Zoom link: https://ucsc.zoom.us/j/92025942801?pwd=UzFxMHdqNnM4ZVdrM0lRcEpPRUVLUT09 Passcode: 689028

Title: Revisiting kinetic mixing constraints on Z' bosons degenerate with the Z boson

Abstract: After a brief review of U(1)' gauge boson phenomenology at colliders, I discuss the field theory complications when a new Z' boson is degenerate with another Standard Model vector resonance.  While some of these complications are reminiscent of neutral kaon oscillation and mixing, we demonstrate that the canonical parameter space of the Z' mass, decay width, and kinetic mixing with the Z boson exhibits novel phenomenology.  We show that a self-consistent treatment of these technical issues rectifies earlier results on the kinetic mixing constraint of Z' bosons degenerate with the Z boson and comment on the prospects from a prospective future e+e- machine operating on the Z pole.

Title: Simulation-based modeling of cluster weak lensing
Abstract: Galaxy clusters are embedded in the most massive bound structures in the Universe. These structures formed from gravitationally amplified peaks in the primordial matter distribution making their properties sensitive to cosmology. In the standard approach the abundances of clusters as a function of their mass are used to constrain cosmology. Because cluster masses cannot be measured directly this approach relies on observable proxies of cluster mass that are calibrated using weak gravitational lensing. Robustly marginalizing over these mass-observable relations is therefore critical to accurately measuring cosmology with clusters. Recently, data from clusters identified in the Dark Energy Survey (DES) were found to be in significant tension with a variety of other probes, including a 5.6-sigma tension with cosmic microwave background data. This tension was likely caused by incomplete modeling of the impact of cluster selection. We have developed a novel framework to forward model cluster selection in cosmological simulations to address this discrepancy. When applied to the same DES cluster data we have found that this framework can consistently describe the DES cluster data assuming a Planck cosmology, thereby resolving the tension observed in earlier analyses of the DES cluster data.