Particle Physics Project Prioritization Panel
The Particle Physics Project Prioritization Panel (P5) is a scientific advisory panel tasked with recommending plans for U.S. investment in particle physics research over the next ten years, on the basis of various funding scenarios. The P5 is a temporary subcommittee of the High Energy Physics Advisory Panel (HEPAP), which serves the Department of Energy's Office of Science and the National Science Foundation. , the panel was chaired by Steven Ritz of the University of California, Santa Cruz.

2014 Report 
In 2013, HEPAP was asked to convene a panel (the P5) to evaluate research priorities in the context of anticipated developments in the field globally in the next 20 years. Recommendations were to be made on the basis of three funding scenarios for high-energy physics:
 A constant funding level for the next three years followed by an annual 2% increase, relative to the FY2013 budget
 A constant funding level for the next three years followed by an annual 3% increase, relative to the proposed FY2014 budget
 An unconstrained budget

In May 2014, the first P5 report since 2008 was released. The 2014 report identified five "science drivers"—goals intended to inform funding priorities—drawn from a year-long discussion within the particle physics community. These science drivers are:
 Use of the Higgs boson as a tool for further inquiry
 Investigation of the physics of neutrino mass
 Investigation of the physics of dark matter
 Investigation of the physics of dark energy and cosmic inflation
 Exploration of new particles, interactions, and physics principles

Recommendations 
In pursuit of the five science drivers, the 2014 report identified three "high priority large category" projects meriting significant investment in the FY2014–2023 period, regardless of the broader funding situation: the High Luminosity Large Hadron Collider (a proposed upgrade to the Large Hadron Collider located at CERN in Europe); the International Linear Collider (a proposed electron-positron collider, likely hosted in Japan); and the Long Baseline Neutrino Facility (an expansion of the proposed Long Baseline Neutrino Experiment, to be constructed at Fermilab in Illinois and at the Homestake Mine in South Dakota).

In addition to these large projects, the report identified numerous smaller projects with potential for near-term return on investment, including the Mu2e experiment, second- and third-generation dark matter experiments, particle-physics components of the Large Synoptic Survey Telescope (LSST), cosmic microwave background experiments, and a number of small neutrino experiments.

The report made several recommendations for significant shifts in priority, namely:
 An increase in the proportion of the high-energy physics budget devoted to construction of new facilities, from 15% to 20%-25%
 An expansion in scope of the Long Baseline Neutrino Experiment to a major international collaboration, including redirection of resources from other R&D projects to the development of higher powered proton beams for the neutrino facility
 Increased funding for second-generation dark matter detection experiments
 Increased funding of cosmic microwave background (CMB) research

The panel stressed that the most conservative of the funding scenarios considered would endanger the ability of the U.S. to host a major particle physics project while maintaining the necessary supporting elements.