CMS-PAS-SUS-23-016

CMS-PAS-SUS-23-016
Search for new physics in the final state of a single photon and large missing transverse energy in proton-proton collisions at $\sqrt{s}=$ 13 TeV
CMS Collaboration
28 March 2025

Abstract: A search for new physics in the final state of a single photon and high missing transverse energy is performed using proton-proton collision data at a center-of-mass energy of $\sqrt{s}=$ 13 TeV. The analysis is performed on a data sample corresponding to an integrated luminosity of 101.3 fb $^{-1}$ , collected using the CMS detector in 2017 and 2018. A statistical combination is performed with an earlier search based on 35.9 fb $^{-1}$ , collected in 2016. No deviations from the predictions of the standard model are observed. The results are interpreted in the context of dark matter production and models containing extra spatial dimensions, and limits on new physics parameters are calculated at the 95% confidence level. For the two simplified dark matter production models considered, the observed (expected) lower limits on the mediator masses are both 1085 (1300) GeV for 1 GeV dark matter mass. For an effective electroweak-dark matter contact interaction, the observed (expected) lower limit on the suppression parameter $\Lambda$ is 937 (1000) GeV. For the ADD model, which provides the framework for extra dimensions aspects, values of the effective Planck scale up to 3.17-3.20 TeV are excluded between 3 and 6 extra spatial dimensions.
Links: CDS record (PDF) ; Physics Briefing ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Leading order diagrams of the simplified DM model (left), EWK-DM effective interaction (center), and graviton (G) production in the ADD model (right), with a final state of a photon and large $p_{\mathrm{T}}^\text{miss}$ . Particles $\chi$ and $\overline{\chi}$ are the DM and its antiparticle, and $\Phi$ in the simplified DM model represents a vector or axial-vector mediator.
png pdf	Figure 1-a: Leading order diagrams of the simplified DM model (left), EWK-DM effective interaction (center), and graviton (G) production in the ADD model (right), with a final state of a photon and large $p_{\mathrm{T}}^\text{miss}$ . Particles $\chi$ and $\overline{\chi}$ are the DM and its antiparticle, and $\Phi$ in the simplified DM model represents a vector or axial-vector mediator.
png pdf	Figure 1-b: Leading order diagrams of the simplified DM model (left), EWK-DM effective interaction (center), and graviton (G) production in the ADD model (right), with a final state of a photon and large $p_{\mathrm{T}}^\text{miss}$ . Particles $\chi$ and $\overline{\chi}$ are the DM and its antiparticle, and $\Phi$ in the simplified DM model represents a vector or axial-vector mediator.
png pdf	Figure 1-c: Leading order diagrams of the simplified DM model (left), EWK-DM effective interaction (center), and graviton (G) production in the ADD model (right), with a final state of a photon and large $p_{\mathrm{T}}^\text{miss}$ . Particles $\chi$ and $\overline{\chi}$ are the DM and its antiparticle, and $\Phi$ in the simplified DM model represents a vector or axial-vector mediator.
png pdf	Figure 2: Prefit distribution of $E_{\mathrm{T}}^{\gamma}$ / $p_{\mathrm{T}}^\text{miss}$ for the 2017 (left) and 2018 (right) datasets. Templates for signal hypotheses are shown overlaid as light green and magenta dashed lines along with their cross section value. The gray band represents the total systematic and statistical uncertainties.
png pdf	Figure 2-a: Prefit distribution of $E_{\mathrm{T}}^{\gamma}$ / $p_{\mathrm{T}}^\text{miss}$ for the 2017 (left) and 2018 (right) datasets. Templates for signal hypotheses are shown overlaid as light green and magenta dashed lines along with their cross section value. The gray band represents the total systematic and statistical uncertainties.
png pdf	Figure 2-b: Prefit distribution of $E_{\mathrm{T}}^{\gamma}$ / $p_{\mathrm{T}}^\text{miss}$ for the 2017 (left) and 2018 (right) datasets. Templates for signal hypotheses are shown overlaid as light green and magenta dashed lines along with their cross section value. The gray band represents the total systematic and statistical uncertainties.
png pdf	Figure 3: Prefit distribution of $\Delta \phi(p_{\mathrm{T}}^\text{miss}, \gamma)$ for the 2017 (left) and 2018 (right) datasets. Templates for signal hypotheses are shown overlaid as light green and magenta dashed lines along with their cross section value. The gray band represents the total systematic and statistical uncertainties.
png pdf	Figure 3-a: Prefit distribution of $\Delta \phi(p_{\mathrm{T}}^\text{miss}, \gamma)$ for the 2017 (left) and 2018 (right) datasets. Templates for signal hypotheses are shown overlaid as light green and magenta dashed lines along with their cross section value. The gray band represents the total systematic and statistical uncertainties.
png pdf	Figure 3-b: Prefit distribution of $\Delta \phi(p_{\mathrm{T}}^\text{miss}, \gamma)$ for the 2017 (left) and 2018 (right) datasets. Templates for signal hypotheses are shown overlaid as light green and magenta dashed lines along with their cross section value. The gray band represents the total systematic and statistical uncertainties.
png pdf	Figure 4: Comparison of data and background post-fit distributions in the $\mathrm{e} \gamma$ (left) and $\mu \gamma$ (right) CR using the combined 2017 and 2018 dataset. The last bin of the distribution includes the overflow events. The ratios of data to the background predictions are shown in the lower panels, with the uncertainty bands including the combination of all systematic uncertainties.
png pdf	Figure 4-a: Comparison of data and background post-fit distributions in the $\mathrm{e} \gamma$ (left) and $\mu \gamma$ (right) CR using the combined 2017 and 2018 dataset. The last bin of the distribution includes the overflow events. The ratios of data to the background predictions are shown in the lower panels, with the uncertainty bands including the combination of all systematic uncertainties.
png pdf	Figure 4-b: Comparison of data and background post-fit distributions in the $\mathrm{e} \gamma$ (left) and $\mu \gamma$ (right) CR using the combined 2017 and 2018 dataset. The last bin of the distribution includes the overflow events. The ratios of data to the background predictions are shown in the lower panels, with the uncertainty bands including the combination of all systematic uncertainties.
png pdf	Figure 5: Comparison of data and background post-fit distributions in the $\mathrm{e} \mathrm{e} \gamma$ (left) and $\mu \mu \gamma$ (right) CR using the combined 2017 and 2018 dataset. The last bin of the distribution includes the overflow events. The ratios of data to the background predictions are shown in the lower panels, with the uncertainty bands including the combination of all systematic uncertainties.
