Search for heavy Majorana or Dirac neutrinos and right-handed W gauge bosons in final states with charged leptons and jets in pp collisions at $$\sqrt{s}=13$$ TeV with the ATLAS detector

Abstract

Abstract A search for heavy right-handed Majorana or Dirac neutrinos $$N_{\textrm{R}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>N</mml:mi> <mml:mtext>R</mml:mtext> </mml:msub> </mml:math> and heavy right-handed gauge bosons $$W_{\textrm{R}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>W</mml:mi> <mml:mtext>R</mml:mtext> </mml:msub> </mml:math> is performed in events with energetic electrons or muons, with the same or opposite electric charge, and energetic jets. The search is carried out separately for topologies of clearly separated final-state products (“resolved” channel) and topologies with boosted final states with hadronic and/or leptonic products partially overlapping and reconstructed as a large-radius jet (“boosted” channel). The events are selected from pp collision data at the LHC with an integrated luminosity of 139 fb $$^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow/> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> collected by the ATLAS detector at $$\sqrt{s} = 13$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>13</mml:mn> </mml:mrow> </mml:math> TeV. No significant deviations from the Standard Model predictions are observed. The results are interpreted within the theoretical framework of a left-right symmetric model, and lower limits are set on masses in the heavy right-handed $$W_{\textrm{R}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>W</mml:mi> <mml:mtext>R</mml:mtext> </mml:msub> </mml:math> boson and $$N_{\textrm{R}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>N</mml:mi> <mml:mtext>R</mml:mtext> </mml:msub> </mml:math> plane. The excluded region extends to about $$m(W_{\textrm{R}}) = 6.4$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>m</mml:mi> <mml:mo>(</mml:mo> <mml:msub> <mml:mi>W</mml:mi> <mml:mtext>R</mml:mtext> </mml:msub> <mml:mo>)</mml:mo> <mml:mo>=</mml:mo> <mml:mn>6.4</mml:mn> </mml:mrow> </mml:math> TeV for both Majorana and Dirac $$N_{\textrm{R}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>N</mml:mi> <mml:mtext>R</mml:mtext> </mml:msub> </mml:math> neutrinos at $$m(N_{\textrm{R}})&lt;1$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>m</mml:mi> <mml:mo>(</mml:mo> <mml:msub> <mml:mi>N</mml:mi> <mml:mtext>R</mml:mtext> </mml:msub> <mml:mo>)</mml:mo> <mml:mo>&lt;</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> TeV. $$N_{\textrm{R}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>N</mml:mi> <mml:mtext>R</mml:mtext> </mml:msub> </mml:math> with masses of less than 3.5 (3.6) TeV are excluded in the electron (muon) channel at $$m(W_{\textrm{R}})=4.8$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>m</mml:mi> <mml:mo>(</mml:mo> <mml:msub> <mml:mi>W</mml:mi> <mml:mtext>R</mml:mtext> </mml:msub> <mml:mo>)</mml:mo> <mml:mo>=</mml:mo> <mml:mn>4.8</mml:mn> </mml:mrow> </mml:math> TeV for the Majorana neutrinos, and limits of $$m(N_{\textrm{R}})$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>m</mml:mi> <mml:mo>(</mml:mo> <mml:msub> <mml:mi>N</mml:mi> <mml:mtext>R</mml:mtext> </mml:msub> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> up to 3.6 TeV for $$m(W_{\textrm{R}}) = 5.2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>m</mml:mi> <mml:mo>(</mml:mo> <mml:msub> <mml:mi>W</mml:mi> <mml:mtext>R</mml:mtext> </mml:msub> <mml:mo>)</mml:mo> <mml:mo>=</mml:mo> <mml:mn>5.2</mml:mn> </mml:mrow> </mml:math> (5.0) TeV in the electron (muon) channel are set for the Dirac neutrinos. These constitute the most stringent exclusion limits to date for the model considered.