2 The
Recommended
Particle Physics
Program

2.1Overview

A particle physics program that tackles the most important questions in each of the science drivers maximizes its potential for groundbreaking scientific discovery. Executing such a program requires a balanced portfolio of large, medium, and small projects, coupled with substantial investments in forward-looking R&D and the development of a skilled workforce for the nation.

Building upon the foundations laid by the previous P5, our recommended program completes ongoing projects and capitalizes on their momentum. A suite of new initiatives at a range of scales includes major projects that will shape the scientific landscape over the next two decades. The prioritized time sequencing of recommended projects and R&D, summarized in Figure 1, reflects our current understanding of the scientific landscape and its associated uncertainties.

The overall program is carefully constructed to be compatible with the baseline budget scenario provided by DOE. To achieve that, we recommend continuing specific projects, strategically advancing some to the construction phase, and delaying others. As shown in Figure 1, in some cases individual phases or elements of large-scale projects had to be prioritized separately. The process and criteria by which the recommended initiatives were selected are laid out in section 1.5.

We note our commitment to the ongoing projects described in section 1. The scientific direction and balance of the recommended new initiatives are summarized below.

DUNE will comprehensively explore the quantum realm of neutrinos, potentially unearthing new physics beyond current theoretical frameworks. Early implementation of the accelerator upgrade ACE-MIRT advances the DUNE program significantly, hastening the definite discovery of the neutrino mass ordering. This upgrade in conjunction with the deployment of the third far detector and a more capable near detector are indispensable components of the re-envisioned next phase of DUNE. R&D for an advanced fourth detector enables the expansion of the physics program of LBNF. These substantial initiatives find synergy with smaller-scale experiments to elucidate the mysteries of neutrinos.

A Higgs factory is the next step toward fully revealing the secrets of the Higgs boson within the quantum realm. We advocate substantial US participation in the design and construction of accelerators and detectors for an off-shore facility, and we advocate investment of effort to support development of the Future Circular Collider-electron (e^–) positron (e⁺) (FCC-ee) and the International linear Collider (ILC), along with a parallel and increasingly intensive program of R&D pursuing revolutionary accelerator and detector technologies. These are crucial for a leadership role in the design and construction of the Higgs factory and for our aspiration to lead and potentially host a next high-energy collider facility beyond the Higgs factory.

There is a compelling physics case for constructing a 10 TeV or more pCM collider. Such a collider would search for direct evidence and quantum imprints of new particles and forces at unprecedented energies. There are several approaches: a 10 TeV muon collider, a 100 TeV proton-proton collider such as FCC-hh at CERN, or possibly a 10 TeV high-energy e⁺e^– or γ-γ collider based on the wakefield acceleration technology. Any of them would enable a comprehensive physics portfolio that includes ultimate measurements in the Higgs sector, a broad search program providing access to new hidden sectors by producing a substantially higher mediator mass or probing even smaller coupling, and opportunities to produce new particles directly. All options for a 10 TeV pCM collider are new technologies under development and R&D is required before we can embark on building a new collider.

Further insights will be gained over this decade through collaboration and planning with international partners and dedicated R&D efforts aimed at addressing technical challenges. A panel in the latter part of the decade will be able to harness this information to make further decisions on the path toward future colliders.

A transformative next-generation CMB experiment, CMB-S4, will plumb the secrets of the primordial universe during and immediately after a period of rapid expansion; it should reveal signatures of new physics at energies far beyond the reach of colliders. The ongoing galaxy survey program, enhanced by the Dark Energy Spectroscopic Instrument initiative DESI-II, investigates the cause for a more recent era of accelerated expansion. Together, they promise revolutionary insight into the drivers of cosmic evolution.

In parallel, a strong R&D effort builds toward the ultimate next-generation wide-field spectroscopic survey Spec-S5, which will study the possible time evolution of dark energy and provide a test of inflation complementary to CMB-S4. Development of the emerging technology of line-intensity mapping could create a 3D map of the universe and enable theoretically clean and powerful tests of cosmology.

Another suite of experiments pursues the undetermined nature of the dark matter that gravitationally influences our universe. Select dark matter experiments searching for WIMPs will reach critical discovery potential for a broad range of WIMP masses. Smaller-scale experiments will survey the wider set of dark matter theories and their parameter space. In total, these efforts promise an unprecedented view of the hidden universe.

A new DOE portfolio of agile projects across all science drivers complements existing opportunities within NSF. This portfolio plays a pivotal role in achieving a balanced and forward-looking program.

