AEgIS Collaboration

AEgIS Collaboration
Name	AEgIS Collaboration
Formation	2008
Headquarters	CERN
Fields	Particle physics; Atomic physics

AEgIS Collaboration The AEgIS Collaboration is an international research consortium formed to measure the gravitational interaction of antihydrogen using precision techniques developed in antimatter physics and accelerator technology. Based at CERN and working alongside experiments such as ALPHA (experiment), ATRAP, ASACUSA, and GBAR, the collaboration leveraged expertise from institutions including Università di Milano, Université de Genève, Max Planck Institute for Nuclear Physics, Universidad Autónoma de Madrid, and Politecnico di Milano to design, build, and operate a dedicated apparatus at the Antiproton Decelerator complex.

Introduction

AEgIS was established to address foundational questions in modern physics by testing the influence of gravity on antimatter species in a laboratory environment, linking experimental programs at facilities like the Antiproton Decelerator with theoretical frameworks advanced by physicists at institutions such as CERN, Imperial College London, University of Manchester, ETH Zurich, and Université Paris-Saclay. The collaboration combined techniques from Penning trap spectroscopy groups in Max Planck Institute for Nuclear Physics and University of Tokyo with atom interferometry concepts developed at Stanford University, MIT, and University of California, Berkeley to pursue a measurement of the free-fall acceleration of antihydrogen.

Scientific Goals and Motivation

AEgIS aimed to perform a direct test of the weak equivalence principle for antimatter by measuring the gravitational acceleration, g, of antihydrogen atoms. This goal connected to theoretical questions addressed by researchers at CERN, Fermi National Accelerator Laboratory, SLAC National Accelerator Laboratory, Perimeter Institute for Theoretical Physics, and Institute for Advanced Study concerning CPT symmetry, charge-parity-time invariance debated by groups at Princeton University and Caltech, and alternative gravity models explored by theorists at Harvard University and University of Cambridge. The motivation drew on precision antimatter measurements from collaborations such as ALPHA (experiment), ATRAP, and BASE, and intersected with spectroscopy programs at Paul Scherrer Institute and Rutherford Appleton Laboratory.

Experimental Setup and Methods

AEgIS developed an apparatus that combined antiproton capture from the Antiproton Decelerator with positron accumulation from facilities similar to those used by AIST and Universidad de Zaragoza. The experiment employed nested Penning trap systems, a cold converter for forming antihydrogen via charge-exchange with Rydberg positronium inspired by techniques at Max Planck Institute for Nuclear Physics and University College London, and a horizontal moiré deflectometer akin to atom interferometry setups at University of Vienna and University of Innsbruck. Key components included superconducting magnets supplied and tested in collaboration with groups at CERN and Berkeley Lab, ultra-high vacuum systems developed with support from Oxford University and University of Glasgow, and detection systems using microchannel plates and silicon detectors similar to those used by ALICE (A Large Ion Collider Experiment) and LHCb for annihilation vertex reconstruction.

Key Results and Publications

AEgIS reported milestones including production of pulsed antihydrogen beams, demonstrations of Rydberg-state formation, and development of moiré deflectometry techniques, with papers coauthored by teams from CERN, Università di Milano, University of Geneva, Max Planck Institute for Nuclear Physics, and Universidad Autónoma de Madrid. Results were disseminated at conferences such as the International Conference on Atomic Physics, European Physical Society Conference on High Energy Physics, AAAS Annual Meeting, International Conference on Precision Physics of Simple Atomic Systems, and published in journals including Physical Review Letters, Nature Physics, New Journal of Physics, European Physical Journal D, and Journal of Physics B. The collaboration’s experimental methods influenced subsequent proposals and comparative analyses by researchers at Stanford University, MIT, Caltech, Harvard University, and Princeton University.

Collaboration Structure and Participating Institutions

AEgIS was organized with a spokesperson, technical coordinators, and working groups for trapping, positronium formation, beamline optics, detectors, and analysis. Participating institutions spanned Europe and beyond: CERN (host), Università di Milano, IHEP (China), Max Planck Institute for Nuclear Physics, University of Manchester, Imperial College London, University of Geneva, Paul Scherrer Institute, Universidad Autónoma de Madrid, Politecnico di Milano, University of Zurich, ETH Zurich, University of Barcelona, University of Liverpool, University of Aarhus, University of Tokyo, University of Melbourne, University of Tokyo, UNAM, National University of Singapore, Kyoto University, Lomonosov Moscow State University, Budker Institute of Nuclear Physics, Rutherford Appleton Laboratory, STFC Rutherford Appleton Laboratory, Institut Laue–Langevin, CEA Saclay, Université Paris-Sud, University of Warsaw, Jagiellonian University, Masaryk University, University of Innsbruck, University of Vienna, University of Geneva, University of Bern, University of Padua, University of Pisa, Politecnico di Torino, Universidade de Lisboa, Universidade de Coimbra, University of Edinburgh, University of Glasgow, University of Birmingham, University of Oxford, Columbia University, University of California, Berkeley, Lawrence Berkeley National Laboratory, Fermi National Accelerator Laboratory, SLAC National Accelerator Laboratory, Perimeter Institute for Theoretical Physics, Institute for Advanced Study, Harvard University, Caltech, Princeton University.

Future Plans and Upgrades

Planned directions included improved antihydrogen production rates, implementation of higher Rydberg states following theoretical work at Perimeter Institute for Theoretical Physics and Institute for Advanced Study, deployment of enhanced atom interferometry techniques inspired by Stanford University and MIT, and integration with next-generation deceleration and cooling methods under discussion with CERN and accelerator groups at Fermi National Accelerator Laboratory and SLAC National Accelerator Laboratory. Upgrades considered cryogenic traps, advanced positron accumulators from projects led by Universidad de Zaragoza and Max Planck Institute for Nuclear Physics, and new detection systems developed in collaboration with Lawrence Berkeley National Laboratory, Rutherford Appleton Laboratory, and Paul Scherrer Institute to reach sensitivities competitive with parallel efforts at ALPHA (experiment), ATRAP, and GBAR.

Category:Particle physics collaborations