A theoretical underpinning of the standard model of fundamental particles and interactions is CPT invariance, which requires that the laws of physics be invariant under the combined discrete operations of charge conjugation, parity and time reversal. Antimatter, the existence of which was predicted by Dirac, can be used to test the CPT theorem—experimental investigations involving comparisons of particles with antiparticles are numerous1. Cold atoms and anti-atoms, such as hydrogen and antihydrogen, could form the basis of a new precise test, as CPT invariance implies that they must have the same spectrum. Observations of antihydrogen in small quantities and at high energies have been reported at the European Organization for Nuclear Research (CERN)2 and at Fermilab3, but these experiments were not suited to precision comparison measurements. Here we demonstrate the production of antihydrogen atoms at very low energy by mixing trapped antiprotons and positrons in a cryogenic environment. The neutral anti-atoms have been detected directly when they escape the trap and annihilate, producing a characteristic signature in an imaging particle detector.
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Hagiwara, K. et al. The review of particle physics. Phys. Rev. D 66, 010001 (2002)
Baur, G. et al. Production of antihydrogen. Phys. Lett. B 368, 251–258 (1996)
Blanford, G. et al. Observation of atomic antihydrogen. Phys. Rev. Lett. 80, 3037–3040 (1998)
Niering, M. et al. Measurement of the hydrogen 1S-2S transition frequency by phase coherent comparison with a microwave cesium fountain clock. Phys. Rev. Lett. 84, 5496–5499 (2000)
Hellemans, A. Through the looking glass. Nature 406, 556–558 (2000)
Dehmelt, H. Experiments with an isolated subatomic particle at rest. Rev. Mod. Phys. 62, 525–530 (1990)
Fujiwara, M. C. et al. Producing slow antihydrogen for a test of CPT symmetry with ATHENA. Hyperfine Interactions (in the press)
Testera, G. et al. Toward the production of antihydrogen at rest in ATHENA. Nucl. Instrum. Methods A 461, 253–255 (2001)
Surko, C. M., Gilbert, S. J. & Greaves, R. G. Non-Neutral Plasma Physics (eds Bollinger, J. J., Spencer, R. L. & Davidson, R. C.) Vol. 3, 3–12 (American Institute of Physics, New York, 1999)
Jørgensen, L. V., van der Werf, D. P., Watson, T. L., Charlton, M. & Collier, M. J. T. Nonneutral Plasma Physics (eds Anderegg, F., Schweikhard, L. & Driscoll, C. F.) Vol. 4, 35–44 (American Institute of Physics, New York, 2002)
Gabrielse, G., Rolston, S., Haarsma, L. & Kells, W. Antihydrogen production using trapped plasmas. Phys. Lett. A 129, 38–42 (1988)
Tinkle, M. D., Greaves, R. G., Surko, C. M., Spencer, R. L. & Mason, G. W. Low-order modes as diagnostics of spheroidal non-neutral plasmas. Phys. Rev. Lett. 72, 352–355 (1994)
Regenfus, C. A cryogenic silicon micro strip and pure-CsI detector for detection of antihydrogen annihilations. Nucl. Instrum. Methods A (in the press)
Bendiscioli, G. & Kharzeev, D. Antinucleon–nucleon and antinucleon–nucleus interaction, a review of experimental data. Rivista Nuovo. Cim. 17(6), 1–42 (1994)
Amsler, C. et al. Temperature dependence of pure CsI: scintillation light yield and decay time. Nucl. Instrum. Methods A 480, 494–500 (2002)
Charlton, M. & Humberston, J. W. Positron Physics (Cambridge Univ. Press, Cambridge, 2001)
Gabrielse, G. et al. First positron cooling of antiprotons. Phys. Lett. B 507, 1–6 (2001)
Calligarich, E., Dolfini, R., Genoni, M. & Rotondi, A. A fast algorithm for vertex estimation. Nucl. Instrum. Methods A 311, 151–155 (1992)
The authors comprise the ATHENA Collaboration. We would like to thank G. Bendiscioli, S. Bricola, P. Chiggiato, J. Hansen, H. Higaki, A. Lanza, C. Marciano, O. Meshkov, P. Salvini, G. Sobrero, B. Schmid and E. Søndergaard. We also thank the CERN AD team and C. Surko, who provided essential advice. This work was supported by Istituto Nazionale di Fisica Nucleare (Italy), Conselho Nacional de Desenvolvimento Científico e Technológico, Fundação de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ) e Fundação CCMN/UFRJ (Brazil), Grant-in-Aid for Creative Basic Research of Monbukagakusho (Japan), the Swiss National Science Foundation, the Danish Natural Science Research Council, The UK Engineering and Physical Sciences Research Council (EPSRC), The EU (Eurotraps Network), and the Royal Society. L.V.J., M.H.H., M.C. and J.S.H. acknowledge the work of the late B. Deutch.
The authors declare that they have no competing financial interests.
About this article
Cite this article
Amoretti, M., Amsler, C., Bonomi, G. et al. Production and detection of cold antihydrogen atoms. Nature 419, 456–459 (2002) doi:10.1038/nature01096
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (2020)
Bremsstrahlung at Low-Energy Electron–Nucleus Collisions in the Quantizing Magnetic Field. I. Distant Collisions
Radiophysics and Quantum Electronics (2019)
Journal of Physics B: Atomic, Molecular and Optical Physics (2019)
Physical Review A (2019)
Journal of Modern Optics (2019)