Realizing the full potential of the experimental landscape requires not just targeted R&D, but substantial strategic investments in theory and infrastructure. Just as hints of new physics revealed by experiment drive new theoretical developments, theory guides experimental inquiries and enriches our understanding of fundamental principles. A coordinated effort that develops shared cyberinfrastructure, harnesses emerging technologies, and leverages national initiatives such as AI, microelectronics, and quantum information science (QIS) benefits all aspects of our scientific program. Equally crucial, key facilities must be maintained and developed in alignment with the long-term vision outlined in this report.

An ambitious, effective scientific program thrives when pursued by a vibrant scientific community. We therefore endorse strategic initiatives to collectively amplify and strengthen the workforce while fostering a healthy working environment. These initiatives are designed to uphold ethical conduct of research, dismantle barriers to entry and retention, recruit broadly, and pave new pathways of opportunity. This commitment nurtures an advanced technological workforce not only adept in particle physics but also equipped to contribute to the technological advancements essential for the nation.

The vision outlined in this report provides opportunities for paradigm-shifting discoveries. By deciphering the quantum realm, illuminating the hidden universe, and exploring new paradigms in physics, we step further into our quantum universe. Some of the priorities are designed to adapt naturally as this landscape evolves over the next decade, while others are designed to drive that evolution.

2.2Recommendations

To drive US particle physics forward and maintain strong global leadership, we advocate a comprehensive and balanced program that strategically addresses the three science themes and their six interwoven drivers. The numerical order of the recommendations listed below is not meant to reflect their relative priority; instead it is used to group them thematically. The lists under the recommendations are not prioritized, except for the list of major projects under Recommendation 2. Each recommendation is stated in boldface, followed by concise, lettered explanations of how the recommendation can be realized. The impact of alternative budget scenarios on the different elements of the program is discussed in section 2.6.

A Full List of Recommendations is provided at the end of the report. That list includes Area Recommendations (section 6) in addition to those here.

Recommendation 1: As the highest priority independent of the budget scenarios, complete construction projects and support operations of ongoing experiments and research to enable maximum science.

We reaffirm the previous P5 recommendations on major initiatives:

1. HL-LHC (including ATLAS and CMS detectors, as well as Accelerator Upgrade Project) to start addressing why the Higgs boson condensed in the universe (reveal the secrets of the Higgs boson, section 3.2), to search for direct evidence for new particles (section 5.1), to pursue quantum imprints of new phenomena (section 5.2), and to determine the nature of dark matter (section 4.1).
2. The first phase of DUNE and PIP-II to determine the mass ordering among neutrinos, a fundamental property and a crucial input to cosmology and nuclear science (elucidate the mysteries of neutrinos, section 3.1).
3. The Vera C. Rubin Observatory to carry out the LSST, and the LSST Dark Energy Science Collaboration, to understand what drives cosmic evolution (section 4.2).

In addition, we recommend continued support for the following ongoing experiments at the medium scale (project costs > $50M for DOE and > $4M for NSF), including completion of construction, operations, and research:

1. NOvA, SBN, and T2K (elucidate the mysteries of neutrinos, section 3.1).
2. DarkSide-20k, LZ, SuperCDMS, and XENONnT (determine the nature of dark matter, section 4.1).
3. DESI (understand what drives cosmic evolution, section 4.2).
4. Belle II, LHCb, and Mu2e (pursue quantum imprints of new phenomena, section 5.2).

The agencies should work closely with each major project to carefully manage the costs and schedule to ensure that the US program has a broad and balanced portfolio.

Recommendation 2: Construct a portfolio of major projects that collectively study nearly all fundamental constituents of our universe and their interactions, as well as how those interactions determine both the cosmic past and future.

