Probing right-handed neutrinos via trilepton signals at the HL-LHC

Neutrino oscillation experiments have provided direct evidence for the existence of neutrino masses. The seesaw mechanism explains the smallness of these masses through the introduction of heavy right-handed neutrino (RHN) states. The RHN states can also generate Dirac neutrino masses at tree or loop level. These heavy states can exist at the electroweak scale, approximately in the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mi mathvariant="script">O</a:mi><a:mo stretchy="false">(</a:mo><a:mi>GeV</a:mi><a:mo stretchy="false">)</a:mo></a:mrow></a:math> range, and can be investigated through current and future collider experiments. This scenario, where other new physics interactions occur at scales much higher than the RHN scale, can be described using an effective field theory (EFT) framework known as <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"><f:msub><f:mi>N</f:mi><f:mi>R</f:mi></f:msub></f:math>-EFT. This study focuses on constraining the Wilson coefficients of <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"><h:msub><h:mi>N</h:mi><h:mi>R</h:mi></h:msub></h:math>-EFT operators, which primarily contribute to trilepton production and missing energy signals at the LHC. We examine both the scenarios where the RHN mass <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"><j:msub><j:mi>M</j:mi><j:mi>N</j:mi></j:msub></j:math> is less than and greater than the <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"><l:mi>W</l:mi></l:math> boson mass <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"><n:msub><n:mi>M</n:mi><n:mi>W</n:mi></n:msub></n:math>, and provide predictions for the High-Luminosity run of the LHC.