| 1. |
- Akhmedov, Evgeny K., et al.
(författare)
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Series expansions for three-flavor neutrino oscillation probabilities in matter
- 2004
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Ingår i: Journal of High Energy Physics (JHEP). - : IOP Publishing. - 1126-6708 .- 1029-8479. ; 2004:04, s. 078-
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Tidskriftsartikel (refereegranskat)abstract
- We present a number of complete sets of series expansion formulas for neutrino oscillation probabilities in matter of constant density for three flavors. In particular, we study expansions in the mass hierarchy parameter alpha = Deltam(21)(2)/Deltam(31)(2) and mixing parameter s(13) = sin theta(13) up to second order and expansions only in alpha and only in s(13) up to first order. For each type of expansion we also present the corresponding formulas for neutrino oscillations in vacuum. We perform a detailed analysis of the accuracy of the different sets of series expansion formulas and investigate which type of expansion is most accurate in different regions of the parameter space spanned by the neutrino energy E, the baseline length L, and the expansion parameters alpha and s(13). We also present the formulas for series expansions in alpha and in s(13) up to first order for the case of arbitrary matter density profiles. Furthermore, it is shown that in general all the 18 neutrino and antineutrino oscillation probabilities can be expressed through just two independent probabilities.
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| 2. |
- Akhmedov, Evgeny, et al.
(författare)
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T violation in neutrino oscillations in matter
- 2001
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Ingår i: Nuclear Physics B. - : Elsevier Science B.V.. - 0550-3213 .- 1873-1562. ; 608:02-jan, s. 394-422
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Tidskriftsartikel (refereegranskat)abstract
- We consider the interplay of fundamental and matter-induced T violation effects in neutrino oscillations in matter. After discussing the general features of these effects we derive a simple approximate analytic expression for the T-violating probability asymmetry DeltaP(ab)(T) for three-flavour neutrino oscillations in a matter with an arbitrary density profile in terms of the two-flavour neutrino amplitudes. Explicit examples are given for the cases of a two-layer medium and for the adiabatic Emit in the general case. We then discuss implications of the obtained results for long baseline experiments. We show, in particular, that asymmetric matter effects cannot hinder the determination of the fundamental CP- and T-violating phase delta (CP) in the long baseline experiments as far as the error in this determination is larger than 1% at 99% CL. Since there are no T-violating effects in the two-flavour case, and in the limits of vanishing theta (13) or Deltam(21)(2) the three-flavour neutrino oscillations effectively reduce to the two-flavour ones, studying the T-violating asymmetries ApT ab can in principle provide us with a complementary means of measuring theta (13) and Deltam(21)(2).
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| 3. |
- Bilenky, Samoil M., et al.
(författare)
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Tests of CPT invariance at neutrino factories
- 2002
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Ingår i: Physical Review D. Particles and fields. - : The American Physical Society. - 0556-2821 .- 1089-4918. ; 65:7, s. 073024-1-073024-6
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Tidskriftsartikel (refereegranskat)abstract
- 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 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)-(m) over bar (3)\less than or similar to1.9x10(-4) eV could be achieved.
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| 4. |
- Duerr, Michael, et al.
(författare)
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On the quantitative impact of the Schechter-Valle theorem
- 2011
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :6, s. 091-
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Tidskriftsartikel (refereegranskat)abstract
- We evaluate the Schechter-Valle (Black Box) theorem quantitatively by considering the most general Lorentz invariant Lagrangian consisting of point-like operators for neutrinoless double beta decay. It is well known that the Black Box operators induce Majorana neutrino masses at four-loop level. This warrants the statement that an observation of neutrinoless double beta decay guarantees the Majorana nature of neutrinos. We calculate these radiatively generated masses and find that they are many orders of magnitude smaller than the observed neutrino masses and splittings. Thus, some lepton number violating New Physics (which may at tree-level not be related to neutrino masses) may induce Black Box operators which can explain an observed rate of neutrinoless double beta decay. Although these operators guarantee finite Majorana neutrino masses, the smallness of the Black Box contributions implies that other neutrino mass terms (Dirac or Majorana) must exist. If neutrino masses have a significant Majorana contribution then this will become the dominant part of the Black Box operator. However, neutrinos might also be predominantly Dirac particles, while other lepton number violating New Physics dominates neutrinoless double beta decay. Translating an observed rate of neutrinoless double beta decay into neutrino masses would then be completely misleading. Although the principal statement of the Schechter-Valle theorem remains valid, we conclude that the Black Box diagram itself generates radiatively only mass terms which are many orders of magnitude too small to explain neutrino masses. Therefore, other operators must give the leading contributions to neutrino masses, which could be of Dirac or Majorana nature.
