Bulletin of the American Physical Society
Mid-Atlantic Section 2022 Meeting
Volume 67, Number 20
Friday–Sunday, December 2–4, 2022; University Park, PA, Pennsylvania State University
Session C03: Dark Matter and Cosmology |
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Chair: Miguel Mostafa, Pennsylvania State University Room: Pennsylvania State University Osmond 105 |
Saturday, December 3, 2022 9:00AM - 9:35AM |
C03.00001: First results from the LUX-ZEPLIN (LZ) dark matter experiment Invited Speaker: Carmen Carmona-Benitez LUX-ZEPLIN (LZ) is a direct detection dark matter experiment currently being operated at the Sanford Underground Research Facility (SURF) in Lead, South Dakota. It utilizes 7 tonnes of liquid xenon in a dual phase time projection chamber, surrounded by an instrumented xenon "skin" region and gadolinium-loaded liquid scintillator outer detector all contained within an ultra-pure water tank. The experiment looks 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 and spin-dependent 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. |
Saturday, December 3, 2022 9:35AM - 10:10AM |
C03.00002: Gravitational focusing effects on streaming dark matter as a new detection concept Invited Speaker: Abaz Kryemadhi Cosmological simulations of dark matter (DM) indicate the presence of many fine-grained streams at the location of the solar system. The fine-grained streams have small velocity dispersion which could be beneficial for strong gravitational effects (GF). Solar and planetary GF is effective for the slow DM particles, with possible strong flux enhancements produced for streams of axions and WIMPs. In this work we add the combined GF by the Sun and the Earth, before a stream reaches the detectors. Spatiotemporal transient density enhancements are computed, which are of interest for certain DM experiments. Due to the built-in gravitational flux enhancements, advantages are expected when compared to the detection schemes designed for the smooth Standard Halo Model. The present simulation focuses on fine-grained streams but it can be applied to any configuration of DM propagating inside the solar system. |
Saturday, December 3, 2022 10:10AM - 10:22AM |
C03.00003: Brownian Axion-like Particles Shuyang Cao, Daniel Boyanovsky We studied the non-equilibrium dynamics of an axion-like particle (ALP) weakly coupled to a thermal bath and misaligned initial conditions. The ALP’s in-in effective action is obtained to leading order in the ALP coupling to the bath but to all orders in the couplings among the bath’s degrees of freedom. The ALP obeys an effective Langevin equation with noise and friction kernels satisfying the fluctuation dissipation relation. The solution exhibits damping of the misaligned condensate and thermalization with the bath. It describes a mixed dark matter scenario where the initial (cold) component decays and the thermalized (hot) component grows. Specifically, we consider the ALP-photon coupling gaE·B to lowest order, valid from recombination onwards. UV divergences of the ALP self-energy require higher order derivative terms in the effective action. When T>>ma, the long-wavelength relaxation rate is substantially enhanced ΓT/Γ0=4T/ma and the finite temperature effective ALP mass is mT2=ma2[1-(T/Tc)4], with Tc∝√(ma/g), suggesting the possibility of an inverted phase transition, which when combined with higher derivative terms may indicate exotic new phases. These may yield cosmological consequences on structure formation, the effective number of relativistic species and cosmic birefringence. |
Saturday, December 3, 2022 10:22AM - 10:34AM |
C03.00004: Primordial cosmology with quadratic curvature terms Mauricio Gamonal, Eugenio Bianchi We study the tensor and scalar primordial power spectrum in an effective theory of gravity described by R + R2 + Weyl2. Higher order derivatives in time due to the Weyl-squared term are treated self-consistently by applying the reduction of order technique. Corrections to the predictions of Starobinsky inflation are discussed. |
Saturday, December 3, 2022 10:34AM - 10:46AM |
C03.00005: A Lower Bound on the Mass of Compact Objects from Dissipative Dark Matter James Gurian, Michael Ryan, Sarah Schon, Donghui Jeong, Sarah E Shandera We study the fragmentation scale of dark gas formed in dissipative dark-matter halos and show that the simple atomic-dark-matter model consistent with all current observations can create low-mass fragments that can evolve into compact objects forbidden by stellar astrophysics. We model the collapse of the dark halo's dense core by tracing the thermochemical evolution of a uniform-density volume element under two extreme assumptions for density evolution: hydrostatic equilibrium and pressure-free collapse. We then compute the opacity-limited minimum fragment mass from the minimum temperature achieved in these calculations. The results indicate that much of the parameter space is highly unstable to small-scale fragmentation. |
Saturday, December 3, 2022 10:46AM - 10:58AM |
C03.00006: Deriving amplitude relations with differential operators in Anti-de Sitter embedding space Pranav Diwakar, Aidan Herderschee, Radu Roiban, Fei Teng There has been recent interest in extending color-kinematics duality to curved-space. We introduce a representation in which correlators are realized as differential operators - built from AdS symmetry group generators - acting on contact diagrams known as D-functions, which can be used to render the duality manifest. The structure of the flat-space BCJ relations and the commutation properties of Mandelstam invariants suggest that the AdS generalization is obtained by replacing the latter with the multi-particle Casimir invariants of the conformal group. |
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