Feynman diagrams of $\mathrm{Z'}\to\mu^{-}\mu^{+}$ with a $\mathrm{Z'}$ boson produced via $\mathrm{s}\overline{\mathrm{b}}\to\mathrm{Z'}$, with one $\mathrm{b}$ quark and one $\overline{\mathrm{s}}$ quark in the final state.

Distribution of $\min(m_{\mu\mathrm{b}})$ as obtained from simulation in events with $N_{\mathrm{b}} \geq 1$ passing all the other selection requirements. In this search, we require $\min(m_{\mu\mathrm{b}})>175~\mathrm{GeV}$. The stacked histogram displays the expected distribution from the simulation of the SM backgrounds, while the overlaid open histograms illustrate the size and shape of the $\mathrm{Z'}$ contribution from the LFU model described in Eq. (1), for several $\mathrm{Z'}$ mass hypotheses. For illustrative purposes, we choose couplings $|g_{\ell}| = |g_{\nu}| = |g_{\mathrm{b}}| = 0.03$ and $\delta_{\mathrm{bs}}=0$. The contribution of background processes other than DY and $\mathrm{t}\overline{\mathrm{t}}$ is so small that it is only barely visible at the bottom of the stacked histogram. The hatched region indicates the statistical uncertainty arising from the limited size of the SM simulated samples. Histograms are normalized to unit area.

Distributions of $m_{\mu\mu}$ in the $N_{\mathrm{b}}=1$ event category. The stacked histogram displays the expected distribution from the SM background simulation. The overlaid open distributions illustrate the $\mathrm{Z'}$ contribution from the LFU model at $|g_{\ell}| = |g_{\nu}| = |g_{\mathrm{b}}| = 0.03$ and $\delta_{\mathrm{bs}}=0$ for a variety of $\mathrm{Z'}$ mass hypotheses. The observed data are shown as black points with statistical error bars. The hatched region indicates the statistical uncertainty arising from the limited size of the SM simulated samples. The size of the bins increases as a function of $m_{\mu\mu}$. In extracting the results of the search, the background is estimated directly from data, so the SM background simulation is only illustrative in these distributions.

Distributions of $m_{\mu\mu}$ in the $N_{\mathrm{b}}\geq 2$ event category. The stacked histogram displays the expected distribution from the SM background simulation. The overlaid open distributions illustrate the $\mathrm{Z'}$ contribution from the LFU model at $|g_{\ell}| = |g_{\nu}| = |g_{\mathrm{b}}| = 0.03$ and $\delta_{\mathrm{bs}}=0$ for a variety of $\mathrm{Z'}$ mass hypotheses. The observed data are shown as black points with statistical error bars. The hatched region indicates the statistical uncertainty arising from the limited size of the SM simulated samples. The size of the bins increases as a function of $m_{\mu\mu}$. In extracting the results of the search, the background is estimated directly from data, so the SM background simulation is only illustrative in these distributions.

Invariant mass $m_{\mu\mu}$ distributions in the $N_{\mathrm{b}} = 1$ category, shown together with the corresponding selected background functional forms used as input to the $discrete~profiling$ method when probing the $m_{\mathrm{Z'}}=500~\mathrm{GeV}$ hypothesis. The expected signal distribution for the LFU model described in Eq. (1), with couplings $|g_{\ell}| = |g_{\nu}| = |g_{\mathrm{b}}| = 0.03$ and $\delta_{\mathrm{bs}}=0$, is overlaid. The displayed mass range corresponds to the fit window used for this $m_{\mathrm{Z'}}$ hypothesis, which is $\pm 10\, \sigma_{\mathrm{mass}}$ around the probed $m_{\mathrm{Z'}}$ value. While the likelihood fits are performed on unbinned data, here we present the data in binned histograms with binning chosen to reflect the size of $\sigma_{\mathrm{mass}}$.

Invariant mass $m_{\mu\mu}$ distributions in the $N_{\mathrm{b}} \geq 2$ category, shown together with the corresponding selected background functional forms used as input to the $discrete~profiling$ method when probing the $m_{\mathrm{Z'}}=500~\mathrm{GeV}$ hypothesis. The expected signal distribution for the LFU model described in Eq. (1), with couplings $|g_{\ell}| = |g_{\nu}| = |g_{\mathrm{b}}| = 0.03$ and $\delta_{\mathrm{bs}}=0$, is overlaid. The displayed mass range corresponds to the fit window used for this $m_{\mathrm{Z'}}$ hypothesis, which is $\pm 10\, \sigma_{\mathrm{mass}}$ around the probed $m_{\mathrm{Z'}}$ value. While the likelihood fits are performed on unbinned data, here we present the data in binned histograms with binning chosen to reflect the size of $\sigma_{\mathrm{mass}}$.

