Looking Inside Jets
Looking Inside Jets

Author: Simone Marzani

Publisher: Springer

Published: 2019-05-11

Total Pages: 205

ISBN-13: 3030157091

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This concise primer reviews the latest developments in the field of jets. Jets are collinear sprays of hadrons produced in very high-energy collisions, e.g. at the LHC or at a future hadron collider. They are essential to and ubiquitous in experimental analyses, making their study crucial. At present LHC energies and beyond, massive particles around the electroweak scale are frequently produced with transverse momenta that are much larger than their mass, i.e., boosted. The decay products of such boosted massive objects tend to occupy only a relatively small and confined area of the detector and are observed as a single jet. Jets hence arise from many different sources and it is important to be able to distinguish the rare events with boosted resonances from the large backgrounds originating from Quantum Chromodynamics (QCD). This requires familiarity with the internal properties of jets, such as their different radiation patterns, a field broadly known as jet substructure. This set of notes begins by providing a phenomenological motivation, explaining why the study of jets and their substructure is of particular importance for the current and future program of the LHC, followed by a brief but insightful introduction to QCD and to hadron-collider phenomenology. The next section introduces jets as complex objects constructed from a sequential recombination algorithm. In this context some experimental aspects are also reviewed. Since jet substructure calculations are multi-scale problems that call for all-order treatments (resummations), the bases of such calculations are discussed for simple jet quantities. With these QCD and jet physics ingredients in hand, readers can then dig into jet substructure itself. Accordingly, these notes first highlight the main concepts behind substructure techniques and introduce a list of the main jet substructure tools that have been used over the past decade. Analytic calculations are then provided for several families of tools, the goal being to identify their key characteristics. In closing, the book provides an overview of LHC searches and measurements where jet substructure techniques are used, reviews the main take-home messages, and outlines future perspectives.

Advances in Jet Substructure at the LHC
Advances in Jet Substructure at the LHC

Author: Roman Kogler

Publisher: Springer Nature

Published: 2021-05-10

Total Pages: 287

ISBN-13: 3030728587

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This book introduces the reader to the field of jet substructure, starting from the basic considerations for capturing decays of boosted particles in individual jets, to explaining state-of-the-art techniques. Jet substructure methods have become ubiquitous in data analyses at the LHC, with diverse applications stemming from the abundance of jets in proton-proton collisions, the presence of pileup and multiple interactions, and the need to reconstruct and identify decays of highly-Lorentz boosted particles. The last decade has seen a vast increase in our knowledge of all aspects of the field, with a proliferation of new jet substructure algorithms, calculations and measurements which are presented in this book. Recent developments and algorithms are described and put into the larger experimental context. Their usefulness and application are shown in many demonstrative examples and the phenomenological and experimental effects influencing their performance are discussed. A comprehensive overview is given of measurements and searches for new phenomena performed by the ATLAS and CMS Collaborations. This book shows the impressive versatility of jet substructure methods at the LHC.

Jet Substructure Without Trees
Jet Substructure Without Trees

Author:

Publisher:

Published: 2011

Total Pages: 22

ISBN-13:

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We present an alternative approach to identifying and characterizing jet substructure. An angular correlation function is introduced that can be used to extract angular and mass scales within a jet without reference to a clustering algorithm. This procedure gives rise to a number of useful jet observables. As an application, we construct a top quark tagging algorithm that is competitive with existing methods. In preparation for the LHC, the past several years have seen extensive work on various aspects of collider searches. With the excellent resolution of the ATLAS and CMS detectors as a catalyst, one area that has undergone significant development is jet substructure physics. The use of jet substructure techniques, which probe the fine-grained details of how energy is distributed in jets, has two broad goals. First, measuring more than just the bulk properties of jets allows for additional probes of QCD. For example, jet substructure measurements can be compared against precision perturbative QCD calculations or used to tune Monte Carlo event generators. Second, jet substructure allows for additional handles in event discrimination. These handles could play an important role at the LHC in discriminating between signal and background events in a wide variety of particle searches. For example, Monte Carlo studies indicate that jet substructure techniques allow for efficient reconstruction of boosted heavy objects such as the W{sup {+-}} and Z° gauge bosons, the top quark, and the Higgs boson.

Measuring the Standard Model and Searching for New Physics with Jet Substructure Using the ATLAS Detector
Measuring the Standard Model and Searching for New Physics with Jet Substructure Using the ATLAS Detector

Author: Maximilian Swiatlowski

Publisher:

Published: 2015

Total Pages:

ISBN-13:

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Collisions at the Large Hadron Collider have offered an unprecedented window into some of the highest energy scales ever observed in experiments. Understanding these collisions, especially those that produce particles charged under quantum chromodynamics (QCD), requires a deep understanding of jets: the collimated sprays of particles produced by the parton shower and hadronization processes which emerge from the asymptotic freedom of QCD. Recent theoretical advances and the unprecedented capabilities of the ATLAS detector have enabled a new class of jet physics measurements based on the internal structure of jets, referred to as jet substructure. Three new types of measurements relying on jet substructure are presented. The first is a set of measurements sensitive which can discriminate between jets initiated by quarks and gluons. Separation is possible by studying variables sensitive to the magnitude of the color charge. Several such variables are measured, and a data-driven technique is used to construct a tagger, the first of its kind at a hadron collider, which can improve the sensitivity of searches for new physics in hadronic final states. A second measurement studies the color connections of jets in top-antitop events using an observable called the jet pull angle: sensitivity to the color representation of particles decaying to dijet pairs at a hadron collider is demonstrated for the first time. A final analysis searches for R-parity violating supersymmetry (SUSY) in all hadronic final states. These classes of models remove the characteristic missing energy signature which existing SUSY searches rely on, and require new discrimination techniques. Jet substructure provides a powerful handle to analyze these very high multiplicity states using a variable called the total jet mass. No signal is observed over the Standard Model (SM) prediction, and new limits are set on these previously unexplored models. The techniques of jet substructure lie at the hearts of all of these analyses, enabling both new measurements of SM phenomena and entirely new searches for physics beyond the SM.