Physics with near detectors at a neutrino factory

TL;DR

This paper analyzes how near detectors at a neutrino factory influence measurements of neutrino oscillations and non-standard interactions, emphasizing systematics, detector classes, and the importance of near detectors for precise physics results.

Contribution

It introduces different classes of near detectors and evaluates their roles, especially in systematics control and non-standard interaction detection, including the impact of the neutrino factory's baseline configuration.

Findings

Near detectors are essential for atmospheric parameter measurements with a single baseline.

Systematic errors can be mitigated by multiple baselines, reducing the need for near detectors.

Near detectors with tau detection improve sensitivity to non-standard interactions.

Abstract

We discuss the impact of near detectors at a neutrino factory both on standard oscillation and non-standard interaction measurements. Our systematics treatment includes cross section errors, flux errors, and background uncertainties, and our near detector fluxes include the geometry of the neutrino source and the detector. Instead of a specific detector concept, we introduce qualitatively different classes of near detectors with different characteristics, such as near detectors catching the whole neutrino flux (near detector limit) versus near detectors observing a spectrum similar to that of the far detector (far detector limit). We include the low energy neutrino factory in the discussion. We illustrate for which measurements near detectors are required, discuss how many are needed, and what the role of the flux monitoring is. For instance, we demonstrate that near detectors are mandatory for the leading atmospheric parameter measurements if the neutrino factory has only one baseline, whereas systematical errors partially cancel if the neutrino factory complex includes the magic baseline. Finally, near detectors with nu_tau detection are shown to be useful for non-standard interactions.