Muon anomalous magnetic moment in the excited fermion paradigm

Extensions of the standard model featuring excited fermions present an interesting framework that motivates the search for exotic particles at the LHC. Additionally, these extensions offer potential explanations for the muon’s anomalous magnetic moment and other precision observables, shedding light on the energy scale and key parameters of the new theory. Our analysis focuses on the one-loop radiative correction originating from excited lepton doublet and triplet states using the effective Lagrangian approach. The bounds derived from the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mo stretchy="false">(</a:mo><a:mi>g</a:mi><a:mo>−</a:mo><a:mn>2</a:mn><a:msub><a:mo stretchy="false">)</a:mo><a:mi>μ</a:mi></a:msub></a:math> anomaly can be complemented with the ones arising from other observables, like the electroweak precision observable <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi mathvariant="normal">Δ</e:mi><e:mi>ρ</e:mi></e:math> and the signals from direct LHC searches to constrain the effective theory. Our results suggest that the <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"><h:mo stretchy="false">(</h:mo><h:mi>g</h:mi><h:mo>−</h:mo><h:mn>2</h:mn><h:msub><h:mo stretchy="false">)</h:mo><h:mi>μ</h:mi></h:msub></h:math> anomaly can be addressed within a very narrow region of the effective theory scale. Consequently, this imposes indirect constraints on the parameter space of excited fermions.