Improved measurement of the semileptonic decay Ds+→K0e+νe

Analyzing <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msup><a:mi>e</a:mi><a:mo>+</a:mo></a:msup><a:msup><a:mi>e</a:mi><a:mo>−</a:mo></a:msup></a:math> collision data corresponding to an integrated luminosity of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mn>7.33</c:mn><c:mtext> </c:mtext><c:mtext> </c:mtext><c:msup><c:mi>fb</c:mi><c:mrow><c:mo>−</c:mo><c:mn>1</c:mn></c:mrow></c:msup></c:math> collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, we measure the branching fraction of the semileptonic decay <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:msubsup><e:mi>D</e:mi><e:mi>s</e:mi><e:mo>+</e:mo></e:msubsup><e:mo stretchy="false">→</e:mo><e:msup><e:mi>K</e:mi><e:mn>0</e:mn></e:msup><e:msup><e:mi>e</e:mi><e:mo>+</e:mo></e:msup><e:msub><e:mi>ν</e:mi><e:mi>e</e:mi></e:msub></e:math> to be <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"><h:mo stretchy="false">(</h:mo><h:mn>2.98</h:mn><h:mo>±</h:mo><h:mn>0.2</h:mn><h:msub><h:mn>3</h:mn><h:mrow><h:mi>stat</h:mi></h:mrow></h:msub><h:mo>±</h:mo><h:mn>0.1</h:mn><h:msub><h:mn>2</h:mn><h:mrow><h:mi>syst</h:mi></h:mrow></h:msub><h:mo stretchy="false">)</h:mo><h:mo>×</h:mo><h:msup><h:mn>10</h:mn><h:mrow><h:mo>−</h:mo><h:mn>3</h:mn></h:mrow></h:msup></h:math>. Based on fit to the partial decay rates in various <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"><l:msup><l:mi>q</l:mi><l:mn>2</l:mn></l:msup></l:math> intervals, the product value of <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"><n:msubsup><n:mi>D</n:mi><n:mi>s</n:mi><n:mo>+</n:mo></n:msubsup><n:mo stretchy="false">→</n:mo><n:msup><n:mi>K</n:mi><n:mn>0</n:mn></n:msup></n:math> hadronic form factor and Cabibbo-Kobayashi-Maskawa element is measured to be <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:msubsup><q:mi>f</q:mi><q:mo>+</q:mo><q:msup><q:mi>K</q:mi><q:mn>0</q:mn></q:msup></q:msubsup><q:mo stretchy="false">(</q:mo><q:mn>0</q:mn><q:mo stretchy="false">)</q:mo><q:mo stretchy="false">|</q:mo><q:msub><q:mi>V</q:mi><q:mrow><q:mi>c</q:mi><q:mi>d</q:mi></q:mrow></q:msub><q:mo stretchy="false">|</q:mo><q:mo>=</q:mo><q:mn>0.143</q:mn><q:mo>±</q:mo><q:mn>0.01</q:mn><q:msub><q:mn>1</q:mn><q:mrow><q:mi>stat</q:mi></q:mrow></q:msub><q:mo>±</q:mo><q:mn>0.00</q:mn><q:msub><q:mn>3</q:mn><q:mrow><q:mi>syst</q:mi></q:mrow></q:msub></q:math>. With <w:math xmlns:w="http://www.w3.org/1998/Math/MathML" display="inline"><w:mo stretchy="false">|</w:mo><w:msub><w:mi>V</w:mi><w:mrow><w:mi>c</w:mi><w:mi>d</w:mi></w:mrow></w:msub><w:mo stretchy="false">|</w:mo><w:mo>=</w:mo><w:mn>0.22486</w:mn><w:mo>±</w:mo><w:mn>0.00067</w:mn></w:math> as an input, the hadronic form factor is evaluated to be <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML" display="inline"><ab:msubsup><ab:mi>f</ab:mi><ab:mo>+</ab:mo><ab:msup><ab:mi>K</ab:mi><ab:mn>0</ab:mn></ab:msup></ab:msubsup><ab:mo stretchy="false">(</ab:mo><ab:mn>0</ab:mn><ab:mo stretchy="false">)</ab:mo><ab:mo>=</ab:mo><ab:mn>0.636</ab:mn><ab:mo>±</ab:mo><ab:mn>0.04</ab:mn><ab:msub><ab:mn>9</ab:mn><ab:mrow><ab:mi>stat</ab:mi></ab:mrow></ab:msub><ab:mo>±</ab:mo><ab:mn>0.01</ab:mn><ab:msub><ab:mn>3</ab:mn><ab:mrow><ab:mi>syst</ab:mi></ab:mrow></ab:msub></ab:math>. The branching fraction and form factor measurements are factors of 1.6 and 1.7 more precise than the previous world averages, respectively.