Antihydrogen

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Antihydrogen is the antimatter counterpart to hydrogen . The atomic nucleus consists of an antiproton , the atomic shell of a positron .

History of anti-hydrogen production

At the end of 1995, the CERN research center near Geneva succeeded for the first time in producing a few atoms of anti-hydrogen. The working group under Walter Oelert from Forschungszentrum Jülich put together an antiproton as a nucleus with a positron. In the following two years, researchers at Fermilab in the USA repeated and improved the experiment.

Normal hydrogen (an atom and an element ) consists of a proton as the nucleus and the elementary particle electron as the outer shell. For every elementary particle there is an antiparticle with the property of being reversely electrically charged. An electron has a simple negative elementary charge . Its antiparticle, the positron, carries a positive elementary charge.

Antiparticles seldom occur in normal nature, as they convert into radiation and / or other particle-antiparticle pairs when they come into contact with particles (see annihilation ). For example, they are artificially produced in particle accelerators with a very high level of technical effort. It is therefore a peculiarity when two antiparticles can be united to form an anti-atom. Physicists have been speculating for a long time about whether antiatoms behave like normal matter. However, this question can only be answered if you have enough antiatoms to measure their spectra , i.e. the wavelengths of the light emitted or absorbed by them.

The particles produced at CERN and Fermilab were still too “hot”: They moved so quickly that they were unsuitable for spectroscopic examinations. In 2002 two international working groups at CERN succeeded in producing anti-hydrogen in larger quantities (around 50,000 atoms) with the ATRAP and ATHENA experimental facilities . The ATHENA working group under the leadership of the CERN physicist Rolf Landua defeated the ATRAP working group (under Gerald Gabrielse ) by a few weeks in the "race" for the detection of cold anti-hydrogen.

An international research group ALPHA led by Jeffrey Hangst from Aarhus University at CERN succeeded in storing it in a magnetic trap, a modified Ioffe trap , for closer investigations at temperatures a few degrees above absolute zero . 38 anti-hydrogen atoms could be examined for 172 ms. In 2011 it was possible to store 309 anti-hydrogen atoms for over 1,000 seconds (over 16 minutes). The first measurement of a transition in anti-hydrogen was published in 2012 by the same group. In the follow-up experiment ALPHA-2, the 1S – 2S transition could be measured in 2016 using laser spectroscopy . 25,000 anti-atoms were generated per run and around 14 were captured; in 2017, around 15,000 anti-atoms could be examined over the course of ten weeks.

The storage of anti-hydrogen in a neutral trap is necessary to prevent the anti-atoms e.g. B. by means of laser cooling or by means of sympathetic cooling (cooling of other atoms or ions that serve as coolants) to temperatures of a few millikelvin or even microkelvin and then to perform high-resolution laser spectroscopy on anti-hydrogen. The aim of laser spectroscopy is to measure the 1S – 2S line with a resolution comparable to that achieved in the working group of Theodor W. Hänsch on hydrogen. By comparing the 1S – 2S transition frequency in hydrogen and anti-hydrogen, one tests the CPT theorem , a cornerstone of modern physics. In the ALPHA-2 experiment, the equality of the transition frequencies of hydrogen and anti-hydrogen and thus the prediction of the CPT theorem was initially confirmed with an accuracy of 2 · 10 −10 , and in 2017 even with an accuracy of 2 · 10 −12 .

Another goal is the more detailed examination of gravitation theories. Since antimatter has positive mass in the sense of the general theory of relativity , it can be assumed that it behaves like ordinary matter in the gravitational field. In principle, this can be tested more precisely with the electromagnetically neutral anti-hydrogen atoms than with charged particles, because their electromagnetic interaction is much stronger than gravity and would interfere with these measurements. To check this, the AEGIS experiment was developed at the Antiproton Decelerator at CERN. This is currently (2013) in the preparatory phase.

