A testable conventional hypothesis for the DAMA-LIBRA annual modulation

TL;DR

This paper proposes that the DAMA-LIBRA annual modulation signal could be caused by cosmic ray muons interacting with the detector, suggesting a testable hypothesis involving time correlations and temperature effects.

Contribution

It introduces a new hypothesis linking the DAMA-LIBRA signal to cosmic ray muons and proposes specific experimental tests to verify this explanation.

Findings

Energy depositions by UV irradiation show delayed pulses.

The same behavior may occur for ionization or excitation energy deposits.

The hypothesis can be tested with current data and low-temperature operation.

Abstract

The annual modulation signal observed by the DAMA-LIBRA Collaboration (D-L) may plausibly be explained as a consequence of energy deposited in the NaI(Tl) crystals by cosmic ray muons penetrating the detector. Delayed pulses in the approximate energy range of interest have been observed as a sequel to energy deposited by UV irradiation. The same behavior may be reasonably expected to occur for energy deposited by any source of ionization or excitation. D-L can test this hypothesis by searching for time correlations between muon events and pulses in modulation energy range in current data, and by renewed operation of the array at a sufficiently low temperature that would freeze out the phenomenon.