BQ1: What are ultimate laws of nature?

Duke's nuclear and particle physics programs, along with a new program in cosmology, explore some of the most compelling mysteries in contemporary physics. These include the essence of dark matter and dark energy, the possibility of hidden symmetries of nature and the mechanisms that break them, and the fundamental nature of the vacuum that ultimately drove the evolution of the early universe. We exploit strong connections to major research facilities on four continents to study exotic forms of nuclear matter, fundamental symmetries of nature, characteristics of the Higgs boson, neutrino interactions, and more. New opportunities in experimental cosmology will strengthen existing efforts by providing complementary avenues for exploration. Finally, experimental and theoretical investigations of the strong nuclear force are providing further insights into the fundamental laws of nature. This broad range of programs at Duke both complement and enrich each other in our quest to understand the ultimate laws of Nature.

The visible world surrounding us is made up of molecules and atoms which in turn consist of protons, neutrons and electrons. Today we know that neutrons and protons are actually composite particles and that the basic building blocks of matter are quarks and gluons interacting through the known basic forces of nature. The general theory that describes all elementary particles that we know of as well as their interactions is known as the Standard Model of particle physics. Over the past 20 years, discoveries of the top quark (1995), the tau neutrino (2000), and more recently the Higgs boson (2012), have impressively confirmed the validity of the Standard Model. However, many unsolved questions remain. For example, the nearly-perfect symmetry between matter and antimatter in the Standard Model implies neither should have survived a second after the Big Bang, yet we live in a Universe that is dominated by matter. And while the Higgs particle provides mass for elementary particles, it does not explain the mass of the proton, neutron, or most composite particles. As noted earlier, we have only vague clues about the nature of dark energy or dark matter, but we know they are much more widespread than the atoms and molecules we understand.

An overriding goal of modern particle physics, nuclear physics, and cosmology is to provide explanations for these puzzles. Remarkably, there are close connections between these seemingly disjoint fields of research. For example, collisions of heavy nuclei at the Large Hadron Collider (LHC) recreate conditions that prevailed a few microseconds after the Big Bang and in turn cosmological observations provide hints about yet undiscovered forms of matter and energy.

One strength of Duke physics is the Triangle Universities Nuclear Laboratory (TUNL), a U.S. Department of Energy (DOE) Center of Excellence that focuses on low-energy nuclear physics research, with a portfolio that includes study of the strong nuclear force, nuclear structure, nuclear astrophysics, fundamental symmetries, and neutrino physics. The latter two areas are driven by the search for new physics beyond the Standard Model. TUNL operates the High-Intensity Gamma-Ray Source (HIGS), which is the most intense laser-Compton gamma-ray source in the world. TUNL provides opportunities for students to gain hands-on experience within a wide range of experimental nuclear science. In addition – and complementary to local research at TUNL  – a significant number of faculty and students participate in high profile international scientific enterprises at facilities such as the Large Hadron Collider (Geneva), the Kamioka Observatory (Japan), and a host of experiments at U.S. National Laboratories such as Brookhaven National Lab, Jefferson Lab, Fermilab and Oak Ridge National Lab.

Over the last decade the department has made strategic faculty appointments in nuclear and particle physics, and has established collaborations with faculty working in related areas in mathematics. We have made significant contributions to major international projects. For example, we have contributed to the discovery of the Higgs particle, the top quark, and the Quark-Gluon Plasma; performed the world's best measurements of the mass of the W boson, which correctly predicted the mass of the Higgs particle prior to its discovery; played major roles in the measurement of neutrino oscillation parameters; played leadership roles in the discovery of coherent elastic neutrino-nucleus scattering; discovered a new mechanism of fermion mass generation that may be of interest for physics beyond the standard model; played leadership roles in the study of the nucleon structure such as the proton charge radius, electromagnetic polarizabilities, spin and the three-dimensional imaging of the nucleon; developed effective field theories of QCD and weak interactions, made predictions of properties of recently discovered exotic hadrons, such as heavy meson molecules and doubly charm baryons; and played leadership roles in multiple international experiments.

Many of these programs are continuing or moving into new stages. Examples include the upgrade of the Large Hadron Collider (LHC); an observational cosmology program with the Large Synoptic Survey Telescope (LSST); the search for CP violation in neutrinos in new long-baseline experiments; the expansion of the COHERENT neutrino program at the Spallation Neutron Source; creation of a unique calibration facility for neutrino and dark matter experiments at TUNL; the search for a neutron electric dipole moment, which is a test of CP violation; new searches for neutrinoless double beta decay as a test for lepton-number violation; experiments to unravel the mysteries of the nucleon spin and mass, and to probe new physics at TeV scales using high-energy electron beams; and a new generation of experiments to probe matter at extreme conditions.

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