Search for long-lived particles decaying to leptons with large impact parameter in proton–proton collisions at $$\sqrt{s} = 13\,\text {Te}\text {V} $$

Abstract

Abstract A search for new long-lived particles decaying to leptons using proton–proton collision data produced by the CERN LHC at $$\sqrt{s}=13\,\text {Te}\text {V} $$ <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:mspace/> <mml:mrow> <mml:mtext>Te</mml:mtext> <mml:mspace/> </mml:mrow> </mml:mrow> </mml:math> is presented. Events are selected with two leptons (an electron and a muon, two electrons, or two muons) that both have transverse impact parameter values between 0.01 and 10 $$\,\text {cm}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mspace/> <mml:mtext>cm</mml:mtext> </mml:mrow> </mml:math> and are not required to form a common vertex. Data used for the analysis were collected with the CMS detector in 2016, 2017, and 2018, and correspond to an integrated luminosity of 118 (113) $$\,\text {fb}^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mspace/> <mml:msup> <mml:mtext>fb</mml:mtext> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> in the $${{\mathrm{e}}_{\mathrm{}}^{\mathrm{}}} {{\mathrm{e}}_{\mathrm{}}^{\mathrm{}}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msubsup> <mml:mi>e</mml:mi> <mml:mrow> <mml:mrow/> </mml:mrow> <mml:mrow/> </mml:msubsup> <mml:msubsup> <mml:mi>e</mml:mi> <mml:mrow> <mml:mrow/> </mml:mrow> <mml:mrow/> </mml:msubsup> </mml:mrow> </mml:math> channel ( $${{\mathrm{e}}_{\mathrm{}}^{\mathrm{}}} {\upmu } $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msubsup> <mml:mi>e</mml:mi> <mml:mrow> <mml:mrow/> </mml:mrow> <mml:mrow/> </mml:msubsup> <mml:mi>μ</mml:mi> </mml:mrow> </mml:math> and $${\upmu } {\upmu } $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mi>μ</mml:mi> </mml:mrow> </mml:math> channels). The search is designed to be sensitive to a wide range of models with displaced $${{\mathrm{e}}_{\mathrm{}}^{\mathrm{}}} {\upmu } $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msubsup> <mml:mi>e</mml:mi> <mml:mrow> <mml:mrow/> </mml:mrow> <mml:mrow/> </mml:msubsup> <mml:mi>μ</mml:mi> </mml:mrow> </mml:math> , $${{\mathrm{e}}_{\mathrm{}}^{\mathrm{}}} {{\mathrm{e}}_{\mathrm{}}^{\mathrm{}}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msubsup> <mml:mi>e</mml:mi> <mml:mrow> <mml:mrow/> </mml:mrow> <mml:mrow/> </mml:msubsup> <mml:msubsup> <mml:mi>e</mml:mi> <mml:mrow> <mml:mrow/> </mml:mrow> <mml:mrow/> </mml:msubsup> </mml:mrow> </mml:math> , and $${\upmu } {\upmu } $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mi>μ</mml:mi> </mml:mrow> </mml:math> final states. The results constrain several well-motivated models involving new long-lived particles that decay to displaced leptons. For some areas of the available phase space, these are the most stringent constraints to date.