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Summary
This report provides a long-term assessment of and outlook for nuclear physics.
The first phase of the report articulates the scientific rationale and objectives of the
field, while the second phase provides a global context for the field and its long-
term priorities and proposes a framework for progress through 2020 and beyond.
The full statement of task for the committee is given in Appendix A.
Nuclear physics today is a diverse field, encompassing research that spans
dimensions from a tiny fraction of the volume of the individual particles (neutrons
and protons) in the atomic nucleus to the enormous scales of astrophysical objects
in the cosmos. Its research objectives include the desire not only to better under-
stand the nature of matter interacting at the nuclear level, but also to describe the
nature of neutrinos and the state of the universe that existed at the big bang and
that can now be studied in the most advanced colliding-beam accelerators, where
strong forces are the dominant interactions.
The impact of nuclear physics extends well beyond furthering our scientific
knowledge of the nucleus and nuclear properties. Nuclear science and its tech-
niques, instruments, and tools are widely used to address major societal prob-
lems in medicine, border protection, national security, nonproliferation, nuclear
forensics, energy technology, and climate research. Further, the tools developed
by nuclear physicists often have important applications to other basic sciences—
medicine, computational science, and materials research, among others—while
its discoveries impact astrophysics, particle physics, and cosmology, and help to
describe the physics of complex systems that arise in many fields.
In the second phase of the study, developing a framework for progress though
1
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2 Nuclear Physics
2020 and beyond, the committee carefully considered the balance between univer-
sities and government facilities in terms of research and workforce development
and the role of international collaboration in leveraging future investments. The
committee sought to address the means by which the balance between the various
objectives of nuclear physics could be sustainable in the long term.
In summary, the committee finds that nuclear science in the United States is a
vital enterprise that provides a steady stream of discoveries about the fundamental
nature of subatomic matter that is enabling a new understanding of our world.
The scientific results and technical developments of nuclear physics are also being
used to enhance U.S. competition in innovation and economic growth and are
having a tremendous interdisciplinary impact on other fields, such as astrophysics,
biomedical physics, condensed matter physics, and fundamental particle physics.
The application of this new knowledge is contributing in a fundamental way to the
health and welfare of the nation. The committee’s findings and recommendations
are summarized below.
FOLLOWING THROUGH WITH THE LONG-RANGE PLAN
The nuclear physics program in the United States has been especially well
managed. Among the activities engaged in by the nuclear physics community is a
recurring long-range planning process conducted under the auspices of the Nuclear
Science Advisory Committee (NSAC) of the Department of Energy (DOE) and the
National Science Foundation. This process includes a strong bottom-up empha-
sis and produces reports every 5 to 7 years that provide guidance to the funding
agencies supporting the field. The choices made in NSAC’s latest long-range plan,
the Long Range Plan of 2007, have helped to move the field along and set it on its
present course, and the scientific opportunities that process recognized as impor-
tant will enable significant discoveries over the coming decade.
Exploitation of Current Opportunities
Carrying through with the investments recommended in the 2007 Long Range
Plan is the consequence of careful planning and sometimes difficult choices. The
tradition of community engagement in the planning process has served the U.S.
nuclear physics community well. A number of small and a few sizable resources
have been developed since 2007 that are providing new opportunities to develop
nuclear physics.
Finding: By capitalizing on strategic investments, including the ongoing
upgrade of the continuous electron beam accelerator facility (CEBAF) at
the Thomas Jefferson National Accelerator Facility and the recently com-
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Summary 3
pleted upgrade of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven
National Laboratory, as well as other upgrades to the research infrastructure,
nuclear physicists will confront new opportunities to make fundamental
discoveries and lay the groundwork for new applications.
Conclusion: Exploiting strategic investments should be an essential compo-
nent of the U.S. nuclear science program in the coming decade.
The Facility for Rare Isotope Beams
After years of development and hard work involving a large segment of the U.S.
nuclear physics community and the DOE, a major, world-leading new accelerator
is being constructed in the United States.
Finding: The Facility for Rare Isotope Beams is a major new strategic invest-
ment in nuclear science. It will have unique capabilities and will offer oppor-
tunities to answer fundamental questions about the inner workings of the
atomic nucleus, the formation of the elements in our universe, and the
evolution of the cosmos.
Recommendation: The Department of Energy’s Office of Science, in conjunc-
tion with the state of Michigan and Michigan State University, should work
toward the timely completion of the Facility for Rare Isotope Beams and the
initiation of its physics program.
Underground Science in the United States
In recent decades the U.S. program in nuclear science has enabled important
experimental discoveries such as the nature of neutrinos and the fundamental reac-
tions fueling stars, often with the aid of carefully designed experiments conducted
underground, where the backgrounds from cosmic radiation are especially low.
The area of underground experimentation is a growing international enterprise
in which U.S. nuclear scientists often play a key role.
Recommendation: The Department of Energy, the National Science Foun-
dation, and, where appropriate, other funding agencies should develop and
implement a targeted program of underground science, including important
experiments on whether neutrinos differ from antineutrinos, on the nature
of dark matter, and on nuclear reactions of astrophysical importance. Such a
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4 Nuclear Physics
program would be substantially enabled by the realization of a deep under-
ground laboratory in the United States.
BUILDING THE FOUNDATION FOR THE FUTURE
Nuclear physics in the United States is a diverse enterprise requiring the coop-
eration of many institutions. The subject of nuclear physics has evolved signifi-
cantly since its beginnings in the early twentieth century. To continue to be healthy
the enterprise will require that attention be paid to elements essential to the vitality
of the field.
