It has been claimed that wave packets must be covariant and also that decohered neutrino oscillations are always revived during measurement. These conjectures are supported by general arguments which are not specific to the electroweak theory, and so if they are true for neutrinos they will also be true for simplified models. In this paper we produce such a simplified model in which the neutrino wave function, including its entanglement with the source particle and the environment, can be calculated explicitly in quantum field theory. It exhibits neutrino oscillation, which is reduced at late times by decoherence due to interactions of the source with the environment. One simple lesson from this model is that only the difference between the environmental interactions before and after neutrino emission can reduce the amplitude of neutrino oscillations. The model will be used to test the conjectures in a companion paper.It has been claimed that wave packets must be covariant and also that decohered neutrino oscillations are always revived during measurement. These conjectures are supported by general arguments which are not specific to the electroweak theory, and so if they are true for neutrinos they will also be true for simplified models. In this paper we produce such a simplified model in which the neutrino wave function, including its entanglement with the source particle and the environment, can be calculated explicitly in quantum field theory. It exhibits neutrino oscillation, which is reduced at late times by decoherence due to interactions of the source with the environment. One simple lesson from this model is that only the difference between the environmental interactions before and after neutrino emission can reduce the amplitude of neutrino oscillations. The model will be used to test the conjectures in a companion paper.

arXiv:1902.03934Feb 11, 20192 citations

Measuring entangled neutrino states in a toy model QFT

Hosam Mohammed, Jarah Evslin, Emilio Ciuffoli

Localized wave packet treatments of neutrino oscillations by various groups lead to mutually inconsistent predictions. The neutrino wave packet description arises as an approximate substitute for the evolution of an entangled state which is not localized. The disagreements arise from qualitative differences in the framework which are not specific to electroweak interactions, and so have analogues in simpler models. Therefore in this note we introduce a toy model which allows one to explicitly test these predictions while consistently keeping track of the entanglement of the neutrinos and the source particles. Our study is robust as we use only the Schrodinger picture evolution equations on the entangled state, which are solved explicitly without recourse to the wave packet approximation.Localized wave packet treatments of neutrino oscillations by various groups lead to mutually inconsistent predictions. The neutrino wave packet description arises as an approximate substitute for the evolution of an entangled state which is not localized. The disagreements arise from qualitative differences in the framework which are not specific to electroweak interactions, and so have analogues in simpler models. Therefore in this note we introduce a toy model which allows one to explicitly test these predictions while consistently keeping track of the entanglement of the neutrinos and the source particles. Our study is robust as we use only the Schrodinger picture evolution equations on the entangled state, which are solved explicitly without recourse to the wave packet approximation.

Nuclear Physics BJul 9, 20205 citations

Yet another QFT model of neutrino oscillations

Walter Grimus

We consider a quantum field theory (QFT) model of neutrino oscillations in vacuum that attempts to take into account that the neutrino source particle and the neutrino detection particle both interact with their respective environments by collisions. Our model is minimal in a twofold sense. Firstly we simply assume that neutrino production and detection take place in between collisions in time intervals $Δt$ and $τ$ , respectively. Secondly, we only introduce the two wave packets that are absolutely necessary which are those of the neutrino source and the neutrino detection particle. Within this model we find that, for all practical purposes, there are no decoherence effects in the neutrino oscillation amplitude and oscillations occur in space not in time. Moreover, our model leads to the correct time correlation between neutrino production and detection and to a factorization of the event rate of the compound neutrino production--detection process into decay rate, oscillation probability and detection cross section.We consider a quantum field theory (QFT) model of neutrino oscillations in vacuum that attempts to take into account that the neutrino source particle and the neutrino detection particle both interact with their respective environments by collisions. Our model is minimal in a twofold sense. Firstly we simply assume that neutrino production and detection take place in between collisions in time intervals $Δt$ and $τ$, respectively. Secondly, we only introduce the two wave packets that are absolutely necessary which are those of the neutrino source and the neutrino detection particle. Within this model we find that, for all practical purposes, there are no decoherence effects in the neutrino oscillation amplitude and oscillations occur in space not in time. Moreover, our model leads to the correct time correlation between neutrino production and detection and to a factorization of the event rate of the compound neutrino production--detection process into decay rate, oscillation probability and detection cross section.

arXiv:2303.16655Mar 29, 20230 citations

Where neutrino decoherence lies

Emilio Ciuffoli, Jarah Evslin

Abstract Recently, several studies of neutrino oscillations in the vacuum have not found the decoherence long expected from the separation of wave packets of neutrinos in different mass eigenstates. We show that such decoherence will, on the other hand, be present in a treatment including any mechanism which leads to a dependence of the final state on both the neutrino’s emission and absorption time. Using a simplified model in $1+1$ 1 + 1 d, we show that if the positions of the final state particles are measured, or equivalently entangled with the environment, then decoherence will damp neutrino oscillations. We also show that wave packet spreading can cause the decoherence to eventually saturate, without completely suppressing the oscillations. These results are not an artifact of the approximation used: we show that, considering the $V-A$ V - A model in $3+1$ 3 + 1 d, the difference would be simply a total multiplicative factor that would not affect the oscillation probability nor the decoherence.Abstract Recently, several studies of neutrino oscillations in the vacuum have not found the decoherence long expected from the separation of wave packets of neutrinos in different mass eigenstates. We show that such decoherence will, on the other hand, be present in a treatment including any mechanism which leads to a dependence of the final state on both the neutrino’s emission and absorption time. Using a simplified model in $$1+1$$ 1 + 1 d, we show that if the positions of the final state particles are measured, or equivalently entangled with the environment, then decoherence will damp neutrino oscillations. We also show that wave packet spreading can cause the decoherence to eventually saturate, without completely suppressing the oscillations. These results are not an artifact of the approximation used: we show that, considering the $$V-A$$ V - A model in $$3+1$$ 3 + 1 d, the difference would be simply a total multiplicative factor that would not affect the oscillation probability nor the decoherence.