These projects have the potential to transcend and transform our current paradigms. They inspire collaboration and international cooperation in advancing the frontiers of human knowledge. Plan and start the following major initiatives in order of priority from highest to lowest:

1. CMB-S4, which looks back at the earliest moments of the universe to probe physics at the highest energy scales. It is critical to install telescopes at and observe from both the South Pole and Chile sites to achieve the science goals (section 4.2).
2. Re-envisioned second phase of DUNE with an early implementation of an enhanced 2.1 MW beam—ACE-MIRT—a third far detector, and an upgraded near-detector complex as the definitive long-baseline neutrino oscillation experiment of its kind (section 3.1).
3. An off-shore Higgs factory, realized in collaboration with international partners, in order to reveal the secrets of the Higgs boson. The current designs of FCC-ee and ILC meet our scientific requirements. The US should actively engage in feasibility and design studies. Once a specific project is deemed feasible and well-defined (see also Recommendation 6), the US should aim for a contribution at funding levels commensurate to that of the US involvement in the LHC and HL-LHC, while maintaining a healthy US on-shore program in particle physics (section 3.2).
4. An ultimate Generation 3 (G3) dark matter direct detection experiment reaching the neutrino fog, in coordination with international partners and preferably sited in the US (section 4.1).
5. IceCube-Gen2 for study of neutrino properties using non-beam neutrinos complementary to DUNE and for indirect detection of dark matter covering higher mass ranges using neutrinos as a tool (section 4.1).

The prioritization principles behind these recommendations can be found in sections 1.6 and 8.1.

IceCube-Gen2 also has a strong science case in multi-messenger astrophysics together with gravitational wave observatories. We recommend that NSF expand its efforts in multi-messenger astrophysics, a unique program in the NSF Division of Physics, with US involvement in the Cherenkov Telescope Array (CTA; recommendation 3c), a next-generation gravitational wave observatory, and IceCube-Gen2.

Recommendation 3: Create an improved balance between small-, medium-, and large-scale projects to open new scientific opportunities and maximize their results, enhance workforce development, promote creativity, and compete on the world stage.

In order to achieve this balance across all project sizes we recommend the following:

1. Implement a new small-project portfolio at DOE, Advancing Science and Technology through Agile Experiments (ASTAE), across science themes in particle physics with a competitive program and recurring funding opportunity announcements. This program should start with the construction of experiments from the Dark Matter New Initiatives (DMNI) by DOE-HEP (section 6.2).
2. Continue Mid-Scale Research Infrastructure (MSRI) and Major Research Instrumentation (MRI) programs as a critical component of the NSF research and project portfolio.
3. Support DESI-II for cosmic evolution, LHCb upgrade II and Belle II upgrade for quantum imprints, and US contributions to the global CTA Observatory for dark matter (sections 4.2, 5.2, and 4.1).

The Belle II recommendation includes contributions towards the SuperKEKB accelerator.

Recommendation 4: Support a comprehensive effort to develop the resources—theoretical, computational, and technological—essential to our 20-year vision for the field. This includes an aggressive R&D program that, while technologically challenging, could yield revolutionary accelerator designs that chart a realistic path to a 10 TeV pCM collider.

Investing in the future of the field to fulfill this vision requires the following:

1. Support vigorous R&D toward a cost-effective 10 TeV pCM collider based on proton, muon, or possible wakefield technologies, including an evaluation of options for US siting of such a machine, with a goal of being ready to build major test facilities and demonstrator facilities within the next 10 years (sections 3.2, 5.1, 6.5, and Recommendation 6).
2. Enhance research in theory to propel innovation, maximize scientific impact of investments in experiments, and expand our understanding of the universe (section 6.1).
3. Expand the General Accelerator R&D (GARD) program within HEP, including stewardship (section 6.4).
4. Invest in R&D in instrumentation to develop innovative scientific tools (section 6.3).
5. Conduct R&D efforts to define and enable new projects in the next decade, including detectors for an e⁺e^– Higgs factory and 10 TeV pCM collider, Spec-S5, DUNE FD4, Mu2e-II, Advanced Muon Facility, and line intensity mapping (sections 3.1, 3.2, 4.2, 5.1, 5.2, and 6.3).
6. Support key cyberinfrastructure components such as shared software tools and a sustained R&D effort in computing, to fully exploit emerging technologies for projects. Prioritize computing and novel data analysis techniques for maximizing science across the entire field (section 6.7).
7. Develop plans for improving the Fermilab accelerator complex that are consistent with the long-term vision of this report, including neutrinos, flavor, and a 10 TeV pCM collider (section 6.6).

We recommend specific budget levels for enhanced support of these efforts and their justifications as Area Recommendations in section 6.

Recommendation 5: Invest in initiatives aimed at developing the workforce, broadening engagement, and supporting ethical conduct in the field. This commitment nurtures an advanced technological workforce not only for particle physics, but for the nation as a whole.

