Study of the lineshape of the <math display='"inline"'> <mrow> <msub> <mrow> <mi>χ</mi> </mrow> <mrow> <mi>c</mi> <mn>1</mn> </mrow> </msub> <mo stretchy='"false"'>(</mo> <mn>3872</mn> <mo stretchy='"false"'>)</mo> </mrow> </math> stat