Revealing dipion correlations for the observed substructure near the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:msup> <mml:mrow> <mml:mi>π</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow>

Based on the world’s largest <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mi>ψ</a:mi> <a:mo stretchy="false">(</a:mo> <a:mn>3686</a:mn> <a:mo stretchy="false">)</a:mo> </a:mrow> </a:math> data sample, the BESIII Collaboration recently reported a substructure near the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:msup> <e:mi>π</e:mi> <e:mo>+</e:mo> </e:msup> <e:msup> <e:mi>π</e:mi> <e:mo>−</e:mo> </e:msup> </e:math> mass threshold in the decay <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mrow> <g:mi>ψ</g:mi> <g:mo stretchy="false">(</g:mo> <g:mn>3686</g:mn> <g:mo stretchy="false">)</g:mo> <g:mo stretchy="false">→</g:mo> <g:mi>J</g:mi> <g:mo>/</g:mo> <g:mi>ψ</g:mi> <g:msup> <g:mrow> <g:mi>π</g:mi> </g:mrow> <g:mrow> <g:mo>+</g:mo> </g:mrow> </g:msup> <g:msup> <g:mrow> <g:mi>π</g:mi> </g:mrow> <g:mrow> <g:mo>−</g:mo> </g:mrow> </g:msup> </g:mrow> </g:math> , challenging the established understanding of the dipion invariant mass spectrum. We propose that this substructure arises directly from dipion correlations. Using a chiral unitary approach, we successfully reproduce the observed anomaly, thereby providing strong evidence of dipion correlation in heavy quarkonium decays. This approach also allows us to predict the corresponding dipion correlation function.