Matter Oscillations Research Articles

‘‘Sonoluminescence’’ from the early Universe

The tens of microkelvin variations in the temperature of the cosmic microwave background (CMB) across the sky are snapshots of the Universe at 400<th>000 years of age and a Rosetta Stone for unraveling its earliest history. During the first 400<th>000 years the lumpy distribution of dark matter excited gravity-driven acoustic oscillations of the ordinary matter. Pressure provided by the photons in the CMB, which were tightly coupled to the ordinary matter, acted as the restoring force for these compressional modes. During an oscillation, photons were alternately compressed and heated, and rarefied and cooled. Ordinary matter and photons decoupled at 400<th>000 years, and CMB photons streamed freely to us, creating a snapshot of modes caught at maximum compression (hot spots) and maximum rarefaction (cold spots) at this early time. The pattern of hot and cold spots on the CMB sky today is being used to determine the curvature of the Universe, the Hubble constant, the total amount of ordinary matter and of dark matter, and to test theories of the early Universe including inflation.

Optimizing T-violating effects for neutrino oscillations in matter

Matter effects may strongly enhance the Jarlskog factor J in T- and CP-violating three-neutrino oscillation probabilities. However, we show that when J is enhanced, the same matter effects suppress the oscillating factors and increase the oscillation length. The net result is that there is no large enhancement in measurable probabilities for earth-bound experiments using neutrino parameters suggested by current experiments. We show that by an appropriate choice of the experimental parameters, neutrino energy and travel length, the T-violating probability can be enhanced by matter effects over their vacuum values by 50%. Our approach is analytical, allowing considerable insight into the underlying physics.

Matter effects in oscillations of neutrinos traveling short distances in matter

It is well known that when the distance t traveled by neutrinos in matter is short, matter effects in oscillations of neutrino flavour are small and decrease with decreasing t more rapidly than the oscillations effects themselves. We discuss the reason for this and demonstrate that under certain circumstances this statement is no longer correct. In particular, we show that if neutrinos propagate significant distances in vacuum before entering matter (or after exiting it), matter effects in short- t neutrino oscillations can be significantly enhanced. Implications for oscillations of solar and atmospheric neutrinos with nearly horizontal trajectories inside the Earth and for accelerator experiments are considered. We also comment on neutrino oscillations in matter due to flavour changing neutral currents.

Neutrino Oscillations in Matter and Their Applications

In this paper, an introduction to the evolution operator method for three flavor neutrino oscillations in matter based on the Cayley–Hamilton formalism is presented as well as some its theoretical and experimental applications.

CPT-Odd resonances in neutrino oscillations

We consider the consequences for future neutrino factory experiments of small CPT-odd interactions in neutrino oscillations. The nu(&mgr;)-->nu(&mgr;) and nu;(&mgr;)-->nu;(&mgr;) survival probabilities at a baseline L = 732 km can test for CPT-odd contributions at orders of magnitude better sensitivity than present neutrino sector limits. Interference between the CPT-violating interaction and CPT-even mass terms in the Lagrangian can lead to a resonant enhancement of the oscillation amplitude. For oscillations in matter, a simultaneous enhancement of both neutrino and antineutrino oscillation amplitudes is possible.

Oscillations of Static Discs around Schwarzschild Black Holes: Effect of Self-Gravitation

Abstract The oscillations of accretion-disc matter about roughly circular motion may produce a quasi-periodic variation in the observed signal (Ipser 1996, AAA 65.067.047). They were studied theoretically on non-gravitating, test discs, in a pseudo-Newtonian manner as well as in general relativity, both in static and in stationary fields. The present paper shows how the radial profiles of oscillation frequencies can be modified by the self-gravity of the disc. Exact superpositions of a Schwarzschild black hole with the Lemos and Letelier (1994, AAA 61.067.077) annular discs (static thin discs obtained by inversion of the first Morgan-Morgan solution) are considered to be simple (static) models of an accretion system. Both the epicyclic and perpendicular frequencies are plotted against the Schwarzschild radius, the circumferential radius, and the proper distance from the horizon. The curves indicate that in the innermost parts more massive discs are more stable with respect to horizontal perturbations, whereas they are less stable with respect to vertical perturbations. In the case of a sequence of discs interpretable as counter-rotating particles on stable time-like circular geodesics and having their inner rims just on marginally stable circular orbits, oscillations of the inner parts get faster with increasing disc mass; the maximum of the epicyclic frequency, important for trapping of the low-frequency modes near the inner radius, moves to smaller radii and becomes somewhat higher.

