1,134 research outputs found
Black holes and the double copy
Recently, a perturbative duality between gauge and gravity theories (the
double copy) has been discovered, that is believed to hold to all loop orders.
In this paper, we examine the relationship between classical solutions of
non-Abelian gauge theory and gravity. We propose a general class of gauge
theory solutions that double copy to gravity, namely those involving stationary
Kerr-Schild metrics. The Schwarzschild and Kerr black holes (plus their
higher-dimensional equivalents) emerge as special cases. We also discuss plane
wave solutions. Furthermore, a recently examined double copy between the
self-dual sectors of Yang-Mills theory and gravity can be reinterpreted using a
momentum-space generalisation of the Kerr-Schild framework.Comment: 22 pages; typos corrected and references adde
The SAGEX Review on Scattering Amplitudes, Chapter 12: Amplitudes and collider physics
We explore how various topics in modern scattering amplitudes research find
application in the description of collider physics processes. After a brief
review of experimentally measured quantities and how they are related to
amplitudes, we summarise recent developments in perturbative QFT, and how they
have impacted our ability to do precision physics with colliders. Next, we
explain how the study of (next-to-)soft radiation is directly relevant to
increasing theoretical precision for key processes at the LHC and related
experiments. Finally, we describe the various techniques that are used to turn
theoretical calculations into something more closely approaching the output of
a particle accelerator.Comment: 32 pages, see also the overview article arXiv:2203.1301
Law of refraction for generalised confocal lenslet arrays
We derive the law of generalised refraction for generalised confocal lenslet
arrays, which are arrays of misaligned telescopes. We have implemented this law
of refraction in TIM, a custom open-source ray tracer.Comment: 4 pages, 3 figure
Top polarisation studies in and production
The polarisation of top quarks produced in high energy processes can be a
very sensitive probe of physics beyond the Standard Model. The kinematical
distributions of the decay products of the top quark can provide clean
information on the polarisation of the produced top and thus can probe new
physics effects in the top quark sector. We study some of the recently proposed
polarisation observables involving the decay products of the top quark in the
context of and production. We show that the effect of the top
polarisation on the decay lepton azimuthal angle distribution, studied recently
for these processes at leading order in QCD, is robust with respect to the
inclusion of next-to-leading order and parton shower corrections. We also
consider the leptonic polar angle, as well as recently proposed energy-related
distributions of the top decay products. We construct asymmetry parameters from
these observables, which can be used to distinguish the new physics signal from
the background and discriminate between different values of
and in a general type II two-Higgs doublet model. Finally, we show
that similar observables may be useful in separating a Standard Model
signal from the much larger QCD induced top pair production background.Comment: 33 pages, 35 figures, references adde
Boosting Higgs CP properties via VH Production at the Large Hadron Collider
We consider ZH and WH production at the Large Hadron Collider, where the
Higgs decays to a bb pair. We use jet substructure techniques to reconstruct
the Higgs boson and construct angular observables involving leptonic decay
products of the vector bosons. These efficiently discriminate between the
tensor structure of the HVV vertex expected in the Standard Model and that
arising from possible new physics, as quantified by higher dimensional
operators. This can then be used to examine the CP nature of the Higgs as well
as CP mixing effects in the HZZ and HWW vertices separately.Comment: 5 pages, 3 figures. v2: two references added and typo correcte
Web matrices : structural properties and generating combinatorial identities
In this paper we present new results for the combinatorics of web diagrams and web worlds. These are discrete objects that arise in the physics of calculating scattering amplitudes in non-abelian gauge theories. Web-colouring and web-mixing matrices (collectively known as web matrices) are indexed by ordered pairs of web-diagrams and contain information relating the number of colourings of the first web diagram that will produce the second diagram. We introduce the black diamond product on power series and show how it determines the web-colouring matrix of disjoint web worlds. Furthermore, we show that combining known physical results with the black diamond product gives a new technique for generating combinatorial identities. Due to the complicated action of the product on power series, the resulting identities appear highly non-trivial. We present two results to explain repeated entries that appear in the web matrices. The first of these shows how diagonal web matrix entries will be the same if the comparability graphs of their associated decomposition posets are the same. The second result concerns general repeated entries in conjunction with a flipping operation on web diagrams. We present a combinatorial proof of idempotency of the web-mixing matrices, previously established using physical arguments only. We also show how the entries of the square of the web-colouring matrix can be achieved by a linear transformation that maps the standard basis for formal power series in one variable to a sequence of polynomials. We look at one parameterized web world that is related to indecomposable permutations and show how determining the web-colouring matrix entries in this case is equivalent to a combinatorics on words problem
The MC@NLO 4.0 Event Generator
This is the user's manual of MC@NLO 4.0. This package is a practical
implementation, based upon the Fortran HERWIG and Herwig++ event generators, of
the MC@NLO formalism, which allows one to incorporate NLO QCD matrix elements
consistently into a parton shower framework. Processes available in this
version include the hadroproduction of single vector and Higgs bosons, vector
boson pairs, heavy quark pairs, single top, single top in association with a W,
single top in association with a charged Higgs in type I or II 2HDM models,
lepton pairs, and Higgs bosons in association with a W or Z. Spin correlations
are included for all processes except ZZ production. This document is
self-contained, but we emphasise the main differences with respect to previous
versions.Comment: 36 pages, no figure
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