[Paper Review] Neutrino oscillation bounds on quantum decoherence

Valentina De Romeri, C. Giunti+2 more|arXiv (Cornell University)|Jun 26, 2023

Neutrino Physics Research4 citations

TL;DR

This paper investigates quantum decoherence in neutrino oscillations using a phenomenological open quantum systems framework, analyzing data from reactor (RENO, Daya Bay, KamLAND) and accelerator (NOvA, MINOS/MINOS+, T2K) experiments. It sets the most stringent constraints to date on decoherence parameters, with bounds as low as $\Gamma_{ij} \lesssim 8 \times 10^{-27}$ GeV at 90% confidence level, and projects improved sensitivities for future facilities DUNE and JUNO across various energy-dependent models.

ABSTRACT

We consider quantum-decoherence effects in neutrino oscillation data. Working in the open quantum system framework we adopt a phenomenological approach that allows to parameterize the energy dependence of the decoherence effects. We consider several phenomenological models. We analyze data from the reactor experiments RENO, Daya Bay and KamLAND and from the accelerator experiments NOvA, MINOS/MINOS+ and T2K. We obtain updated constraints on the decoherence parameters quantifying the strength of damping effects, which can be as low as $Γ_{ij} \lesssim 8 imes 10^{-27}$ GeV at 90% confidence level in some cases. We also present sensitivities for the future facilities DUNE and JUNO.

Motivation & Objective

• To constrain quantum decoherence effects in neutrino oscillations using a phenomenological open quantum systems approach.
• To analyze energy-dependent decoherence parameters $\Gamma_{ij} \propto E^n$ across multiple experimental datasets.
• To update and extend existing bounds on decoherence, particularly for negative exponents $n < 0$, which were previously less constrained.
• To project sensitivities for future experiments DUNE and JUNO on decoherence parameters.
• To assess the robustness of standard neutrino oscillation parameters under decoherence, especially $\sin^2\theta_{13}$ and $\Delta m_{21}^2$.

Proposed method

• Adopt a phenomenological open quantum systems framework to model neutrino decoherence as energy-dependent damping in oscillation probabilities.
• Parameterize decoherence effects via $\Gamma_{ij} \propto E^n$, allowing for $n \geq 0$, $n = 0$, and $n < 0$ to cover diverse physical origins.
• Perform individual global fits to data from RENO, Daya Bay, KamLAND, NOvA, MINOS/MINOS+, and T2K, with dedicated priors on oscillation parameters.
• Use Markov Chain Monte Carlo (MCMC) methods to compute 90% confidence level upper limits on $\Gamma_{ij}$ for each model and $n$.
• Compare results across models (A–G) with different $\Gamma_{ij}$ nonzero, identifying the most constraining experiment per case.
• Project sensitivities for DUNE and JUNO by simulating expected data under the same framework.

Experimental results

Research questions

• RQ1 What are the tightest constraints on energy-dependent neutrino decoherence parameters $\Gamma_{ij} \propto E^n$ from current reactor and accelerator experiments?
• RQ2 How do bounds on $\Gamma_{ij}$ vary with the exponent $n$, especially for negative values $n < 0$?
• RQ3 Which experiment provides the most stringent bound for each decoherence model and $n$ value?
• RQ4 To what extent are standard neutrino oscillation parameters like $\sin^2\theta_{13}$ and $\Delta m_{21}^2$ affected by decoherence in current data?
• RQ5 How will future experiments DUNE and JUNO improve sensitivity to quantum decoherence compared to current bounds?

Key findings

• The strongest bound on any $\Gamma_{ij}$ parameter is $\Gamma_{ij} \lesssim 8 \times 10^{-27}$ GeV at 90% confidence level, achieved in model F with $n = -2$.
• For negative exponents $n < 0$, the paper reports the most stringent bounds to date, improving previous limits by up to two orders of magnitude in some cases.
• The RENO experiment sets the tightest bound in model A ($\Gamma_{21}$ only) at $1.0 \times 10^{-24}$ GeV, while KamLAND sets the limit in model B at $7.9 \times 10^{-27}$ GeV.
• NOvA data is analyzed for the first time in this context, contributing to bounds in models D and E with $\Gamma_{31}$ and $\Gamma_{21}$, respectively.
• Sensitivities for DUNE and JUNO indicate that bounds for $n \geq 0$ can be significantly improved, with DUNE expected to outperform current experiments.
• The analysis shows that $\sin^2\theta_{13}$ measurements at Daya Bay and RENO are sensitive to decoherence, necessitating free parameters in subsequent analyses.