matter–antimatter asymmetry

matter–antimatter asymmetry
Name	Matter–antimatter asymmetry
Field	Physics

Contents

matter–antimatter asymmetry

Matter–antimatter asymmetry describes the observed dominance of matter over antimatter in the observable Universe. It is central to questions addressed by projects and institutions such as CERN, Fermilab, SLAC National Accelerator Laboratory, Max Planck Society and programs like Large Hadron Collider experiments, ATLAS experiment, CMS experiment, LHCb experiment and Belle II. The problem ties to historical and theoretical developments involving figures and entities such as Andrei Sakharov, Albert Einstein, Paul Dirac, Enrico Fermi and concepts explored at facilities like Brookhaven National Laboratory, DESY, Kavli Institute.

Overview

The asymmetry contrasts predictions from early analyses by Paul Dirac, predictions tested in contexts like Big Bang nucleosynthesis studied by teams associated with NASA and European Space Agency missions such as Planck (spacecraft), WMAP and the Hubble Space Telescope. It motivates theoretical work at institutions including Princeton University, Harvard University, University of Cambridge, California Institute of Technology, Stanford University and University of Tokyo. Historical experimental milestones include results from CERN ISR, discoveries related to CP violation first observed in Cronin and Fitch experiments with the Kaon system, and later studies in the B meson sector at Belle and BaBar.

Observational evidence comes from measurements by collaborations and missions such as Planck (spacecraft), WMAP, Sloan Digital Sky Survey, Large Synoptic Survey Telescope teams and telescopes like Keck Observatory and Very Large Telescope. Observations of the Cosmic microwave background anisotropies, light-element abundances from Big Bang nucleosynthesis constrained by analyses at Institute for Advanced Study and surveys by European Southern Observatory strongly indicate a baryon asymmetry parameter measured by experiments at Particle Data Group collaborations and reviewed in reports from National Academy of Sciences. Direct searches for cosmic antimatter by instruments like AMS-02, PAMELA and Fermi Gamma-ray Space Telescope find no large regions of antimatter in the local Milky Way or nearby Andromeda Galaxy, informing theoretical bounds developed by groups at Massachusetts Institute of Technology, University of Chicago and Columbia University.

The basic conditions formulated by Andrei Sakharov motivate many models explored at centers such as CERN, Perimeter Institute, Institute for Nuclear Theory and university groups including University of Pennsylvania and Yale University. Sakharov’s three conditions—baryon number violation, C and CP violation, and departure from thermal equilibrium—are implemented in frameworks that reference mechanisms like electroweak baryogenesis, leptogenesis and scenarios involving heavy states from Grand Unified Theory proposals formulated by authors at Princeton University and University of Chicago. CP violation measured in experiments at KEK and SLAC links to theoretical constructs in models developed by researchers associated with Niels Bohr Institute, CERN Theory Division and the Perimeter Institute for Theoretical Physics.

Proposed baryogenesis mechanisms span work by theorists affiliated with Harvard University, Caltech, Stanford University, University of Oxford and laboratories like Los Alamos National Laboratory. Mechanisms include electroweak baryogenesis linked to dynamics at the Electroweak scale and studied in lattice calculations at Rutherford Appleton Laboratory, Brookhaven National Laboratory and Argonne National Laboratory; leptogenesis scenarios tied to seesaw mechanism models often associated with CERN Theory Division and University of Tokyo; and models from Grand Unified Theories inspired by groups at Fermilab and Princeton University. Additional proposals such as Affleck–Dine mechanism and scenarios involving axion physics have been advanced by researchers at Perimeter Institute, Max Planck Institute for Physics and Institute for Advanced Study.

Experimental constraints arise from collider experiments at Large Hadron Collider, precision flavor physics at Belle II and LHCb, neutrino experiments like Super-Kamiokande, DUNE, T2K and NOvA, and direct searches for baryon-number violation such as proton decay experiments at Super-Kamiokande and planned detectors at Hyper-Kamiokande. Measurements of CP violation by collaborations including BaBar, Belle, LHCb and neutrino facilities influence model-building at CERN, Fermilab and KEK. Cosmological constraints from Planck (spacecraft), WMAP and large-scale surveys by Sloan Digital Sky Survey and teams at European Southern Observatory limit parameters in leptogenesis and electroweak scenarios, while antimatter searches by AMS-02 and Fermi Gamma-ray Space Telescope further restrict exotic proposals developed at Los Alamos National Laboratory and Lawrence Berkeley National Laboratory.

The asymmetry informs our understanding of Big Bang cosmology as explored by researchers at Instituto de Astrofísica de Canarias, Institute of Cosmology and Gravitation, Kavli Institute for Cosmology and observational programs like Dark Energy Survey and Euclid (spacecraft). It affects models of cosmic evolution considered by theorists at Princeton University, University of Cambridge, Yale University and University of California, Berkeley, and has implications for structure formation in the Milky Way and galaxy formation studied by teams at Max Planck Institute for Astrophysics, Harvard–Smithsonian Center for Astrophysics and Space Telescope Science Institute. Resolving the origin of the asymmetry remains a major goal for collaborative programs involving CERN, Fermilab, KEK, JAXA and international consortia planning future facilities.