Neutrino oscillations at an entry-level neutrino factory and beyond

We consider the parameters of an entry-level neutrino factory designed to make the first observation of ${\ensuremath{\nu}}_{e}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{\ensuremath{\mu}}$ oscillations, measure the corresponding amplitude ${\mathrm{sin}}^{2}2{\ensuremath{\theta}}_{13},$ and determine the sign of the atmospheric-scale $\ensuremath{\delta}{m}_{32}^{2}$ via matter effects. A 50 kt detector, a stored muon energy ${E}_{\ensuremath{\mu}}>~20 \mathrm{GeV}$ and ${10}^{19}$ muon decays would enable these goals to be met provided ${\mathrm{sin}}^{2}2{\ensuremath{\theta}}_{13}>0.01.$ The determination of the sign of $\ensuremath{\delta}{m}_{32}^{2}$ also requires a baseline $L>~2000 \mathrm{km}.$ An upgraded neutrino factory with $\mathrm{O}{(10}^{20})$ decays would enable the first observation of ${\ensuremath{\nu}}_{e}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ oscillations. With $\mathrm{O}{(10}^{21})$ decays the effects of a large $\mathrm{CP}$ phase could be measured in the case of the large angle matter oscillation solution to the solar neutrino anomaly. Our analysis includes a family of three-neutrino models that can account for the atmospheric and solar neutrino oscillation indications.

Geophysical constraints on mirror matter within the Earth

We have performed a detailed investigation of geophysical constraints on the possible admixture of mirror matter inside the Earth. On the basis of the preliminary reference Earth model---the ``standard model'' of the Earth's interior---we have developed a method which allows one to compute changes in various quantities characterizing the Earth (mass, moment of inertia, normal mode frequencies, etc.) due to the presence of mirror matter. As a result we have been able to obtain for the first time the direct upper bounds on the possible concentration of the mirror matter in the Earth. In terms of the ratio of the mirror mass to the Earth mass a conservative upper bound is $3.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}.$ We then analyzed possible mechanisms (such as lunar and solar tidal forces, meteorite impacts and earthquakes) of exciting mirror matter oscillations around the Earth's center. Such oscillations could manifest themselves through global variations of the gravitational acceleration at the Earth's surface. We conclude that such variations are too small to be observed. Our results are valid for other types of hypothetical matter coupled to ordinary matter by gravitation only (e.g. the shadow matter of superstring theories).

Macroscopic forces driven by resonant neutrino conversion

We show that neutrino oscillations in matter are always accompanied by collective forces on the medium. This effect may produce interesting consequences for the background and the neutrino oscillations themselves. The force is maximal in the case of resonant neutrino conversion in the adiabatic regime. We study here the forces driven by ν e − ν μ, τ and ν e − ν s MSW conversion and shortly discuss their possible relevance for the dynamics of a type II supernova.

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.

Mirror matter and heavy singlet neutrino oscillations in the early universe

We investigate the mixing of heavy gauge singlet neutrinos in a mirror matter model employing the seesaw mechanism. The parameter constraints that must be satisfied to prevent the overproduction of mirror matter in the early universe are deduced. We find that no fine tuning in the heavy neutral fermion sector is required for this mirror matter model to satisfy cosmological constraints. Baryogenesis scenarios are briefly discussed in the context of the mirror model.

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.

Magnetic oscillations in dense cold quark matter with four-fermion interactions

The phase structures of Nambu-Jona-Lasinio models with one or two flavours have been investigated at non-zero values of $\mu$ and $H$, where $H$ is an external magnetic field and $\mu$ is the chemical potential. In the phase portraits of both models there arise infinitely many massless chirally symmetric phases, as well as massive ones with spontaneously broken chiral invariance, reflecting the existence of infinitely many Landau levels. Phase transitions of first and second orders and a lot of tricritical points have been shown to exist in phase diagrams. In the massless case, such a phase structure leads unavoidably to the standard van Alphen-de Haas magnetic oscillations of some thermodynamical quantities, including magnetization, pressure and particle density. In the massive case we have found an oscillating behaviour not only for thermodynamical quantities, but also for a dynamical quantity as the quark mass. Besides, in this case we have non-standard, i.e. non-periodic, magnetic oscillations, since the frequency of oscillations is an $H$-dependent quantity.

