Particle Physics

The sexaquark, a hypothetical stable and neutral six-quark state, has been recently proposed as a dark matter candidate. Here, I argue it is very unlikely sexaquarks could consistently compose more than a billionth of the dark matter abundance for a wide range of scattering cross sections and annihilation rates. To draw these conclusions, I will connect several topics, including the sexaquark freeze-out abundance, dark matter direct detection constraints, neutrino experiments, and accumulation mechanisms for sexaquarks in the Earth. I will show how the sexaquark cosmology enforces that a large contribution to dark matter is only possible with a similarly large antisexaquark population. This population, however, would leave a stark annihilation signal in a detector such as Super-Kamiokande. I will summarize with how sexaquarks as a large component of the dark matter is incompatible with current observational data.

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The cosmic microwave background is a sensitive probe of early-Universe physics, and yet fundamental constants at recombination can differ from their present-day values due to degeneracies in the standard cosmological model. Such scenarios have been invoked to reconcile discrepant measurements of the present-day expansion rate, but even absent such motivation they raise the intriguing possibility of yet-undiscovered physics coupled directly to Standard Model particles. I will discuss theories in which a new scalar field shifts the electron's mass at early times; viable models are already stringently constrained by measurements of quasar absorption lines, the abundances of light elements, and the universality of free fall. I will show that the remaining parameter space is exactly that which allows not only the primary cosmic microwave background but also low-redshift distances to be consistent with observations. After presenting the results of parameter inference I will discuss additional cosmological and laboratory signatures of the model.

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Zoom link https://pitp.zoom.us/j/99705853481?pwd=MTZRWC9hREkvOXpiZkxCM3UvdnRNQT09