

Tommy Ohlsson

Publications and source records attributed to Tommy Ohlsson.

At least 109 records · Page 6Linked to original sources
arXiv2002

Testing CPT Invariance with Neutrinos

We investigate possible tests of CPT invariance on the level of event rates at neutrino factories. We do not assume any specific model, but phenomenological differences in the neutrino-antineutrino masses and mixing angles in a Lorentz invariance preserving context, which could be induced by physics beyond the Standard Model. We especially focus on the muon neutrino and antineutrino disappearance channels in order to obtain constraints on the neutrino-antineutrino mass and mixing angle differences. In a typical neutrino factory setup simulation, we find, for example, that $|m_3 - \bar{m}_3| \lesssim 1.9 \cdot 10^{-4} \mathrm{eV}$ and $|θ_{23} -\bar θ_{23}| \lesssim 2^\circ$.

hep-ph↗
arXiv2002

A Flavor Symmetry Model for Bilarge Leptonic Mixing and the Lepton Masses

We present a model for leptonic mixing and the lepton masses based on flavor symmetries and higher-dimensional mass operators. The model predicts bilarge leptonic mixing (i.e., the mixing angles theta_{12} and theta_{23} are large and the mixing angle theta_{13} is small) and an inverted hierarchical neutrino mass spectrum. Furthermore, it approximately yields the experimental hierarchical mass spectrum of the charged leptons. The obtained values for the leptonic mixing parameters and the neutrino mass squared differences are all in agreement with atmospheric neutrino data, the Mikheyev--Smirnov--Wolfenstein large mixing angle solution of the solar neutrino problem, and consistent with the upper bound on the reactor mixing angle. Thus, we have a large, but not close to maximal, solar mixing angle theta_{12}, a nearly maximal atmospheric mixing angle theta_{23}, and a small reactor mixing angle theta_{13}. In addition, the model predicts theta_{12} ~= pi/4 - theta_{13}.

hep-ph↗
arXiv2002

Could One Find Petroleum Using Neutrino Oscillations in Matter?

In neutrino physics, it is now widely believed that neutrino oscillations are influenced by the presence of matter, modifying the energy spectrum produced by a neutrino beam traversing the Earth. Here, we will discuss the reverse problem, i.e. what could be learned about the Earth's interior from a single neutrino baseline energy spectrum, especially about the Earth's mantle. We will use a statistical analysis with a low-energy neutrino beam under very optimistic assumptions. At the end, we will note that it is hard to find petroleum with such a method, though it is not too far away from technical feasibility.

hep-ph↗
arXiv2002

Bilarge leptonic mixing from Abelian horizontal symmetries

We construct and present a model for leptonic mixing based on higher-dimensional operators, using the Froggatt-Nielsen mechanism, and Abelian horizontal symmetries (flavor symmetries) of continuous and discrete type. Our model naturally yields bilarge leptonic mixing, coming from both the charged leptons and the neutrinos, and an inverted neutrino mass hierarchy spectrum. The obtained values of the parameters, i.e., the leptonic mixing parameters and the neutrino mass squared differences, are all consistent with the atmospheric neutrino data and the Mikheyev-Smirnov-Wolfenstein large mixing angle solution for the solar neutrino problem.

hep-ph↗
arXiv2002

Effects of random matter density fluctuations on the neutrino oscillation transition probabilities in the Earth

In this paper, we investigate the effects of random fluctuations of the Earth matter density for long baselines on the neutrino oscillation transition probabilities. We especially identify relevant parameters characterizing the matter density noise and calculate their effects by averaging over statistical ensembles of a large number of matter density profiles. For energies and baselines appropriate to neutrino factories, absolute errors on the relevant appearance probabilities are at the level of $|ΔP_{αβ}| \sim 10^{-4}$ (with perhaps $|ΔP_{μe}|/P_{μe} \sim 1%$ for neutrinos), whereby a modest improvement in understanding of the geophysical data should render such effects unimportant.

hep-ph↗
arXiv2002

Tests of CPT Invariance at Neutrino Factories

We investigate possible tests of CPT invariance on the level of event rates at neutrino factories. We do not assume any specific model but phenomenological differences in the neutrino-antineutrino masses and mixing angles in a Lorentz invariance preserving context, such as it could be induced by physics beyond the Standard Model. We especially focus on the muon neutrino and antineutrino disappearance channels in order to obtain constraints on the neutrino-antineutrino mass and mixing angle differences; we found, for example, that the sensitivity $|m_3 - \bar{m}_3| \lesssim 1.9 \cdot 10^{-4} \mathrm{eV}$ could be achieved.

hep-ph↗
arXiv2001

Decays of supernova neutrinos

Supernova neutrinos could be well-suited for probing neutrino decay, since decay may be observed even for very small decay rates or coupling constants. We will introduce an effective operator framework for the combined description of neutrino decay and neutrino oscillations for supernova neutrinos, which can especially take into account two properties: One is the radially symmetric neutrino flux, allowing a decay product to be re-directed towards the observer even if the parent neutrino had a different original direction of propagation. The other is decoherence because of the long baselines for coherently produced neutrinos. We will demonstrate how to use this effective theory to calculate the time-dependent fluxes at the detector. In addition, we will show the implications of a Majoron-like decay model. As a result, we will demonstrate that for certain parameter values one may observe some effects which could also mimic signals similar to the ones expected from supernova models, making it in general harder to separate neutrino and supernova properties.