png pdf	Figure 5-a: Comparison of data and background post-fit distributions in the $\mathrm{e} \mathrm{e} \gamma$ (left) and $\mu \mu \gamma$ (right) CR using the combined 2017 and 2018 dataset. The last bin of the distribution includes the overflow events. The ratios of data to the background predictions are shown in the lower panels, with the uncertainty bands including the combination of all systematic uncertainties.
png pdf	Figure 5-b: Comparison of data and background post-fit distributions in the $\mathrm{e} \mathrm{e} \gamma$ (left) and $\mu \mu \gamma$ (right) CR using the combined 2017 and 2018 dataset. The last bin of the distribution includes the overflow events. The ratios of data to the background predictions are shown in the lower panels, with the uncertainty bands including the combination of all systematic uncertainties.
png pdf	Figure 6: Comparison of data and background post-fit distributions for vertical region (left) and horizontal region (right) using combined 2017 and 2018 dataset. Templates for signal hypotheses are shown overlaid as light green and magenta dashed lines along with their cross section value. The last bin of the distribution includes the overflow events.
png pdf	Figure 6-a: Comparison of data and background post-fit distributions for vertical region (left) and horizontal region (right) using combined 2017 and 2018 dataset. Templates for signal hypotheses are shown overlaid as light green and magenta dashed lines along with their cross section value. The last bin of the distribution includes the overflow events.
png pdf	Figure 6-b: Comparison of data and background post-fit distributions for vertical region (left) and horizontal region (right) using combined 2017 and 2018 dataset. Templates for signal hypotheses are shown overlaid as light green and magenta dashed lines along with their cross section value. The last bin of the distribution includes the overflow events.
png pdf	Figure 7: The ratio of 95% CL upper cross section limits to the theoretical cross section ( $\mu_{95}$ ), for DM simplified models with vector (left) and axial-vector (right) mediators, using full 2016-2018 dataset corresponding to an integrated luminosity of 137.2 fb $^{-1}$ , assuming $g_{\mathrm{q}}=$ 0.25 and $g_{\text{DM}}=$ 1. Expected $\mu_{95} =$ 1 contours are overlaid in red. The region under the observed contour is excluded. For DM simplified model parameters in the region below the lower violet dot-dash contour, and also above the corresponding upper contour in the right hand plot, cosmological DM abundance exceeds the density observed by the Planck satellite experiment.
png pdf	Figure 7-a: The ratio of 95% CL upper cross section limits to the theoretical cross section ( $\mu_{95}$ ), for DM simplified models with vector (left) and axial-vector (right) mediators, using full 2016-2018 dataset corresponding to an integrated luminosity of 137.2 fb $^{-1}$ , assuming $g_{\mathrm{q}}=$ 0.25 and $g_{\text{DM}}=$ 1. Expected $\mu_{95} =$ 1 contours are overlaid in red. The region under the observed contour is excluded. For DM simplified model parameters in the region below the lower violet dot-dash contour, and also above the corresponding upper contour in the right hand plot, cosmological DM abundance exceeds the density observed by the Planck satellite experiment.
png pdf	Figure 7-b: The ratio of 95% CL upper cross section limits to the theoretical cross section ( $\mu_{95}$ ), for DM simplified models with vector (left) and axial-vector (right) mediators, using full 2016-2018 dataset corresponding to an integrated luminosity of 137.2 fb $^{-1}$ , assuming $g_{\mathrm{q}}=$ 0.25 and $g_{\text{DM}}=$ 1. Expected $\mu_{95} =$ 1 contours are overlaid in red. The region under the observed contour is excluded. For DM simplified model parameters in the region below the lower violet dot-dash contour, and also above the corresponding upper contour in the right hand plot, cosmological DM abundance exceeds the density observed by the Planck satellite experiment.
png pdf	Figure 8: The 90% CL exclusion limits on the $\chi$ -nucleon spin-independent (left) and spin-dependent (right) scattering cross sections involving vector and axial-vector operators, respectively, using full 2016-2018 dataset as a function of the $M_{\text{DM}}$ . Simplified model DM parameters of $g_{\mathrm{q}}=$ 0.25 and $g_{\text{DM}}=$ 1 are assumed. The region to the upper left of the contour is excluded. On the plots, the median expected 90% CL curve overlaps the observed 90% CL curve. Also shown are corresponding exclusion contours, where regions above the curves are excluded, from the recent results by CDMSLite [47], LUX [48], PandaX-II [49], XENON1T [50], CRESST-II [51], PICO-60 [52], IceCube [53], PICASSO [54] and Super-Kamiokande [55] Collaborations.
png pdf	Figure 8-a: The 90% CL exclusion limits on the $\chi$ -nucleon spin-independent (left) and spin-dependent (right) scattering cross sections involving vector and axial-vector operators, respectively, using full 2016-2018 dataset as a function of the $M_{\text{DM}}$ . Simplified model DM parameters of $g_{\mathrm{q}}=$ 0.25 and $g_{\text{DM}}=$ 1 are assumed. The region to the upper left of the contour is excluded. On the plots, the median expected 90% CL curve overlaps the observed 90% CL curve. Also shown are corresponding exclusion contours, where regions above the curves are excluded, from the recent results by CDMSLite [47], LUX [48], PandaX-II [49], XENON1T [50], CRESST-II [51], PICO-60 [52], IceCube [53], PICASSO [54] and Super-Kamiokande [55] Collaborations.
png pdf	Figure 8-b: The 90% CL exclusion limits on the $\chi$ -nucleon spin-independent (left) and spin-dependent (right) scattering cross sections involving vector and axial-vector operators, respectively, using full 2016-2018 dataset as a function of the $M_{\text{DM}}$ . Simplified model DM parameters of $g_{\mathrm{q}}=$ 0.25 and $g_{\text{DM}}=$ 1 are assumed. The region to the upper left of the contour is excluded. On the plots, the median expected 90% CL curve overlaps the observed 90% CL curve. Also shown are corresponding exclusion contours, where regions above the curves are excluded, from the recent results by CDMSLite [47], LUX [48], PandaX-II [49], XENON1T [50], CRESST-II [51], PICO-60 [52], IceCube [53], PICASSO [54] and Super-Kamiokande [55] Collaborations.
png pdf	Figure 9: The 95% CL observed and expected lower limits on $\Lambda$ for an effective EWK-DM contact interaction, as a function of DM mass $M_{\text{DM}}$ using full 2016-2018 dataset corresponding to an integrated luminosity of 137.2 fb $^{-1}$ .
png pdf	Figure 10: Lower limit on the fundamental Planck scale $M_\mathrm{D}$ as a function of number of extra dimension $n$ , using the 2017 and 2018 dataset with an integrated luminosity of 101.3 fb $^{-1}$ (shown in dark pink), and the full 2016-2018 dataset with an integrated luminosity of 137.2 fb $^{-1}$ (shown in green).

