Interpreting the LSND anomaly: sterile neutrinos or CPT-violation or…?

Струмиа, Алессандро

doi:10.1016/s0370-2693(02)02042-7

Cited by 115 publications

(110 citation statements)

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“…The point is that if CPT is Violated in the neutrino sector, then such violations will imply signals in atmospheric and solar ν oscillations. The analysis of [53] combined recent results from KamLAND [54] with atmospheric data, as well as recent WMAP satellite data [6]. The results of such an analysis are given in fig.…”

Section: Cpt Breaking Through Locality Violation and Neutrino Anomalimentioning

confidence: 97%

“…The phenomenology of the model has been analyzed in [53], where it was argued that a compilation of all available data from current neutrino experiments does not seem to favor CPT Violating scenaria for neutrino mass spectra. The point is that if CPT is Violated in the neutrino sector, then such violations will imply signals in atmospheric and solar ν oscillations.…”

Section: Cpt Breaking Through Locality Violation and Neutrino Anomalimentioning

confidence: 99%

“…Since such models violate CPT through the ill-definition of a scattering matrix, as explained above, they may provide a natural explanation for the LSND anomaly, provided the latter is confirmed by future experiments. If this is the case, phenomenological analyses such as that in [53] have to be redone by taking into account decoherence effects in the dynamics of neutrinos.…”

Section: Cpt Breaking Through Locality Violation and Neutrino Anomalimentioning

confidence: 99%

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On CPT Symmetry: Cosmological, Quantum-Gravitational and Other Possible Violations and Their Phenomenology

Mavromatos

2004

Springer Proceedings in Physics

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Abstract. I discuss various ways in which CPT symmetry may be violated, and their phenomenology in current or immediate future experimental facilities, both terrestrial and astrophysical. Specifically, I discuss first violations of CPT symmetry due to the impossibility of defining a scattering matrix as a consequence of the existence of microscopic or macroscopic space-time boundaries, such as Planck-scale Black-Hole (event) horizons, or cosmological horizons due to the presence of a (positive) cosmological constant in the Universe. Second, I discuss CPT violation due to breaking of Lorentz symmetry, which may characterize certain approaches to quantum gravity, and third, I describe models of CPT non invariance due to violations of locality of interactions. In each of the above categories I discuss experimental sensitivities. I argue that the majority of Lorentz-violating cases of CPT breaking, with minimal (linear) suppression by the Planck-mass scale, are already excluded by current experimental tests. There are however some (stringy) models which can evade these constraints. CPT Breaking and the Scattering MatrixThe symmetry under the successive operations (in any order) of charge conjugation, C, parity (reflexion), P, and time reversal, T, known as CPT, is a fundamental symmetry of any local quantum field theory in flat space time, under the following assumptions [1]:• (i) Unitarity and the proper definition of a scattering matrix, • (ii) Lorentz Invariance and • (iii) Locality of InteractionsIn the presence of gravity, i.e. non-Minkowski,non-flat space time backgrounds, CPT symmetry may be violated, at least in in its strong form. This is indeed the case of singular space-time gravitational backgrounds, such as black holes, or in general space times with boundaries. The reason is that in such cases the presence of these boundaries jeopardizes requirements (i) and (ii) of the CPT theorem. In a quantum context, a Black hole evaporates due to Hawking radiation, and as such it may 'capture' for ever information on matter states passing nearby, as depicted schematically in figure 1. In such a case, one may not be able to define properly asymptotic state vectors |ψ > in a quantum context, given that Planck size black hole horizons appear as fluctuations of the geometry, and hence an asymptotic observer will necessarily trace out the information captured by the horizons. This means that the out states will be necessarily described by density matrices, ρ = Tr unobs |ψ >< ψ|. One has therefore an evolution from pure states to mixed, and unitarity is lost. The problem in defining asymptotic state vectors also implies the impossibility of defining a proper scattering S-matrix, since the latter connects by definition "in" and "out" state vectors: |OU T >= S|IN >. Instead, one can only define a Hawking $-matrix [2], which connects IN and OUT mixed states described by density matrices:where $ = SS † , with S = e iHt the S-matrix, and H the Hamiltonian of the matter subsystem. The $-matrix has no inverse, as a consequence...