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| 5. |
- Lindner, Manfred, et al.
(författare)
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A combined treatment of neutrino decay and neutrino oscillations
- 2001
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Ingår i: Nuclear Physics B. - : Elsevier Science B.V.. - 0550-3213 .- 1873-1562. ; 607:02-jan, s. 326-354
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Tidskriftsartikel (refereegranskat)abstract
- Neutrino decay in vacuum has often been considered as an alternative to neutrino oscillations. Because nonzero 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 in which we study the physical implications of neutrino oscillations with intermediate decays.
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| 6. |
- Lindner, Manfred, et al.
(författare)
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Decays of supernova neutrinos
- 2002
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Ingår i: Nuclear Physics B. - : Elsevier Science B.V.. - 0550-3213 .- 1873-1562. ; 622:02-jan, s. 429-456
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 7. |
- Lindner, Manfred, et al.
(författare)
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Seesaw mechanisms for Dirac and Majorana neutrino masses
- 2002
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Ingår i: Physical Review D. Particles and fields. - : The American Physical Society. - 0556-2821 .- 1089-4918. ; 65:5, s. 053014-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the seesaw mechanism for generally non-fine-tuned n x 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 seesaw mechanism. In particular, we study 4 x 4 and 6 x 6 mass matrix textures and give some examples in order to highlight these types of texture. Next, we present a model scheme based on non-Abelian and discrete symmetries satisfying 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.
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| 8. |
- Lindner, Manfred, et al.
(författare)
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Soft L-e - L-mu - L-tau flavour symmetry breaking and sterile neutrino keV Dark Matter
- 2011
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; 2011:01, s. 034-
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Tidskriftsartikel (refereegranskat)abstract
- We discuss how a L-e - L-mu - L-tau flavour symmetry that is softly broken leads to keV sterile neutrinos, which are a prime candidate for Warm Dark Matter. This is to our knowledge the first model where flavour symmetries are applied simultaneously to active and sterile neutrinos explaining at the same time active neutrino properties and this peculiar Dark Matter scenario. The essential point is that different scales of the symmetry breaking and the symmetry preserving entries in the mass matrix lead to one right- handed neutrino which is nearly massless compared to the other two. Furthermore, we naturally predict vanishing theta(13) and maximal theta(23), while the correct value of theta(12) must come from the mixing of the charged leptons. We can furthermore predict an exact mass spectrum for the light neutrinos, which will be testable in the very near future.
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| 9. |
- Lindner, Manfred, et al.
(författare)
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Tomography of the Earth's core using supernova neutrinos
- 2003
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Ingår i: Astroparticle physics. - : Elsevier B.V.. - 0927-6505 .- 1873-2852. ; 19:6, s. 755-770
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the possibility to use the neutrinos coming from a future galactic supernova explosion to perform neutrino oscillation tomography of the Earth's core. We propose to use existing or planned detectors, resulting in an additional payoff. Provided that all of the discussed uncertainties can be reduced as expected, we find that the average matter densities of the Earth's inner and outer cores could be measured with a precision competitive with geophysics. However, since seismic waves are more sensitive to matter density jumps than average matter densities, neutrino physics would give partly complementary information.
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| 10. |
- Weise, Anja, et al.
(författare)
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High-throughput sequencing of microdissected chromosomal regions.
- 2010
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Ingår i: European Journal of Human Genetics. - : Springer Science and Business Media LLC. - 1018-4813 .- 1476-5438. ; 18:4, s. 457-62
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Tidskriftsartikel (refereegranskat)abstract
- The linkage of disease gene mapping with DNA sequencing is an essential strategy for defining the genetic basis of a disease. New massively parallel sequencing procedures will greatly facilitate this process, although enrichment for the target region before sequencing remains necessary. For this step, various DNA capture approaches have been described that rely on sequence-defined probe sets. To avoid making assumptions on the sequences present in the targeted region, we accessed specific cytogenetic regions in preparation for next-generation sequencing. We directly microdissected the target region in metaphase chromosomes, amplified it by degenerate oligonucleotide-primed PCR, and obtained sufficient material of high quality for high-throughput sequencing. Sequence reads could be obtained from as few as six chromosomal fragments. The power of cytogenetic enrichment followed by next-generation sequencing is that it does not depend on earlier knowledge of sequences in the region being studied. Accordingly, this method is uniquely suited for situations in which the sequence of a reference region of the genome is not available, including population-specific or tumor rearrangements, as well as previously unsequenced genomic regions such as centromeres.
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