arXiv subjects

Sampsa Vihonen

Publications and source records attributed to Sampsa Vihonen.

At least 19 recordsLinked to original sources

arXiv2026

Revealing precision bounds on neutrino oscillation parameters with quantum estimation theory

Quantum estimation theory provides ultimate precision bounds on parameter estimation, independent of experimental setups. In this article, we apply this theoretical framework to neutrino oscillations, aiming to clarify some subtle issues and reveal the maximum achievable precision of oscillation parameters. First, taking the example of two-flavor oscillations, we clarify how the quantum Fisher information (QFI) depends on the choice of bases when the basis transformation itself involves the parameters in question. Then, for three-flavor oscillations, we compute the QFI matrix for electron and muon neutrino states in the flavor basis and derive analytical expressions and numerical results for both diagonal and off-diagonal elements. The implications of off-diagonal correlations for multiparameter estimation are discussed, and the quantum Cram\'{e}r-Rao bounds on the precision of oscillation parameters for typical reactor and long-baseline accelerator neutrino experiments are obtained. Our results establish a theoretical benchmark for the ultimate precision achievable in future neutrino oscillation experiments.

hep-ph↗

arXiv2025

One-Loop Effects in the Neutrino Matter Potential and Implications for Non-Standard Interactions

In this work, we emphasize that it is necessary to take into account one-loop corrections of $2.0\%$ to the neutrino matter potential in the precision measurements of neutrino oscillation parameters and in the experimental searches for new physics beyond the Standard Model. With the numerical simulation of the DUNE experiment, we study how radiative corrections to the matter potential affect neutrino oscillation probabilities, and thus, the event rates in the presence of neutrino non-standard interactions (NSIs). We find that neglecting one-loop corrections may lead to wrong conclusions for the discovery of NSIs. The implications for the determination of neutrino mass ordering and constraints on the NSI parameters in future long-baseline accelerator neutrino experiments are explored in a quantitative way.

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arXiv2025

Effects of the Matter Potential at One-Loop Level on Neutrino Oscillations in Long-Baseline Experiments

In this work, we investigate in a quantitative way how much radiative corrections to the matter potential for neutrino oscillations can impact the sensitivity to neutrino mass ordering in long-baseline accelerator experiments. Using numerical simulations for the future experiment DUNE, we find that the statistical significance for excluding the incorrect mass ordering can be enhanced by about $0.4σ$ if a one-loop correction of $2.0\%$ -- based on the Fermi coupling constant $G^{}_μ$ derived from measurements of muon lifetime -- is included. The radiative corrections at one-loop level lead to resolving the neutrino mass ordering at $5σ$ confidence level 4-9 days earlier than at tree level. In contrast, the sensitivity to leptonic CP violation in DUNE is essentially unchanged. Finally, we emphasize that one-loop corrections should be incorporated into analyses of future neutrino oscillation data in a consistent and systematic manner.

hep-ph↗

arXiv2025

Revisiting series expansions of neutrino oscillation and decay probabilities in matter

We present analytic expressions for three-flavor neutrino oscillations in presence of invisible neutrino decay and matter effects. Using the well-known Cayley-Hamilton formalism, the leading-order terms are derived for oscillation probabilities in all major channels assuming the neutrino mass eigenstate $ν_3$ to decay. Our work extends and complements previous studies utilizing the Cayley-Hamilton theorem, providing the series expansions for $ν_e \rightarrow ν_e$, $ν_e \rightarrow ν_μ$, $ν_e \rightarrow ν_τ$, $ν_μ\rightarrow ν_μ$ and $ν_μ\rightarrow ν_τ$. The accuracy of the analytical formulas is investigated by comparing the results with numerically calculated probabilities. We also comment on the implications on unitarity violation.

