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CMS-EXO-17-010 ; CERN-EP-2021-029
Search for strongly interacting massive particles generating trackless jets in proton-proton collisions at $\sqrt{s} = $ 13 TeV
CMS Collaboration
19 May 2021
Eur. Phys. J. C 82 (2022) 213
Abstract: A search for dark matter in the form of strongly interacting massive particles (SIMPs) using the CMS detector at the LHC is presented. The SIMPs would be produced in pairs that manifest themselves as pairs of jets without tracks. The energy fraction of jets carried by charged particles is used as a key discriminator to suppress efficiently 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 with the CMS detector in 2016. No significant excess of events is observed above the expected background. For the simplified dark matter model under consideration, SIMPs with masses up to 100 GeV are excluded and further sensitivity is explored towards higher masses.
Links: e-print arXiv:2105.09178 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ;
Figures & Tables Summary References CMS Publications
Figures

png pdf 		Figure 1:
A Feynman diagram showing SIMP pair production via the s-channel exchange of a new scalar mediator.

png pdf 		Figure 2:
Left: comparison of the leading jet $ {p_{\mathrm {T}}} $ spectrum between jets clustered at the generator level (dashed lines) and after detector simulation (solid lines), arising from the GEANT4 SIMP simulation at masses of 1 GeV (blue lines) and 1000 GeV (green lines); right : the ratio of the reconstruction-level and generator-level jet transverse momenta for the GEANT4 SIMP simulation at masses of 1 GeV (dark blue, long-dashed line) and 1000 GeV (green, short-dashed line), including a comparison to a simulation where a 1 GeV SIMP is replaced by a neutron (red, solid line).

png pdf 		Figure 2-a:
Comparison of the leading jet $ {p_{\mathrm {T}}} $ spectrum between jets clustered at the generator level (dashed lines) and after detector simulation (solid lines), arising from the GEANT4 SIMP simulation at masses of 1 GeV (blue lines) and 1000 GeV (green lines).

png pdf 		Figure 2-b:
The ratio of the reconstruction-level and generator-level jet transverse momenta for the GEANT4 SIMP simulation at masses of 1 GeV (dark blue, long-dashed line) and 1000 GeV (green, short-dashed line), including a comparison to a simulation where a 1 GeV SIMP is replaced by a neutron (red, solid line).

png pdf 		Figure 3:
Distributions of the number of jets with $ {p_{\mathrm {T}}} > $ 30 GeV and $ {| \eta |} < $ 5 (left), and the value of ChF of the two leading jets (right). The simulated QCD multijet background is compared with the signal expected for three different SIMP masses, with their cross sections scaled as indicated in the legend. The baseline selection is applied, except the events with three or more jets with $ {p_{\mathrm {T}}} > $ 30 GeV and $ {| \eta |} < $ 5 are included in the number of jets in the left plot.

png pdf 		Figure 3-a:
Distribution of the number of jets with $ {p_{\mathrm {T}}} > $ 30 GeV and $ {| \eta |} < $ 5. The simulated QCD multijet background is compared with the signal expected for three different SIMP masses, with their cross sections scaled as indicated in the legend. The baseline selection is applied. The events with three or more jets with $ {p_{\mathrm {T}}} > $ 30 GeV and $ {| \eta |} < $ 5 are included in the plot.

png pdf 		Figure 3-b:
The value of ChF of the two leading jets. The simulated QCD multijet background is compared with the signal expected for three different SIMP masses, with their cross sections scaled as indicated in the legend. The baseline selection is applied.

png pdf 		Figure 4:
The number of background events obtained from the 1- and 2-leg predictions using reconstructed objects in simulation, compared to the direct prediction from MC simulation, shown for various upper ChF thresholds. The bottom panel shows the ratios of the MC prediction to the 1-leg and the 2-leg background predictions.

png pdf 		Figure 5:
The number of background events obtained from the 1- and 2-leg predictions derived from data, together with the direct observation in data, in bins in ChF, where either the leading or subleading jet has a ChF within the bin edges, and both have a ChF below the upper bin threshold. The bottom panel shows the ratios of the observation in data to the 1-leg and the 2-leg background predictions.

png pdf 		Figure 6:
The expected and observed 95% CL upper limits on the production cross section for SIMPs with masses between 1 and 1000 GeV, with the assumption that the SIMP interaction in the detector can be approximated as neutron-like. The theoretical prediction of a simplified model incorporating this approximation and including a scalar mediator with couplings $g_\chi = $ $-$1 and $g_\mathrm{q} = $ 1 is also shown (red line). For masses above 100 GeV, where the modelling of the SIMP-nucleon interaction becomes more speculative, the obtained cross section upper limits are increasingly uncertain (shaded area).
Tables

