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Coherence of neutrino oscillations in the wave packet approach

High Energy Physics - Phenomenology · Submitted 18 Nov 1997 · 13 references

Pith's verdict: A useful, compact extension of the wave-packet formalism with a real algebra slip in Eq. (13) that shifts, but does not kill, the new coherence bound.

T0 · AI review

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arXiv IDhep-ph/9711363 (version 2)
Pith IDMTEJWZZ7, Pith's permanent record of this paper and its review
CitationC. Giunti, C.W. Kim. "Coherence of neutrino oscillations in the wave packet approach." arXiv:hep-ph/9711363 (1997). https://pith.science/paper/MTEJWZZ7
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Referee report
The paper

The paper claims

Precise measurement of the particles that detect a neutrino can stretch the distance over which its mass states still interfere, but a wave-packet calculation puts a ceiling on that stretch, set by the neutrino energy and the mass-squared差距

The reading

Neutrino oscillations only happen if the different mass eigenstates in a neutrino beam stay coherent long enough to interfere at the detector. Earlier wave-packet treatments of this effect accounted for the production process but dropped the corresponding coherence widths of the detection process. This paper adds them back: the detected neutrino is described by its own gaussian wave packet, and the transition amplitude becomes an overlap integral between the propagating packet and that detection packet. The result confirms that sharply measuring the energies of the particles involved in detection widens the effective packet and lengthens the coherence length, but it also shows the gain cannot run away: past a bound set by the neutrino energy and the mass-squared difference, the interference is washed out no matter how good the energy measurement is.

What carries the argument

The load-bearing device is the overlap integral between two gaussian wave packets: the propagating state produced at the source and a separate gaussian state representing the neutrino the detector is able to absorb. Their widths add in quadrature, $1sigma_x^2 = 1sigma_{xP}^2 + 1sigma_{xD}^2$, which is what lets the detection process enter the coherence length at all. The second device is the average of the probability over the detection time $T$, which is not measured in real experiments. That average converts the packet-separation gaussian into the damping factor $1exp[-(L/L_{1mathrm{coh}}^{ab})^2]$ multiplied by $F_{ab} = 1exp[-2pi^2(1-1xi)^2 (1sigma_x/L_{1mathrm{osc}}^{ab})^2]$, where $1xi$ parametrizes how the mass eigenstate energies are fixed by production kinematics. The interplay of these two exponentials is what produces both the claimed gain and the claimed ceiling.

Extended reading notes

Core claim

The paper's central claim is that the coherence length of neutrino oscillations has an upper bound. Working in the wave-packet formalism, the authors write the flavor-changing amplitude as the overlap $A_{1D0}(L,T) = 1int dx 1langle1 u_1beta(x-L)|1 u_1alpha(x,T)1rangle$ of the propagating neutrino state with a detection state that carries its own momentum width $1sigma_{pD}$, so that the width controlling coherence is $1sigma_x^2 = 1sigma_{xP}^2 + 1sigma_{xD}^2$ rather than the production width alone. Averaging the resulting probability over the unmeasured detection time $T$ gives the standard oscillation phase together with a damping factor $1exp[-(L/L_{1mathrm{coh}}^{ab})^2]$ and an extra factor $F_{ab}$, with $L_{1mathrm{coh}}^{ab} = 4sqrt{2}1sigma_x E^2/|1Delta m_{ab}^2|$. Because a precise energy measurement in the detector means a small $1sigma_{pD}$ and hence a large $1sigma_{xD}$, the coherence length can indeed be increased, as Kiers, Nussinov and Weiss had observed. But once $1sigma_x$ exceeds the oscillation length, the phase of the interference term depends sensitively on the unmeasured $T$, and the time average erases the interference. That yields the ceiling $L_{1mathrm{coh}}^{ab} 1lesssim E,(L_{1mathrm{osc}}^{ab})^2 = 16pi^2 E^3/(1Delta m_{ab}^2)^2$, beyond which the coherence length stops being a meaningful quantity because coherence is lost at every distance.

Load-bearing premise

The derivation treats the detected neutrino as a gaussian wave packet sharing the propagating states' average momenta and averages the probability over all detection times from minus to plus infinity, an approximation the authors themselves note gives the detector an unphysical response before the neutrino arrives.

