Measurement of multi-jets and vector boson plus jets production in ATLAS

TL;DR

ATLAS measures multijet and vector-boson–plus–jets final states to test QCD and EW dynamics at the LHC, using Run 2 data at $\sqrt{s}=13~\mathrm{TeV}$ with an integrated luminosity of about $140~\mathrm{fb}^{-1}$. The study combines jet-substructure observables (jet track functions and the Lund Jet Plane) with heavy-flavour and electroweak processes (W+jets, Z+heavy-flavour jets) to test perturbative QCD, parton-shower modeling, and PDFs. It compares state-of-the-art predictions including NLO/NNLO QCD and NLO EW corrections across multiple flavour schemes and MC generators to identify successes and tuning needs, finding good agreement in many regions but notable tensions in high-$p_T$ and collinear configurations. These measurements provide stringent constraints for MC tuning, hadronization models, and flavour-scheme choices, informing Run 3 and HL-LHC analyses.

Abstract

The production of multiple jets or vector bosons in association with jets at the LHC provides a unique testing ground for Quantum Chromodynamics (QCD) in the high-energy regime. With the increasing precision of the ATLAS measurements, detailed studies have become possible on observables that probe different aspects of QCD, such as the topological configurations between vector bosons and jets, jet substructure features, and heavy-flavor jet contributions. These measurements also play a key role in improving the precision of the determination of the strong coupling constant. Recent ATLAS results in these areas are presented, offering new insights into QCD dynamics and the performance of state-of-the-art theoretical predictions.

Figures (6)

• Figure 1: The unfolded central (a) and forward (b) normalized differential cross-sections as a function of $r_q$ for data compared to predictions from several MC generators ATLAS:2923297.
• Figure 2: Slice of measured W jet LJP as function of $\ln(R/\Delta R)$ATLAS:LJP.
• Figure 3: Feynman diagrams for $W$+jets production. In Figure (a), the $t$-channel shows the back-to-back region, while in Figure (b), the $s$-channel represents the collinear region.
• Figure 4: Measured W+jets fiducial cross-section in signal regions ATLAS:2920036.
• Figure 5: Differential cross-section measurements in the inclusive phase space as a function of $\Delta R_{\mathrm{min}}(\ell, \mathrm{jet}^{100}_i)$ (a) and $p_{T}^{\ell\nu}/p_{T}^{\mathrm{closest~jet}}$ (b) ATLAS:2920036..