1 Introduction
3
difficulty of accurately understanding even small experimental effects and correctly
estimating corresponding systematic uncertainties, a process which takes years to
complete due to the complexity of the LHC experiments.
This leaves three choices for our immediate hopes to find BSM effects: either
measure rare processes, becoming accessible only now with the large amount of
data, find novel ways to perform searches for BSM effects, or devise complementary
strategies for precision measurements. This book describes techniques related to the
internal structure of jets, offering the possibility to advance on all three of these
topics. The versatility of jet substructure techniques results from the presence of jets
in virtually every process in high energy pp collisions. The substructure of these
jets contains information about their origin and the underlying dynamics. For example, jet substructure allows to distinguish quark from gluon jets, remove the effects
from uncorrelated radiation from multiple simultaneous pp collisions, identify jets
originating from collimated decays of W , Z , H bosons or top quarks, or reduce
the influence of non-perturbative effects and thus improve the precision of measurements. Since either one or more of these aspects are important for every analysis
of LHC data, jet substructure techniques have percolated into all physics analysis
groups of the ATLAS and CMS Collaborations.
1 The physics of jet substructure has
enhanced the physics potential of the LHC and will continue to do so in the years to
come.
The aim of this book is to review the most important developments in the field
of jet substructure from an experimentalists’ point of view. This encompasses theoretical and algorithmic developments, analytic calculations, advances in modelling,
experimental studies of substructure observables and commissioning of new tools,
measurements of substructure observables, measurements making use of them, as
well as direct searches for BSM effects with jet substructure. It is my intention to
put these developments into a larger context, showing the relevance of this relatively
young field to particle physics as a whole. The versatility of jet substructure leads
from scientific gains in precision studies of Quantum Chromodynamics (QCD), to
the determination of fundamental parameters of the SM, to searches for new physical
phenomena at the highest energy scales. If there are BSM effects observable at the
LHC, jet substructure techniques will play an important role to discover them.
2
1 Jet substructure has also become a field of study in heavy ion collisions, which are not discussed
in this book.
2 While some aspects of LHC physics may not have direct connections to jet substructure techniques,
the advancements in this field result in new developments of reconstruction algorithms, influencing
all stages of data analyses.
3
difficulty of accurately understanding even small experimental effects and correctly
estimating corresponding systematic uncertainties, a process which takes years to
complete due to the complexity of the LHC experiments.
This leaves three choices for our immediate hopes to find BSM effects: either
measure rare processes, becoming accessible only now with the large amount of
data, find novel ways to perform searches for BSM effects, or devise complementary
strategies for precision measurements. This book describes techniques related to the
internal structure of jets, offering the possibility to advance on all three of these
topics. The versatility of jet substructure techniques results from the presence of jets
in virtually every process in high energy pp collisions. The substructure of these
jets contains information about their origin and the underlying dynamics. For example, jet substructure allows to distinguish quark from gluon jets, remove the effects
from uncorrelated radiation from multiple simultaneous pp collisions, identify jets
originating from collimated decays of W , Z , H bosons or top quarks, or reduce
the influence of non-perturbative effects and thus improve the precision of measurements. Since either one or more of these aspects are important for every analysis
of LHC data, jet substructure techniques have percolated into all physics analysis
groups of the ATLAS and CMS Collaborations.
1 The physics of jet substructure has
enhanced the physics potential of the LHC and will continue to do so in the years to
come.
The aim of this book is to review the most important developments in the field
of jet substructure from an experimentalists’ point of view. This encompasses theoretical and algorithmic developments, analytic calculations, advances in modelling,
experimental studies of substructure observables and commissioning of new tools,
measurements of substructure observables, measurements making use of them, as
well as direct searches for BSM effects with jet substructure. It is my intention to
put these developments into a larger context, showing the relevance of this relatively
young field to particle physics as a whole. The versatility of jet substructure leads
from scientific gains in precision studies of Quantum Chromodynamics (QCD), to
the determination of fundamental parameters of the SM, to searches for new physical
phenomena at the highest energy scales. If there are BSM effects observable at the
LHC, jet substructure techniques will play an important role to discover them.
2
1 Jet substructure has also become a field of study in heavy ion collisions, which are not discussed
in this book.
2 While some aspects of LHC physics may not have direct connections to jet substructure techniques,
the advancements in this field result in new developments of reconstruction algorithms, influencing
all stages of data analyses.