Neutrino propagation in matter

The enhancement of neutrino oscillations in matter is briefly reviewed. Exact and approximate solutions of the equations describing neutrino oscillations in matter are discussed. The role of stochasticity of the media that the neutrinos propagate through is elucidated.

Splitting of three nearly mass-degenerate neutrinos

Assuming the canonical seesaw mechanism together with an SO(3) family symmetry for leptons, broken only by the charged-lepton masses, I show that the three neutrinos of Majorana mass m 0 are split radiatively in two loops by a maximum finite calculable amount of order 10 −9 m 0 . This is very suitable for dark matter and vacuum solar neutrino oscillations. I also discuss how atmospheric neutrino oscillations can be incorporated.

Parametric resonance in neutrino oscillations in matter

Neutrino oscillations in matter can exhibit a specific resonance enhancement — parametric resonance, which is different from the MSW resonance. Oscillations of atmospheric and solar neutrinos inside the earth can undergo parametric enhancement when neutrino trajectories cross the core of the earth. In this paper we review the parametric resonance of neutrino oscillations in matter. In particular, physical interpretation of the effect and the prospects of its experimental observation in oscillations of solar and atmospheric neutrinos in the earth are discussed.

Phenomenology of neutrino oscillations

This review is focused on neutrino mixing and neutrino oscillations in the light of the recent experimental developments. After discussing possible types of neutrino mixing for Dirac and Majorana neutrinos and considering in detail the phenomenology of neutrino oscillations in vacuum and matter, we review all existing evidence and indications in favour of neutrino oscillations that have been obtained in the atmospheric, solar and LSND experiments. We present the results of the analyses of the neutrino oscillation data in the framework of mixing of three and four massive neutrinos and investigate possibilities to test the different neutrino mass and mixing schemes obtained in this way. We also discuss briefly future neutrino oscillation experiments.

Solar antineutrinos from fluctuating magnetic fields at Kamiokande

We consider the effect of a strongly chaotic magnetic field at the narrow bottom of the convective zone of the Sun together with resonant matter oscillations on the production of electron Majorana antineutrinos. Even for moderate levels of noise, we show that it is possible to obtain a small but significant probability for ν e→ ν e conversions (1–3%) at the energy range 2–10 MeV for large regions of the mixing parameter space while still satisfying present (Super)-Kamiokande antineutrino bounds and observed total rates. In the other hand it would be possible to obtain information about the solar magnetic internal field if antineutrino bounds reach the 1% level and a particle physics solution to the SNP is assumed. The mechanism presented here has the advantage of being independent of the largely unknown magnetic profile of the Sun and the intrinsic neutrino magnetic moment.

Zenith distribution of atmospheric neutrino events and electron neutrino mixing

Assuming atmospheric neutrino oscillations with dominant nu_mu<--->nu_tau transitions, we discuss how subdominant nu_e mixing (within the Chooz reactor bounds) can alter the zenith distributions of neutrino-induced electrons and muons. We isolate two peculiar distortion effects, one mainly related to nu_e mixing in vacuum and the other to matter oscillations, that may be sufficiently large to be detected by the SuperKamiokande atmospheric nu experiment. These effects (absent for pure two-flavor nu_mu<--->nu_tau transitions) do not vanish in the limit of energy-averaged oscillations.

On Resonances and Mixing Angles in Three Neutrino Oscillations in Matter

We find exact analytical expressions for mixing angles in matter in the context of three generation neutrino oscillations in matter to discuss the role of resonances in this phenomenon. We show that some knowledge from conventional two neutrino MSW effect, which has been extended to approximated solutions to three neutrino oscillations, has to be abandoned in this exact approach. We observe that maximal values for the mixing angles in matter are found in nonresonant regions and stationary phases do not coincide anymore with resonances in this simple extension of the MSW effect. We present a general way to identify a resonance and discuss what we can physically expect in these regions