Abstract
<jats:p> A search for new physics in events featuring a single photon and missing transverse momentum is presented, using proton-proton <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msqrt> <a:mi>s</a:mi> </a:msqrt> <a:mo>=</a:mo> <a:mn>13</a:mn> <a:mtext> </a:mtext> <a:mtext> </a:mtext> <a:mi>TeV</a:mi> </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>101</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 by the CMS experiment at the CERN LHC between 2017 and 2018. This analysis, combined with a previous study of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mn>36</e:mn> <e:mtext> </e:mtext> <e:mtext> </e:mtext> <e:msup> <e:mi>fb</e:mi> <e:mrow> <e:mo>−</e:mo> <e:mn>1</e:mn> </e:mrow> </e:msup> </e:math> of 2016 data (totaling <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mn>137</g:mn> <g:mtext> </g:mtext> <g:mtext> </g:mtext> <g:msup> <g:mi>fb</g:mi> <g:mrow> <g:mo>−</g:mo> <g:mn>1</g:mn> </g:mrow> </g:msup> </g:math> ), reveals no significant deviations from standard model expectations. The results are then used to establish 95% confidence level limits on parameters in theoretical models involving dark matter and large extra dimensions. Compared to the 2016-only analysis, this search achieves up to a 14% improvement in exclusion reach for mediator masses in simplified dark matter models, along with 11% and 10% enhancements in the limits on the effective field theory suppression scale and the fundamental Planck scale, respectively. These results are the most stringent constraints on these parameters to date. </jats:p>