Search for Spontaneous Radiation from Wave Function Collapse in the Majorana Demonstrator

Area of Science:

• Experimental particle physics
• Quantum mechanics foundations
• Cosmology

Background:

• The Majorana Demonstrator searches for neutrinoless double-beta decay and rare events below 100 keV.
• Wave function collapse models, like CSL, aim to resolve the quantum measurement problem.
• CSL models predict detectable x-ray radiation signatures.

Purpose of the Study:

• To test the continuous spontaneous localization (CSL) model using data from the Majorana Demonstrator.
• To search for predicted x-ray radiation signatures in a specific energy range.
• To set stringent upper limits on the CSL model's collapse rate (λ).

Main Methods:

• Utilized a 37.5 kg-y enriched germanium exposure from the Majorana Demonstrator (Dec 2015 - Nov 2019).
• Searched for x-ray radiation in the 19-100 keV range.
• Explored both non-mass-proportional and mass-proportional CSL versions with different emission assumptions.

Main Results:

• No evidence of CSL-predicted x-ray radiation was found.
• Established the most stringent upper limits to date for the white CSL model on the collapse rate, λ.
• Achieved a 40-100 times improvement in sensitivity over previous searches for large parameter space regions.

Conclusions:

• The Majorana data strongly constrain the CSL model, ruling out significant portions of its parameter space.
• The results provide an order of magnitude improvement for the Diòsi-Penrose model's lower bound.
• This experiment significantly advances the search for new physics beyond the Standard Model and probes fundamental quantum mechanics.