Search for solar axion emission from 7Li and D(p,gamma)3He nuclear decays with the CAST gamma-ray calorimeter

TL;DR

This study searches for high-energy axions emitted from specific nuclear decays in the Sun using a gamma-ray calorimeter, aiming to detect particles that could solve the strong-CP problem, but finds no excess signal.

Contribution

First helioscope-based search for high-energy solar axions from 7Li and D(p,gamma)3He nuclear transitions using a gamma-ray calorimeter.

Findings

No excess axion signal detected above background.

Sets new limits on axion-nucleon coupling constants.

Demonstrates feasibility of helioscope approach for high-energy axion detection.

Abstract

We present the results of a search for a high-energy axion emission signal from 7Li (0.478 MeV) and D(p,gamma)3He (5.5 MeV) nuclear transitions using a low-background gamma-ray calorimeter during Phase I of the CAST experiment. These so-called "hadronic axions" could provide a solution to the long-standing strong-CP problem and can be emitted from the solar core from nuclear M1 transitions. This is the first such search for high-energy pseudoscalar bosons with couplings to nucleons conducted using a helioscope approach. No excess signal above background was found.