Comparing the antiproton and proton, and opening the way to cold antihydrogen

G. Gabrielse*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

47 Scopus citations


Our TRAP collaboration has developed and demonstrated slowing, trapping, and electron-cooling techniques that enable antiproton storage in thermal equilibrium at 4.2K. This is an average energy that is more than 1010 times lower than the energy of any previously available antiprotons. Months-long confinement of a single antiproton, at a background pressure <5×10-17 torr, and nondestructive detection of the radio signal from a single trapped antiproton, made it possible to show that the charge-to-mass ratios of the antiproton and proton differ in magnitude by <9 parts in 1011. This 90 parts per trillion comparison is nearly a milion times more accurate than previous comparisons, and is the most stringent test of PCT invariance with a baryon system by a similar amount. The avaibility of extremely cold antiprotons makes it possible to pursue the production of antihydrogen that is cold enough to trap for precise laser spectroscopy. The closest approach to cold antihydrogen to date is our simultaneous confinement of 4.2K antiprotons and positrons. All cold antiproton experiments so far were carried out at the CERN Laboratory with antiprotons coming from its Low Energy Antiproton Ring (LEAR). This unique facility has now closed. Future antihydrogen experiments will be pursued at the new Antiproton Decelerator ring at CERN, which was constructed for this purpose. Using the techniques developed by TRAP, antiprotons will be accumulated within traps rather than in storage rings, thereby reducing the operating expenses to CERN.

Original languageEnglish (US)
Pages (from-to)1-39
Number of pages39
JournalAdvances in Atomic, Molecular and Optical Physics
Issue numberC
StatePublished - Dec 1 2001

ASJC Scopus subject areas

  • Statistical and Nonlinear Physics
  • Electronic, Optical and Magnetic Materials

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