Abstract (data abstract)

A search is performed for events consistent with the pair production of a new heavy particle that acts as a mediator between a dark sector and normal matter, and that decays to a light quark and a new fermion called a dark quark. The search is based on data corresponding to an integrated luminosity of 16.1 fb$^{-1}$ from proton-proton collisions at $\sqrt{s}=13$ TeV collected by the CMS experiment at the LHC in 2016. The dark quark is charged only under a new quantum-chromodynamics-like force, and forms an ``emerging jet'' via a parton shower, containing long-lived dark hadrons that give rise to displaced vertices when decaying to standard model hadrons. The data are consistent with the expectation from standard model processes. Limits are set at 95% confidence level excluding dark pion decay lengths between 5 and 225 mm for dark mediators with masses between 400 and 1250 GeV. Decay lengths smaller than 5 and greater than 225 mm are also excluded in the lower part of this mass range. The dependence of the limit on the dark pion mass is weak for masses between 1 and 10 GeV. This analysis is the first dedicated search for the pair production of a new particle that decays to a jet and an emerging jet.

Figure 2 ($IP_\mathrm{2D}$)

Contents of Figure 2.

10.17182/hepdata.88380.v1/t1

Distributions of $\langle IP_{\mathrm{2D}}\rangle$ for background (black) and for signals with a mediator mass of 1 TeV and a dark...
Figure 3 ($\alpha_\mathrm{3D}$)

Contents of Figure 3.

10.17182/hepdata.88380.v1/t2

Distributions of $\alpha_\mathrm{3D}$ for background (black) and for signals with a mediator mass of 1 TeV and a dark pion...
Figure 4 (Signal acceptance)

Contents of Figure 4.

10.17182/hepdata.88380.v1/t3

The signal acceptance A, defined as the fraction of simulated signal events passing the selection criteria, for models with a...
Figure 5 (Misidentification probability)

Contents of Figure 5.

10.17182/hepdata.88380.v1/t4

Measured misidentification probability distribution as a function of track multiplicity for the EMJ-1 criteria group defined in Table 2. The...
Figure 7 (left)

Contents of Figure 7 (left).

10.17182/hepdata.88380.v1/t5

The $H_\mathrm{T}$ distribution for the observed data events (black points) and the predicted background estimation (blue) for selection set 8...
Figure 7 (right)

Contents of Figure 7 (right).

10.17182/hepdata.88380.v1/t6

The number of associated tracks distribution for the observed data events (black points) and the predicted background estimation (blue) for...
Figure 8 (left)

Contents of Figure 8 (left).

10.17182/hepdata.88380.v1/t7

The $H_\mathrm{T}$ distribution for the observed data events (black points) and the predicted background estimation (blue) for selection set 9...
Figure 8 (right)

Contents of Figure 8 (right).

10.17182/hepdata.88380.v1/t8

The number of associated tracks distribution for the observed data events (black points) and the predicted background estimation (blue) for...
Figure 10 (2D limits)

Contents of Figure 10.

10.17182/hepdata.88380.v1/t9

Upper limits at 95% CL on the signal cross section for models with dark pion mass $(m_{\pi_\mathrm{DK}})$ of 5 GeV...
Figure 10 (Exclusion contours)

Contents of Figure 10.

10.17182/hepdata.88380.v1/t10

Dark mediator mass exclusion limits at 95% CL derived from theoretical cross sections for models with dark pion mass $(m_{\pi_\mathrm{DK}})$...

Figure 2 ($IP_\mathrm{2D}$)

Figure 3 ($\alpha_\mathrm{3D}$)

Figure 4 (Signal acceptance)

Figure 5 (Misidentification probability)

Figure 7 (left)

Figure 7 (right)

Figure 8 (left)

Figure 8 (right)

Figure 10 (2D limits)

Figure 10 (Exclusion contours)

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