Editorial extensions

If this is right

  • Coherence lengths quoted for oscillation experiments should be computed from the larger of the production and detection coherence widths, not from the production width alone.
  • An experiment that measures the recoil particles' energies very precisely gains coherence length only up to $16pi^2 E^3/(1Delta m^2)^2$; beyond that the gain does not translate into visible oscillations.
  • In the opposite regime, where the effective packet width exceeds the oscillation length, the observable transition probability flattens to the averaged value $1sum_a |U_{1alpha a}|^2|U_{1beta a}|^2$ with no oscillatory term.
  • The same washout logic applies when the source distance $L$ rather than the time $T$ is unknown, which the authors note is the situation relevant to neutrino oscillations in the early universe.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • The ceiling is a statement about the unmeasured time, not about the neutrino itself: if a detection scheme could time-stamp the interaction to within the oscillation period, the interference the paper says is washed out would in principle be recoverable.
  • Because the bound scales as $E^3/(1Delta m^2)^2$, the loss of coherence is most severe for low-energy neutrinos with large mass splittings, which is the regime of solar and reactor neutrinos rather than accelerator beams.
  • The authors' own footnote concedes that the gaussian detection packet lets the detector respond before the neutrino arrives; a retarded, causal packet would likely soften rather than remove the ceiling, and checking whether the bound survives that replacement is a concrete calculational target.
Original abstract

The temporal and spatial coherence widths of the microscopic process by which a neutrino is detected are incorporated in the quantum mechanical wave packet treatment of neutrino oscillations, confirming the observation of Kiers, Nussinov and Weiss that an accurate measurement of the energies of the particles participating in the detection process can increase the coherence length. However, the wave packet treatment presented here shows that the coherence length has an upper bound, determined by the neutrino energy and the mass-squared difference, beyond which the coherence of the oscillation process is lost.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13-20260917 via OpenRouter, question bank abstract-p1-20260923, 2026-09-23: 1 request, 2,408 input tokens, $0.0001 reported.

What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.89 · human participants 0.02 · controlled comparison 0.02 · randomized assignment 0.01 · states quantitative result 0.61 · compares with prior results 0.91 · mentions code or data availability 0.01.

The abstract, sentence by sentence

arXiv listing abstract v2. Results and the main claim are underlined; .

The temporal and spatial coherence widths of the microscopic process by which a neutrino is detected are incorporated in the quantum mechanical wave packet treatment of neutrino oscillations, confirming the observation of Kiers, Nussinov and Weiss that an accurate measurement of the energies of the particles participating in the detection process can increase the coherence length. However, the wave packet treatment presented here shows that the coherence length has an upper bound, determined by the neutrino energy and the mass-squared difference, beyond which the coherence of the oscillation process is lost.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 The temporal and spatial coherence widths of the microscopic process by which a neutrino is detected are incorporated in the quantum mechanical wave packet treatment of neutrino oscillations, confirming the observation of Kiers, Nussinov and Weiss that an accurate measurement of the energies of the particles participating in the detection process can increase the coherence length. contribution 0.50 0.27 0.11 asserted 0.98
s1 However, the wave packet treatment presented here shows that the coherence length has an upper bound, determined by the neutrino energy and the mass-squared difference, beyond which the coherence of the oscillation process is lost. result 0.98 0.90 0.79 asserted 1.00

What kind of paper the classifier reports this is: theoretical result 1.00 · evidence from proof or derivation 0.98.

What was examined, and what was not

sources read
  • arXiv listing abstract v2
not examined
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  • figures and tables
  • references and citing sentences
  • relations to other papers
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  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

References
How the literature uses it

36 arXiv papers cite this in 59 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 35 sentences without a confident label

Contests it 1 paper
  • This differs from statements frequently found in the literature, e.g., Refs. [ref] , where it is said that all neutrino mass eigenstates are produced at the moment the source decays, and the different mass eigenstates propagate with different velocities in the lab frame.

    Neutrino Oscillation Measurements Computed in Quantum Field Theory · Discussion and Conclusions · contest 0.79

Uses its method or tool 5 papers
Compares with it 2 papers
Cites it as background 13 papers

Discussion

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