![](https://csdnimg.cn/release/download_crawler_static/12356740/bg9.jpg)
and M
had
are the means of the corresponding mass distributions. The values of M
lep
,
σ
M
lep
, M
had
, and σ
M
had
are derived using a sample of simulated events in which all four
partons of the final state top quark decay products are matched to a reconstructed jet
used in the hypothesis. In each event, the tt pair reconstructed with the smallest value of
χ
2
(labeled χ
2
min
) is chosen. In events with a t-tagged jet, M
had
is given by the mass of
the large-radius jet calculated using the soft drop algorithm. This choice is made because,
compared to the conventional jet mass, the soft dropped mass is much less dependent on
the jet p
T
, and therefore on the resonance mass in a given signal hypothesis. Moreover,
this provides greater discrimination between background and signal.
Events in the signal region are required to have χ
2
min
< 30 for all lepton+jets categories.
This upper threshold on χ
2
min
reduces the contribution of events from non-tt background
processes and maximizes the expected sensitivity of the analysis to new resonances.
Finally, to further enhance sensitivity, events are categorized according to the number
of t-tagged and b-tagged jets as follows: events with one t-tagged jet (1 t tag); events
with zero t-tagged jets and at least one b-tagged jet (0 t tag, 1 b tag); and events with zero
t-tagged and b-tagged jets (0 t tag, 0 b tag).
5.2 Fully hadronic channel
The fully hadronic channel requires that at least two jets satisfy kinematic and t tagging
selection criteria. The data were collected online with a trigger requiring the scalar sum of
the AK4 jet energies (H
T
) to be larger than 800 GeV. The trigger selection has an efficiency
of above 95%, as measured in simulation, for events that satisfy the offline requirement
H
T
> 1000 GeV. The event reconstruction is performed using only AK8 jets. The two
leading jets are required to have p
T
> 500 GeV, rapidity |y| < 2.4, and both are required
to be t tagged. A back-to-back topology is selected by requiring the azimuthal separation
of the two leading jets to satisfy |∆φ| > 2.1.
Events are further categorized into six regions based on two criteria: the rapidity
difference (∆y) between the two AK8 jets and the number of jets with at least one b-
tagged subjet for the two highest p
T
jets. Events can contain 0, 1, or 2 jets with a b-tagged
subjet, and they are separated into bins of |∆y| < 1.0 and |∆y| > 1.0.
5.3 Tagging variables in lepton+jets and fully hadronic channels
The distributions of the two variables used in the t tagging algorithm, τ
32
and M
SD
, are
shown in figure 2 for the lepton+jets channel (upper row) and the fully hadronic channel
(lower row). Each of the figures is obtained after removing the selection on the quan-
tity being plotted, while maintaining all other analysis-level selections. We observe good
agreement between data and simulation in the lepton+jets decay channel, where simulated
events are divided into contributions from generator-level top quarks and other jets from
t
t events and subdominant background processes. The fully hadronic channel also shows
good agreement between the simulated distribution and data. The small discrepancies do
not affect the analysis, as it relies on data to estimate the NTMJ contribution to the back-
ground. Some discrepancy is visible at high values of τ
32
, however this region is excluded
by the selection used for t tagging.
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