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Carlo Giunti

Publications and source records attributed to Carlo Giunti.

At least 73 records · Page 4Linked to original sources
arXiv2008

nu_e Disappearance in MiniBooNE

The anomalous excess of low-energy nu_e events measured in the MiniBooNE experiment is explained through a renormalization of the absolute neutrino flux and a simultaneous disappearance of the nu_e's in the beam, which is compatible with that indicated by the results of Gallium radioactive source experiments. We present the results of the fit of MiniBooNE data (P(nu_e->nu_e) = 0.64 +0.08 -0.07) and the combined fit of MiniBooNE data and the nu_e disappearance measured in the Gallium radioactive source experiments, which gives P(nu_e->nu_e) = 0.82 +- 0.04. We show that our interpretation of the data is also compatible with an old indication in favor of nu_e disappearance found from the analysis of the results of beam-dump experiments, leading to P(nu_e->nu_e) = 0.80 +0.03 -0.04.

hep-ph↗
arXiv2008

Rates of Processes with Coherent Production of Different Particles and the GSI Time Anomaly

With the help of an analogy with a double-slit experiment, it is shown that the standard method of calculation of the rate of an interaction process by adding the rates of production of all the allowed final states, regardless of a possible coherence among them, is correct. It is a consequence of causality. The claims that the GSI time anomaly is due to the mixing of neutrinos in the final state of the electron-capture process are refuted. It is shown that the GSI time anomaly may be due to quantum beats due to the existence of two coherent energy levels of the decaying ion with an extremely small energy splitting (about 10^{-15} eV) and relative probabilities having a ratio of about 1/99.

hep-ph↗
arXiv2008

Neutrino Flavor States and the Quantum Theory of Neutrino Oscillations

The standard theory of neutrino oscillations is reviewed, highlighting the main assumptions: the definition of the flavor states, the equal-momentum assumption and the time = distance assumption. It is shown that the standard flavor states are correct approximations of the states that describe neutrinos in oscillation experiments. The equal-momentum assumption is shown to be unnecessary for the derivation of the oscillation probability. The time = distance assumption derives from the wave-packet character of the propagating neutrinos. We present a simple quantum-mechanical wave-packet model which allows us to describe the coherence and localization of neutrino oscillations.

hep-ph↗
arXiv2007

Short-Baseline Active-Sterile Neutrino Oscillations?

We suggest the possibility that the anomalies observed in the LSND experiment and the Gallium radioactive source experiments may be due to neutrino oscillations generated by a large squared-mass difference of about 20 - 30 eV^2. We consider the simplest 3+1 four-neutrino scheme that can accommodate also the observed solar and atmospheric neutrino oscillations. We show that, in this framework, the disappearance of nu_e and nu_mu in short-baseline neutrino oscillation experiments is mainly due to active-sterile transitions. The implications of the first MiniBooNE results, appeared after the completion of this paper, are discussed in an addendum.

hep-ph↗
arXiv2006

Neutrino Flavor States and the Quantum Theory of Neutrino Oscillations

The definition and derivation of flavor neutrino states in the framework of standard Quantum Field Theory is reviewed, clarifying some subtle points. It is shown that a flavor neutrino state that describes a neutrino produced or detected in a charged-current weak interaction process depends on the process under consideration and is appropriate for the description of neutrino oscillations as well as for the calculation of neutrino production or detection rates. Hence, we have a consistent framework for the description of neutrino oscillations and interactions in neutrino oscillation experiments. The standard flavor neutrino states are obtained as approximations which describe neutrinos in experiments that are not sensitive to the dependence of neutrino interactions on the neutrino mass differences. It is also shown that the oscillation probability can be derived either through the usual light-ray time = distance approximation or through an average of the space-time dependent oscillation probability over the unobserved propagation time.

hep-ph↗
arXiv2006

Theory and Phenomenology of Neutrino Mixing

We review some fundamental aspects of the theory of neutrino masses and mixing. The results of neutrino oscillation experiments are interpreted as evidence of three-neutrino mixing. Implications for the mixing parameters and the neutrino masses are discussed, with emphasis on the connection with the measurements of the absolute values of neutrino masses in beta decay and neutrinoless double-beta decay experiments and cosmological observations.

