Since their discovery in 1932 by Chadwick, neutrons have been a critical probe in physics and sciences in general. It was Fermi who first realized that neutrons which are traveling slow enough would be totally reflected by a material surface. These slow moving neutrons can be trapped in material bottles and are called ultracold neutrons (UCN). Experiments performed with UCN take advantage of their slow velocities and long trapping time. Currently, UCN hold the world leading sensitivity of the neutron lifetime, a parameter critical to our understanding of the Weak force and Big Bang Nucleosynthesis. UCN are competitive in measuring decay correlations of the neutron and constraining tensor interactions. They are also used to search for Dark Matter and other exotic particles and interactions. Furthermore, UCN are responsible for the world limit on the sensitivity of the permanent neutron electric dipole moment (nEDM), a T and P symmetry violating observable. By the CPT theorem EDMs also violate CP. The Sakharov conditions require a new CP violating interaction for the observed dominance of matter over anti-matter. Thus, a new source of CP violation is expected, and is perhaps mediated by particles beyond the Standard Model. The present limit, 3×10⁻²⁶ e cm, already has a reach for new CP violating physics generically at the TeV, and up to the PeV scale in some specific supersymmetric models. Future experiments plan to increase the sensitivity by up to two orders of magnitude. The goal sensitivities of these experiments are challenging targets, and require fascinating technological achievements for their success.

A new generation of experiments taking advantage of the upgraded electron beam facility at Jefferson Laboratory aims to explore the three-dimensional partonic structure of the proton with unprecedented precision. One of those is the CEBAF Large Acceptance Spectrometer (CLAS12), where semi-inclusive deep-inelastic scattering (SIDIS) events can be detected over a wide kinematic range. In SIDIS events, the incoming electron scatters off a quark in the proton which subsequently hadronizes into a detected final state. The quantum numbers of the hadronic final state are correlated to the quantum numbers of the parent quark and can therefore be used to extract information about the partonic content of the nucleon. Arguably, most information about parton distribution functions has been extracted from final states, where a single, spinless hadron such as a pion or kaon has been detected. Using more complex final states that can carry angular momentum quantum numbers, such as hadron-pairs or polarized hyperons, allows access to spin orbit correlations the hadronization process and a more targeted access to complex dynamics inside the proton. This talk will discuss di-hadron channels to extract parton distributions from SIDIS data taken at CLAS12 as well as the measurement of the corresponding fragmentation functions (FFs). Fragmentation functions describe the formation of hadrons from quarks and can be measured in e+e- annihilation. Here measurements of di-hadron and polarized lambda FFs at the B-factory Belle will be discussed

The only practical way to experimentally verify the nature of neutrinos is via the observation of neutrinoless double-beta decay. EXO-200, the first current generation neutrinoless double-beta decay searches to begin taking data, wrapped up data taking at the end of last year. While the final results to be presented by EXO-200 will continue to advance the field, EXO-200 has long since served its primary mission as a prototype for a tonne scale next generation search: nEXO. I intend to impress you with the success of EXO-200 and build on this to convince you that nEXO has every chance of observing neutrinoless double-beta decay while being the most likely to achieve the best sensitivity of proposed next generation searches.

Measurements of the neutron electric dipole moment (nEDM) are currently of considerable experimental interest due to their high probability of being able to discover new physics within and beyond the Standard Model in the next generation of experiments.   The current upper limit of the nEDM of 3e-26 ecm and the next generation of experiment plan to improve on this by making measurements that are up by up to two orders of magnitude more precise.  One of these next generation experiments is the SNS nEDM experiment which will run at the Spallation Neutron Source in Tennessee.

The SNS nEDM experiment plans to calculate the nEDM by measuring the change in the difference of the precession frequencies of polarized neutrons and helium-3 that coexist together in a uniform magnetic field when a strong electric field is reversed.  To maintain the helium-3 polarization as it is transported from the beam source to the measurement cell a complex series of magnets are required.  I will discuss the design process of the magnets that starts with FEA simulation of the winding and the fields in Comsol Multiphysics, the creation of a CAD model from the simulation and how 3D printing can be used to prototype the magnets, as well as built the final magnet design.

What would happen if we were to compress the sun to the size of Lexington and then add a bit more mass? Would this object expand, contract, or stay the same size? Nuclear astrophysics research aims to answer this and other seemingly simple questions. This talk will focus on the nuclear physics of the outer layers of accreting neutron stars. I will show how properties of atomic nuclei impact dense matter constraints obtained for these objects. I will also discuss recent experimental work dedicated toward constraining properties of key nuclei.

The Muon g-2 experiment (E989) at Fermilab is aiming at measuring the anomalous magnetic moment of the muon (aμ) at a precision of ∼140 ppb. aμ was measured at a precision of 540 part-per-billion (ppb) in the previous Muon g-2 experiment (E821), and its result deviated from the theoretical calculation by ∼3.7σ. This discrepancy is arguably the strongest existing hint for physics beyond the SM. The new experiment E989 will either confirm or resolve it. In this experiment, the muon anomalous precession angular frequency ωa and the magnetic field in which the muon precesses are measured. ωa is measured by detecting the decay positrons in 24 calorimeter stations, and the magnetic field is measured by Nuclear Magnetic Resonance (NMR) probes. In this seminar, I will give a detailed description of the high precision magnetic field measurement system and its analysis framework. The NMR frequency extraction methods and their implementation using GPU for fast online feedback will be highlighted. The overall performance of the magnetic field measurement system in Run1 and recent upgrades for Run2 will be discussed.

Host: Prof. Tim Gorringe

I will review the concept of a Lifshitz point, and its possible relevance to the phase diagram of QCD, especially in contrast to the standard paradigm of a critical endpoint. I will stress on how fluctuations dramatically alter the phase diagram, yielding a Lifshitz regime. Possible signatures in heavy ion collisions are discussed.

Host: Ivan Horvath

The CP violating effects observed thus far appear only in flavor-changing processes and in a manner consistent with the predictions of the Standard Model (SM). The observed baryon asymmetry of the universe suggests that new mechanisms of CP violation beyond the SM should appear. Most searches for new sources of CP violation focus on processes that break P and CP, whereas processes that would break C and CP are not well studied. The decay η →π+ π- π0 is an ideal process in which to search for C and CP violation. In this talk, I will analyze the C and CP violating patterns in the Dalitz plot distribution of η → π+ π- π0decay and discuss the implications of existing experiments.

Host: Susan Gardner