[Paper Review] Direct neutrino mass search

Christian Weinheimer|arXiv (Cornell University)|Oct 21, 2002

Neutrino Physics Research4 citations

TL;DR

This paper proposes the KATRIN experiment as the next-generation direct neutrino mass search, using tritium beta decay with a MAC-E-Filter to achieve sub-eV sensitivity. By precisely measuring the electron energy spectrum near the endpoint, it aims to determine the absolute neutrino mass scale, a key goal in particle physics and cosmology.

ABSTRACT

With the compelling evidence for massive neutrinos from recent neutrino oscillation experiments, one of the most fundamental tasks of particle physics over the next years will be the determination of the absolute mass scale of neutrinos, which has crucial implications for cosmology, astrophysics and particle physics. Neutrino oscillation experiments can measure squared mass differences but not masses. The latter have to be determined in a different way. The direct mass experiments investigate -- besides time-of-flight measurements -- the kinematics of weak decays obtaining information on the neutrino mass without further requirements. Here the tritium beta decay experiments give the most stringent results. The current tritium beta decay experiments at Mainz and Troitsk are reaching their sensitivity limit. The different options for a next generation direct neutrino mass experiment with sub-eV sensitivity are discussed. The KATRIN experiment, which will investigate the tritium beta spectrum with a MAC-E-Filter of 1 eV resolution, is being prepared to reach a sub-eV sensitivity.

Motivation & Objective

• To determine the absolute neutrino mass scale, which remains unknown despite evidence of neutrino mass from oscillation experiments.
• To overcome the limitations of neutrino oscillation experiments, which measure mass squared differences but not absolute masses.
• To extend the sensitivity of direct neutrino mass searches beyond current limits set by the Mainz and Troitsk experiments.
• To prepare and evaluate next-generation experimental options for achieving sub-eV sensitivity in neutrino mass measurements.
• To establish the KATRIN experiment as the leading approach for direct neutrino mass determination using tritium beta decay with high-energy resolution.

Proposed method

• Utilizes tritium beta decay as the primary process to probe neutrino mass through kinematic analysis of the electron energy spectrum.
• Employs a MAC-E-Filter (Magnetic Adiabatic Collimation with Emitting Filter) to achieve an energy resolution of 1 eV.
• Measures the electron energy distribution near the endpoint of the tritium beta decay spectrum, where the neutrino mass affects the shape.
• Applies high-precision spectroscopy to detect small distortions in the spectrum caused by non-zero neutrino mass.
• Uses background suppression and ultra-high vacuum conditions to ensure measurement sensitivity.
• Relies on statistical analysis of electron counts near the endpoint to extract the neutrino mass limit.

Experimental results

Research questions

• RQ1 What is the absolute mass scale of neutrinos, and how can it be measured directly?
• RQ2 How can tritium beta decay be used to extract neutrino mass with sub-eV sensitivity?
• RQ3 What are the technical and experimental challenges in pushing the sensitivity of direct neutrino mass searches beyond current limits?
• RQ4 How does the MAC-E-Filter technique enable improved energy resolution for neutrino mass measurements?
• RQ5 What are the key design and performance requirements for the next-generation KATRIN experiment?

Key findings

• The KATRIN experiment is designed to achieve sub-eV sensitivity in the direct measurement of neutrino mass.
• The MAC-E-Filter provides an energy resolution of 1 eV, enabling precise spectroscopy of the tritium beta decay spectrum near the endpoint.
• Current tritium beta decay experiments at Mainz and Troitsk are approaching their sensitivity limits, necessitating next-generation experiments.
• The kinematic analysis of weak decays, particularly tritium beta decay, offers a direct method to determine neutrino mass without additional assumptions.
• The experiment is being prepared to provide the most stringent constraints on the absolute neutrino mass scale to date.
• The method relies on detecting small spectral distortions near the endpoint, which are directly related to the neutrino mass.