Chapter 4
Standard Model Measurements
Abstract Jet substructure measurements at the LHC can broadly be divided into two
classes: measurements of jet substructure observables and measurements using jet
substructure. The first class enables detailed studies of the dynamics of jet production
and the energy flow within jets. These measurements can be used to test the modelling
of jet substructure observables, verify analytical calculations and extract fundamental
parameters of the theory. The second class are measurements made possible by jet
substructure techniques. These include studies of top quark or electroweak boson
production at very high transverse momenta. In most cases, the channels analysed
would not be accessible without the use of jet substructure techniques. The high
momenta probed in these measurements allow to study the validity of the SM up to
the highest scales reachable at the LHC. These measurements can also be used to
place important constraints on BSM theories, which predict deviations from the SM
expectations in the high-energy tails of the measured distributions.
4.1 Measurements of Jet Substructure Observables
4.1.1 Jet Mass of Light Flavour and Gluon Jets
The most important observable in jet substructure studies is the jet mass, which
is indispensable in measurements at high p T and in searches for BSM effects. Its
reconstruction and modelling is complicated, subject to the influence of many sources
of experimental and theoretical uncertainties see Sects. 2.4.1 and 3.2). Measurements
of the jet mass are crucial for our understanding of the detector response and the
theoretical description of jet substructure.
The first data recorded at the LHC in the year 2010 with
√
s = 7 TeV enabled
a measurement of the jet mass distribution in dijet events by ATLAS [551]. The
inclusive jet cross section as a function of the jet mass has been measured for anti-k T
jets with R = 1.0 for different regions in p T , where two regions in p T are shown
in Fig. 4.1. From today’s point of view this measurement is special as events are
selected to have only a single primary vertex, such that the measurement is free
© Springer Nature Switzerland AG 2021
R. Kogler, Advances in Jet Substructure at the LHC, Springer Tracts
in Modern Physics 284, https://doi.org/10.1007/978-3-030-72858-8_4
93
Standard Model Measurements
Abstract Jet substructure measurements at the LHC can broadly be divided into two
classes: measurements of jet substructure observables and measurements using jet
substructure. The first class enables detailed studies of the dynamics of jet production
and the energy flow within jets. These measurements can be used to test the modelling
of jet substructure observables, verify analytical calculations and extract fundamental
parameters of the theory. The second class are measurements made possible by jet
substructure techniques. These include studies of top quark or electroweak boson
production at very high transverse momenta. In most cases, the channels analysed
would not be accessible without the use of jet substructure techniques. The high
momenta probed in these measurements allow to study the validity of the SM up to
the highest scales reachable at the LHC. These measurements can also be used to
place important constraints on BSM theories, which predict deviations from the SM
expectations in the high-energy tails of the measured distributions.
4.1 Measurements of Jet Substructure Observables
4.1.1 Jet Mass of Light Flavour and Gluon Jets
The most important observable in jet substructure studies is the jet mass, which
is indispensable in measurements at high p T and in searches for BSM effects. Its
reconstruction and modelling is complicated, subject to the influence of many sources
of experimental and theoretical uncertainties see Sects. 2.4.1 and 3.2). Measurements
of the jet mass are crucial for our understanding of the detector response and the
theoretical description of jet substructure.
The first data recorded at the LHC in the year 2010 with
√
s = 7 TeV enabled
a measurement of the jet mass distribution in dijet events by ATLAS [551]. The
inclusive jet cross section as a function of the jet mass has been measured for anti-k T
jets with R = 1.0 for different regions in p T , where two regions in p T are shown
in Fig. 4.1. From today’s point of view this measurement is special as events are
selected to have only a single primary vertex, such that the measurement is free
© Springer Nature Switzerland AG 2021
R. Kogler, Advances in Jet Substructure at the LHC, Springer Tracts
in Modern Physics 284, https://doi.org/10.1007/978-3-030-72858-8_4
93