Exclusion limits at $95\%$ CL on the number of selected BSM events with $N_{\mathrm{b}} \geq 1$ as functions of $m_{\mathrm{Z'}}$ for $f_{2\mathrm{b}}=0$. The quantity $f_{2\mathrm{b}}$ is the fraction of BSM events passing the analysis selection that have at least two $\mathrm{b}$ quark jets. The solid black (dashed red) curve represents the observed (median expected) exclusion. The inner green (outer yellow) band indicates the region containing $68~(95)\%$ of the distribution of limits expected under the background-only hypothesis.

Exclusion limits at $95\%$ CL on the number of selected BSM events with $N_{\mathrm{b}} \geq 1$ as functions of $m_{\mathrm{Z'}}$ for $f_{2\mathrm{b}}=0.25$. The quantity $f_{2\mathrm{b}}$ is the fraction of BSM events passing the analysis selection that have at least two $\mathrm{b}$ quark jets. The solid black (dashed red) curve represents the observed (median expected) exclusion. The inner green (outer yellow) band indicates the region containing $68~(95)\%$ of the distribution of limits expected under the background-only hypothesis.

Exclusion limits at $95\%$ CL on the number of selected BSM events with $N_{\mathrm{b}} \geq 1$ as functions of $m_{\mathrm{Z'}}$ for $f_{2\mathrm{b}}=0.75$. The quantity $f_{2\mathrm{b}}$ is the fraction of BSM events passing the analysis selection that have at least two $\mathrm{b}$ quark jets. The solid black (dashed red) curve represents the observed (median expected) exclusion. The inner green (outer yellow) band indicates the region containing $68~(95)\%$ of the distribution of limits expected under the background-only hypothesis.

Exclusion limits at $95\%$ CL on the number of selected BSM events with $N_{\mathrm{b}} \geq 1$ as functions of $m_{\mathrm{Z'}}$ for $f_{2\mathrm{b}}=1$. The quantity $f_{2\mathrm{b}}$ is the fraction of BSM events passing the analysis selection that have at least two $\mathrm{b}$ quark jets. The solid black (dashed red) curve represents the observed (median expected) exclusion. The inner green (outer yellow) band indicates the region containing $68~(95)\%$ of the distribution of limits expected under the background-only hypothesis.

Observed (solid) and median expected (dashed) exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution, marked by the dotted curves. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Observed exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=350~\mathrm{GeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Expected exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=350~\mathrm{GeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=350~\mathrm{GeV}$. The coupling values are shown at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid.

Observed exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=500~\mathrm{GeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Expected exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=500~\mathrm{GeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=500~\mathrm{GeV}$. The coupling values are shown at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid.

Observed exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=700~\mathrm{GeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Expected exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=700~\mathrm{GeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=700~\mathrm{GeV}$. The coupling values are shown at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid.

Observed exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=1~\mathrm{TeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Expected exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=1~\mathrm{TeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=1~\mathrm{TeV}$. The coupling values are shown at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid.

Observed exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=1.5~\mathrm{TeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Expected exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=1.5~\mathrm{TeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=1.5~\mathrm{TeV}$. The coupling values are shown at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid.

Observed exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=2~\mathrm{TeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Expected exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=2~\mathrm{TeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $\delta_{\mathrm{bs}}=0$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=2~\mathrm{TeV}$. The coupling values are shown at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid.

Observed (solid) and median expected (dashed) exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution, marked by the dotted curves. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Observed exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=350~\mathrm{GeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Expected exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=350~\mathrm{GeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=350~\mathrm{GeV}$. The coupling values are shown at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid.

Observed exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=500~\mathrm{GeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Expected exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=500~\mathrm{GeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=500~\mathrm{GeV}$. The coupling values are shown at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid.

Observed exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=700~\mathrm{GeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Expected exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=700~\mathrm{GeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=700~\mathrm{GeV}$. The coupling values are shown at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid.

Observed exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=1~\mathrm{TeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Expected exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=1~\mathrm{TeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=1~\mathrm{TeV}$. The coupling values are shown at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid.

Observed exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=1.5~\mathrm{TeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Expected exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=1.5~\mathrm{TeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=1.5~\mathrm{TeV}$. The coupling values are shown at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid.

