Search for the radiative decays D 0 → γ K ¯ 1 ( 1270 ) 0 and D + → γ K 1 ( 1270 ) +

This is the authors' abstract. We don't add key points for this paper.

A search for the radiative decays <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msup> <a:mi>D</a:mi> <a:mn>0</a:mn> </a:msup> <a:mo stretchy="false">→</a:mo> <a:mi>γ</a:mi> <a:msub> <a:mover accent="true"> <a:mi>K</a:mi> <a:mo stretchy="false">¯</a:mo> </a:mover> <a:mn>1</a:mn> </a:msub> <a:mo stretchy="false">(</a:mo> <a:mn>1270</a:mn> <a:msup> <a:mo stretchy="false">)</a:mo> <a:mn>0</a:mn> </a:msup> </a:math> and <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"> <h:msup> <h:mi>D</h:mi> <h:mo>+</h:mo> </h:msup> <h:mo stretchy="false">→</h:mo> <h:mi>γ</h:mi> <h:msub> <h:mi>K</h:mi> <h:mn>1</h:mn> </h:msub> <h:mo stretchy="false">(</h:mo> <h:mn>1270</h:mn> <h:msup> <h:mo stretchy="false">)</h:mo> <h:mo>+</h:mo> </h:msup> </h:math> is conducted using <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"> <m:mn>20.3</m:mn> <m:mtext> </m:mtext> <m:mtext> </m:mtext> <m:msup> <m:mi>fb</m:mi> <m:mrow> <m:mo>−</m:mo> <m:mn>1</m:mn> </m:mrow> </m:msup> </m:math> of <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"> <o:msup> <o:mi>e</o:mi> <o:mo>+</o:mo> </o:msup> <o:msup> <o:mi>e</o:mi> <o:mo>−</o:mo> </o:msup> </o:math> annihilation data collected at the center-of-mass energy <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"> <q:msqrt> <q:mi>s</q:mi> </q:msqrt> <q:mo>=</q:mo> <q:mn>3.773</q:mn> <q:mtext> </q:mtext> <q:mtext> </q:mtext> <q:mi>GeV</q:mi> </q:math> by the BESIII detector operating at the BEPCII collider. No significant signals are observed, and upper limits on the branching fractions of <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"> <s:msup> <s:mi>D</s:mi> <s:mn>0</s:mn> </s:msup> <s:mo stretchy="false">→</s:mo> <s:mi>γ</s:mi> <s:msub> <s:mover accent="true"> <s:mi>K</s:mi> <s:mo stretchy="false">¯</s:mo> </s:mover> <s:mn>1</s:mn> </s:msub> <s:mo stretchy="false">(</s:mo> <s:mn>1270</s:mn> <s:msup> <s:mo stretchy="false">)</s:mo> <s:mn>0</s:mn> </s:msup> </s:math> and <z:math xmlns:z="http://www.w3.org/1998/Math/MathML" display="inline"> <z:msup> <z:mi>D</z:mi> <z:mo>+</z:mo> </z:msup> <z:mo stretchy="false">→</z:mo> <z:mi>γ</z:mi> <z:msub> <z:mi>K</z:mi> <z:mn>1</z:mn> </z:msub> <z:mo stretchy="false">(</z:mo> <z:mn>1270</z:mn> <z:msup> <z:mo stretchy="false">)</z:mo> <z:mo>+</z:mo> </z:msup> </z:math> at 90% confidence level are determined to be <eb:math xmlns:eb="http://www.w3.org/1998/Math/MathML" display="inline"> <eb:mn>7.8</eb:mn> <eb:mo>×</eb:mo> <eb:msup> <eb:mn>10</eb:mn> <eb:mrow> <eb:mo>−</eb:mo> <eb:mn>4</eb:mn> </eb:mrow> </eb:msup> </eb:math> and <gb:math xmlns:gb="http://www.w3.org/1998/Math/MathML" display="inline"> <gb:mn>3.9</gb:mn> <gb:mo>×</gb:mo> <gb:msup> <gb:mn>10</gb:mn> <gb:mrow> <gb:mo>−</gb:mo> <gb:mn>5</gb:mn> </gb:mrow> </gb:msup> </gb:math> , respectively. This represents the first test of the vector meson dominance mechanism in the radiative decays of charmed mesons to axial-vector mesons.