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arXiv2024

Constraining dark matter from strong phase transitions in a $U(1)_{L_μ-L_τ}$ model: Implications for neutrino masses and muon $g-2$

In this paper, we study a non-minimal gauged $U(1)_{L_μ-L_τ}$ model, where we add two complex singlet scalars, three right-handed Majorana neutrinos (RHN), and a vector-like dark fermion to the Standard Model (SM), all non-trivially charged under the extra gauge symmetry. The model offers an easy resolution to the muon $(g-2)$ anomaly, which fixes the scale of spontaneous symmetry breaking. Furthermore, the two-zero minor structure in the RHN mass matrix provides successful predictions for neutrino oscillation parameters, including the Dirac phase. The extended scalar sector can easily induce first-order phase transitions. We identify all possible phase transition patterns in the three-dimensional field space. We quantify the associated gravitational waves from the sound wave source and demonstrate that the signatures can be observed in future space-based experiments. We find that strong first-order phase transitions require large values of scalar quartic couplings which constrain the scalar dark matter (DM) relic density to a maximum of $10^{-2}$ and $10^{-5}$ when we consider the DM direct detection bound. Nonetheless, the model successfully explains the DM relic density via contribution from the vector-like dark fermion. We show the allowed range of the model parameters that can address all the beyond SM issues targeted in this study.

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arXiv2023

Ultralight dark matter in long-baseline accelerator neutrino oscillations

We present a systematic study of the effects of ultralight dark matter (ULDM) on neutrino oscillations using the latest long-baseline data from the T2K and NO$\nu$A experiments. Our analysis covers both flavor-universal and flavor-general scalar interactions, as well as vector interactions associated with the $L_e - L_\mu$ and $L_\mu - L_\tau$ gauge symmetries. Importantly, we explicitly consider the coherence properties of the ULDM by incorporating the resulting stochastic fluctuations into our statistical analysis. We find that in the low-mass regime, $m_\phi \lesssim 10^{-17}$ eV, where the stochastic effects are maximal, the constraints on the ULDM couplings are relaxed by roughly an order of magnitude compared to those in the high-mass regime,$m_\phi \gtrsim 10^{-15}$ eV, where such fluctuations are effectively averaged out. While the combined T2K and NO$\nu$A datasets impose nontrivial exclusion limits on the ULDM interactions, we do not find statistically significant evidence that these effects can alleviate the current tension in determining the charge-parity (CP) violating phase $\delta_{CP}$ between the two experiments. Therefore, it will be essential for future high-precision facilities to further probe the ULDM scenarios and achieve a definitive measurement of $\delta_{CP}$.

hep-ph↗

arXiv2022

Non-minimal Lorentz invariance violation in light of muon anomalous magnetic moment and long-baseline neutrino oscillation data

In light of the increasing hints of new physics at the muon $g-2$ and neutrino oscillation experiments, we consider the recently observed tension in the long-baseline neutrino oscillation experiments as a potential indication of Lorentz invariance violation. For this purpose, the latest data from T2K and NO$ν$A is analysed in presence of non-minimal Lorentz invariance violation. Indeed, we find that isotropic violation in dimensions $D =$ 4, 5 and 6 can alleviate the tension in neutrino oscillation data by 0.4$-$2.4$σ$ CL significance, with the isotropic coefficient $γ^{(5)}_{ττ} =$ 3.58$\times$10$^{-32}$GeV$^{-1}$ yielding the best fit. At the same time, the anomalous muon $g-2$ result can be reproduced with an additional non-isotropic violation of $d^{zt} =$ -1.7$\times$10$^{-25}$. The analysis highlights the possibility of simultaneous relaxation of experimental tensions with Lorentz invariance violation of mixed nature.

hep-ph↗

arXiv2022

Snowmass2021 Whitepaper: Muonium to antimuonium conversion

The spontaneous muonium to antimuonium conversion is one of the interesting charged lepton flavor violation processes. It serves as a clear indication of new physics and plays an important role in constraining the parameter space beyond Standard Model. MACE is a proposed experiment to probe such a phenomenon and expected to enhance the sensitivity to the conversion probability by more than two orders of magnitude from the current best upper constraint obtained by the PSI experiment two decades ago. Recent developments in the theoretical and experimental aspects to search for such a rare process are summarized.

hep-ph↗

arXiv2022

Feasibility study of an accelerator neutrino experiment in China

Future accelerator neutrino experiments will provide a powerful tool to measure standard oscillation parameters and search for new physics. In this context, we discuss the prospects of building an accelerator neutrino experiment in China. The feasibility of such facilities is investigated by evaluating their prospects to the standard mixing parameters. As an example, we consider an SPPC-based neutrino beamline and CJPL-based neutrino detector with 1736 km baseline length. We find this setup able to significantly improve the precision on $δ_{CP}$, $θ_{23}$ and $Δm_{31}^2$.

