The advent of back-scattered laser beams for e[sup+]e[sup -] colliders will allow detailed studies of a large array of high energy[gamma][gamma] and[gamma]e collision processes with polarized beams. These include tests of electroweak theory in photon-photon annihilation such as[gamma][gamma][yields] W[sup+]W[sup -], [gamma][gamma][yields] Higgs bosons, and higher-order loop processes, such as[gamma][gamma][yields][gamma][gamma], H[sup 0]Z[sup 0] and ZZ: Methods for measuring the anomalous magnetic and quadrupole moments of the W and Z gauge bosons to high precision in polarized electron-photon and photon-photon collisions are discussed. Since each photon can be resolved into a W[sup+]W[sup -] pair, high energy photon-photon collisions can also provide a remarkably background-free laboratory for studying WW collisions and annihilation. I also review high energy[gamma][gamma] and e[gamma] tests of quantum chromodynamics, including the production of two gluon jets in photon-photon collisions, deeply virtual Compton scattering on a photon target, and leading-twist single-spin asymmetries for a photon polarized normal to a production plane. Exclusive hadron production processes in photon-photon collisions provide important tests of QCD at the amplitude level, particularly as measures of hadron distribution amplitudes which are also important for the analysis of exclusive semi-leptonic and two-body hadronic B-decays.

Two-photon physics, i.e. photon-photon collisions in electron-positron colliders, a relatively new field in elementary particle physics, has become very popular in the last 20 years. Many experiments have been performed in this field, and the theoretical implications (in particular in quantum chromodynamics) have been studied in much detail. Nine international workshops devoted to two-photon physics have taken place between 1973 and 1992.This meeting was particularly timely, since a new generation of electron-positron colliders is presently being built or planned. These colliders will involve a large spectrum of beam energies, but their common characteristics should be a high particle flux (luminosity). This should allow for measuring many new phenomena as well as for studying known processes with much higher precision than before. Particularly promising is the prospect of building a dedicated high-energy photon collider; this should become possible using a laser technique allowing for the “conversion” of a linear electron beam into a photon beam.Over 60 physicists (both experimentalists and theorists), mainly from European countries (France, Britain, Italy, Germany, Russia, as well as Sweden and Switzerland), discussed these new possibilities at the above meeting. Over 30 talks were presented and many extended debates took place.

Photon-photon interactions have been an important probe into fundamental particle physics. Until recently, the only way to produce photon-photon collisions was parasitically in the collision of charged particles. Recent advances in short-pulse laser technology have made it possible to consider producing high intensity, tightly focused beams of real photons through Compton scattering. A linear e{sup +}e{sup -} collider could thus be transformed into a photon-photon collider with the addition of high power lasers. In this paper they show that it is possible to make a competitive photon-photon collider experiment using the currently mothballed Stanford Linear Collider. This would produce photon-photon collisions in the GeV energy range which would allow the discovery and study of exotic heavy mesons with spin states of zero and two.

This thesis reports on the first studies of Standard Model photon production at the Large Hadron Collider (LHC) using the ATLAS detector. Standard Model photon production is a large background in the search for Higgs bosons decaying into photon pairs, and is thus critical to understand. The thesis explains the techniques used to reconstruct and identify photon candidates using the ATLAS detector, and describes a measurement of the production cross section for isolated prompt photons. The thesis also describes a search for the Higgs boson in which the analysis techniques used in the measurement are exploited to reduce and estimate non-prompt backgrounds in diphoton events.

Understanding of protons and neutrons, or "nucleons"â€"the building blocks of atomic nucleiâ€"has advanced dramatically, both theoretically and experimentally, in the past half century. A central goal of modern nuclear physics is to understand the structure of the proton and neutron directly from the dynamics of their quarks and gluons governed by the theory of their interactions, quantum chromodynamics (QCD), and how nuclear interactions between protons and neutrons emerge from these dynamics. With deeper understanding of the quark-gluon structure of matter, scientists are poised to reach a deeper picture of these building blocks, and atomic nuclei themselves, as collective many-body systems with new emergent behavior. The development of a U.S. domestic electron-ion collider (EIC) facility has the potential to answer questions that are central to completing an understanding of atoms and integral to the agenda of nuclear physics today. This study assesses the merits and significance of the science that could be addressed by an EIC, and its importance to nuclear physics in particular and to the physical sciences in general. It evaluates the significance of the science that would be enabled by the construction of an EIC, its benefits to U.S. leadership in nuclear physics, and the benefits to other fields of science of a U.S.-based EIC.

The proceedings blend current and future two-photon physics. Developments since the last Photon-Photon Workshop four years ago are summarized, and the future of the field is projected, not only at existing accelerators, but also at heavy-ion colliders B-factories, and especially linear colliders with back-scattered laser beams.

The work presented in this book is based on the proton-proton collision data from the Large Hadron Collider at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector in 2015 and 2016. The research program of the ATLAS experiment includes the precise measurement of the parameters of the Standard Model, and the search for signals of physics beyond the SM. Both these approaches are pursued in this thesis, which presents two different analyses: the measurement of the Higgs boson mass in the di-photon decay channel, and the search for production of supersymmetric particles (gluinos, squarks or winos) in a final state containing two photons and missing transverse momentum. Finally, ATLAS detector performance studies, which are key ingredients for the two analyses outlined before, are also carried out and described.