The gluon distribution function grows with lower and lower momentum fraction very fast. As the total scattering cross section is bound by quantum mechanics, the raise of the gluon density has to be tamed, which is explained by gluon recombination under the color glass condensate (CGC) framework. A definitive discovery of nonlinear effects in QCD and as such the saturation regime would significantly improve our understanding of the nucleon structure and of nuclear interactions at high energy. Two particle azimuthal correlation is one of the most direct and sensitive channels to access the underlying nonlinear gluon dynamics. In this talk, we will present the recent results of forward di-hadron correlations measured at RHIC, together with the signatures of gluon saturation predicted by CGC. New opportunities for measurements with the STAR forward upgrade and future EIC to study the nonlinear effects in QCD will also be discussed.

Precision nuclear physics experiments have long played an important role in searches for physics Beyond the Standard Model (BSM). The traditional particle detection technologies of many of these experiments, semiconductor and scintillation detectors, face fundamental performance limitations that greatly restrict the sensitivity achievable. A new detector paradigm for charged particle detection has the potential to dramatically improve sensitivity in BSM searches. We are working toward this goal by adapting Thermal Kinetic Inductance Detectors (TKIDs) for external charged particle detection. These cryogenic detectors, used in X-ray and gamma spectroscopy as well as dark matter searches, have shown photon energy resolutions on the order of tens of eV and can be multiplexed to create large area detectors. However, TKIDs have not yet been developed for non-embedded charged particle detection. We have designed a Charged Particle TKID (CP-TKID) prototype to optimized for the  detection of the neutron beta decay electron.  In this seminar, I will discuss the development of our initial prototype design and our efforts to characterize its response.

The era of multi-messenger astronomy has unlocked new probes of physics, allowing natural experiments to be carried out on matter at extremes unattainable using terrestrial experiments. Neutron stars, and their mergers, are natural sites to seek probes of nuclear physics, as these compact objects contain the densest matter in the universe. I will discuss multi-messenger astrophysical observables from the point of view of nuclear physics constraints. In particular I will highlight resonant shattering flares (RSFs), which can provide strong constraints on the nuclear symmetry energy parameters of nuclear matter, comparable to those obtained by terrestrial nuclear experiments, such as those found in dipole polarizability and neutron skin thickness measurements.

Pulsar Timing Arrays (PTAs) are exceptionally sensitive detectors in the nHz to uHz frequency window. While their primary purpose is to detect the stochastic gravitational wave background, they can also be used to search for new physics. Ultralight dark matter (ULDM), with mass between 10^{-23} eV and 10^{-20} eV, can generate a variety of different signals within the sensitivity window of PTAs. I will give an overview of the effects which have been studied previously, and then discuss new signals generated by variations in the fundamental constants. There are two main avenues to induce a PTA signal via variations in fundamental constants: changing the pulsar spin rate, e.g., by fluctutating particle masses, or shifting the reference clock. Using the standard analysis pipeline of the PTA collaborations, PTAs are shown to be competitive with atomic clock and torsion balance constraints for many ULDM models, especially those varying the electron and muon mass. Lastly, I will discuss how future PTAs may improve the sensitivity, and unique correlations in the signals which may further distinguish them from background.

LUX-ZEPLIN (LZ) is a direct detection dark matter experiment currently being operated at the Sanford Underground Research Facility (SURF) in Lead, South Dakota. The experiment utilizes 7 tonnes of liquid xenon in a dual phase time projection chamber to look for dark matter in the form of Weakly Interacting Massive Particles (WIMPs), as well as a broad range of other novel physics signals. LZ has recently released its first WIMP search results with an exposure of 60 live days using a fiducial mass of 5.5 tonnes. These results set new limits on spin-independent WIMP-nucleon cross-sections for WIMP masses above 9 GeV/c^2. This talk will give an overview of the LZ detector, a description of the first results, and a brief look at the science program that is now accessible with the LZ experiment.

Abstract: Rapid advancement in neutron-star observations allows unprecedented empirical access to cold, ultra-dense QCD matter, complementing collider experiments. The combination of these observations with theoretical calculations reveals previously inaccessible features of the equation of state and the phase diagram of QCD. In this talk, I demonstrate how perturbative-QCD calculations at asymptotically high densities robustly constrain the equation of state at neutron-star densities using a new method solely based on causality and stability. I confront these calculations with neutron-star observations in a Gaussian-process-based Bayesian framework and demonstrate that the perturbative-QCD calculations offer significant and nontrivial information, going beyond that which is obtainable from current observations. The main effect of the QCD input is to soften the equation of state at high densities, supporting the hypothesis that most massive neutron stars have quark matter cores.

Abstract: Axions are hypothetical particles that may explain the observed dark matter (DM) density and the non-observation of a neutron electric dipole moment. An increasing number of axion laboratory searches are underway worldwide, but these efforts are made difficult by the fact that the axion mass is largely unconstrained. If the axion is generated after inflation there is a unique mass that gives rise to the observed DM abundance; due to nonlinearities and topological defects known as axion strings, computing this mass accurately has been a challenge for four decades. Recent works, making use of large static lattice simulations, have led to largely disparate predictions for the axion mass, spanning the range from 25 microelectronvolts to over 500 microelectronvolts. In this talk, I will show that adaptive mesh refinement (AMR) simulations are better suited for axion cosmology than the previously-used static lattice simulations. Using dedicated AMR simulations we obtain an over three orders of magnitude leap in dynamic range and provide evidence that axion strings radiate their energy with a scale-invariant spectrum, to within ∼5% precision, leading to a mass prediction in the range (40,180) microelectronvolts. I will also comment on future development.

Abstract: Understanding the internal structure and dynamics of protons and neutrons, the complex many-body systems consisting of strongly-interacting quarks and gluons is at the core of exploring the visible matter universe. Gluons, which serve as mediator bosons of the strong interaction, play a key role in the nucleon’s mass and spin structures. In contrast, understanding of the gluon distributions and their role in hadron structures remains one of the most challenging but fundamental issues in nuclear and particle physics. In this talk, I will present lattice QCD calculations of matrix elements of bilocal operators composed of two gluon fields that can be used to determine the unpolarized and polarized gluon distributions. In particular, I will focus on the first lattice QCD determination of the gluon helicity parton distribution function with numerical evidence toward disfavoring negative gluon polarization in the nucleon.

Abstract: Next generation neutrino oscillation experiments are poised to provide answers to key questions about the nature of the neutrino. The axial form factor is a vital ingredient in the nucleon amplitudes used to predict quasielastic scattering, a primary signal measurement process for flagship neutrino oscillation experiments. The uncertainty on this form factor is vastly underestimated by the typical dipole parameterization and a model independent determination is not well constrained by elementary target data. To fulfill this experimental need, Lattice QCD can be used to compute, from first principles, the interaction of a nucleon with a weak current in the absence of a nuclear medium. Results from LQCD calculations will significantly improve constraints on the uncertainty of nucleon amplitudes and allow for a theoretically robust, systematically improvable error budget. Recent calculations of the nucleon axial vector coupling have demonstrated that sub-percent precision is within reach of current generation calculations. These LQCD results will permit factorization of uncertainties originating from nucleon and nuclear sources in order to better isolate the source of discrepancies with experimental data. In this talk, I will summarize the current state of Lattice QCD calculations of the nucleon quasielastic axial form factor and the implications of those calculations for long baseline neutrino oscillation experiments. I will show some preliminary results for LQCD calculations of the axial form factor and outline the path toward achieving a result with a complete error budget.