Chapter 1: Introduction

Abstract

The 2020 update of the European Strategy for Particle Physics Update (ESPPU) outlined the current status and prospects in the field, and identified priorities for future particle physics accelerator facilities. In time order, these are: completion and commissioning of the CERN High Luminosity LHC (HL-LHC); a future electron-positron Higgs factory; and a future hadron collider at the highest achievable energy and luminosity.

It is recognised in the community, and was acknowledged in the ESPPU, that construction of the next generations of colliders will be extremely challenging. In most cases, there are major technical obstacles to meeting the exceptional performance requirements. As documented throughout this report, achieving our long-term scientific goals will require the exploration and maturation of new technologies, materials and techniques to well beyond the current state of the art. Since many of these technologies are unique to particle physics in their immediate application, then this can only result from a new and extended phase of R&D organised within our own institutes and in conjunction with industry and related scientific fields. This is similar to the precursor R&D that led to the successful delivery of previous generations of machines, but is likely to be longer in duration and wider in scope.