CMS-PAS-BPH-23-007

CMS-PAS-BPH-23-007
Measurements of the $\Upsilon$ (1S) meson production in association with a Z boson in proton-proton collisions at $\sqrt{s}=$ 13 TeV
CMS Collaboration
21 January 2025

Abstract: The first measurement of the associated production of an $\Upsilon$ (1S) meson with a Z boson using the four-muon final state is presented. The analysis is based on proton-proton data at $\sqrt{s}=$ 13 TeV, collected with the CMS detector in 2016--2018 and corresponding to an integrated luminosity of 138 fb $^{-1}$ . Using the production of the Z boson decaying into four muons as a normalization channel, we measure the ratio of the fiducial cross section $\sigma(\mathrm{pp}\rightarrow\mathrm{Z}+\Upsilon(\mathrm{1S})) \mathcal{B} (\mathrm{Z}\rightarrow\mu^{+}\mu^{-}) \mathcal{B} (\Upsilon\mathrm{(1S)}\rightarrow\mu^{+}\mu^{-})$ to the fiducial cross section $\sigma(\mathrm{pp}\rightarrow Z)\mathcal{B} (Z\rightarrow\mu^{+}\mu^{-}\mu^{+}\mu^{-})$ . The ratio is found to be $\mathcal{R}_{\mathrm{Z}+\Upsilon\mathrm{(1S)}} = [$ 21.1 $\pm$ 5.5 $\mathrm{(stat)} \pm 0.6\mathrm{(syst)}] \times 10^{-3}$ . We also perform a calculation of the effective double-parton scattering cross section, $\sigma_{\textrm{eff}}$ , which is found to be 13.0 $^{+7.8}_{-3.5}$ mb. In addition, we measure $\sigma_{\textrm{eff}}$ differentially, first as a function of the transverse momentum of the $\Upsilon$ (1S) meson, and then as a function of the transverse momentum of the Z boson.
Links: CDS record (PDF) ; Physics Briefing ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Example Fenyman diagrams for the production of an $\Upsilon\mathrm{(nS)}$ meson with a Z boson via SPS (left) and DPS (right).
png pdf	Figure 1-a: Example Fenyman diagrams for the production of an $\Upsilon\mathrm{(nS)}$ meson with a Z boson via SPS (left) and DPS (right).
png pdf	Figure 1-b: Example Fenyman diagrams for the production of an $\Upsilon\mathrm{(nS)}$ meson with a Z boson via SPS (left) and DPS (right).
png pdf	Figure 2: Invariant mass distributions for the $\Upsilon\mathrm{(nS)}$ (left) and Z (right) candidates. In each panel, the data are represented by the points, with the vertical bars showing the statistical uncertainties, and the solid curve is the overall fit to data. The red, yellow, and green shaded regions correspond to the signal yields for the three $\Upsilon$ (nS) states.
png pdf	Figure 2-a: Invariant mass distributions for the $\Upsilon\mathrm{(nS)}$ (left) and Z (right) candidates. In each panel, the data are represented by the points, with the vertical bars showing the statistical uncertainties, and the solid curve is the overall fit to data. The red, yellow, and green shaded regions correspond to the signal yields for the three $\Upsilon$ (nS) states.
png pdf	Figure 2-b: Invariant mass distributions for the $\Upsilon\mathrm{(nS)}$ (left) and Z (right) candidates. In each panel, the data are represented by the points, with the vertical bars showing the statistical uncertainties, and the solid curve is the overall fit to data. The red, yellow, and green shaded regions correspond to the signal yields for the three $\Upsilon$ (nS) states.
png pdf	Figure 3: Distribution of rapidity (left) and azimuthal (right) separations between the $\Upsilon\mathrm{(1S)}$ meson and the Z boson in data (black markers), and the extracted DPS (green histogram), SPS (blue histogram), and SPS+DPS (red histogram) contributions from the template fit to data. The distributions and corresponding uncertainties are obtained after the \it sPlot weights' application from an unbinned template fit to the $\Delta y$ and $\Delta\phi$ variables.
png pdf	Figure 4: Measurement of $\sigma_\mathrm{eff}$ in bins of the $\Upsilon\mathrm{(1S)}$ meson (left) and Z boson (right) $p_{\mathrm{T}}$ . The data are represented by the points with the black vertical bars showing the statistical uncertainties and the red vertical bars showing the total uncertainties. The horizontal bars represent the bin widths, and the $x$ axis position of each marker corresponds to the median of the $p_{\mathrm{T}}$ distribution within the respective bin.
png pdf	Figure 4-a: Measurement of $\sigma_\mathrm{eff}$ in bins of the $\Upsilon\mathrm{(1S)}$ meson (left) and Z boson (right) $p_{\mathrm{T}}$ . The data are represented by the points with the black vertical bars showing the statistical uncertainties and the red vertical bars showing the total uncertainties. The horizontal bars represent the bin widths, and the $x$ axis position of each marker corresponds to the median of the $p_{\mathrm{T}}$ distribution within the respective bin.
png pdf	Figure 4-b: Measurement of $\sigma_\mathrm{eff}$ in bins of the $\Upsilon\mathrm{(1S)}$ meson (left) and Z boson (right) $p_{\mathrm{T}}$ . The data are represented by the points with the black vertical bars showing the statistical uncertainties and the red vertical bars showing the total uncertainties. The horizontal bars represent the bin widths, and the $x$ axis position of each marker corresponds to the median of the $p_{\mathrm{T}}$ distribution within the respective bin.

Tables
png pdf	Table 1: Fiducial selections in the signal $\mathrm{Z}(\to \mu^{+}\mu^{-}) + \Upsilon\mathrm{(1S)}(\to \mu^{+}\mu^{-})$ and normalization $\mathrm{Z}\to\mu^{+}\mu^{-}\mu^{+}\mu^{-}$ channels.
png pdf	Table 2: Values of $\mathcal{R}_{\mathrm{Z}+\Upsilon\mathrm{(1S)}}$ , $\mathcal{R}^\mathrm{DPS}_{\mathrm{Z}+\Upsilon\mathrm{(1S)}}$ , and $\sigma_\mathrm{eff}$ in bins of the $\Upsilon\mathrm{(1S)}$ meson and Z boson $p_{\mathrm{T}}$ .

Summary

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