First result of the experimental search for the 9.4 keV solar axion reactions with Kr-83 in the copper proportional counter

TL;DR

This paper reports an experimental search for solar axions at 9.4 keV using a krypton-filled copper counter, setting new upper limits on axion mass after 26.5 days of data collection in a low-background underground lab.

Contribution

It presents the first experimental search for 9.4 keV solar axions using resonant absorption in Kr-83, establishing new upper limits on axion mass.

Findings

No axion signals detected after 26.5 days

Set upper limit on axion mass at 130 eV

Demonstrated feasibility of underground krypton-based detection

Abstract

The experimental search for solar hadronic axions is started at the Baksan Neutrino Observatory of the Institute for Nuclear Researches Russian Academy of Science. It is assumed that axions are created in the Sun during M1-transition between the first thermally excited level at 9.4 keV and the ground state in Kr-83. The experiment is based on axion detection via resonant absorption process by the same nucleus in the detector. The big copper proportional counter filled with krypton is used to detect signals from axions. The experimental setup is situated in the deep underground low background laboratory. No evidence of axion detection were found after the 26.5 days data collection. Resulting new upper limit on axion mass is m_{A} < 130 eV at 95% C.L.