arXiv:2205.05367The European Physical Journal CDec 6, 20223 citations

Neutrino Oscillations in the Vacuum

Emilio Ciuffoli, Jarah Evslin, Hosam Mohammed

The initial configuration of a neutrino experiment consists of wave packets, created by the experimenter. Unmeasured final states are essentially delocalized, but it is conventional to nonetheless treat them as localized wave packets as they are in a sense measured by the environment. In this note we consider an experiment in the vacuum, and so there is no environment and the unmeasured final states are not localized. We introduce a simplified but consistent model of neutrino interactions and numerically evolve the system over a finite time using the Hamiltonian to obtain the oscillation probability. All particles involved in neutrino production or detection, localized or not, are treated and evolved consistently in quantum field theory, keeping all entanglements.The initial configuration of a neutrino experiment consists of wave packets, created by the experimenter. Unmeasured final states are essentially delocalized, but it is conventional to nonetheless treat them as localized wave packets as they are in a sense measured by the environment. In this note we consider an experiment in the vacuum, and so there is no environment and the unmeasured final states are not localized. We introduce a simplified but consistent model of neutrino interactions and numerically evolve the system over a finite time using the Hamiltonian to obtain the oscillation probability. All particles involved in neutrino production or detection, localized or not, are treated and evolved consistently in quantum field theory, keeping all entanglements.

arXiv:1909.13529Sep 30, 20190 citations

Quantum Decoherence in Neutrino Oscillations

Emilio Ciuffoli

Quantum decoherence in neutrino oscillations was theorized almost 50 years ago, however there is still no clear theoretical understanding of this phenomenon, not even agreement on whether or not it could be observed at all. Treating all particles, including the source and detector, consistently in QFT, we are working on a model where the decoherence emerges from the time evolution of the initial state. We started by studying some simplified cases, obtaining nonetheless interesting results: we have shown that environmental interactions play crucial role in the emergence of decoherence, and if the neutrino creation happens in vacuum there is no maximal coherence length. We have also shown that some of the assumptions commonly used in literature (such as the covariance of the wavepackets) are inconsistent, since the time evolution would break the Lorentz invariance; moreover we have seen that, contrary to the usual intuition, the uncertainty on the detector momentum does not always play a relevant role in decoherence, at least as long as the detector particle is non-relativistic, since its contribution is suppressed by a factor proportional to p/M. Finally, we also notice the emergence of a new quantum effect: when the first neutrinos arrive, the oscillations do not starts immediately but only a very short amount of time; however, since the time window when this effect would be observable is extremely small, the precision required to measure such an effect is most likely well beyond the current technical capabilitiesQuantum decoherence in neutrino oscillations was theorized almost 50 years ago, however there is still no clear theoretical understanding of this phenomenon, not even agreement on whether or not it could be observed at all. Treating all particles, including the source and detector, consistently in QFT, we are working on a model where the decoherence emerges from the time evolution of the initial state. We started by studying some simplified cases, obtaining nonetheless interesting results: we have shown that environmental interactions play crucial role in the emergence of decoherence, and if the neutrino creation happens in vacuum there is no maximal coherence length. We have also shown that some of the assumptions commonly used in literature (such as the covariance of the wavepackets) are inconsistent, since the time evolution would break the Lorentz invariance; moreover we have seen that, contrary to the usual intuition, the uncertainty on the detector momentum does not always play a relevant role in decoherence, at least as long as the detector particle is non-relativistic, since its contribution is suppressed by a factor proportional to p/M. Finally, we also notice the emergence of a new quantum effect: when the first neutrinos arrive, the oscillations do not starts immediately but only a very short amount of time; however, since the time window when this effect would be observable is extremely small, the precision required to measure such an effect is most likely well beyond the current technical capabilities

International Workshop on Neutrinos from Accelerators (NuFact)Mar 31, 20220 citations

Δt

and

τ

, respectively. Secondly, we only introduce the two wave packets that are absolutely necessary which are those of the neutrino source and the neutrino detection particle. Within this model we find that, for all practical purposes, there are no decoherence effects in the neutrino oscillation amplitude and oscillations occur in space not in time. Moreover, our model leads to the correct time correlation between neutrino production and detection and to a factorization of the event rate of the compound neutrino production--detection process into decay rate, oscillation probability and detection cross section.

1+1

1 + 1 d, we show that if the positions of the final state particles are measured, or equivalently entangled with the environment, then decoherence will damp neutrino oscillations. We also show that wave packet spreading can cause the decoherence to eventually saturate, without completely suppressing the oscillations. These results are not an artifact of the approximation used: we show that, considering the

V-A

V - A model in

3+1

3 + 1 d, the difference would be simply a total multiplicative factor that would not affect the oscillation probability nor the decoherence.