Direct neutrino-mass measurement based on 259 days of KATRIN data

Area of Science:

• Particle Physics
• Cosmology
• Astroparticle Physics

Background:

• Neutrino mass is a key indicator of physics beyond the Standard Model.
• The absolute neutrino mass impacts fundamental physics and cosmological models.
• Precision measurements are crucial for understanding neutrino properties.

Purpose of the Study:

• To search for the effective electron antineutrino mass using high-precision tritium beta decay spectroscopy.
• To constrain the neutrino mass scale and test the Standard Model.
• To improve upon previous experimental limits for neutrino mass.

Main Methods:

• Utilizing the KATRIN (KArlsruhe TRItium Neutrino) experiment for precision spectroscopy of tritium beta decay.
• Analyzing data from the first five measurement campaigns, collecting 36 million electrons over 259 days.
• Focusing on the kinematic endpoint of the beta decay spectrum to detect minute mass effects.

Main Results:

• Derived a best-fit value for the effective electron antineutrino mass squared of [Formula: see text] eV².
• Established a new upper limit for the neutrino mass of m_ν < 0.45 eV at 90% confidence level.
• Achieved a substantial reduction in background levels and improved systematic uncertainties.

Conclusions:

• The KATRIN experiment has significantly tightened the upper limit on the neutrino mass, nearly halving the previous bound.
• This result provides stringent constraints on neutrino properties and their implications for beyond Standard Model physics.
• Continued measurements will further refine neutrino mass determination and its cosmological impact.