2022-26 Draft v1 Prepared by the Subatomic Physics LRP Committee Contents 1 Executive Summary1 2 Science Drivers and Canadian Impact2 2.1 Higgs, physics at the electroweak scale and beyond...................3 2.2 Fundamental symmetries and observed asymmetries..................7 2.3 Neutrino properties......................................9 2.4 Dark Matter and potential dark sectors........................... 11 2.5 New physical principles and structures........................... 13 2.6 Hadron properties and phases............................... 15 2.7 Nuclear structure....................................... 16 2.8 Cosmic formation of nuclei.................................. 18 2.9 Impact and Synergies with other fields........................... 19 3 Canadian Subatomic Physics Research Plan 21 3.1 Science opportunities for Canada.............................. 21 3.2 Infrastructure and Enabling technologies......................... 25 3.3 Research Portfolio....................................... 28 3.4 Science Recommendations................................. 29 4 Realizing the Research Plan 34 4.1 Canadian Subatomic Physics Community......................... 34 4.2 Funding............................................. 39 4.3 Infrastructure and Technical Support............................ 43 4.4 Research Policy........................................ 46 5 Subatomic Physics and Society 48 5.1 Subatomic Physics Training for the Knowledge Economy................ 48 5.2 Technological applications of SAP research........................ 50 5.3 Commercial opportunities.................................. 50 5.4 Cultural benefits........................................ 51 Appendices 52 A Case Studies 53 B Glossary 54 C Terms of Reference 55 C.1 Context............................................. 55 C.2 Committee........................................... 55 C.3 Mandate............................................. 56 C.4 Process and timeline..................................... 56 C.5 Deliverables.......................................... 57 C.6 Conflicts of interest and confidentiality........................... 57 i Contents ii D Long Range Plan Committee Membership 58 D.1 Committee Members..................................... 58 D.2 Ex-officio Members & Observers.............................. 58 E Long Range Planning process 59 E.1 Timeline............................................. 59 E.2 Confidentiality and Conflicts of Interest........................... 60 1 1 2 Executive Summary 3 [The Executive Summary will be included in v2 of the Report.] 1 4 2 5 Science Drivers and Canadian Impact 6 The overarching goal of subatomic physics is to push the knowledge frontier of what the Universe 7 is made of at the very smallest distance scales. In doing so, subatomic physics has been able to 8 distill and translate observations of natural phenomena into universal laws expressed by a few 9 mathematical equations. The existence of this expansive theoretical scaffolding is the very reason 10 specific questions about the Universe can be formulated and we can advance systematically in 11 the exploration of the unknown. 12 The field of subatomic physics research has progressed significantly over the past couple of 13 decades, driven by technological advances, computing power, and theoretical developments. As 14 a prime example, the discovery of the Higgs boson in 2012 at the LHC provided the capstone for 15 the Standard Model of particle physics, but many questions remain as ‘science drivers’ for the 16 field and indeed the Higgs has now become a tool to push forward our understanding. 17 The LRP Committee identified eight science drivers for the field of subatomic physics research 18 in 2022, that encapsulate a number of underlying questions: 19 • Higgs Physics, the Electroweak Scale and Beyond 20 – What is the precise nature of the Higgs sector and the flavour sector of the Standard 21 Model? What is the physics of electroweak symmetry breaking? What lies beyond the 22 electroweak scale? 23 • Fundamental Symmetries and observed Asymmetries 24 – What are the fundamental symmetries in nature, and how do we explain observed 25 imbalances, e.g. the matter-antimatter symmetry in the universe? 26 • Neutrino Properties 27 – What is the nature of neutrino mass and of neutrino interactions? 28 • Dark Matter & potential Dark Sectors 29 – What is the nature of dark matter in the universe, and its interactions? Is dark matter 30 part of a more extended dark sector? 31 • New Physical Principles & Structures 2 2.1. Higgs, physics at the electroweak scale and beyond 3 32 – What principles and formal theoretical structures underly the forces/matter in the 33 universe? How is gravity to be understood at the quantum level? 