Session Q4: Invited Session: Cosmic Particle Probes of Fundamental Physics

Particle Physics Beyond Laboratory Energies

The highest energy interactions of hadrons, photons and neutrinos have been observed exploiting cosmic rather than terrestrial particle beams. We will review what we have learned recently about Standard Model physics and beyond from cosmic ray detectors covering surface areas of many thousands of square kilometers, arrays of air Cherenkov telescopes, and kilometer-scale neutrino detectors. We will also speculate on the science reach of next-generation experiments.   

The Holometer: A Measurement of Planck Scale Quantum Geometry

Direct experiments show that light and matter obey fundamental quantum principles such as nonlocality, superposition and entanglement. On the other hand, standard, experimentally verified particle theory generally assumes that space-time itself obeys classical determinism and locality -- an approximation that cannot be reconciled with quantum matter and general relativity at intervals shorter than the Planck scale, or with the theory of black holes. These suggest that geometry has nonlocal quantum states and finite, holographic information content. The hints of new Planck scale physics open up a new experimental path: in some theories of quantum geometry, new degrees of freedom cause fluctuations in position with detectable, uniquely quantum correlations. We are developing an experiment called the Fermilab Holometer, a correlated pair of high-bandwidth Michelson interferometers. It is the first, and at present unique experiment designed to prepare and measure a coherent quantum state of position over an extended region in space. The sensitivity to transverse position noise, expressed in spectral density units, is smaller than a Planck time. When operating at its design noise limit, it will either detect or rule out some candidate forms of holographic quantum geometry.   

The Mysterious Neutrinos -- Clues from Astrophysics and Cosmology

The potential importance of neutrinos to understanding astrophysics and cosmology is enormous. Neutrinos can reveal the interior conditions of dense objects; their energy and mass density help shape the visible universe. However, this promise has barely been exploited, due to the difficulties of detecting neutrinos and their subtle effects. We are entering an era where rapid progress is expected in both the detection of neutrinos from astrophysical sources and in revealing the effects of neutrinos on cosmological measurements. Progress in these areas will simultaneously test the properties of neutrinos -- e.g., self-interactions, the existence of sterile neutrinos, and the absolute neutrino mass scale -- with a sensitivity that will be difficult, if not impossible, to match in the lab.