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Section: Cpt Breaking Through Locality Violation and Neutrino Anomalimentioning

confidence: 97%

Section: Cpt Breaking Through Locality Violation and Neutrino Anomalimentioning

confidence: 99%

Section: Cpt Breaking Through Locality Violation and Neutrino Anomalimentioning

confidence: 99%

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On CPT Symmetry: Cosmological, Quantum-Gravitational and Other Possible Violations and Their Phenomenology

Mavromatos

2004

Springer Proceedings in Physics

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“…III C), which both require at least one keV neutrino, while the other two mostly sterile states help "explain" the existing oscillation data where, for all practical purposes, the heaviest neutrino decouples and we are left with an effective 3 + 1 or 3 + 2 picture. We remind readers that a third possibility (2+2 ‡ ) is currently ruled out by solar and atmospheric data [12,13,14] and will be ignored. 3 + 1 schemes that address the LSND anomaly are also disfavored by global analysis of short baseline oscillation experiments [12,13,14,15], and for this reason, we mostly concentrate on 3 + 2 fits to the LSND anomaly [15].…”

Section: Oscillation Phenomenology and Current Evidence For Low-mentioning

confidence: 99%

Neutrino phenomenology of very low-energy seesaw scenarios

2007

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The Standard Model augmented by the presence of gauge-singlet right-handed neutrinos proves to be an ideal scenario for accommodating nonzero neutrino masses. Among the new parameters of this "New Standard Model" are right-handed neutrino Majorana masses M . Theoretical prejudice points to M much larger than the electroweak symmetry breaking scale, but it has recently been emphasized that all M values are technically natural and should be explored. Indeed, M around 1 − 10 eV can accommodate an elegant oscillation solution to the LSND anomaly, while other M values lead to several observable consequences. We consider the phenomenology of low energy (M 1 keV) seesaw scenarios. By exploring such a framework with three right-handed neutrinos, we can consistently fit all oscillation data -including those from LSND -while partially addressing several astrophysical puzzles, including anomalous pulsar kicks, heavy element nucleosynthesis in supernovae, and the existence of warm dark matter. Furthermore, low-energy seesaws -regardless of their relation to the LSND anomaly -can also be tested by future tritium beta-decay experiments, neutrinoless double-beta decay searches, and other observables. We estimate the sensitivity of such probes to M .

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“…This LSND anomaly has yet to be confirmed, and the MiniBooNE experiment at Fermilab [9] should very soon give a definitive confirmation or refutation. Numerous attempts to solve the LSND puzzle, however, have already been proposed [10]. It has been shown that oscillations with extra sterile neutrinos can fit the LSND anomaly [11].…”

Section: Introductionmentioning

confidence: 99%

eV seesaw with four generations

Hou

Soddu

2006

Physics Letters B

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We extend the eV seesaw scenario to four lepton generations. The LSND anomaly is taken as the right-handed seesaw scale, i.e. mR ∼ eV. The fourth generation then gives a heavy pseudo-Dirac neutrino which largely decouples from other generations, and is relatively stable. One effectively has a 3 + 3 solution to the LSND anomaly, where we illustrate with numerical solutions. Our study seems to indicate that the third mixing angle sin 2 θ13 may be less than 0.01.

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Interpreting the LSND anomaly: sterile neutrinos or CPT-violation or…?

Cited by 115 publications

References 50 publications

On CPT Symmetry: Cosmological, Quantum-Gravitational and Other Possible Violations and Their Phenomenology

On CPT Symmetry: Cosmological, Quantum-Gravitational and Other Possible Violations and Their Phenomenology

Neutrino phenomenology of very low-energy seesaw scenarios

eV seesaw with four generations

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