Observed exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=2~\mathrm{TeV}$. The exclusion limits are given up to coupling values at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid. The enclosed regions are excluded.

Exclusion limits at $95\%$ CL in the $|g_{\mathrm{b}}|$--$|g_{\ell}|$ plane for the LFU model, with $|\delta_{\mathrm{bs}}|=0.25$ and $|g_{\nu}|=|g_{\ell}|$, for $m_{\mathrm{Z'}}=2~\mathrm{TeV}$. The coupling values are shown at which the $\mathrm{Z'}$ width is equal to half of the $\mu\mu$ invariant mass resolution. Beyond these coupling values, the narrow width approximation intrinsic to the search strategy is not considered valid.

Exclusion limits at $95\%$ CL in the $|\theta_{23}|$--$|g_{\mathrm{Z'}}|$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for $m_{\mathrm{Z'}}=500~\mathrm{GeV}$. The solid black (dashed red) curves represent the observed (median expected) exclusions. The dotted curves denote the coupling values at which the $\mathrm{Z'}$ width equals one half of the $\mu\mu$ invariant mass resolution. For larger values of the couplings, the narrow width approximation intrinsic to the search strategy is not considered valid. The region enclosed between the solid black (dashed red) and dotted curves is (expected to be) excluded. The dotted curve for $m_{\mathrm{Z'}}=500~\mathrm{GeV}$ lies beyond the displayed $|g_{\mathrm{Z'}}|$ range and is, therefore, not shown. The shaded blue area represents the region preferred from the global fit in JHEP 04 (2023) 033 at $95\%$ CL. The region above the green dash-dotted curve is incompatible at $95\%$ CL with the measurement of the mass difference between the mass eigenstates of the neutral $\mathrm{B}_\mathrm{s}$ mesons.

Observed exclusion limits at $95\%$ CL in the $|\theta_{23}|$--$|g_{\mathrm{Z'}}|$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for $m_{\mathrm{Z'}}=500~\mathrm{GeV}$.

Expected exclusion limits at $95\%$ CL in the $|\theta_{23}|$--$|g_{\mathrm{Z'}}|$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for $m_{\mathrm{Z'}}=500~\mathrm{GeV}$.

Exclusion limits at $95\%$ CL in the $|\theta_{23}|$--$|g_{\mathrm{Z'}}|$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for $m_{\mathrm{Z'}}=1~\mathrm{TeV}$. The solid black (dashed red) curves represent the observed (median expected) exclusions. The dotted curves denote the coupling values at which the $\mathrm{Z'}$ width equals one half of the $\mu\mu$ invariant mass resolution. For larger values of the couplings, the narrow width approximation intrinsic to the search strategy is not considered valid. The region enclosed between the solid black (dashed red) and dotted curves is (expected to be) excluded. The shaded blue area represents the region preferred from the global fit in JHEP 04 (2023) 033 at $95\%$ CL. The region above the green dash-dotted curve is incompatible at $95\%$ CL with the measurement of the mass difference between the mass eigenstates of the neutral $\mathrm{B}_\mathrm{s}$ mesons.

Observed exclusion limits at $95\%$ CL in the $|\theta_{23}|$--$|g_{\mathrm{Z'}}|$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for $m_{\mathrm{Z'}}=1~\mathrm{TeV}$.

Expected exclusion limits at $95\%$ CL in the $|\theta_{23}|$--$|g_{\mathrm{Z'}}|$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for $m_{\mathrm{Z'}}=1~\mathrm{TeV}$.

Exclusion limits at $95\%$ CL in the $|\theta_{23}|$--$|g_{\mathrm{Z'}}|$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for $m_{\mathrm{Z'}}=1~\mathrm{TeV}$. The coupling values are shown at which the $\mathrm{Z'}$ width equals one half of the $\mu\mu$ invariant mass resolution. For larger values of the couplings, the narrow width approximation intrinsic to the search strategy is not considered valid.

Exclusion limits at $95\%$ CL in the $|\theta_{23}|$--$|g_{\mathrm{Z'}}|$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for $m_{\mathrm{Z'}}=1.5~\mathrm{TeV}$. The solid black (dashed red) curves represent the observed (median expected) exclusions. The dotted curves denote the coupling values at which the $\mathrm{Z'}$ width equals one half of the $\mu\mu$ invariant mass resolution. For larger values of the couplings, the narrow width approximation intrinsic to the search strategy is not considered valid. The region enclosed between the solid black (dashed red) and dotted curves is (expected to be) excluded. The shaded blue area represents the region preferred from the global fit in JHEP 04 (2023) 033 at $95\%$ CL. The region above the green dash-dotted curve is incompatible at $95\%$ CL with the measurement of the mass difference between the mass eigenstates of the neutral $\mathrm{B}_\mathrm{s}$ mesons.