hep-ph↗
arXiv2005

Absolute Neutrino Masses

The main aspects of the phenomenology of absolute neutrino masses are reviewed, focusing on the limits on neutrino masses obtained in tritium beta decay experiments, cosmological observations and neutrinoless double-beta decay experiments.

hep-ph↗
arXiv2004

Neutrino Mixing

In this review we present the main features of the current status of neutrino physics. After a review of the theory of neutrino mixing and oscillations, we discuss the current status of solar and atmospheric neutrino oscillation experiments. We show that the current data can be nicely accommodated in the framework of three-neutrino mixing. We discuss also the problem of the determination of the absolute neutrino mass scale through Tritium beta-decay experiments and astrophysical observations, and the exploration of the Majorana nature of massive neutrinos through neutrinoless double-beta decay experiments. Finally, future prospects are briefly discussed.

hep-ph↗
arXiv2004

Theory of Neutrino Oscillations

We present a derivation of the flavor neutrino states which describe neutrinos produced or detected in charged-current weak-interaction processes, including those operating in neutrino oscillation experiments. We also present a covariant derivation of the probability of neutrino oscillations which is consistent with the fact that flavor is Lorentz-invariant. Finally, we clarify the negative answers to three commonly asked questions: "Do charged leptons oscillate?"; "Is the standard phase wrong by a factor of 2?" "Are flavor neutrinos described by Fock states?".

hep-ph↗
arXiv2004

Fock States of Flavor Neutrinos are Unphysical

It is shown that it is possible to construct an infinity of Fock spaces of flavor neutrinos depending on arbitrary unphysical mass parameters, in agreement with the theory of Blasone and Vitiello in the version proposed by Fujii, Habe and Yabuki. However, we show that these flavor neutrino Fock spaces are clever mathematical constructs without physical relevance, because the hypothesis that neutrinos produced or detected in charged-current weak interaction processes are described by flavor neutrino Fock states implies that measurable quantities depend on the arbitrary unphysical flavor neutrino mass parameters.

hep-ph↗
arXiv2004

Flavor Neutrinos States

It is shown that a flavor neutrino state that describes a neutrino produced or detected in a charged-current weak interaction process depends on the process under consideration and is appropriate for the description of neutrino oscillations as well as for the calculation of neutrino production or detection rates. Hence, we have a consistent framework for the description of neutrino oscillations and interactions.

hep-ph↗
arXiv2004

Theory of Neutrino Oscillations

We review critically the main assumptions on which the standard theory of neutrino oscillations is based. We show that all assumptions are realistic, except the so-called "equal momentum assumption", which however is irrelevant. We conclude that the standard expression for the probability of neutrino oscillations is robust.

hep-ph↗
arXiv2004

Theory of Neutrino Oscillations

We review critically the main assumptions on which the standard theory of neutrino oscillations is based. We show that all assumptions are realistic, except the so-called "equal momentum assumption", which however is irrelevant. We briefly review the covariant plane-wave derivation of neutrino oscillations and a quantum field theoretical wave packet model of neutrino oscillations. We show that both approaches lead to the standard expression for the oscillation phase. The wave packet model allows also to describe the coherence of the oscillations and the localization of the production and detection processes.

hep-ph↗
arXiv2004

Neutrino Interferometry In Curved Spacetime

Gravitational lensing introduces the possibility of multiple (macroscopic) paths from an astrophysical neutrino source to a detector. Such a multiplicity of paths can allow for quantum mechanical interference to take place that is qualitatively different to neutrino oscillations in flat space. After an illustrative example clarifying some under-appreciated subtleties of the phase calculation, we derive the form of the quantum mechanical phase for a neutrino mass eigenstate propagating non-radially through a Schwarzschild metric. We subsequently determine the form of the interference pattern seen at a detector. We show that the neutrino signal from a supernova could exhibit the interference effects we discuss were it lensed by an object in a suitable mass range. We finally conclude, however, that -- given current neutrino detector technology -- the probability of such lensing occurring for a (neutrino-detectable) supernova is tiny in the immediate future.

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