hep-ex↗

arXiv2022

Overview of the physics prospects in MOMENT

MuOn-decay MEdium-baseline NeuTrino beam facility (MOMENT) is a recently proposed neutrino oscillation experiment that is currently under consideration in China. Based on a novel accelerator concept, MOMENT is capable of delivering 15 MW neutrino beam produced with the decay of positively and negatively charged muons. In this study, the physics performance of MOMENT is briefly reviewed in its baseline setup, involving a 150 km baseline length and large gadolinium-doped Water Cherenkov detector. The prospects are discussed in the case of precision measurements on the Dirac CP phase $δ_{CP}$, which MOMENT is shown to be able to measure by about 8$^\circ$...18$^\circ$ resolution at 1$σ$ CL. It is examined how MOMENT performs as an independent experiment and also as a complementary facility to the future superbeam experiments.

hep-ex↗

arXiv2022

Precision measurements and tau neutrino physics in a future accelerator neutrino experiment

We investigate prospects of building a future accelerator-based neutrino oscillation experiment in China, including site selection, beam optimization and tau neutrino physics aspects. CP violation, non-unitary mixing and non-standard neutrino interactions are discussed. We simulate neutrino beam setups based on muon and beta decay techniques and compare Chinese laboratory sites by their expected sensitivities. A case study on Super Proton-Proton Collider and China JinPing Laboratory is also presented. It is shown that the muon-decay-based beam setup can measure the Dirac CP phase by about 14.2$^\circ$ precision at 1$\,σ$ CL, whereas non-unitarity can be probed down to $|α_{i j}| \lesssim$ 0.37 ($i \neq j =$ 1, 2, 3) and non-standard interactions to $|ε^m_{\ell \ell'}| \lesssim$ 0.11 ($\ell \neq \ell' = e$, $μ$, $τ$) at 90% CL, respectively.

hep-ph↗

arXiv2021

Exploring SMEFT Induced Non-Standard Interactions from COHERENT to Neutrino Oscillations

We investigate the prospects of next-generation neutrino oscillation experiments DUNE, T2HK and JUNO including TAO within Standard Model Effective Field Theory (SMEFT). We also re-interpret COHERENT data in this framework. Considering both charged and neutral current neutrino Non-Standard Interactions (NSIs), we analyse dimension-6 SMEFT operators and derive lower bounds to UV scale $Λ$. The most powerful probe is obtained on ${\cal O}_{{ledq}_{1211}}$ with $Λ\gtrsim$ 450 TeV due to the electron neutrino sample in T2HK near detector. We find DUNE and JUNO to be complementary to T2HK in exploring different subsets of SMEFT operators at about 25 TeV. We conclude that near detectors play a significant role in each experiment. We also find COHERENT with CsI and LAr targets to be sensitive to new physics up to $\sim$900 GeV.

hep-ph↗

arXiv2021

Non-standard interactions in SMEFT confronted with terrestrial neutrino experiments

The Standard Model Effective Field Theory (SMEFT) provides a systematic and model-independent framework to study neutrino non-standard interactions (NSIs). We study the constraining power of the on-going neutrino oscillation experiments T2K, NO$ν$A, Daya Bay, Double Chooz and RENO in the SMEFT framework. A full consideration of matching is provided between different effective field theories and the renormalization group running at different scales, filling the gap between the low-energy neutrino oscillation experiments and SMEFT at the UV scale. We first illustrate our method with a top-down approach in a simplified scalar leptoquark model, showing more stringent constraints from the neutrino oscillation experiments compared to collider studies. We then provide a bottom-up study on individual dimension-6 SMEFT operators and find NSIs in neutrino experiments already sensitive to new physics at $\sim$20 TeV when the Wilson coefficients are fixed at unity. We also investigate the correlation among multiple operators at the UV scale and find it could change the constraints on SMEFT operators by several orders of magnitude compared with when only one operator is considered. Furthermore, we find that accelerator and reactor neutrino experiments are sensitive to different SMEFT operators, which highlights the complementarity of the two experiment types.

hep-ph↗

arXiv2020

Prospects and requirements of opaque detectors in accelerator neutrino experiments