The following workforce initiatives are detailed in section 7:

1. All projects, workshops, conferences, and collaborations must incorporate ethics agreements that detail expectations for professional conduct and establish mechanisms for transparent reporting, response, and training. These mechanisms should be supported by laboratory and funding agency infrastructure. The efficacy and coverage of this infrastructure should be reviewed by a HEPAP subpanel.
2. Funding agencies should continue to support programs that broaden engagement in particle physics, including strategic academic partnership programs, traineeship programs, and programs in support of dependent care and accessibility. A systematic review of these programs should be used to identify and remove barriers.
3. Comprehensive work-climate studies should be conducted with the support of funding agencies. Large collaborations and national laboratories should consistently undertake such studies so that issues can be identified, addressed, and monitored. Professional associations should spearhead field-wide work-climate investigations to ensure that the unique experiences of individuals engaged in smaller collaborations and university settings are effectively captured.
4. Funding agencies should strategically increase support for research scientists, research hardware and software engineers, technicians, and other professionals at universities.
5. A plan for dissemination of scientific results to the public should be included in the proposed operations and research budgets of experiments. The funding agencies should include funding for the dissemination of results to the public in operation and research budgets.

Recommendation 6: Convene a targeted panel with broad membership across particle physics later this decade that makes decisions on the US accelerator-based program at the time when major decisions concerning an off-shore Higgs factory are expected, and/or significant adjustments within the accelerator-based R&D portfolio are likely to be needed. A plan for the Fermilab accelerator complex consistent with the long-term vision in this report should also be reviewed.

The panel would consider the following:

1. The level and nature of US contribution in a specific Higgs factory including an evaluation of the associated schedule, budget, and risks once crucial information becomes available.
2. Mid- and large-scale test and demonstrator facilities in the accelerator and collider R&D portfolios.
3. A plan for the evolution of the Fermilab accelerator complex consistent with the long-term vision in this report, which may commence construction in the event of a more favorable budget situation.

2.3The Path to 10 TeV pCM

Realization of a future collider will require resources at a global scale and will be built through a world-wide collaborative effort where decisions will be taken collectively from the outset by the partners. This differs from current and past international projects in particle physics, where individual laboratories started projects that were later joined by other laboratories. The proposed program aligns with the long-term ambition of hosting a major international collider facility in the US, leading the global effort to understand the fundamental nature of the universe.

There are multiple complementary technologies that could potentially reach the 10 TeV pCM scale, and the work to determine how to economically reach that goal must go forward. This is why we recommend pursuing revolutionary R&D in areas such as high-field magnets, a multi-megawatt proton driver, wakefield accelerator technology, and muon cooling (Recommendation 4a).

In particular, a muon collider presents an attractive option both for technological innovation and for bringing energy frontier colliders back to the US. The footprint of a 10 TeV pCM muon collider is almost exactly the size of the Fermilab campus. A muon collider would rely on a powerful multi-megawatt proton driver delivering very intense and short beam pulses to a target, resulting in the production of pions, which in turn decay into muons. This cloud of muons needs to be captured and cooled before the bulk of the muons have decayed. Once cooled into a beam, fast acceleration is required to further suppress decay losses.

Each of these steps presents considerable technical challenges, many of which have never been confronted before. This P5 plan outlines an aggressive R&D program to determine the parameters for a muon collider test facility by the end of the decade. This facility would test the feasibility of developing a muon collider in the following decade.

With a 10 TeV pCM muon collider at Fermilab as the long-term vision, a clear path for the evolution of the current proton accelerator complex at Fermilab emerges naturally: a booster replacement with a suitable accumulator/buncher ring would pave the way to a muon collider demonstration facility (Recommendation 4g, 6). The upgraded facility would also generate bright and well-characterized neutrino beams bringing natural synergies with studies of neutrinos beyond DUNE. It would also support beam dump and fixed target experiments for direct searches of new physics. Another synergy is in charged lepton flavor violation. The current round of searches at Mu2e can reveal quantum imprints of new physics at the 100 TeV energy scale, beyond the reach of direct searches at collider facilities in the foreseeable future. An intense muon facility may push this search even further.

Although we do not know if a muon collider is ultimately feasible, the road toward it leads from current Fermilab strengths and capabilities to a series of proton beam improvements and neutrino beam facilities, each producing world-class science while performing critical R&D towards a muon collider. At the end of the path is an unparalleled global facility on US soil. This is our Muon Shot.

