The QCD axion is one of the most compelling solutions of the strong CP problem. There are major current efforts into searching for ultralight axion dark matter, which is believed to be the only phenomenologically viable realization of the QCD axion. Visible axions with decay constants at or below the electroweak scale are believed to have been long excluded by laboratory searches. In this talk, I will revisit experimental constraints on QCD axions in the O(10 MeV) mass range and show that a specific variant of the QCD axion remains compatible with existing constraints. Specifically, the axion must (i) couple predominantly to the first generation of SM fermions; (ii) decay to e+e− with a short lifetime of less than 10^−13 s; and (iii) have suppressed isovector couplings, i.e., if it must be piophobic. Remarkably, these are precisely the properties required to explain recently observed anomalies in nuclear de-excitations of the Be-8 and He-4 nuclei, as well as the 2−3 sigma anomaly in the measurement of the neutral pion branching ratio to e+e-. I will discuss a variety of low-energy axion signatures, such as rare meson decays, nuclear de-excitations via axion emission, and axion production in e+e− annihilation and fixed target experiments.

In this talk I will talk about my recent article where we propose a simpler way to combine the seesaw and the scotogenic approaches, by making dark matter the seed of neutrino mass generation within a low-scale seesaw mechanism. For definiteness we take the inverse seesaw as our template. I will discuss thoroughly both the possibilities of explicit as well as dynamical lepton number violation. For the case of dynamical lepton number violation I will discuss in some detail the phenomenology of invisible Higgs decays with majoron emission, as well as the phenomenology of scotogenic WIMP dark matter.

We present the first lattice-QCD calculation of the unpolarized strange and charm parton distribution functions using large-momentum effective theory (LaMET). We use a lattice ensemble with 2+1+1 flavors of highly improved staggered quarks (HISQ) generated by MILC collaboration, with lattice spacing a ≈ 0.12 fm and Mπ ≈ 310 MeV, and clover valence fermions with two valence pion masses: 310 and 690 MeV. We use momentum-smeared sources to improve the signal up to nucleon boost momentum Pz = 2.18 GeV,  and determine nonperturbative renormalization factors in RI/MOM scheme. We compare our lattice results with the matrix elements obtained from matching the PDFs from CT18NNLO and NNPDF3.1NNLO global fits. Our data support the assumptions of strange-antistrange and charm-anticharm symmetry that are commonly used in global PDF fits.

The parameter ε_K is an important measure of the imbalance between matter and antimatter in the neutral kaon system. In particular, ε_K provides a sensitive probe of new physics and plays a critical role in the global fit of the Cabibbo-Kobayashi-Maskawa matrix. As one of the first discovered sources of CP violation, it has been extensively measured in experiment to per-mil precision. The theoretical calculation of ε_K, however, has historically been plagued by large perturbative errors arising from charm-quark corrections. These errors were larger than the expected magnitude of higher-order electroweak corrections in perturbation theory, rendering these contributions irrelevant. Recently, it was discovered that a simple re-parameterization of the theory drastically reduces perturbative errors, making these higher-order electroweak calculations worth-while. We present the two-loop electroweak contributions from the top quark to ε_K. In the traditional normalization of the weak Hamiltonian, this results in a -1% shift in the top quark contribution.

 I will introduce a class of new mechanisms for low-scale baryogenesis and dark matter production that utilize the CP violation within Standard Model meson systems. Mesogenesismechanisms operate at MeV scales and such, remarkably, are experimentally testable. I will first give an overview of B-Mesogenesis; in which baryogenesis proceeds through the oscillation and subsequent decay into a dark sector of neutral B mesons. B-Mesogenesis is testable at current hadron colliders and B-factories, and I will present results of recent studies that pave the way towards constraining (or discovering) this mechanism. Finally, I will present some recent proposals for charged Mesogenesis which relies on the CP violation of charged D and B mesons. 

Solitons in space–time capable of transporting time-like observers at superluminal speeds have long been tied to violations of the weak, strong, and dominant energy conditions of general relativity. The negative-energy sources required for these solitons must be created through energy-intensive uncertainty principle processes as no such classical source is known in particle physics. This talk presents an approach for overcoming this barrier, explicitly constructing a class of soliton solutions that are capable of superluminal motion and sourced by purely positive energy densities. This is the first example of hyper-fast solitons resulting from conventional sources, reopening the discussion of superluminal mechanisms rooted in conventional physics. I will also comment on the place this work takes in the larger literature, including recent contributions to the literature.