Tables
png pdf	Table 1: Event selection criteria for SR
png pdf	Table 2: Event selection in CR
png pdf	Table 3: Summary of systematic uncertainties considered in the analysis.
png pdf	Table 4: Total yield in vertical and horizontal regions using combined 2017 and 2018 dataset

Summary

Proton-proton collisions producing a high transverse momentum photon and large

$p_{\mathrm{T}}^\text{miss}$ have been investigated to search for new phenomena, using a data set corresponding to 137.2 fb

$^{-1}$ of integrated luminosity recorded at

$\sqrt{s} =$ 13 TeV at the LHC. A simultaneous fit to multiple SR and CR is employed in this analysis, enhancing sensitivity to potential signal events. No deviations from the SM predictions are observed. For the simplified DM production models considered, the observed(expected) lower limit on the mediator mass is 1085 (1300) GeV in both cases for 1 GeV DM mass. For an effective EWK-DM contact interaction, the observed (expected) lower limit on the suppression parameter

$\Lambda$ is 937 (1000) GeV. For the model with extra spatial dimensions, values of the effective Planck scale

$M_\mathrm{D}$ up to 3.20-3.17 TeV are excluded for between 3 and 6 extra dimensions. These limits on

$\Lambda$ and

$M_\mathrm{D}$ are the most sensitive limits from the mono photon final state to date.

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