Searching for Possible Bose-Einstein Condensate States in ¹⁶O via Its 4-α Decay

Recently, an inelastic scattering experiment of ¹⁶O+¹²C was performed at the Beijing Tandem Accelerator Nuclear Physics National of China Institute of Atomic Energy. New evidence for the existence of Bose-Einstein condensation state of ¹⁶O has been obtained. Employing a series of double-sided-silicon-strip-based telescopes, this experiment achieved accurate particle identification and coincidence measurement of 4-α in the decay of ¹⁶O for the first time. Based on this, high-resolution reaction Q-value spectra was obtained and clear 4-α resonance states were reconstructed. In the vicinity of the 4-α separation threshold, 4 highly significant (3 of them above 5σ) resonance states were observed, which decay to the characteristic pattern of ¹²C(Hoyle state)+α, consistent with the predicted Hoyle-BEC structure and its rotating band features. The observation results will promote further theoretical research, and more measurements are needed for these resonance states in experiments.