Addendum to the report on the physics at the HL-LHC, and perspectives for the HE-LHC: Collection of notes from ATLAS and CMS

The “Workshop on the Physics of HL-LHC and Perspectives at HE-LHC” [1], which took place between October 2017 and December 2018 at CERN, represented an LHC-wide effort of experimentalists and theorists with the aim to review and further refine the understanding of the physics potential of the High-Luminosity LHC (HL-LHC), and to prepare the exploitation of the HL-LHC data to the fullest possible extent. The workshop also provided an opportunity to begin a more systematic study of the physics at the High-Energy LHC, a possible new pp collider project in the LHC ring with a centre-of-mass energy of about 27TeV. The HL/HE-LHC workshop studies benefitted from the experience gained with the data analysis and physics simulation of the LHC Runs 1 and 2. The results extend and further refine previous studies produced for the Update of the European Strategy of Particle Physics in 2012–2013 [2], the ECFA HL-LHC workshops in 2013, 2014 and 2016 [3], as well as the Snowmass Workshop on the planning for the Future of U.S. Particle Physics in 2013 [4]. The workshop was organized in five working groups, on QCD, electroweak and top quark physics (WG1), Higgs boson and electroweak symmetry breaking (WG2), Beyond the Standard-Model physics (WG3), flavour physics (WG4), and high-density QCD physics (WG5).The reports from the five working groups are available on the arXiv [5]. The most important results were summarized in two ten-page documents, submitted to the European Strategy Group in December 2018 [6]. This book collects the original notes from the ATLAS and CMS Collaborations, used as input to the workshop and to the reports of the working groups [5].