Observation of the associated production of a single top quark and a $W$ boson in $pp$ collisions at $\sqrt s = $8 TeV
<p>The first observation of the associated production of a single top quark and a <inline-formula><mml:math display="inline"><mml:mi>W</mml:mi></mml:math></inline-formula> boson is presented. The analysis is based on a data set corresponding to an integrated luminosity of <inline-formula><mml:math display="inline"><mml:mrow><mml:mn>12.2</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:msup><mml:mrow><mml:mi>fb</mml:mi></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> of proton-proton collisions at <inline-formula><mml:math display="inline"><mml:mrow><mml:msqrt><mml:mrow><mml:mi>s</mml:mi></mml:mrow></mml:msqrt><mml:mo>=</mml:mo><mml:mn>8</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>TeV</mml:mi></mml:mrow></mml:math></inline-formula> recorded by the CMS experiment at the LHC. Events with two leptons and a jet originating from a <inline-formula><mml:math display="inline"><mml:mrow><mml:mi>b</mml:mi></mml:mrow></mml:math></inline-formula> quark are selected. A multivariate analysis based on kinematic and topological properties is used to separate the signal from the dominant <inline-formula><mml:math display="inline"><mml:mrow><mml:mi>t</mml:mi><mml:mover accent="true"><mml:mrow><mml:mi>t</mml:mi></mml:mrow><mml:mrow><mml:mo stretchy="false">¯</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math></inline-formula> background. An excess consistent with the signal hypothesis is observed, with a significance which corresponds to 6.1 standard deviations above a background-only hypothesis. The measured production cross section is <inline-formula><mml:math display="inline"><mml:mrow><mml:mrow><mml:mn>23.4</mml:mn><mml:mo>±</mml:mo><mml:mn>5.4</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext></mml:mrow><mml:mtext>pb</mml:mtext></mml:mrow></mml:math></inline-formula>, in agreement with the standard model prediction.</p>
arXiv_1401.2942.pdf
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fermilab-pub-14-084-cms.pdf
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