See also

Individual evidence

  1. ↑ G. Baur et al., 'Production of Antihydrogen', Physics Letters B, 368, pp. 251-258 (1996); doi : 10.1016 / 0370-2693 (96) 00005-6 ; Preprint online .
  2. ↑ Tom W. Hijmans: Particle physics: Cold antihydrogen , Nature 419, 439-440 (October 3, 2002) doi: 10.1038 / 419439a .
  3. ↑ M. Amoretti, C. Amsler, G. Bonomi, A. Bouchta, P. Bowe, C. Carraro, CL Cesar, M. Charlton, MJT Collier, M. Doser, V. Filippini, KS Fine, A. Fontana, MC Fujiwara, R. Funakoshi, P. Genova, JS Hangst, RS Hayano, MH Holzscheiter, LV Jørgensen, V. Lagomarsino, R. Landua, D. Lindelöf, E. Lodi Rizzini, M. Macrì, N. Madsen, G. Manuzio, M. Marchesotti, P. Montagna, H. Pruys, C. Regenfus, P. Riedler, J. Rochet, A. Rotondi, G. Rouleau, G. Testera, A. Variola, TL Watson, DP van der Werf: Production and detection of cold antihydrogen atoms , Nature 419, 456-459 (3 October 2002) doi: 10.1038 / nature01096 .
  4. ↑ Andresen, G. et al .: Trapped antihydrogen . In: Nature . 468, No. 7321, 2010. doi : 10.1038 / nature09610 .
  5. ↑ ALPHA Collaboration: Confinement of antihydrogen for 1000 seconds . In: Cornell University . 2011. arxiv : 1104.4982 .
  6. ↑ ALPHA Collaboration: Resonant quantum transitions in trapped antihydrogen atoms . In: Nature . 2012.
  7. ↑ a b M. Ahmadi, BXR Alves, CJ Baker, W. Bertsche, E. Butler, A. Capra, C. Carruth, CL Cesar, M. Charlton, S. Cohen, R. Collister, S. Eriksson, A. Evans, N. Evetts, J. Fajans, T. Friesen, MC Fujiwara, DR Gill, A. Gutierrez, JS Hangst, WN Hardy, ME Hayden, CA Isaac, A. Ishida, MA Johnson, SA Jones, S. Jonsell, L. Kurchaninov, N. Madsen, M. Mathers, D. Maxwell, JTK McKenna, S. Menary, JM Michan, T. Momose, JJ Munich, P. Nolan, K. Olchanski, A. Olin, P. Pusa, C . Ø. Rasmussen, F. Robicheaux, RL Sacramento, M. Sameed, E. Sarid, DM Silveira, S. Stracka, G. Stutter, C. So, TD Tharp, JE Thompson, RI Thompson, DP van der Werf, JS Wurtele: Observation of the 1S – 2S transition in trapped antihydrogen . In: Nature . Accelerated Article Preview Published, December 19, 2016, doi : 10.1038 / nature21040 .
  8. ↑ a b M. Ahmadi, BXR Alves, CJ Baker, W. Bertsche, A. Capra, C. Carruth, CL Cesar, M. Charlton, S. Cohen, R. Collister, S. Eriksson, A. Evans, N. Evetts, J. Fajans, T. Friesen, MC Fujiwara, DR Gill, JS Hangst, WN Hardy, ME Hayden, CA Isaac, MA Johnson, JM Jones, SA Jones, S. Jonsell, A. Khramov, P. Knapp, L Kurchaninov, N. Madsen, D. Maxwell, JTK McKenna, S. Menary, T. Momose, JJ Munich, K. Olchanski, A. Olin, P. Pusa, C. Ø. Rasmussen, F. Robicheaux, RL Sacramento, M. Sameed, E. Sarid, DM Silveira, G. Stutter, C. So, TD Tharp, RI Thompson, DP van der Werf & JS Wurtele: Characterization of the 1S – 2S transition in antihydrogen . In: Nature . Accelerated Article Preview Published, April 4, 2018, doi : 10.1038 / s41586-018-0017-2 .
  9. ^ G. Gabrielse et al .: Background-Free Observation of Cold Antihydrogen with Field-Ionization Analysis of Its States . In: Phys Rev Lett . 89, No. 21, 2002, p. 213401. doi : 10.1103 / PhysRevLett.89.213401 . PMID 12443407 .
  10. ↑ G. Gabrielse et al .: Driven production of cold antihydrogen and the first measured distribution of antihydrogen states . In: Phys Rev Lett . 89, No. 23, 2002, p. 233401. doi : 10.1103 / PhysRevLett.89.233401 . PMID 12485006 .
  11. ^ G. Gabrielse et al .: First Measurement of the Velocity of Slow Antihydrogen Atoms . In: Phys Rev Lett . 93, No. 7, 2004, p. 073401. doi : 10.1103 / PhysRevLett.93.073401 . PMID 15324235 .
  12. ^ CH Storry et al .: First Laser-Controlled Antihydrogen Production . In: Phys Rev Lett . 93, No. 26, 2004, p. 263401. doi : 10.1103 / PhysRevLett.93.263401 . PMID 15697977 .
  13. ↑ Description of the experiment on the AEgIS project website, accessed May 27, 2013

Web links

Wiktionary: Anti-hydrogen  - explanations of meanings, word origins, synonyms, translations