png pdf
 Table 1:
The numbers of background and observed events for different upper bounds on the ChF value. The background estimations are derived using the data-based 2-leg predictions. The expected number of signal events is given for the $m_{\chi} = $ 1, 100, and 1000 GeV scenarios, with the corresponding statistical uncertainties.
Summary
A search has been presented for dark matter in the form of strongly interacting massive particles (SIMPs) manifesting themselves in the detector as trackless jets. 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$^{-1}$ collected by the CMS experiment in 2016, we set first limits on the production cross section for SIMPs with masses between 1 and 1000 GeV at 95% confidence level (CL), using a signal simulation that assumes the SIMP interaction in the detector can be approximated as neutron-like. The signal modelling assumptions stated previously have small uncertainties, and hence a small impact on the cross section upper limits, for SIMP masses up to about 100 GeV, but become increasingly uncertain above 100 GeV, where an improved phenomenology of the SIMP-nucleon interaction would be welcome. Within this framework we exclude SIMPs with masses less than 100 GeV. These limits were obtained for the off-shell production of SIMP pairs, through a new scalar mediator with couplings $g_\chi = $ $-$1 and $g_{\mathrm{q}} = $ 1. An upper limit on the fiducial cross section of 0.18 fb at 95% CL is also provided for a generic signal of high-momentum trackless jets. With this search, strongly interacting massive particles, for which the interaction strength is constrained to generate a trackless jets signature, have been ruled out over a wide mass range.
References
1 E. W. Kolb and M. S. Turner The Early Universe CRC Press. Taylor & Francis Group, 1990 Front. Phys., vol. 69
2 G. Bertone and D. Hooper History of dark matter Rev. Mod. Phys. 90 (2018) 045002 1605.04909
3 N. Daci et al. Simplified SIMPs and the LHC JHEP 11 (2015) 108 1503.05505
4 Y. Bai and A. Rajaraman Dark matter jets at the LHC 1109.6009
5 CMS Collaboration HEPData record for this analysis link
6 ATLAS Collaboration Search for long-lived neutral particles in $ pp $ collisions at $ \sqrt{s} = $ 13 TeV that decay into displaced hadronic jets in the ATLAS calorimeter EPJC 79 (2019) 481 1902.03094
7 J. H. Davis Probing sub-GeV mass strongly interacting dark matter with a low-threshold surface experiment PRL 119 (2017) 211302 1708.01484
8 CRESST Collaboration Results on MeV-scale dark matter from a gram-scale cryogenic calorimeter operated above ground EPJC 77 (2017) 637 1707.06749
9 EDELWEISS Collaboration Searching for low-mass dark matter particles with a massive Ge bolometer operated above-ground PRD 99 (2019) 082003 1901.03588
10 D. Hooper and S. D. McDermott Robust constraints and novel gamma-ray signatures of dark matter that interacts strongly with nucleons PRD 97 (2018) 115006 1802.03025
11 T. Emken and C. Kouvaris How blind are underground and surface detectors to strongly interacting dark matter? PRD 97 (2018) 115047 1802.04764
12 CMS Collaboration Performance of the CMS Level-1 trigger in proton-proton collisions at $ \sqrt{s} = $ 13 TeV JINST 15 (2020) P10017 CMS-TRG-17-001
2006.10165
13 CMS Collaboration The CMS trigger system JINST 12 (2017) P01020 CMS-TRG-12-001
1609.02366
14 CMS Collaboration The CMS experiment at the CERN LHC JINST 3 (2008) S08004 CMS-00-001
15 A. Alloul et al. FeynRules 2.0---A complete toolbox for tree-level phenomenology CPC 185 (2014) 2250 1310.1921
16 J. Alwall et al. The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations JHEP 07 (2014) 079 1405.0301
17 T. Sjostrand et al. An introduction to PYTHIA 8.2 CPC 191 (2015) 159 1410.3012
18 CMS Collaboration Event generator tunes obtained from underlying event and multiparton scattering measurements EPJC 76 (2016) 155 CMS-GEN-14-001
1512.00815
19 GEANT4 Collaboration GEANT4--a simulation toolkit NIMA 506 (2003) 250
20 CMS Collaboration Particle-flow reconstruction and global event description with the CMS detector JINST 12 (2017) P10003 CMS-PRF-14-001
1706.04965
21 M. Cacciari, G. P. Salam, and G. Soyez The anti-$ {k_{\mathrm{T}}} $ jet clustering algorithm JHEP 04 (2008) 063 0802.1189
22 M. Cacciari, G. P. Salam, and G. Soyez FastJet user manual EPJC 72 (2012) 1896 1111.6097
23 CMS Collaboration Jet energy scale and resolution in the CMS experiment in pp collisions at 8 TeV JINST 12 (2017) P02014 CMS-JME-13-004
1607.03663
24 CMS Collaboration Performance of photon reconstruction and identification with the CMS detector in proton-proton collisions at $ \sqrt{s} = $ 8 TeV JINST 10 (2015) P08010 CMS-EGM-14-001
1502.02702
25 CMS Collaboration Performance of missing transverse momentum reconstruction in proton-proton collisions at $ \sqrt{s} = $ 13 TeV using the CMS detector JINST 14 (2019) P07004 CMS-JME-17-001
1903.06078
26 T. Junk Confidence level computation for combining searches with small statistics NIMA 434 (1999) 435 hep-ex/9902006
27 A. L. Read Presentation of search results: the CLs technique JPG 28 (2002) 2693
28 CMS Collaboration CMS luminosity measurements for the 2016 data taking period CMS-PAS-LUM-17-001 CMS-PAS-LUM-17-001
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