astro-ph↗
arXiv2001

See-saw Mechanisms for Dirac and Majorana Neutrino Masses

We investigate the see-saw mechanism for generally non-fine-tuned $n \times n$ mass matrices involving both Dirac and Majorana neutrinos. We specifically show that the number of naturally light neutrinos cannot exceed half of the dimension of the considered mass matrix. Furthermore, we determine a criterion for mass matrix textures leading to light Dirac neutrinos with the see-saw mechanism. Especially, we study $4 \times 4$ and $6 \times 6$ mass matrix textures and give some examples in order to highlight these types of textures. Next, we present a model scheme based on non-Abelian and discrete symmetries fulfilling the above mentioned criterion for light Dirac neutrinos. Finally, we investigate the connection between symmetries and the invariants of a mass matrix on a formal level.

hep-ph↗
arXiv2001

Effects and influences on neutrino oscillations due to a thin density layer perturbation added to a matter density profile

In this paper, we show the effects on the transition probabilities for neutrino oscillations due to a thin constant density layer perturbation added to an arbitrary matter density profile. In the case of two neutrino flavors, we calculate the effects both analytically and numerically, whereas in the case of three neutrino flavors, we perform the studies purely numerically. As an realistic example we consider the effects of the Earth's atmosphere when added to the Earth's matter density profile on the neutrino oscillation transition probabilities for atmospheric neutrinos.

hep-ph↗
arXiv2001

T-violating effects in three flavor neutrino oscillations in matter

In this talk, we consider the interplay of fundamental and matter-induced T-violating effects in neutrino oscillations in matter. We present a simple approximative analytical formula for the T-violating probability asymmetry for three flavor neutrino oscillations in matter with an arbitrary density profile. We also discuss some implications of the obtained results. Since there are no T-violating effects in two flavor neutrino case (in the limit of vanshing $θ_{13}$ or $Δm_{21}^2$, the three flavor neutrino oscillations reduces to the two flavor ones), the T-violating probability asymmetry can, in principle, provide a way to measure $θ_{13}$ and $Δm_{21}^2$.

hep-ph↗
arXiv2001

A combined treatment of neutrino decay and neutrino oscillations

Neutrino decay in vacuum has often been considered as an alternative to neutrino oscillations. Because non-zero neutrino masses imply the possibility of both neutrino decay and neutrino oscillations, we present a model-independent formal treatment of these combined scenarios. For that, we show for the example of Majoron decay that in many cases decay products are observable and may even oscillate. Furthermore, we construct a minimal scenario where we study the physical implications of neutrino oscillations with intermediate decays.

hep-ph↗
arXiv2001

Neutrino oscillations with three flavors in matter of varying density

In this paper, we discuss the evolution operator and the transition probabilities expressed as functions of the vacuum mass squared differences, the vacuum mixing angles, and the matter density parameter for three flavor neutrino oscillations in matter of varying density in the plane wave approximation. The applications of this to neutrino oscillations in a model of the Earth's matter density profile, step function matter density profiles, constant matter density profiles, linear matter density profiles, and finally in a model of the Sun's matter density profile are discussed. We show that for matter density profiles, which do not fluctuate too much, the total evolution operator consisting of $n$ operators can be replaced by one single evolution operator in the semi-classical approximation.

hep-ph↗
arXiv2000

Weak magnetism in chiral quark models

We discuss symmetry breaking in the weak magnetism form factors for the semileptonic octet baryon decays. In the chiral quark model, the symmetry breaking can be accounted for in the masses and the quark spin polarizations can take on more general values due to Goldstone boson depolarization. Here we clarify some features of the chiral quark model prediction for the weak magnetism and compare to the corresponding result of the chiral quark soliton model.

hep-ph↗
arXiv2000

Neutrino oscillations with three flavors in matter: Applications to neutrinos traversing the Earth

Analytic formulas are presented for three flavor neutrino oscillations in matter in the plane wave approximation. We calculate in particular the time evolution operator in both mass and flavor bases. We also find the transition probabilities expressed as functions of the vacuum mass squared differences, the vacuum mixing angles, and the matter density parameter. The application of this to neutrino oscillations for both atmospheric and long baseline neutrinos in a mantle-core-mantle step function model of the Earth's matter density profile is discussed.

hep-ph↗
arXiv2000

Three flavor neutrino oscillations in matter

We derive analytic expressions for three flavor neutrino oscillations in the presence of matter in the plane wave approximation using the Cayley-Hamilton formalism. Especially, we calculate the time evolution operator in both flavor and mass bases. Furthermore, we find the transition probabilities, matter mass squared differences, and matter mixing angles all expressed in terms of the vacuum mass squared differences, the vacuum mixing angles, and the matter density. The conditions for resonance in the presence of matter are also studied in some examples.

hep-ph↗