Opaque detectors are a recently proposed novel detector concept where an opaque scintillator aligned with wavelength-shifting fibers is used to enable the discrimination of electron neutrinos and antineutrinos with a rather low energy threshold. In this work, we investigate the potential effects of the enhanced detection capabilities of the opaque detectors in accelerator neutrino experiments. Focusing on the energy threshold, energy resolution, detection efficiency and background suppression in the analysis of electron-like events, we determine whether using opaque detectors could lead to improvements in the CP violation and light sterile neutrino searches in the future accelerator neutrino experiments. We also identify the minimum requirements for the opaque detectors to reach the designated physics goals in the simulated experiments. We find that a 75.6% fraction of $δ_{CP}$ values could be reached for CP violation discovery by 3$σ$ confidence level or better when opaque detectors of 120 kton and 130 kton fiducial masses are used together with neutrino beams from J-PARC and MOMENT, respectively, whereas near detectors placed about 250 m from sources are sufficient to exclude the gallium anomaly at 2$σ$ confidence level.

physics.ins-det↗

arXiv2019

Precision measurements on $δ_\text{CP}$ in MOMENT

As it is very promising to expect a discovery of CP violation in the leptonic sector, the precision measurement of the Dirac CP phase $δ_\text{CP}$ is going to be one of the key interests in the future neutrino oscillation experiments. In this work, we examine the physics reach of the proposed medium baseline muon decay experiment MOMENT. In order to identify potential bottlenecks and opportunities to improve CP precision in MOMENT, we investigate the effect of statistical error, systematic uncertainties, fraction of the muon beam polarity, and adjusting the baseline length to match the first or second oscillation maximum on the precision measurement of $δ_\text{CP}$. We also simulate superbeam experiments T2K, NO$ν$A, T2HK, DUNE and T2HKK in comparison and complementary to MOMENT. To reach the precision of $δ_\text{CP}$ at 12$^\circ$ or better at 1$σ$ confidence level, we find it sufficient to combine the data of MOMENT, DUNE and T2HK.

hep-ph↗

arXiv2018

Optimizing the $θ_{23}$ octant search in long baseline neutrino experiments

We study the possibility of determining the octant of the neutrino mixing angle $θ_{23}$, that is, whether $θ_{23}> 45^\circ$ or $θ_{23}<45^\circ$, in long baseline neutrino experiments. Here we numerically derived the sensitivity limits within which these experiments can determine, by measuring the probability of the $ν_μ\to ν_{e}$ transitions, the octant of $θ_{23}$ with a $5σ$ certainty. The interference of the CP violation angle $δ$ with these limits, as well as the effects of the baseline length and the run-time ratio of neutrino and antineutrino modes of the beam have been analyzed.

hep-ph↗

arXiv2018

Determination of the $θ_{23}$ octant in long baseline neutrino experiments within and beyond the standard model

The recent data indicate that the neutrino mixing angle $θ_{23}$ deviates from the maximal-mixing value of 45$^\circ$, showing two nearly degenerate solutions, one in the lower octant (LO) ($θ_{23}<45^\circ$) and one in the higher octant (HO) ($θ_{23}>45^\circ$). We investigate, using numerical simulations, the prospects for determining the octant of $θ_{23}$ in the future long baseline oscillation experiments. We present our results as contour plots on the ($θ_{23}-45^\circ$, $δ$)--plane, where $δ$ is the $CP$ phase, showing the true values of $θ_{23}$ for which the octant can be experimentally determined at 3$\,σ$, 2$\,σ$ and 1$\,σ$ confidence level. In particular, we study the impact of the possible nonunitarity of neutrino mixing on the experimental determination of $θ_{23}$ in those experiments.

hep-ph↗

arXiv2018

Effects of BSMs on $θ_{23}$ determination

We investigate the prospects for determining the octant of $θ_{23}$ in the future long baseline oscillation experiments. We present our results as contour plots on the ($θ_{23}-45^\circ$, $δ$)--plane, where $δ$ is the CP phase, showing the true values of $θ_{23}$ for which the octant can be experimentally determined at 3$\,σ$, 2$\,σ$ and 1$\,σ$ confidence level, in particular, the impact of the non-unitarity of neutrino mixing.

hep-ph↗