Abstract

This Letter presents a normalized differential cross-section measurement in a fiducial phase-space region where interference effects between top-quark pair production and associated production of a single top quark with a $W$ boson and a $b$-quark are significant. Events with exactly two leptons ($ee$, $\mu\mu$, or $e\mu$) and two $b$-tagged jets that satisfy a multi-particle invariant mass requirement are selected from $36.1$ fb$^{-1}$ of proton-proton collision data taken at $\sqrt{s}=13$ TeV with the ATLAS detector at the LHC in 2015 and 2016. The results are compared with predictions from simulations using various strategies for the interference. The standard prescriptions for interference modeling are significantly different from each other but are within $2\sigma$ of the data. State-of-the-art predictions that naturally incorporate interference effects provide the best description of the data in the measured region of phase space most sensitive to these effects. These results provide an important constraint on interference models and will guide future model development and tuning.

Table 1

Data from FIGURE 1(a).

10.17182/hepdata.83544.v2/t1

The minimax-mbl distribution in the three-b-tag region, constructed from the two b-jets with largest transverse momentum. The predicted tt+HF contribution...
Table 2

Data from FIGURE 1(b).

10.17182/hepdata.83544.v2/t2

The detector-level minimax-mbl distribution, with signal selection and background estimation as described in the text. The total predicted events are...
Table 3

Data from FIGURE 2.

10.17182/hepdata.83544.v2/t3

The unfolded, normalized differential minimax-mbl cross-section compared with theoretical models of the tt+tWb signal with various implementations of interference effects....
Table 4

Data from AUX FIGURE 3.

10.17182/hepdata.83544.v2/t4

The systematic uncertainty on the unfolded distribution as a function of minimax-mbl, broken down by components.
Table 5

Data from AUX TABLE 1.

10.17182/hepdata.83544.v2/t5

The covariance matrix for the unfolded, normalized data in bins of minimax-mbl shown in Figure 2. Redundant entries are suppressed.
Table 6

Data from AUX FIGURE 4(a).

10.17182/hepdata.83544.v2/t6

Leading lepton transverse momentum distribution for events passing the signal selection in bins of minimax-mbl. The data here are not...
Table 7

Data from AUX FIGURE 4(b).

10.17182/hepdata.83544.v2/t7

Sub-leading lepton transverse momentum distribution for events passing the signal selection in bins of minimax-mbl. The data here are not...
Table 8

Data from AUX FIGURE 5(a).

10.17182/hepdata.83544.v2/t8

Leading lepton pseudorapidity distribution for events passing the signal selection in bins of minimax-mbl. The data here are not unfolded.
Table 9

Data from AUX FIGURE 5(b).

10.17182/hepdata.83544.v2/t9

Sub-leading lepton pseudorapidity distribution for events passing the signal selection in bins of minimax-mbl. The data here are not unfolded.
Table 10

Data from AUX FIGURE 6(a).

10.17182/hepdata.83544.v2/t10

Leading b-jet transverse momentum distribution for events passing the signal selection in bins of minimax-mbl. The data here are not...
Table 11

Data from AUX FIGURE 6(b).

10.17182/hepdata.83544.v2/t11

Sub-leading b-jet transverse momentum distribution for events passing the signal selection in bins of minimax-mbl. The data here are not...
Table 12

Data from AUX FIGURE 7(a).

10.17182/hepdata.83544.v2/t12

Leading b-jet pseudorapidity distribution for events passing the signal selection in bins of minimax-mbl. The data here are not unfolded.
Table 13

Data from AUX FIGURE 7(b).

10.17182/hepdata.83544.v2/t13

Sub-leading b-jet pseudorapidity distribution for events passing the signal selection in bins of minimax-mbl. The data here are not unfolded.
Table 14

Data from AUX FIGURE 8.

10.17182/hepdata.83544.v2/t14

The detector-level minimax-m(bl) distribution for events entering the Z+jets control region.
Table 15

Data from AUX FIGURE 9.

10.17182/hepdata.83544.v2/t15

The detector-level minimax-m(bl) distribution for events entering the same-sign lepton control region.

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