Observed exclusion limits at $95\%$ CL in the $|\theta_{23}|$--$|g_{\mathrm{Z'}}|$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for $m_{\mathrm{Z'}}=1.5~\mathrm{TeV}$.

Expected exclusion limits at $95\%$ CL in the $|\theta_{23}|$--$|g_{\mathrm{Z'}}|$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for $m_{\mathrm{Z'}}=1.5~\mathrm{TeV}$.

Exclusion limits at $95\%$ CL in the $|\theta_{23}|$--$|g_{\mathrm{Z'}}|$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for $m_{\mathrm{Z'}}=1.5~\mathrm{TeV}$. The coupling values are shown at which the $\mathrm{Z'}$ width equals one half of the $\mu\mu$ invariant mass resolution. For larger values of the couplings, the narrow width approximation intrinsic to the search strategy is not considered valid.

Exclusion limits at $95\%$ CL in the $|\theta_{23}|$--$|g_{\mathrm{Z'}}|$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for $m_{\mathrm{Z'}}=2~\mathrm{TeV}$. The solid black (dashed red) curves represent the observed (median expected) exclusions. The dotted curves denote the coupling values at which the $\mathrm{Z'}$ width equals one half of the $\mu\mu$ invariant mass resolution. For larger values of the couplings, the narrow width approximation intrinsic to the search strategy is not considered valid. The region enclosed between the solid black (dashed red) and dotted curves is (expected to be) excluded. The shaded blue area represents the region preferred from the global fit in JHEP 04 (2023) 033 at $95\%$ CL. The region above the green dash-dotted curve is incompatible at $95\%$ CL with the measurement of the mass difference between the mass eigenstates of the neutral $\mathrm{B}_\mathrm{s}$ mesons.

Observed exclusion limits at $95\%$ CL in the $|\theta_{23}|$--$|g_{\mathrm{Z'}}|$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for $m_{\mathrm{Z'}}=2~\mathrm{TeV}$.

Expected exclusion limits at $95\%$ CL in the $|\theta_{23}|$--$|g_{\mathrm{Z'}}|$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for $m_{\mathrm{Z'}}=2~\mathrm{TeV}$.

Exclusion limits at $95\%$ CL in the $|\theta_{23}|$--$|g_{\mathrm{Z'}}|$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for $m_{\mathrm{Z'}}=2~\mathrm{TeV}$. The coupling values are shown at which the $\mathrm{Z'}$ width equals one half of the $\mu\mu$ invariant mass resolution. For larger values of the couplings, the narrow width approximation intrinsic to the search strategy is not considered valid.

Exclusion limits at $95\%$ CL in the $|g_{\mathrm{Z'}}|$--$m_{\mathrm{Z'}}$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for a fixed value of $\theta_{23}=0$. The solid black (dashed red) curve represents the observed (median expected) exclusion. The dotted curve denotes the coupling values at which the $\mathrm{Z'}$ width equals one half of the $\mu\mu$ invariant mass resolution. For larger values of the couplings, the narrow width approximation intrinsic to the search strategy is not considered valid. The region enclosed between the solid black (dashed red) and the dotted curves is (expected to be) excluded. The shaded blue area represents the $|g_{\mathrm{Z'}}|$ range preferred from a global fit in JHEP 04 (2023) 033 at $95\%$ CL.

Observed exclusion limits at $95\%$ CL in the $|g_{\mathrm{Z'}}|$--$m_{\mathrm{Z'}}$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for a fixed value of $\theta_{23}=0$.

Expected exclusion limits at $95\%$ CL in the $|g_{\mathrm{Z'}}|$--$m_{\mathrm{Z'}}$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for a fixed value of $\theta_{23}=0$.

Exclusion limits at $95\%$ CL in the $|g_{\mathrm{Z'}}|$--$m_{\mathrm{Z'}}$ plane for the $B_{3}\!-\!L_{2}$ model from JHEP 04 (2023) 033, for a fixed value of $\theta_{23}=0$. The coupling values are shown at which the $\mathrm{Z'}$ width equals one half of the $\mu\mu$ invariant mass resolution. For larger values of the couplings, the narrow width approximation intrinsic to the search strategy is not considered valid.