34 • Hadron Properties and Phases 35 – How do quarks and gluons give rise to the properties of nucleons and other hadrons, 36 and to the hadronic phases of matter in extreme conditions? 37 • Nuclear Structure 38 – How does nuclear structure emerge from nuclear forces and ultimately from quarks 39 and gluons? 40 • Cosmic Formation of Nuclei 41 – How do the properties of nuclei explain the formation of the elements in the late 42 universe? 43 These science drivers are deeply inter-connected and in combination define three broad 44 science directions in subatomic physics, as illustrated in Fig. 2.1. To address the breadth of these 45 science drivers requires a diversified research program of bold projects with complementary 46 objectives, exploiting a variety of different techniques. In the rest of this chapter, these science 47 drivers are described in more detail, focussing on recent progress and Canadian activities and 48 achievements. Indeed, Canadian subatomic physics has an enviable global reputation, with 49 impact on many of the major projects that have pushed our understanding forward in recent 50 decades. The Council of Canadian Academies’ 2018 report "Competing in a Global Innovation 51 Economy: The Current State of R&D in Canada" highlights the global impact of Canadian 52 subatomic physics research, as measured by average relative citations which grew from 1.79 53 to 2.05 compared to the Canadian average of 1.43. Given its global impact, but relatively small 54 community size, physics and astronomy was highlighted in the report as a research opportunity 55 for Canada, and future opportunities and plans will be described in Chapter 3. 56 2.1. Higgs, physics at the electroweak scale and beyond 57 The discovery of the Higgs boson in 2012 identified one of the main agents for the breaking at low 58 energies of the fundamental electroweak symmetry in nature. Yet, the electroweak sector remains 59 one of the most puzzling aspects of the Standard Model. The Higgs boson is a type of matter that 60 has never been seen before with properties yet to be fully studied. Its mass, for example, is not 61 constrained by any symmetry in the Standard Model, and unlike the mathematical structure of the 62 other forces of nature that are fully specified based on symmetry properties, the addition of Higgs 63 interactions leads to a large number of undetermined parameters in the Standard Model. This 64 makes our current understanding of the role the Higgs boson plays in the Universe particularly 65 ad-hoc and incomplete, and in stark contrast with the structural simplicity of other aspects of the 66 Standard Model. In particular, this raises the fundamental question of what underlying principles 67 determine the properties of the Higgs boson. This question motivates the possible existence of 68 new physics phenomena beyond those described by the Standard Model, but also identifies the 69 Higgs boson as a unique probe to explore physics processes at and beyond the electroweak 70 energy scale. 71 Exploration of physics phenomena at and beyond the electroweak scale is taking place in 72 proton-proton collisions at the LHC and will continue in the coming years at the High-Luminosity 2.1. Higgs, physics at the electroweak scale and beyond 4 Figure 2.1: (Placeholder) Schematic representation of the eight Science drivers and their inter-connections. 2.1. Higgs, physics at the electroweak scale and beyond 5 73 LHC, through both the measurement of known electroweak processes and searches for signatures 74 of new phenomena. Looking forward, a future electron-positron collider, such as the proposed ILC 75 in Japan or FCC-ee in Europe, would operate as a Higgs factory, producing an enormous number 76 of Higgs bosons, thereby making it possible to measure Higgs properties to an unprecedented 77 level of precision, and possibly uncovering hints of physics phenomena beyond those predicted in 78 the Standard Model. 79 Precision measurements of physics processes at lower energies also provide a complementary 80 window into new physics at or beyond the electroweak scale. Indeed, the degree of precision of 81 both measurements and Standard Model predictions is an aspect of subatomic physics research, 82 that is unique among all the sciences, and can be used to reveal small discrepancies arising 83 due to new physics. This sensitivity can be achieved through the study of rare or forbidden 84 processes in the Standard Model; for example, in the decays of tau leptons, kaons, bottom and 85 charm hadrons, or the study of theoretically well-understood processes such as electron-electron 86 scattering. 87 2.1.1. Canadian contributions and achievements 88 Canadian researchers have been and continue to be at the forefront of experimental investigations 89 of physics at the electroweak scale