CERN experiment produces first beam ofantihydrogen atoms for hyperfine study21 January 2014

A photograph of multiple ring electrodes installed in thecusp magnet. Antihydrogen atoms are synthesisedinside the left cylinders and are analysed at the rightelectrodes by the field ionisation technique. Credit: N.Kuroda

(Phys.org) The ASACUSA experiment at CERNhas succeeded for the first time in producing abeam of antihydrogen atoms. In a paper publishedtoday in Nature Communications, the ASACUSAcollaboration reports the unambiguous detection of80 antihydrogen atoms 2.7 metres downstream oftheir production, where the perturbing influence ofthe magnetic fields used initially to produce theantiatoms is small. This result is a significant steptowards precise hyperfine spectroscopy ofantihydrogen atoms.

Primordial antimatter has so far never beenobserved in the Universe, and its absence remainsa major scientific enigma. Nevertheless, it ispossible to produce significant amounts ofantihydrogen in experiments at CERN by mixingantielectrons (positrons) and low energyantiprotons produced by the AntiprotonDecelerator.

The spectra of hydrogen and antihydrogen arepredicted to be identical, so any tiny difference

between them would immediately open a window tonew physics, and could help in solving theantimatter mystery. With its single protonaccompanied by just one electron, hydrogen is thesimplest existing atom, and one of the mostprecisely investigated and best understood systemsin modern physics. Thus comparisons of hydrogenand antihydrogen atoms constitute one of the bestways to perform highly precise tests ofmatter/antimatter symmetry.

Matter and antimatter annihilate immediately whenthey meet, so aside from creating antihydrogen,one of the key challenges for physicists is to keepantiatoms away from ordinary matter. To do so,experiments take advantage of antihydrogen'smagnetic properties (which are similar tohydrogen's) and use very strong non-uniformmagnetic fields to trap antiatoms long enough tostudy them. However, the strong magnetic fieldgradients degrade the spectroscopic properties ofthe (anti)atoms. To allow for clean high-resolutionspectroscopy, the ASACUSA collaborationdeveloped an innovative set-up to transferantihydrogen atoms to a region where they can bestudied in flight, far from the strong magnetic field.

The ASACUSA CUSP apparatuses in the CERNAntiproton Decelerator. Credit: N. Kuroda

"Antihydrogen atoms having no charge, it was a big

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challenge to transport them from their trap. Ourresults are very promising for high-precision studiesof antihydrogen atoms, particularly the hyperfinestructure, one of the two best known spectroscopicproperties of hydrogen. Its measurement inantihydrogen will allow the most sensitive test ofmatter/antimatter symmetry. We are lookingforward to restarting this summer with an evenmore improved set-up," said Yasunori Yamazaki ofRIKEN, Japan, a team leader of the ASACUSAcollaboration. The next step for the ASACUSAexperiment will be to optimize the intensity andkinetic energy of antihydrogen beams, and tounderstand better their quantum state.

Experimental concept of the planned in-flightantihydrogen hyperfine spectroscopy. Antihydrogenatoms are synthesised in the cusp trap (shown withmagnetic field lines in the left). Some of them flow outtowards the downstream (right) direction and aredetected at the end. Credit: E. Widmann and N. Kuroda

Progress with antimatter experiments at CERN hasbeen accelerating in recent years. In 2011, theALPHA experiment announced trapping ofantihydrogen atoms for 1000 seconds and reportedobservation of hyperfine transitions of trappedantiatoms in 2012. In 2013, the ATRAP experimentannounced the first direct measurement of theantiproton's magnetic moment with a fractionalprecision of 4.4 parts in a million.

More information: Paper: dx.doi.org/10.1038/ncomms4089

Provided by CERN

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APA citation: CERN experiment produces first beam of antihydrogen atoms for hyperfine study (2014,January 21) retrieved 20 May 2015 from http://phys.org/news/2014-01-cern-antihydrogen-atoms-hyperfine.html

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