CERN Accelerating science

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: Feynman diagrams of $Z'$ production through radiation in a Drell-Yan process (a), and of the corresponding SM background processes (b - d) with a 4$\mu$ final state. : Caption not extracted

: Feynman diagrams of $Z'$ production through radiation in a Drell-Yan process (a), and of the corresponding SM background processes (b - d) with a 4$\mu$ final state. : Caption not extracted

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: : Distributions of $p_{\text{T}}^{Z_1}$ (a), and $p_{\text{T}}^{Z_2}$ (b), and the mass difference of the $Z_1$ and $Z_2$ candidates (c). Small background contributions are denoted as "other backgrounds", including 4$\mu$ events containing non-prompt muons estimated from data and from $ttV$, $VVV$, and Higgs boson production processes.

: : Distributions of $p_{\text{T}}^{Z_1}$ (a), and $p_{\text{T}}^{Z_2}$ (b), and the mass difference of the $Z_1$ and $Z_2$ candidates (c). Small background contributions are denoted as "other backgrounds", including 4$\mu$ events containing non-prompt muons estimated from data and from $ttV$, $VVV$, and Higgs boson production processes.

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: low mass: $m_{Z'} \leq 42~\GeV$ : high mass: $m_{Z'} \geq 42~\GeV$

: low mass: $m_{Z'} \leq 42~\GeV$ : high mass: $m_{Z'} \geq 42~\GeV$

: The pDNN output discriminant variable distributions for low mass (a) and high mass (b) with a signal sample at 35 \GeV ~and 51 \GeV, respectively. : Caption not extracted

: The pDNN output discriminant variable distributions for low mass (a) and high mass (b) with a signal sample at 35 \GeV ~and 51 \GeV, respectively. : Caption not extracted

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: Mass spectra of $m_{Z2}$ (left) and $m_{Z1}$ (right) for the pDNN-selected events with a signal sample at 15 \GeV ~and 51 \GeV, respectively. : Caption not extracted

: Mass spectra of $m_{Z2}$ (left) and $m_{Z1}$ (right) for the pDNN-selected events with a signal sample at 15 \GeV ~and 51 \GeV, respectively. : Caption not extracted

The $p_0$-value scan across the \Zp mass signal regions.

The $p_0$-value scan across the \Zp mass signal regions.

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: 95\% CL upper limits (expected and observed) on the cross-sections times branching fraction (a) and coupling parameter (b). The discontinuity at 42 GeV represents the border of the low/high mass classifiers. : Caption not extracted

: 95\% CL upper limits (expected and observed) on the cross-sections times branching fraction (a) and coupling parameter (b). The discontinuity at 42 GeV represents the border of the low/high mass classifiers. Considering the dimuon mass resolution of 2\% of the ATLAS detector, the horizontal dashed line in (b) indicates the upper limit on the valid coupling parameter of the model used in this analysis. : Caption not extracted

The coupling parameter $g$ limits from this search as a function of the $Z'$ mass compared to the limits~\cite{Altmannshofer:2016jzy} from the Neutrino Trident (red) and the $B_s$ mixing (green) experimental results.

The coupling parameter $g$ limits from this search as a function of the $Z'$ mass compared to the limits~\cite{Altmannshofer:2016jzy} from the Neutrino Trident (red) and the $B_s$ mixing (green) experimental results.