Calibration of the jet energy scale and resolution of small-radius jets using semileptonic $t\bar{t}$ events with the ATLAS detector

TL;DR

This work presents a data-driven calibration of the hadronic JES and JER for small-radius jets using semileptonic tt̄ events in ATLAS, exploiting the W-boson mass lineshape from hadronic W decays. The forward-folding technique generates templates that encode JES/JER variations, which are then fitted to data to extract per-jet-bin correction factors in the central region (|η|<0.8) across jets with 20–200 GeV pT. Analyses are performed on Run 2 (2015–2018, √s=13 TeV) and Run 3 (2022–2023, √s=13.6 TeV) data, with comprehensive systematic studies covering lepton, jet, and modelling uncertainties. The results show JES corrections near unity (Run 3), but with Run 2 requiring a modest scale-down relative to simulation, while JER corrections remain compatible with unity. The approach yields uncertainties of about 0.9–1.7% on JES and 14–28% on JER (excluding first pT bin sensitivity) and will be combined with other in-situ calibrations to further enhance ATLAS jet performance for precision measurements, including top-quark analyses.

Abstract

A measurement of correction factors for the hadronic jet energy scale and resolution in the ATLAS detector is presented. These correction factors account for differences between simulated and observed data. They are obtained by analysing a selection of top quark events collected in proton-proton collisions by ATLAS between the years 2015 and 2018 at a centre-of-mass energy $\sqrt{s} = 13$ TeV as well as in 2022 and 2023 at $\sqrt{s} = 13.6$ TeV. The forward-folding technique is used to quantify the impact of different jet energy scale or resolution corrections on the reconstructed mass of the hadronically decaying $W$ boson from top-quark decays in simulation. The correction factors are extracted from a fit to the parameterised reconstructed $W$-boson mass distribution to data. The energy scale and resolution corrections are measured as a function of the jet transverse momentum between 20 GeV and 200 GeV and absolute pseudorapidity less than 0.8. The uncertainties in the energy scale range from about 0.93% to about 1.7% for jets between 35 and 200 GeV, while for the energy resolution the uncertainties range from about 14% to 28%. The method presented will be used in conjunction with other techniques to further improve ATLAS jet energy scale and resolution precision.

Figures (9)

• Figure 1: The distribution of the best $\chi^2$ value for the considered permutations for matching reconstructed jets to jets from the top-quark decay in the Run 2 data. Data without the JES in situ calibration (PFlow+JES) are shown as markers and compared to simulation from the signal and background processes. The uncertainty band includes all systematic uncertainties as described in Section \ref{['sec:systematics']}. The bottom panel shows the ratio of the data to the prediction. The dashed line represents the ratio of one. The last bin contains the overflow events.
• Figure 2: Reconstructed hadronically decaying $W$-boson mass after applying all selection criteria in the (a) Run 2 data and (b) Run 3 data without the JES in situ corrections applied (PFlow+JES). The uncertainty band includes all systematic uncertainties. The bottom panels show the ratio of the data to the prediction. The dashed line represents the ratio of one.
• Figure 3: Definition of the analysis regions based on reconstructed and $\eta$ of the two jets identified to originate from the $W$-boson decay. The two jets from $W$ boson are required to have $|\eta|$ < 0.8. The regions shown on the diagonal are the regions where both jets from the $W$ boson fall into the same reconstructed bin, off-diagonal are the regions where the two jets fall into different reconstructed bins. The diagonal region with jets having a reconstructed between 20 and 35 $\text{Ge V}$ is not used due to kinematic restrictions. The numbers in the bins represent the number of selected events in Run 2 data without in situ corrections.
• Figure 4: Reconstructed $W$-boson mass in the region with the two jets from the $W$-boson decay with reconstructed between 50 and 70 $\text{Ge V}$ in the Run 2 simulation. Templates with different (a) JES and (b) JER assumptions represented by the parameters of the forward-folding formula are shown. For the JES (JER) variations shown, the JER (JES) correction is set to one. The differences between the total yields for each distribution come from the acceptance effects due to the changes in the reconstructed jet . The bottom panels show the ratios to the template with nominal (a) JES or (b) JER assumption. The solid line in the bottom panels represents the ratio of one.
• Figure 5: The mean (top plots) and standard deviation (bottom plots) of the $W$-boson mass distribution in a representative reconstructed jet region as a function of the JES (JER) parameter in the Run 2 simulation. (a) and (c) show the diagonal region with reconstructed jet between 50 and 70 $\text{Ge V}$, while (b) and (d) show the off-diagonal region with the leading jet ($\text{jet}_{\text{1}}$) with reconstructed between 150 and 200 $\text{Ge V}$ and the sub-leading jet ($\text{jet}_{\text{2}}$) with reconstructed between 35 and 50 $\text{Ge V}$. The fitted function is shown by the solid line. For the diagonal regions, the bottom panels show the ratio of the mean (standard deviation) value to the fitted function. The dashed line in the bottom panels represents the ratio of one. For the off-diagonal regions, the colour gradient shows the mean (standard deviation) of the $W$-boson mass distribution for the JES (JER) templates.