CMS-PAS-SUS-23-017

CMS-PAS-SUS-23-017
Search for dark matter recoiling from a low-multiplicity jet in proton-proton collisions at $\sqrt{s}=$ 13 TeV
CMS Collaboration
31 March 2025

Abstract: A search for dark matter particles, using events containing an imbalance in transverse momentum and one energetic low-multiplicity jet, is performed using data collected in proton-proton collisions with the CMS detector at a center-of-mass energy of 13 TeV. The analysis is based on a data set corresponding to an integrated luminosity of 138 fb $^{-1}$ collected from 2016-2018. This is the first search using the low-multiplicity jet signature at the LHC and supervised machine learning and data augmentation techniques are used to enhance signal sensitivity. No excess of events over the standard model background expectation is observed. Upper limits on the dark matter production cross sections in simplified models with vector and axial vector mediators are set at the 95% confidence level (CL). Mediator masses of up to $\approx$ 4250 GeV are excluded at 95% CL for dark matter mass of $\approx$ 100 GeV and mediator masses of up to $\approx$ 3500 GeV are excluded at 95% CL for dark matter mass of $\approx$ 550 GeV.
Links: CDS record (PDF) ; Physics Briefing ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Representative Leading Order Feynman Diagram of the signal process.
png pdf	Figure 2: The post-fit distributions of the ML output for the 3 years of data analyzed, 2016 on the top-left, 2017 on the top-right and 2018 at the bottom. In the legend, 'Sys' stands for systematic uncertainties and 'stat' for the statistical uncertainties. The bottom panels of each plot show the ratio between data and background prediction, with the gray band representing the total (Sys+stat) postfit uncertainty.
png pdf	Figure 2-a: The post-fit distributions of the ML output for the 3 years of data analyzed, 2016 on the top-left, 2017 on the top-right and 2018 at the bottom. In the legend, 'Sys' stands for systematic uncertainties and 'stat' for the statistical uncertainties. The bottom panels of each plot show the ratio between data and background prediction, with the gray band representing the total (Sys+stat) postfit uncertainty.
png pdf	Figure 2-b: The post-fit distributions of the ML output for the 3 years of data analyzed, 2016 on the top-left, 2017 on the top-right and 2018 at the bottom. In the legend, 'Sys' stands for systematic uncertainties and 'stat' for the statistical uncertainties. The bottom panels of each plot show the ratio between data and background prediction, with the gray band representing the total (Sys+stat) postfit uncertainty.
png pdf	Figure 2-c: The post-fit distributions of the ML output for the 3 years of data analyzed, 2016 on the top-left, 2017 on the top-right and 2018 at the bottom. In the legend, 'Sys' stands for systematic uncertainties and 'stat' for the statistical uncertainties. The bottom panels of each plot show the ratio between data and background prediction, with the gray band representing the total (Sys+stat) postfit uncertainty.
png pdf	Figure 3: 95% CL upper limits on $\mu = \frac{\sigma}{\sigma_{theory}}$ for the vector mediator, $m_{Z^{\prime}}=$ 1 GeV. Left plot shows upper limits for $m_{DM}=$ 150 GeV for a range of mediator mass and right side plot shows upper limits for $m_{med}=$ 4000 GeV for a range of DM mass. A linear interpolation is performed in between available points. The inner (green) band and the outer (yellow) band indicate the regions containing 68% and 95%, respectively, of the distribution of limits expected under the background-only hypothesis.
png pdf	Figure 3-a: 95% CL upper limits on $\mu = \frac{\sigma}{\sigma_{theory}}$ for the vector mediator, $m_{Z^{\prime}}=$ 1 GeV. Left plot shows upper limits for $m_{DM}=$ 150 GeV for a range of mediator mass and right side plot shows upper limits for $m_{med}=$ 4000 GeV for a range of DM mass. A linear interpolation is performed in between available points. The inner (green) band and the outer (yellow) band indicate the regions containing 68% and 95%, respectively, of the distribution of limits expected under the background-only hypothesis.
png pdf	Figure 3-b: 95% CL upper limits on $\mu = \frac{\sigma}{\sigma_{theory}}$ for the vector mediator, $m_{Z^{\prime}}=$ 1 GeV. Left plot shows upper limits for $m_{DM}=$ 150 GeV for a range of mediator mass and right side plot shows upper limits for $m_{med}=$ 4000 GeV for a range of DM mass. A linear interpolation is performed in between available points. The inner (green) band and the outer (yellow) band indicate the regions containing 68% and 95%, respectively, of the distribution of limits expected under the background-only hypothesis.
png pdf	Figure 4: 95% CL upper limits on $\mu = \frac{\sigma}{\sigma_{theory}}$ for the axial vector mediator, $m_{Z^{\prime}}=$ 1 GeV. Left plot shows upper limits for $m_{DM}=$ 150 GeV for a range of mediator mass and right side plot shows upper limits for $m_{med}=$ 4000 GeV for a range of DM mass. A linear interpolation is performed in between available points. The inner (green) band and the outer (yellow) band indicate the regions containing 68% and 95%, respectively, of the distribution of limits expected under the background-only hypothesis.
png pdf	Figure 4-a: 95% CL upper limits on $\mu = \frac{\sigma}{\sigma_{theory}}$ for the axial vector mediator, $m_{Z^{\prime}}=$ 1 GeV. Left plot shows upper limits for $m_{DM}=$ 150 GeV for a range of mediator mass and right side plot shows upper limits for $m_{med}=$ 4000 GeV for a range of DM mass. A linear interpolation is performed in between available points. The inner (green) band and the outer (yellow) band indicate the regions containing 68% and 95%, respectively, of the distribution of limits expected under the background-only hypothesis.
png pdf	Figure 4-b: 95% CL upper limits on $\mu = \frac{\sigma}{\sigma_{theory}}$ for the axial vector mediator, $m_{Z^{\prime}}=$ 1 GeV. Left plot shows upper limits for $m_{DM}=$ 150 GeV for a range of mediator mass and right side plot shows upper limits for $m_{med}=$ 4000 GeV for a range of DM mass. A linear interpolation is performed in between available points. The inner (green) band and the outer (yellow) band indicate the regions containing 68% and 95%, respectively, of the distribution of limits expected under the background-only hypothesis.
png pdf	Figure 5: Expected and observed exclusion region in the $m_{DM}-m_{med}$ plane for the axial vector mediator (left) and vector mediator (right), for $m_{Z^{\prime}}=$ 1 GeV. The color scale represents the theoretical cross section of the signal process.
png pdf	Figure 5-a: Expected and observed exclusion region in the $m_{DM}-m_{med}$ plane for the axial vector mediator (left) and vector mediator (right), for $m_{Z^{\prime}}=$ 1 GeV. The color scale represents the theoretical cross section of the signal process.
png pdf	Figure 5-b: Expected and observed exclusion region in the $m_{DM}-m_{med}$ plane for the axial vector mediator (left) and vector mediator (right), for $m_{Z^{\prime}}=$ 1 GeV. The color scale represents the theoretical cross section of the signal process.

