Table 1.

Summary of the event selection in the signal and $t\overline{t}$ background control regions used in the analysis. The variables used are the number of leptons ($N^{\mathrm{leptons}}$), the $p_{\mathrm{T}}$ of the leading lepton ($p_{\mathrm{T}}({\ell }_1)$), the dilepton flavour (SF: same-flavour; DF: different flavour), the dilepton invariant mass ($m_{\ell \ell }$), the number of $b$-jets ($N^{b-\mathrm{jets}}$), the number of jets regardless of their flavour ($N^{\mathrm{jets}}$), the $p_{\mathrm{T}}$ of the leading jet ($p_{\mathrm{T}}({\mathrm{jet}}_1)$), the $p_{\mathrm{T}}$ of the $N^{\mathrm{jets}}$-th jet required in each region ($p_{\mathrm{T}}({\mathrm{jet}}_N)$), the missing transverse momentum ($E_{\mathrm{T}}^{\mathrm{miss}}$), the transverse momentum of the dilepton system ($p_{\mathrm{T}}(\ell \ell )$), and the angular separation in the transverse plane between the leptons forming the SFOS pair ($\mathrm{\Delta }{\mathit{\varphi }}^{\ell \ell }$)

	SR2A	SR2B	SR2C	CR2A	CR2C	SR3A	SR3B
$N^{\mathrm{leptons}}$	2	2	2	2	2	3	3
$p_{\mathrm{T}}({\ell }_1)$ (GeV)	$>$25	$>$25	$>$25	$>$25	$>$25	$>$40	$>$60
Dilepton flavour	SF	SF	SF	SF, DF	SF, DF	SF	SF
$|m_{\ell \ell }-m_Z|$ (GeV)	$<$5	$<$10	$<$5	$<$50	$<$50	$<$10	$<$10
				$>$10 (SF)	$>$10 (SF)
$N^{\mathrm{b}\text{-}\mathrm{jets}}$	$\ge$1	$\ge$1	$\ge$1	$\ge$1	$\ge$1	$\ge$1	$\ge$1
$N^{\mathrm{jets}}$	$3$, $4$	$3$, $4$	$\ge$5	$3$, $4$	$\ge$5	$\ge$5	$\ge$5
$p_{\mathrm{T}}({\mathrm{jet}}_1)$ (GeV)	$>$30	$>$30	$>$30	$>$30	$>$30	$>$50	$>$40
$p_{\mathrm{T}}({\mathrm{jet}}_N)$ (GeV)	$>$30	$>$30	$>$30	$>$30	$>$30	$>$30	$>$40
$E_{\mathrm{T}}^{\mathrm{miss}}$(GeV)	$>$160	$>$200	$>$160	$>$160	$>$120	$>$60	$>$60
$p_{\mathrm{T}}(\ell \ell )$ (GeV)	$>$80	$>$160	$>$80	$>$80	$>$80	–	$>$75
$\mathrm{\Delta }{\mathit{\varphi }}^{\ell \ell }$ (rad)	$<$1.5	$<$1.5	$<$1.5	$<$1.5	$<$1.5	–	–