@article { ISI:000368354800041,
	title = {An improved limit on the charge of antihydrogen from stochastic acceleration},
	journal = {NATURE},
	volume = {529},
	number = {7586},
	year = {2016},
	month = {JAN 21},
	pages = {373+},
	abstract = {Antimatter continues to intrigue physicists because of its apparent absence in the observable Universe. Current theory requires that matter and antimatter appeared in equal quantities after the Big Bang, but the Standard Model of particle physics offers no quantitative explanation for the apparent disappearance of half the Universe. It has recently become possible to study trapped atoms(1-4) of antihydrogen to search for possible, as yet unobserved, differences in the physical behaviour of matter and antimatter. Here we consider the charge neutrality of the antihydrogen atom. By applying stochastic acceleration to trapped antihydrogen atoms, we determine an experimental bound on the antihydrogen charge, Qe, of vertical bar Q vertical bar < 0.71 parts per billion (one standard deviation), in which e is the elementary charge. This bound is a factor of 20 less than that determined from the best previous measurement(5) of the antihydrogen charge. The electrical charge of atoms and molecules of normal matter is known(6) to be no greater than about 10(-21)e for a diverse range of species including H-2, He and SF6. Charge-parity-time symmetry and quantum anomaly cancellation(7) demand that the charge of antihydrogen be similarly small. Thus, our measurement constitutes an improved limit and a test of fundamental aspects of the Standard Model. If we assume charge superposition and use the best measured value of the antiproton charge(8), then we can place a new limit on the positron charge anomaly (the relative difference between the positron and elementary charge) of about one part per billion (one standard deviation), a 25-fold reduction compared to the current best measurement(8),(9).},
	issn = {0028-0836},
	doi = {10.1038/nature16491},
	author = {Ahmadi, M. and Baquero-Ruiz, M. and Bertsche, W. and Butler, E. and Capra, A. and Carruth, C. and Cesar, C. L. and Charlton, M. and Charman, A. E. and Eriksson, S. and Evans, L. T. and Evetts, N. and Fajans, J. and Friesen, T. and Fujiwara, M. C. and Gill, D. R. and Gutierrez, A. and Hangst, J. S. and Hardy, W. N. and Hayden, M. E. and Isaac, C. A. and Ishida, A. and Jones, S. A. and Jonsell, S. and Kurchaninov, L. and Madsen, N. and Maxwell, D. and McKenna, J. T. K. and Menary, S. and Michan, J. M. and Momose, T. and Munich, J. J. and Nolan, P. and Olchanski, K. and Olin, A. and Povilus, A. and Pusa, P. and Rasmussen, C. O. and Robicheaux, F. and Sacramento, R. L. and Sameed, M. and Sarid, E. and Silveira, D. M. and So, C. and Tharp, T. D. and Thompson, R. I. and van der Werf, D. P. and Wurtele, J. S. and Zhmoginov, A. I.}
}
