### Search for the chiral magnetic effect via charge-dependent azimuthal correlations relative to spectator and participant planes in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV

The chiral magnetic effect (CME) refers to charge separation along a strong magnetic field due to imbalanced chirality of quarks in local parity and charge-parity violating domains in quantum chromodynamics. The experimental measurement of the charge separation is made difficult by the presence of a major background from elliptic azimuthal anisotropy. This background and the CME signal have different sensitivities to the spectator and participant planes, and could thus be determined by measurements with respect to these planes. We report such measurements in Au+Au collisions at a nucleon-nucleon center-of-mass energy of 200 GeV at the Relativistic Heavy-Ion Collider. It is found that the charge separation, with the flow background removed, is consistent with zero in peripheral (large impact parameter) collisions. Some indication of finite CME signals is seen with a significance of 1--3 standard deviations in mid-central (intermediate impact parameter) collisions. Significant residual background effects may, however, still be present.

### Level Densities from 0-30 MeV

Photon strength, $f(E_{\gamma})$, measured in photonuclear reactions, is the product of the average level density per MeV, $\rho(E_x)$, and the average reduced level width, $\Gamma_{\gamma}/E_{\gamma}^3$ for levels populated primarily by E1 transitions at an excitation energy $E_x=E_{\gamma}$. It can be calculated with the Brink-Axel (BA) formulation modified to include contributions from the Giant Dipole Resonance (GDR) and higher lying resonances. Level densities and reduced widths have been calculated for 17 nuclei with atomic numbers between Z=14-92. Level densities below the GDR energy were calculated with the CT-JPI model and combined with the BA photon strength to determine the associated reduced widths. The reduced widths varied exponentially with level energy and could be extrapolated up to higher energies. The extrapolated widths were then combined with the BA photon strength to determine the level densities at higher energies. The level densities are found to increase exponentially at low energies, peak near the GDR energy due to the appearance of new states at the $2\hbar\omega$ shell closure, and continue to increase less rapidly up to at least 30 MeV. The average level densities have been compared with the Fermi Gas Level Density (FGLD), Back-Shifted Fermi Gas (BSFG), and Hartree-Fock-Bogoliubov (HFB) models. Good agreement is found with the nearly identical FGLD and BDFG models, while the HFB models gives substantially lower level densities. A universal set of FGLD model parameters were determined as a function of mass and temperature that are applicable to all nuclei.

### Dispersion relation analysis of the radiative corrections to $g_A$ in the neutron $β$-decay

We present the first and complete dispersion relation analysis of the inner radiative corrections to the axial coupling constant $g_A$ in the neutron $\beta$-decay. Using experimental inputs from the elastic form factors and the spin-dependent structure function $g_1$, we determine the contribution from the $\gamma W$-box diagram to a precision better than $10^{-4}$. Our calculation indicates that the inner radiative corrections to the Fermi and the Gamow-Teller matrix element in the neutron $\beta$-decay are almost identical, i.e. the ratio $\lambda=g_A/g_V$ is almost unrenormalized. With this result, we predict the bare axial coupling constant to be {$\mathring{g}_A=-1.2754(13)_\mathrm{exp}(2)_\mathrm{RC}$} based on the PDG average $\lambda=-1.2756(13)$

### Investigations of the linear and non-linear flow harmonics using the A Multi-Phase Transport model

The higher-order flow harmonics of the Fourier expansion for the azimuthal distributions of particles are anticipated to be produced by a non-linear response from the lower-order anisotropies, in addition to a linear response from the same-order anisotropies. Detailed study of these higher-order flow harmonics and their non-linear and linear components can be used to constrain the heavy-ion collisions' initial conditions and the system transport properties. The multiparticle azimuthal correlation technique is used within the A Multi-Phase Transport (AMPT) model framework to study the linear and non-linear response to the higher-order flow harmonics, the non-linear response coefficients, and the correlations between different order flow symmetry planes for Au--Au collisions at 200~GeV. The current study shows that the AMPT model can to a good degree describe the experimental measurements and also suggest that conducting detailed measurements over a broad range of system size and beam-energy can serve as an additional constraint for accurate $\eta / \textit{s}$ extraction.

### Characterization of stilbene-d12 for neutron spectroscopy without time of flight

We have experimentally characterized the light-output response of a deuterated trans-stilbene (stilbene-d12) crystal to quasi-monoenergetic neutrons in the 0.8 to 4.4 MeV energy range. These data allowed us to perform neutron spectroscopy measurements of a DT 14.1 MeV source and a PuBe-239 source by unfolding the impinging neutron spectrum from the measured light-output response. The stilbene-d12 outperforms a H1-stilbene of similar size when comparing the shape of the unfolded spectra and the reference ones. These results confirm the viability of non-hygroscopic stilbene-d12 crystal for direct neutron spectroscopy without need for time-of-flight measurements. This capability makes stilbene-d12 a well suited detector for fast-neutron spectroscopy in many applications including nuclear reaction studies, radiation protection, nuclear non-proliferation, and space travel.

### RTP Pockels Cell with Nanometer-Level Position Control

MOLLER is a future experiment designed to measure parity violation in Moller scattering to extremely high precision. MOLLER will measure the right-left scattering differential cross-section parity-violating asymmetry APV , in the elastic scattering of polarized electrons off an unpolarized LH2 target to extreme ppb precision. To make this measurement, the polarized electron source, generated with a circularly polarized laser beam, must have the ability to switch quickly between right and left helicity polarization states. The polarized source must also maintain minimal right-left helicity correlated beam asymmetries, including energy changes, position changes, intensity changes, or spot-size changes. These requirements can be met with appropriate choice and design of the Pockels cell used to generate the circularly polarized light. Rubidium Titanyl Phosphate (RTP) has been used in recent years for ultra-fast Pockels cell switches due to its lack of piezo-electric resonances at frequencies up to several hundred MHz. However, crystal non-uniformity in this material leads to poorer extinction ratios than in commonly used KD*P Pockels cells when used in hald-wave configuration. It leads to voltage dependent beam steering when used in quarter-wave configuration. Here we present an innovative RTP Pockels cell design which uses electric field gradients to counteract crystal non-uniformities and control beam steering down to the nm-level. We demonstrate this RTP Pockels cell design is capable of producing precisely controlled polarized electron beam at Jefferson Laboratory, a national accelerator facility, for current experiments, including the recent PREX II measurement, as well as the future MOLLER experiment.