Unraveling the Scotogenic model at muon collider

Abstract

A bstract The Scotogenic model extends the standard model with three singlet fermion N i and one inert doublet scalar η to address the common origin of tiny neutrino mass and dark matter. For fermion dark matter N 1 , a hierarchical Yukawa structure $$ \mid {y}_{1e}\mid \ll \mid {y}_{1\mu}\mid \sim \mid {y}_{1\tau}\mid \sim \mathcal{O}(1) $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>∣</mml:mo> <mml:msub> <mml:mi>y</mml:mi> <mml:mrow> <mml:mn>1</mml:mn> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∣</mml:mo> <mml:mo>≪</mml:mo> <mml:mo>∣</mml:mo> <mml:msub> <mml:mi>y</mml:mi> <mml:mrow> <mml:mn>1</mml:mn> <mml:mi>μ</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∣</mml:mo> <mml:mo>∼</mml:mo> <mml:mo>∣</mml:mo> <mml:msub> <mml:mi>y</mml:mi> <mml:mrow> <mml:mn>1</mml:mn> <mml:mi>τ</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∣</mml:mo> <mml:mo>∼</mml:mo> <mml:mi>O</mml:mi> <mml:mfenced> <mml:mn>1</mml:mn> </mml:mfenced> </mml:math> is usually favored to satisfy constraints from lepton flavor violation and relic density. Such large μ -related Yukawa coupling would greatly enhance the pair production of charged scalar η ± at the muon collider. In this paper, we investigate the dilepton and mono-photon signature of the Scotogenic model at a 14 TeV muon collider. For the dimuon signature "Image missing", we find that most viable samples can be probed with 200 fb − 1 data. The ditau signature "Image missing" is usually less promising, but it is important to probe the small |y 1 μ | region. The mono-photon signature "Image missing" could also probe the compressed mass region M 1 ≲ $$ {M}_{\eta^{\pm }} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>M</mml:mi> <mml:msup> <mml:mi>η</mml:mi> <mml:mo>±</mml:mo> </mml:msup> </mml:msub> </mml:math> . Masses of charged scalar η ± and dark matter N 1 can be further extracted by a binned likelihood fit of the dilepton energy.