2.4Stewardship of Key Infrastructure and Expertise

Successful completion of the recommended major projects depends on critical US infrastructure (section 6.6), including particular research sites and facilities. DOE National Laboratories are critical research infrastructure that must be maintained and enhanced based on the needs of the particle physics community. This is particularly true for Fermilab as the only dedicated US laboratory for particle physics. The South Pole, a unique site that enables the world-leading science of CMB-S4 and IceCube-Gen2, must be maintained as a premier site of science to allow continued US leadership in these areas. SURF, a deep underground research laboratory supported by the South Dakota Science and Technology Authority, private foundation funds, and DOE, is a critical addition to the suite of US research infrastructure, providing new space and essential infrastructure for DUNE and potentially a G3 dark matter experiment.

In other cases, the infrastructure is technological and intellectual. The GARD program is critical in supporting a broad range of accelerator science and technology (AS&T) for DOE’s Office of Science, separate from the targeted R&D toward future colliders. Along with NSF-funded fundamental accelerator science, GARD supports a broad workforce of essential accelerator expertise. The program also provides stewardship of AS&T for DOE’s Office of Science. This program and the balance across the different research thrusts should be reviewed regularly to ensure alignment with the goals in particle physics. Reviews should be conducted by broad teams, not only specialists.

2.5International and Inter-Agency Partnerships

Major facilities like Fermilab in the US, CERN in Europe, and KEK in Japan have led the worldwide effort to advance accelerator-based studies of particle physics. These facilities have enabled many groundbreaking experiments, and their continued leadership roles as host laboratories for future accelerators, cutting-edge experiments, and hubs for international collaborations are important for progress in the field.

Successful completion of the recommended major projects depends on significant coordination and collaboration among US agencies and international partners. Large international projects such as a Higgs factory and DUNE require not only DOE and NSF, but also the US Department of State and other entities in the federal government to work with global partners to establish the complex frameworks involved.

In the case of the Higgs factory, crucial decisions must be made in consultation with potential international partners. The FCC-ee feasibility study is expected to be completed by 2025 and will be followed by a European Strategy Group update and a CERN council decision on the 2028 timescale. The ILC design is technically ready and awaiting a formulation as a global project. A dedicated panel should review the plan for a specific Higgs factory once it is deemed feasible and well-defined; evaluate the schedule, budget and risks of US participation; and give recommendations to the US funding agencies later this decade (Recommendation 6). When a clear choice for a specific Higgs factory emerges, US efforts will focus on that project, and R&D related to other Higgs factory projects would ramp down.

Parallel to the R&D for a Higgs factory, the US R&D effort should develop a 10 TeV pCM collider, such as a muon collider, a proton collider, or possibly an electron-positron collider based on wakefield technology. The US should participate in the International Muon Collider Collaboration (IMCC) and take a leading role in defining a reference design. We note that there are many synergies between muon and proton colliders, especially in the area of development of high-field magnets. R&D efforts in the next 5-year timescale will define the scope of test facilities for later in the decade, paving the way for initiating demonstrator facilities within a 10-year timescale (Recommendation 6).

For studies of cosmic evolution and astrophysical studies of dark matter, inter-agency coordination and cooperation between DOE, NSF, and NASA using complementary observational approaches has been very productive in building a world-leading scientific program. Such coordination and cooperation should continue.

The field of particle physics is not an isolated endeavor, and it benefits from and contributes to neighboring areas in nuclear physics, astrophysics and astronomy, condensed matter physics, precision physics, computing, instrumentation, material science, and others. At the same time, it provides important theoretical and technological input to these areas, as well as medical, security, and many other fields, some as seemingly unrelated as archaeology. Funding agencies are urged to reach across the traditional boundaries to enhance collaboration, maximize science, and develop a strong workforce for the nation overall.

2.6Adapting to Alternative Budget Scenarios

The program recommendations are built considering the baseline budget scenario for DOE. This scenario assumes budget levels for HEP for fiscal years 2023 through 2027 that are specified in the CHIPS and Science Act of 2022. The baseline budget scenario then increases by 3% per year from fiscal year 2028 through 2033. We assume 3% inflation throughout our exercise, so it provides an initial increase over five years followed by an essentially flat budget in later years. In this scenario, hard choices were required as described in section 8.2. The recommended program is well-balanced and forward-looking, enabling scientific breakthroughs and maintaining scientific and technological leadership.

Two other scenarios were considered by the panel. Figure 2 summarizes the projects recommended under all three scenarios.

