Southeastern Universities Research Association

We study the small-x asymptotics of unpolarized generalized parton distributions (GPDs) and generalized transverse momentum distributions (GTMDs). Unlike the previous works in the literature, we consider the case of non-zero (but small) skewness while allowing for non-linear contributions to the evolution equations. We first show that unpolarized GPDs and GTMDs at small x are related to the eikonal dipole amplitude N, whose small-x evolution is given by the BK/JIMWLK evolution equations, and to the odderon amplitude O, whose evolution is also known in the literature. We then show that the effect of non-zero skewness xi not equal 0 is to modify the value of the evolution parameter (rapidity) in the arguments for the dipole amplitudes N and O from Y = ln(1/x) to Y = ln min {1/vertical bar x vertical bar, 1/vertical bar xi vertical bar}.

Endothermic upscattering of heavy dark matter offers a compelling interpretation of the high-energy nuclear-recoil candidate recently reported by LUX-ZEPLIN (LZ), with a characteristic recoil energy E_R ∝ δ, where δ is the mass splitting between the dark matter states. Cosmological and experimental constraints motivate the depletion of the primordial heavier state, which can be regenerated in the Galactic halo. We show that, if the heavier state decays radiatively, the same mass splitting sets the energy of a gamma-ray line, E_γ≃ δ. For our benchmark, this leads to a sub-MeV line within the projected reach of the Compton Spectrometer and Imager (COSI), scheduled for launch in 2027. The confirmation of the LZ candidate event as a dark matter signal would therefore motivate dedicated searches for sub-MeV gamma-ray lines, with COSI providing a timely opportunity to test this interpretation.

Stress distributions in the deuteron are related to form factors of the asymmetric energy-momentum tensor through three-dimensional Fourier transforms. There are eleven such form factors, which we calculate in an impulse approximation. We compare the obtained form factors to prior results for the six form factors that have been previously calculated. We then elaborate on the formalism for relating the form factors to internal distributions of mass, mass flux, momentum, stresses, and forces, and obtain results for all of these distributions. We obtain the principal stresses for the symmetric part of the stress tensor, and show that the antisymmetric part describes the reorientation of fermion spin by torsion stress when the nucleon moves between the S and D waves. Force distributions in the nucleons depend on the so-called nonconserved form factors through the Cauchy momentum equation, and are nonradial owing to the presence of tensor forces and spin-orbit coupling.

We present our analysis of how the detectability of carbon dioxide (CO _2 ) on an Earth-like planet varies with respect to signal-to-noise ratio (SNR), wavelength, and molecular abundance. Using the Bayesian Analysis for Remote Biosignature Identification on exoEarths methodology, we can determine the optimal long-wavelength cutoff for the future Habitable Worlds Observatory coronagraph. We test 25 evenly spaced 20% bandpasses between 0.8 and 2.0 μ m, and simulate data spanning a range of SNRs and molecular abundance to analyze the relationship between wavelength and detectability for different planetary archetypes. We examine abundance levels from varying Earth epochs and a Venus-like archetype to investigate how detectability would change throughout the evolution of a rocky planet. Here, we present our results on the planetary conditions and technological requirements to strongly detect CO _2 . In addition, we analyze the degeneracy of CO _2 with carbon monoxide (CO), methane (CH _4 ), and water (H _2 O). We determine that any abundance of CO does not achieve strong detections and that CH _4 and H _2 O play a pivotal role in the ability to detect CO _2 . We conclude that the optimal long-wavelength cutoff for the Habitable Worlds Observatory coronagraph should be 1.68 μ m.

Oxygen is a well-studied biosignature. Studying potential abiotic pathways for O2 build-up in exoplanet atmospheres is essential for evaluating whether the detection of O2 would constitute a biosignature detection on other worlds. Previous modeling efforts in the literature demonstrated that detectable abiotic O2 and O3 can be produced through CO2 photolysis for rocky planets around M dwarf stars. Building on modeling approaches from previous studies, we use photochemical simulations to reassess the conditions under which O2 and O3 may accumulate through similar photochemical mechanisms. Using a Mars-like atmospheric composition and planetary parameters, we vary the hydrogen mole fraction to assess how changes in HOx chemistry can affect the resulting accumulation of abiotic O2 and O3. Across the range of hydrogen mole fractions explored, we obtain a maximum O2 abundance of 2.7