Session S01: The Limits of Precision: From Particles to the Universe

Precision Tests of Fundamental Interactions and Their Symmetries using Exotic Ions in Penning Traps

The four fundamental interactions and their symmetries, the fundamental constants as well as the properties of elementary particles like masses and moments, determine the basic structure of the universe and are the basis for our so well tested Standard Model (SM) of physics. Performing stringent tests on these interactions and symmetries in extreme conditions at lowest energies and with highest precision by comparing, e.g., the properties of particles and their counterpart, the antiparticles, will allow us to search for physics beyond the SM. Any improvement of these tests beyond their present limits requires novel experimental techniques.

An overview is given on recent mass and g-factor measurements with extreme precision on single or few cooled ions stored in Penning traps. Among others the most stringent test of bound-state quantum electrodynamics could be performed. Here, the development of a novel technique, based upon the coupling of two ions as an ion crystal, enabled the most precise determination of a g-factor difference to date. This difference, determined for the isotopes ^20,22Ne⁹⁺ with a relative precision of 5.6 × 10⁻¹³ with respect to the g factor, improved the precision for isotopic shifts of g factors by about two orders of magnitude. Our latest results on precision measurements with exotic ions in Penning traps will be presented.   

New JWST Results: Is the Current Tension in Ho Signaling New Physics

The question of whether there is new physics beyond our current standard model, Lambda Cold Dark Matter (LCDM), is a crucial unresolved issue in cosmology today. Recent measurements of the Hubble constant (Ho) using Cepheids and Type Ia supernovae (SNe) appear to differ significantly (5-sigma) from values inferred from the cosmic microwave background (CMB) fluctuations. This discrepancy, if real, could indicate new physics beyond the standard model. In this talk, I will present new results from a James Webb Space Telescope (JWST) program designed to measure Ho, and aimed at reducing current systematic uncertainties. It utilizes three independent methods for measuring the distances to (the same) nearby galaxies that provide a calibration for SNe: Cepheid variables, Tip of the Red Giant Branch (TRGB) stars and J-Region Asymptotic Giant Branch (JAGB) stars. The Near-Infrared Camera on JWST has four times the resolution and ten times the sensitivity of HST in the near infrared, and is critical for ascertaining whether new physics is required beyond the standard model of cosmology.   

Measurements of the muon magnetic moment

The Fermilab muon g-2 experiment recently released an improved measurement of the positive muon magnetic moment anomaly to an accuracy of 0.20 ppm. The anomaly is of interest since it can be predicted with impressive precision and its value is sensitive, via quantum corrections, to the interactions of the muon with the other particles of the Standard Model. Comparison of the measurement result and theoretical predictions thus serves as a powerful test of the completeness of the Standard Model. This comparison has revealed some puzzles, whose resolution might indicate the need for new physics. Details of the Fermilab experiment will be presented, along with a comparison with the theory and future prospects.   

High-precision measurements of fundamental constants, and testing for physics beyond the Standard Model

This is the Invited session sponsored by GPMFC. It covers a range of cutting-edge precision measurements at a range of spatial scales from sub-microscopic to the galactic.