Searching for heavy majorana neutrinos at the FCC-eh via lepton-number-violating and fat-jet final states

Abstract Within the framework of the phenomenological type-I seesaw mechanism, heavy singlet Majorana neutrinos are introduced to explain the origin of neutrino masses. We propose a novel search strategy for these heavy Majorana neutrinos through the lepton-number-violating process $$e^{-}p \rightarrow jN\rightarrow j(\mu ^{+}W^{-})$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>e</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mi>p</mml:mi> <mml:mo>→</mml:mo> <mml:mi>j</mml:mi> <mml:mi>N</mml:mi> <mml:mo>→</mml:mo> <mml:mi>j</mml:mi> <mml:mrow> <mml:mo>(</mml:mo> <mml:msup> <mml:mi>μ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>W</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> at the Future Circular electron-hadron Collider (FCC-eh), which would utilize a 60 GeV electron beam colliding with a 50 TeV proton beam. Focusing on the decay mode $$N\rightarrow \mu ^{+}W^{-}\rightarrow \mu ^{+}J$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>N</mml:mi> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>μ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>W</mml:mi> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>μ</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:mi>J</mml:mi> </mml:mrow> </mml:math> , where J denotes a fat-jet from the hadronic decays of a highly boosted W boson, we investigate the discovery potential of this signature. By performing a detailed signal-to-background analysis and detector simulations, we present $$2\sigma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>2</mml:mn> <mml:mi>σ</mml:mi> </mml:mrow> </mml:math> exclusion limits and $$5\sigma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>5</mml:mn> <mml:mi>σ</mml:mi> </mml:mrow> </mml:math> discovery reaches in terms of parameter space regions.