Tables
png pdf	Table 1: Simulated datasets for the backgrounds, their normalization cross sections along with the references. $H_\mathrm{T}$ is the hadronic transverse momentum.
png pdf	Table 2: ML model input features
png pdf	Table 3: Major uncertainties. All these uncertainties affect the shape of the input variables. The value column represents the effect of each uncertainty as a percentage of the event yield. Most of these uncertainties are correlated amongst processes and eras, except for pencil jet scale factors and misidentification, which are decorrelated across decay modes and eras. In addition, the misidentification uncertainties are correlated across non-QCD processes. QCD (EW) next to the name implies the uncertainty is related to higher order QCD (electroweak) effects.

Summary

A novel search for DM particles is presented, using 138 fb

$^{-1}$ of data recorded by the CMS detector in proton-proton collisions at a center-of-mass energy of 13 TeV. The final state consists of a large transverse momentum imbalance and an energetic low-multiplicity jet, marking the first time such a signal is being probed at the LHC. Supervised machine learning methods and data augmentation techniques are used to increase the sensitivity to the signal. No significant deviation from the standard model predictions is observed. Upper limits on the DM production cross section are set at the 95% confidence level, excluding mediator masses up to

$\approx$ 4250 GeV for a DM mass of

$\approx$ 100 GeV and up to

$\approx$ 3500 GeV for a DM mass of

$\approx$ 550 GeV for both the vector and axial vector mediator scenarios.

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