Transition form factors for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>D</mml:mi> <mml:mo>/</mml:mo> <mml:mi>B</mml:mi> </mml:math> to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline">

We apply the light-cone QCD sum rules with chiral currents to compute transition form factors of the semileptonic decay of the charmed and bottom scalar mesons <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>D</a:mi> <a:mo>/</a:mo> <a:mi>B</a:mi> </a:math> to <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:msub> <c:mi>a</c:mi> <c:mn>0</c:mn> </c:msub> <c:mo stretchy="false">(</c:mo> <c:mn>980</c:mn> <c:mo stretchy="false">)</c:mo> <c:msup> <c:mi>l</c:mi> <c:mo>+</c:mo> </c:msup> <c:msub> <c:mi>ν</c:mi> <c:mi>l</c:mi> </c:msub> </c:math> <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mrow> <g:mo stretchy="false">(</g:mo> <g:mi>l</g:mi> <g:mo>=</g:mo> <g:mi>e</g:mi> <g:mo>,</g:mo> <g:mi>μ</g:mi> <g:mo stretchy="false">)</g:mo> </g:mrow> </g:math> , where the scalar meson <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"> <k:msub> <k:mi>a</k:mi> <k:mn>0</k:mn> </k:msub> <k:mo stretchy="false">(</k:mo> <k:mn>980</k:mn> <k:mo stretchy="false">)</k:mo> </k:math> are firstly regarded as two quark states, and contributions from the tetraquark component are then added via proper modulation of four distribution amplitudes considered. The obtained transition form factors and branching fraction are free of the contribution from the light-cone distribution amplitudes at the level of twist-three and two simple relations connecting their form factors are obtained. Our computations indicates that the decay branch fractions are on the margin of the measurements reported by the Beijing Spectrometer III in the pure two-quark scenario and are in good agreement with observations when tetraquark component is considered.