Nuclear Physics at Universities
America’s world-renowned universities are the discovery engines of the Ameri-
can scientific enterprise and are where the bright young minds of the next gen-
eration are recruited and trained. As with other sciences, it is imperative that
the critical value-added role of universities and university research facilities in
nuclear physics be sustained. Unfortunately, there has been a dramatic decrease
in the number of university facilities dedicated to nuclear science research in the
past decade, including fewer small accelerator facilities at universities as well as a
reduction in technical infrastructure support for university-based research more
generally. These developments could endanger U.S. nuclear science leadership in
the medium and long term.
Finding: The dual role of universities—education and research—is impor-
tant in all aspects of nuclear physics, including the operation of small,
medium, and large facilities, as well as in the design and execution of large
experiments at the national research laboratories. The vitality and sustain-
ability of the U.S. nuclear physics program depend in an essential way on
the intellectual environment and the workforce provided symbiotically by
universities and the national laboratories. The fraction of the nuclear sci-
ence budget reserved for facilities operations cannot continue to grow at
the expense of the resources available to support research without serious
damage to the overall nuclear science program.
Conclusion: In order to ensure the long-term health of the field, it is critical
to establish and maintain a balance between funding of operations at major
facilities and the needs of university-based programs.
A number of specific recommendations for programs to enhance the universi-
ties are discussed in the report. Many of these suggestions are not costly but could
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Summary 5
have significant impact. An example of a modest program that would enhance the
recruitment of early career nuclear scientists and could be provided at relatively
low cost is articulated in the following recommendation:
Recommendation: The Department of Energy and the National Science
Foundation should create and fund two national competitions: one a fellow-
ship program for graduate students that would help recruit the best among
the next generation into nuclear science and the other a fellowship program
for postdoctoral researchers to provide the best young nuclear scientists with
support, independence, and visibility.
Nuclear Physics and Exascale Computing
Enormous advances in computing power are taking place, and computers at
the exascale are expected in the near future. This new capability is a game-changing
event that will clearly impact many areas of science and engineering and will enable
breakthroughs in key areas of nuclear physics. These include providing new under-
standings of, and predictive capabilities for, nuclear forces, nuclear structure and
reaction dynamics, hadronic structure, phase transitions, matter under extreme
conditions, stellar evolution and explosions, and accelerator science. It is essential
for the future health of nuclear physics that there be a clear strategy for advancing
computing capabilities in nuclear physics.
Recommendation: A plan should be developed within the theoretical com-
munity and enabled by the appropriate sponsors that permits forefront
computing resources to be exploited by nuclear science researchers and
establishes the infrastructure and collaborations needed to take advantage
of exascale capabilities as they become available.
Striving to Be Competitive and Innovative
Progress in science has always benefited from cooperation and from competi-
tion. For U.S. nuclear physics to flourish it must be competitive on the international
scene, winning its share of the races to new discoveries and innovations. Providing
a culture of innovation along with an understanding and acceptance of the appro-
priate associated risk must be the goal of the scientific research enterprise. The
committee sees one particular aspect of science management in the United States
where increased flexibility would have large and immediate benefits.
Finding: The range of projects in nuclear physics is broad, and sophisticated
new tools and protocols have been developed for successful management of
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6 Nuclear Physics
the largest of them. At the smaller end of the scale, nimbleness is essential
if the United States is to remain competitive and innovative on the rapidly
expanding international nuclear physics scene.
Recommendation: The sponsoring agencies should develop streamlined and
flexible procedures that are tailored for initiating and managing smaller-
scale nuclear science projects.
Prospects for an Electron-Ion Collider
Accelerators remain one of the key tools of nuclear physics, other fields of basic
and applied research, and societal applications such as medicine. Modifying exist-
ing accelerators to incorporate new capabilities can be an effective way to advance
the frontiers of the science. Of course it is the importance of the physics and of
the potential discoveries enabled by the new capability that must justify the new
investment. There is an initiative developing aimed at a new accelerator capabil-
ity in the United States. Fortunately, the U.S. nuclear physics community has the
mechanisms in place to properly evaluate this initiative. Currently there are sug-
gestions that upgrades to either RHIC or CEBAF would enable the new capability.
Finding: An upgrade to an existing accelerator facility that enables the col-
liding of nuclei and electrons at forefront energies would be unique for
studying new aspects of quantum chromodynamics. In particular, such an
upgrade would yield new information on the role of gluons in protons and
nuclei. An electron-ion collider is currently under scrutiny as a possible
future facility.
Recommendation: Investment in accelerator and detector research and
development for an electron-ion collider should continue. The science
opportunities and the requirements for such a facility should be carefully
evaluated in the next Nuclear Science Long-Range Plan.
Nuclear physics is a discovery-driven enterprise motivated by the desire to
understand the fundamental mechanisms that account for the behavior of matter.
Nevertheless, for its first hundred years, the new knowledge of the nuclear world
has also directly benefited society through many innovative applications. As we
move into the second century of nuclear physics the recommendations above
will ensure a thriving and healthy field that continues to benefit society from new
applications. Recently the stewardship of the nation’s isotope program has been
placed in the DOE Office of Nuclear Physics. This reorganization is appropriate and
provides a fresh opportunity for the nuclear physics community to serve society by
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Summary 7
applying its sciences to the most important of today’s problems in energy, health,
and the environment. The isotopes program under the auspices of that office is
expected to benefit rapidly from new innovations and developments. NSAC and
its subcommittees have provided insightful reports that constitute a roadmap for
the revitalized isotopes program. This advice is timely, coming when important
decisions must be made. The committee sees these developments as an excellent
example of how society’s investments in nuclear physics can help resolve difficult
challenges that face the nation.
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