CMS-PAS-EXO-17-010

CMS-PAS-EXO-17-010
Search for strongly interacting massive particles with trackless jets
CMS Collaboration
July 2020

Abstract: A search for dark matter in the form of strongly interacting massive particles, manifesting themselves as a pair of jets without tracks in the CMS detector at the LHC, is presented. The charged energy fraction of jets is used as a key discriminator to efficiently suppress the large multijet background, and the remaining background is estimated directly from data. The search is performed using proton-proton collision data corresponding to an integrated luminosity of 16.1 fb $^{-1}$ , collected by the CMS detector in 2016. No significant excess of events is observed above the expected background. Strongly interacting massive particles with masses up to 900 GeV are excluded at 95% confidence level for the model under consideration. The presented analysis thus evaluates the sensitivity to an unconventional phase space for new physics for the first time at colliders. In addition to the interpretation in the context of the SIMP model, model-independent limits that can be used for reinterpretation of the results are provided.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to EPJC. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Feynman diagram showing the production of a SIMP pair, through a new low mass mediator.
png pdf	Figure 2: Number of jets with ${p_{\mathrm {T}}} >$ 30 GeV (left) and ChF of the two leading jets (right). The baseline selection is applied, except for the requirement on the number of jets in the corresponding plot. The QCD and SIMP simulations are normalized to 16.1 fb $^{-1}$ .
png pdf	Figure 2-a: Number of jets with ${p_{\mathrm {T}}} >$ 30 GeV. The baseline selection is applied. The QCD and SIMP simulations are normalized to 16.1 fb $^{-1}$ .
png pdf	Figure 2-b: ChF of the two leading jets. The baseline selection is applied, except for the requirement on the number of jets. The QCD and SIMP simulations are normalized to 16.1 fb $^{-1}$ .
png pdf	Figure 3: Closure test in MC, as a function of inclusive ${\rm ChF} < x$ bins.
png pdf	Figure 4: The 1- and 2-leg predictions from data, as well as the direct observation in data, as a function of exclusive bins in ChF, where either the leading or the subleading jet has a ChF within the bin range, and both have a ChF below the upper threshold.
png pdf	Figure 5: The expected 95% CL upper limits on the production cross section for SIMPs with masses between 1 and 1000 GeV, as well as the theoretical prediction (red), with respect to the generator level selection ( $p_T^{\chi} >$ 200 GeV and $\|\eta _{\chi}\| <$ 2.5).

Tables
png pdf	Table 1: Number of predicted (using the 1-leg prediction from data) and observed events for the considered selections. The expected number of signal events is also given for the $m_{\chi} =$ 1 GeV and $m_{\chi} =$ 1000 GeV scenarios, with the corresponding statistical uncertainties.
png pdf	Table 2: The systematic uncertainties taken into account for the signal simulation.

Summary

A search was presented for dark matter in the form of strongly interacting massive particles (SIMPs) manifesting themselves in the detector as a pair of jets without tracks. The large multijet background is efficiently suppressed using the charged energy fraction of jets as the key discriminator. The remaining background is estimated directly from data. Using proton-proton collision data corresponding to an integrated luminosity of 16.1 fb

$^{-1}$ of integrated luminosity collected by the CMS experiment in 2016, we set first limits on a potential SIMP signal, excluding SIMP masses up to 900 GeV at 95% confidence level. A model-independent fiducial cross section upper limit of 0.18 fb at 95% confidence level is also provided for a generic fiducial signal of high-momentum trackless jets. The presented analysis thus evaluates the sensitivity to an unconventional phase space for new physics for the first time at colliders, providing both the interpretation in the context of the SIMP model, as well as model-independent limits that can be used for reinterpretation of the results.

References
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