Neutrino oscillations and Non-Standard Interactions (1710.09360v2)

Abstract: Current neutrino experiments measure the neutrino mixing parameters with an unprecedented accuracy. The upcoming generation of experiments will be sensitive to subdominant effects that can give information on the unknown neutrino parameters: the Dirac CP-violating phase, the mass ordering and the $\theta_{23}$ octant. Determining the exact values of neutrino mass and mixing parameters is crucial to test neutrino models and flavor symmetries. In the first part of this review, we summarize the current status of neutrino oscillation parameters. We consider the most recent data from solar experiments and the atmospheric data from Super-Kamiokande, IceCube and ANTARES. We implement the data from the reactor experiments KamLAND, Daya Bay, RENO and Double Chooz as well as the long baseline data from MINOS, T2K and NOvA. If in addition to the standard interactions, neutrinos have subdominant Non-Standard Interactions (NSI) with matter, extracting the values of these parameters will suffer from new degeneracies. We review such effects and formulate the conditions on the NSI parameters under which the precision measurement of neutrino oscillation parameters can be distorted. Like standard weak interactions, NSI can be categorized into Charged and Neutral Current NSI. Our focus will be on NC NSI since it is possible to build a class of models giving rise to sizeable NC NSI with effects on neutrino oscillations. These models are based on new $U(1)$ gauge symmetry with a boson of mass $\lesssim 10$ MeV. The UV complete model should be electroweak invariant which implies that along with neutrinos, charged fermions acquire new interactions on which there are strong bounds. We enumerate the bounds that exist on such models and show that it is possible to build viable models avoiding all the bounds. We review methods to test these models and suggest approaches to break the degeneracies caused by NSI.

• The paper demonstrates that non-standard interactions can obscure precise neutrino mixing measurements.
• It employs theoretical models with light mediators and U(1) gauge symmetries to explore NSI effects.
• The study outlines strategies for future experiments like JUNO and DUNE to disentangle NSI impacts.

An Overview of Neutrino Oscillations and Non-Standard Interactions

The paper on neutrino oscillations and non-standard interactions (NSI) provides a comprehensive examination of how neutrinos, despite their elusive nature, hold crucial information about fundamental forces and particles. It underscores the precision with which current and forthcoming neutrino experiments measure the mixing parameters, the potential for discerning unknown features like the Dirac CP-violating phase, and the intricate role of non-standard interactions in these processes.

Current Understanding and Challenges

Neutrino experiments have significantly advanced our understanding, pinpointing neutrino mixing parameters with remarkable precision. Key parameters under intense investigation include the Dirac CP-violating phase in the PMNS matrix, neutrino mass ordering, and the octant of the mixing angle θ_23. The determination of these parameters is instrumental in verifying neutrino models and investigating flavor symmetries within the framework of neutrino physics.

Despite advancements, extracting precise measurements of neutrino parameters can be complex if NSIs are present. The paper describes how neutrino propagation and interactions might be influenced by such undiscovered NSIs, potentially leading to results obscured by degeneracies and ambiguities in the extracted values.

Non-Standard Interactions (NSI)

NSIs offer an intriguing extension for understanding neutrino properties and interactions, classified into Charged Current (CC) and Neutral Current (NC) interactions. The paper focuses primarily on NC NSI, as models can give rise to sizeable effects on neutrino oscillations through new U(1) gauge symmetries and gauge bosons with a mass less than approximately 10 MeV. Notably, such NSIs necessitate a delicate balance to avoid inconsistencies with existing constraints and maintain viable model scenarios.

One of the primary challenges in accommodating NSIs is preventing distortion of precision measurements of neutrino oscillation parameters. Various models have been explored to mitigate this, including those relying on light mediators for the interaction, which often invoke gauge symmetries like U(1) extensions.

Implications for Future Experiments

The research elucidates potential implications and methodological innovations in future experimental designs, including JUNO, RENO50, and DUNE, to effectively isolate and examine NSI effects. Theoretical models suggest using novel mediums and baseline combinations that differ in composition to resolve existing degeneracies and enhance parameter sensitivity.

Future experiments running in tandem, such as T2HK, T2HKK, and others, are expected to yield significant information on neutrino behavior, improving our understanding of NSIs. These experiments can serve as a potent criterion for the parameters associated with NSIs, helping to anticipate and characterize their potential influence on measurable neutrino oscillation results.

Summary

This paper makes a strong contribution to theoretical and experimental physics by placing the phenomenon of neutrino oscillations within a more complex framework where NSIs might play a significant role. It presents a case for continued exploration into how neutrinos interact beyond the established standard model, suggesting that such advancements might reveal new physics insights applicable to broader scientific paradigms.

While the pursuit of resolving these NSI-induced challenges remains ongoing, the outlined methodologies and theoretical models in this paper offer promising pathways for future discourse and discovery in neutrino physics and beyond.