2.6.1  –Less Favorable Budget Scenario

We are charged to discuss a less favorable budget scenario that forces us to make more drastic and challenging choices. This scenario assumes budget increases of 2% per year during fiscal years 2024 to 2033 for DOE HEP, which is an erosion against an assumed 3% annual inflation rate. Under this scenario, some interesting scientific opportunities are still achievable, but scientific progress is significantly slowed.

In this scenario, we would aim for a program that covers most areas of particle physics for the next 10 years, maintaining continuity and exploiting the ongoing projects in Recommendation 1 as our highest priority. The agencies should launch the same major initiatives as outlined in Recommendation 2, some of them with significantly reduced scope:

1. CMB-S4 without reduction in scope.
2. DUNE Third Far Detector (FD3), but defer ACE-MIRT and the More Capable Near Detector (MCND).
3. Contribution to an off-shore Higgs factory delayed and at a reduced level.
4. Reduced participation in an off-shore G3 dark matter experiment and no SURF expansion.
5. IceCube-Gen2 without reduction in scope.

The rationale for this prioritization is given in section 8.3. Recommendations 3 and 4 are crucial for maintaining the health and balance of the field. While these recommendations still apply, they receive reduced support in scenarios between the baseline and less favorable conditions. Reductions to all items in these two recommendations should be proportionate. Research must be supported at least at the current level. Recommendation 5 is deemed a high priority and is supported in all scenarios. Recommendation 6 applies in all scenarios.

This less favorable scenario will lead to a loss of US leadership in many areas, especially the science of the G3 dark matter experiment, and will damage our reputation as a reliable international host for DUNE and as a partner for a Higgs factory. We still make investments in the future, but at a significantly reduced level for small-scale experiments, including ASTAE, theory, computing, instrumentation, and collider R&D. In this scenario, it would be increasingly difficult to maintain US competitiveness as an international partner in accelerator technology. See section 8.3 for more details.

2.6.2  –More Favorable Budget Scenario

In a budget outlook more favorable than the baseline budget scenario, we urge the funding agencies to support additional scientific opportunities. Even a small increase in the overall budget enables a large return on the investment, serving as a catalyst to accelerate scientific discovery and to unlock new pathways of inquiry. The opportunities include R&D, small projects, and the construction of advanced detectors for flagship projects in the US. They are listed below in four categories from small to large in budget size:

1. R&D
   1. Increase investment in detector R&D targeted toward future collider concepts for a Higgs factory and 10 TeV pCM collider in order to accelerate US leadership in this area.
   2. Pursue an expanded DOE AS&T initiative to develop foundational technologies for particle physics that can benefit applications across science, medicine, security, and industry.
   3. Pursue broad accelerator science and technology development at both DOE and NSF, including partnerships modeled on the plasma science partnership.
2. Small Projects
   Expand the portfolio of agile experiments to pursue new science, enable discovery across the portfolio of particle physics, and provide significant training and leadership opportunities for early career scientists.
3. Medium Projects
   1. Initiate construction of Spec-S5 as the world-leading study of cosmic evolution, with applications to neutrinos and dark matter, once its design matures.
   2. Initiate construction of an advanced fourth far detector (FD4) for DUNE that will expand its neutrino oscillation physics and broaden its science program.
   3. Initiate construction of a second G3 dark matter experiment to maximize discovery potential when combined with the first one.
4. Large Projects
   Evolve the infrastructure of the Fermilab accelerator complex to support a future 10 TeV pCM collider as a global facility. A positive review of the design by a targeted panel may expedite its execution (Recommendation 6).

Figure 1  –  Program and Timeline in Baseline Scenario (B)

Approximate timeline of the recommended program within the baseline scenario. Projects in each category are in chronological order. For IceCube-Gen2 and CTA, we do not have information on budgetary constraints and hence timelines are only technically limited. The primary/secondary driver designation reflects the panel’s understanding of a project’s focus, not the relative strength of the science cases. Projects that share a driver, whether primary or secondary, generally address that driver in different and complementary ways.

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Science Experiments

Advancing Science and Technology through Agile Experiments

Science Enablers

Increase in Research and Development

Figure 2  –  Construction in Various Budget Scenarios

Medium and large-scale US investments in new construction projects for possible budget scenarios. The projects are ordered in three budget brackets according to the number of “N” entries and then by approximate budget sizes. For the off-shore Higgs factory, test facilities & demonstrators, see Recommendation 6. See the caption of Figure 1 concerning the science drivers, and Section 8 for the rationale behind these choices.

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