CMS reports a simultaneous measurement of 25 N-subjettiness observables in 1-, 2-, and 3-prong jets, unfolded to stable particles with particle-level correlations for QCD modeling.
Canonical reference
Looking inside jets: an introduction to jet substructure and boosted-object phenomenology
Canonical reference. 80% of citing Pith papers cite this work as background.
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abstract
The study of the internal structure of hadronic jets has become in recent years a very active area of research in particle physics. Jet substructure techniques are increasingly used in experimental analyses by the LHC collaborations, both in the context of searching for new physics and for Standard Model measurements. On the theory side, the quest for a deeper understanding of jet substructure algorithms has contributed to a renewed interest in all-order calculations in QCD. This has resulted in new ideas about how to design better observables and how to provide a solid theoretical description for them. In the last years, jet substructure has seen its scope extended, for example, with an increasing impact in the study of heavy-ion collisions, or with the exploration of deep-learning techniques. Furthermore, jet physics is an area in which experimental and theoretical approaches meet together, where cross-pollination and collaboration between the two communities often bear the fruits of innovative techniques. Despite the wealth of literature on this topic, we feel that a comprehensive and, at the same time, pedagogical introduction to jet substructure is still missing. This makes the endeavour of approaching the field particularly hard, as newcomers have to digest an increasing number of substructure algorithms and techniques, too often characterised by opaque terminology and jargon. Furthermore, while first-principle calculations in QCD have successfully been applied in order to understand and characterise the substructure of jets, they often make use of calculational techniques, such as resummation, which are not the usual textbook material. Thus, the idea of combining our experience in different aspects of jet substructure phenomenology to put together this set of lecture notes, which we hope could help and guide someone who moves their first steps in the physics of jet substructure.
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representative citing papers
In large-Nc and harmonic oscillator limits, medium-induced splittings are computed analytically double-differential in z and θ, with an improved semi-hard approximation validated for high-energy partons.
CMS measures soft-drop groomed radius and momentum balance plus a charged fragmentation function for b jets, observing dead-cone suppression compared to inclusive jets.
Bayesian constraints on early-time jet quenching from large collision systems yield predictions of measurable energy loss in oxygen-oxygen collisions.
Spectral-function features fed to a dense network improve expected gluino-mass reach by ~150 GeV over ATLAS Gtt-0L-C and ~250 GeV over kinematics-only ML for the fully hadronic channel.
Proof-of-principle for hadron-in-fat-jet AI tagging that yields an expected 95% CL limit of B(W±→π±γ) < 2.78×10^{-5} at 450 fb^{-1}.
Derives Lindblad evolution for color dipole in QCD plasma and demonstrates quasi-factorization of Wigner distribution violated by color decoherence factor controlled by theta_qqbar/theta_c ratio.
Explainability techniques applied to LundNet show that assigned node importance correlates with classical jet substructure observables such as N-subjettiness ratios and energy correlation functions, with shifts across transverse-momentum regimes.
Comparative analysis of published jet quenching data shows radius dependence differs between single-jet and dijet selections and between experiments, but fractional energy loss S_loss reduces sensitivity to the pp spectral shape for cross-experiment comparisons.
A primer by six leading developers maps the full Monte Carlo chain (matrix elements, parton showers, hadronisation, detector simulation, tuning, analysis) and the computing and reproducibility issues that come with it.
citing papers explorer
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Simultaneous measurements of $N$-subjettiness observables in jets from gluons and light-flavour quarks, and in decays of boosted W bosons and top quarks
CMS reports a simultaneous measurement of 25 N-subjettiness observables in 1-, 2-, and 3-prong jets, unfolded to stable particles with particle-level correlations for QCD modeling.
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Full energy fraction and angular dependence of medium-induced splittings in the large-$N_c$ limit
In large-Nc and harmonic oscillator limits, medium-induced splittings are computed analytically double-differential in z and θ, with an improved semi-hard approximation validated for high-energy partons.
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Jet fragmentation function and groomed substructure of bottom quark jets in proton-proton collisions at 5.02 TeV
CMS measures soft-drop groomed radius and momentum balance plus a charged fragmentation function for b jets, observing dead-cone suppression compared to inclusive jets.
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Bayesian Constraints on Pre-Equilibrium Jet Quenching and Predictions for Oxygen Collisions
Bayesian constraints on early-time jet quenching from large collision systems yield predictions of measurable energy loss in oxygen-oxygen collisions.
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Machine learning fully hadronic events with spectral functions
Spectral-function features fed to a dense network improve expected gluino-mass reach by ~150 GeV over ATLAS Gtt-0L-C and ~250 GeV over kinematics-only ML for the fully hadronic channel.
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"Hadron-in-fat-jet'' AI Tagging to Detect Rare Decays Such as $W^{\pm}\to\pi^{\pm}\gamma$
Proof-of-principle for hadron-in-fat-jet AI tagging that yields an expected 95% CL limit of B(W±→π±γ) < 2.78×10^{-5} at 450 fb^{-1}.
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Open quantum system approach to the transverse momentum broadening of a colour dipole
Derives Lindblad evolution for color dipole in QCD plasma and demonstrates quasi-factorization of Wigner distribution violated by color decoherence factor controlled by theta_qqbar/theta_c ratio.
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Explainable AI for Jet Tagging: A Comparative Study of GNNExplainer, GNNShap, and GradCAM for Jet Tagging in the Lund Jet Plane
Explainability techniques applied to LundNet show that assigned node importance correlates with classical jet substructure observables such as N-subjettiness ratios and energy correlation functions, with shifts across transverse-momentum regimes.
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Jet Radius Dependence of Energy Loss in Pb+Pb Collisions: A Comparative Analysis of the Ratio of Nuclear Modification Factors and Fractional Energy Loss
Comparative analysis of published jet quenching data shows radius dependence differs between single-jet and dijet selections and between experiments, but fractional energy loss S_loss reduces sensitivity to the pp spectral shape for cross-experiment comparisons.
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The Monte Carlo Ecosystem in High-Energy Physics: A Primer
A primer by six leading developers maps the full Monte Carlo chain (matrix elements, parton showers, hadronisation, detector simulation, tuning, analysis) and the computing and reproducibility issues that come with it.