The Future of US Particle Physics: The Energy Frontier Report – 2021 US Community Study on the Future of Particle Physics

Abstract

The Energy Frontier (EF) aims at investigating the fundamental physics of the Universe at the highest energies or -equivalently -the shortest timescales after the Big Bang. We investigate open questions and explore the unknown using various probes to discover and characterize the nature of new physics, through the breadth and multitude of collider physics signatures. While the naturalness principle suggests new physics to lie at mass scales close to the electroweak scale, in many cases direct searches for specific models have placed strong bounds around 1-2 TeV. Thus, the energy frontier has moved beyond the TeV scale and the exploration of the 10 TeV scale becomes crucial to shed light on physics beyond the Standard Model (SM).We need to use both energy reach and precision measurements to push beyond the 1 TeV scale in our exploration. The quest for new physics will be thus conducted in a two-tier approach: 1) looking for indirect evidence of beyond-the-Standard-Model physics (BSM) through precision measurements of the properties of the Higgs boson and other SM particles, and 2) searching for direct evidence of BSM physics at the energy frontier, reaching multi-TeV scales.The EF currently has a top-notch program with the LHC and the High Luminosity LHC (HL-LHC) at CERN, which sets the basis for the EF vision. The EF supports continued strong US participation in the success of the LHC, and the HL-LHC construction, operations, computing and software, and most importantly in the physics research programs, including auxiliary experiments.The discussions on projects that extend the reach of the HL-LHC underlined that preparations for the next collider experiments have to start now to maintain and strengthen the vitality and motivation of the community. Colliders are the ultimate tool to carry out such a program thanks to the broad and complementary set of measurements and searches they enable. Several projects have been proposed such as ILC, CLIC, FCC-ee, CEPC, Cool Copper Collider (C 3 ) or HELEN for e + e − Higgs Factories, and CLIC at 3 TeV centre-of-mass energy, FCC-hh, SPPC and Muon Collider for multi-TeV colliders. For a detailed discussion of timeline, cost, challenges of those accelerator projects we refer to the Accelerator Frontier Integration Task-Force (ITF) report [1] and Appendix A.3. Dedicated fora were established across frontiers to bring together diverse expertise in the study of future e + e − and µ + µ − colliders. Results from their studies are available in their reports [2, 3] and have informed the studies presented in this report.All proposed collider physics experiments need complex detectors as well as software and computing infrastructure, with cutting-edge technologies to meet their ambitious physics goals. The needs extend beyond generic R&D. Experience from R&D and building previous experiments informs us that it takes about 10 years from CD-0 (Critical Decision -0) to the end of construction of a collider detector. For e + e − Higgs factories, immediate investment in targeted detector R&...

Feebly-interacting particles: FIPs 2020 workshop report

“…To achieve the most comprehensive coverage of LLP's at the HL LHC, dedicated transverse LLP detectors are an essential piece of the puzzle. The importance of such auxiliary detectors at the LHC was stressed in particular in the recent Snowmass energy frontier summary report [1043]. MATHUSLA, CODEX-b and ANUBIS represent three different locations and detector concepts, covering a range of costs and providing sensitivities that are complementary to existing or approved detectors.…”

Dark Matter Complementarity (Snowmass 2021 Cross Frontier Report: Extended Version)

“…The existing and future program of DM searches at collider experiments is expansive, ranging from numerous signals of the canonical WIMP (featuring in supersymmetric theories), to lighter thermally-produced DM particles and the higher-mass mediators of their interaction, to extended dark sectors with complex, experimentally challenging phenomenology. More information can be found in the Energy Frontier report [4] and more-detailed topical group report [17].…”

“…A chapter on the vision of the Energy Frontier can be found in Ref. [4] and can be summarized as follows:…”

“…Specific realizations of these models are used as benchmarks by the collider and accelerator communities, see the generic BSM-mediated benchmark models in Refs. [4,71] and the vector portal DM models in Refs. [72,73].…”

“…This is the case of smaller Rare Processes and Precision Frontier accelerator experiments that can be co-located with Energy Frontier collider experiments, using the same high-energy beams to produce different kinds of DM. Such experiments are discussed in depth in the Rare and Precision Frontier and their connection to collider experiments is discussed in the Energy Frontier report [4].…”