[Paper Review] Production process dependence of neutrino flavor conversion

Subhendra Mohanty|arXiv (Cornell University)|Jun 11, 1997

Neutrino Physics Research4 references3 citations

TL;DR

This paper investigates how the production process of neutrinos—specifically the lifetime of the parent resonance—affects flavor oscillation patterns. Using a covariant wave-packet approach, it shows that long-lived resonances suppress spatial oscillations, leading to a uniform conversion probability independent of baseline; this explains the LSND experiment's enhanced sensitivity to Δm² due to muon decay production, which acts as an effective baseline via the decay lifetime.

ABSTRACT

We perform a covariant wave-packet analysis of neutrino oscillations taking into account the lifetime of the neutrino production process . We find that flavor oscillations in space are washed out when the neutrinos are produced from long lived resonances - and what may be observed in appearance/disappearance experiments is a uniform conversion probability independent of distance. The lifetime of the resonance which produces the neutrinos acts as the the effective baseline of the experiment. For this reason the LSND experiment where neutrinos are produced from muon decay has two orders of magnitude more sensitivity to neutrino mass square difference than other experiments where the neutrinos are produced from pion or kaon decays.

Motivation & Objective

• To understand how the production mechanism of neutrinos influences their flavor oscillation behavior.
• To analyze the impact of the parent particle's lifetime on the coherence and spatial evolution of neutrino wave packets.
• To explain the enhanced sensitivity of the LSND experiment to neutrino mass-squared differences compared to other experiments.
• To clarify why appearance/disappearance experiments may observe uniform conversion probabilities in certain production scenarios.
• To establish a theoretical framework linking production dynamics to effective baseline in neutrino oscillation experiments.

Proposed method

• A covariant wave-packet formalism is employed to model neutrino production and propagation, incorporating finite production duration and decay width.
• The analysis accounts for the finite lifetime of the parent resonance (e.g., muons in LSND), treating it as a source of quantum uncertainty in the production process.
• The time evolution of the neutrino state is computed using relativistic quantum field theory techniques, including interference effects between different production amplitudes.
• The flavor transition probability is derived in the wave-packet framework, with explicit dependence on the production process duration and momentum spread.
• The effective baseline is shown to be determined by the decay width of the parent particle, not just the geometric distance.
• Comparative analysis is performed between neutrino production from pions/kaons (short-lived) and muons (long-lived), highlighting differences in oscillation visibility.

Experimental results

Research questions

• RQ1 How does the finite lifetime of a neutrino-producing resonance affect the spatial coherence of neutrino oscillations?
• RQ2 Why does the LSND experiment exhibit significantly higher sensitivity to Δm² compared to experiments using pion or kaon decays?
• RQ3 To what extent are flavor oscillations washed out when neutrinos are produced from long-lived resonances?
• RQ4 Can the effective baseline in neutrino oscillation experiments be determined by the production process rather than geometric distance?
• RQ5 What is the role of wave-packet overlap and coherence in determining observable oscillation probabilities in different production scenarios?

Key findings

• Neutrino flavor oscillations in space are suppressed when produced from long-lived resonances, leading to a loss of spatial periodicity.
• The effective baseline for oscillation experiments is determined by the decay width of the parent particle, not just the physical distance traveled.
• In the LSND experiment, muon decay (with a lifetime of ~2.2 μs) provides an effective baseline of ~100 m, enhancing sensitivity to small Δm² values by two orders of magnitude.
• For short-lived decays (e.g., pions, kaons), oscillations are observable as a function of distance, while for long-lived sources, the oscillation probability becomes uniform.
• The wave-packet approach confirms that coherence is lost over distances comparable to the production duration, washing out spatial oscillations.
• The model explains the LSND anomaly's detectability in terms of production dynamics rather than solely kinematic parameters.