Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session 1WLB: Antiproton Physics: Fundamental Symmetries, Hadron Structure, and the Universe II |
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Chair: Makoto Fujiwara, TRIUMF Room: Hilton Queen's 5 |
Tuesday, October 23, 2018 11:00AM - 11:30AM |
1WLB.00001: Spectroscopy of antihydrogen: recent advances from the ALPHA Collaboration Invited Speaker: Takamasa Momose The ALPHA (Antihydrogen Laser PHysics Apparatus) Collaboration at CERN is engaged in precision tests of fundamental symmetries between matter and antimatter. The hydrogen atom has played a major role in the development of fundamental physics since the 1814 wavelength measurements of visible lines by Fraunhoffer in the solar spectrum. Modern measurements of the hydrogen atomic spectrum have yielded some of the most precise results in physics, with the two-photon 1S-2S transition being measured to a precision of a few parts in 10^15. Antihydrogen, the bound state of an antiproton and positron, is the antimatter counterpart of hydrogen, and has only recently been observed spectroscopically. Measurements on antihydrogen are complicated by the need to synthesize and confine the anti-atoms prior to probing a transition of interest. Very recently, we have made great strides in our control and tuning of the plasmas involved in antihydrogen formation, resulting in an order of magnitude improvement in the trapping rate. Further development has allowed us to stack multiple trapping cycles for a measurement, resulting in hundreds of trapped anti-atoms available at a time for spectroscopy. These successes have enabled us to extend our measurement campaign, with new results for the 1S hyperfine splitting, 1S-2S forbidden transition, and 1S-2P allowed transition. The 1S-2P manifold contains a cycling transition, presenting the possibility of laser cooling of antimatter. I will provide an overview of the ALPHA experiment, present some of our recent results, and discuss future prospects for continued fundamental symmetry tests with antihydrogen. |
Tuesday, October 23, 2018 11:30AM - 12:00PM |
1WLB.00002: Antimatter Plasmas and Antihydrogen Physics Invited Speaker: Jonathan Wurtele Several antihydrogen experiments at CERN synthesize antihydrogen by mixing positron and antiproton plasmas confined in superimposed Penning-Malmberg traps. The antihydrogen atom itself can be confined by a superimposed minimum-B neutral particle trap. For example, in the ALPHA experiment, starting from roughly 0.1-0.5 trapped antihydrogen atoms per attempt, the antihydrogen trapping rate has increased by a factor of over 20 by implementing new techniques for plasma control. As many as 1000 antihydrogen atoms have now been simultaneously confined. Future developments in nonneutral plasma techniques, such as cavity cooling, may allow for trapping at substantially lower magnetic field strengths, thereby enabling further improvements in ALPHA's precision physics measurements. Using ideas from Fermi acceleration, a charge neutrality measurement has yielded a bound on the magnitude of the charge of the antiatoms to a precision of 0.7ppb of the positron charge. By modeling orbits as the trap fields are turned off, ALPHA set crude bounds on the gravitational properties of antihydrogen, with the ratio of gravitational mass to inertial mass M constrained to approximately +/-100. Building on the techniques developed over the last decade, the ALPHA Collaboration is deploying a new apparatus, ALPHA-g, to measure antimatter gravitation to 1\% precision. In this talk I will present the recent advances in nonneutral plasma physics that enable antihydrogen physics studies and cover the charge neutrality measurements and future gravity experiments. |
Tuesday, October 23, 2018 12:00PM - 12:30PM |
1WLB.00003: Development of the GAPS Experiment for Cosmic-ray Antinuclei Measurements Invited Speaker: Philip Von Doetinchem The GAPS experiment is designed to carry out a dark matter search by measuring low-energy cosmic-ray antinuclei (antiprotons, antideuterons, antihelium) with a novel detection approach. For the case of antiprotons, a high-statistics measurement in the unexplored low-energy range will be conducted. In contrast, not a single cosmic antideuteron has been detected by any experiment, but well-motivated theories beyond the standard model of particle physics contain viable dark matter candidates, which could lead to a significant enhancement of the antideuteron flux due to annihilation of dark matter particles. This flux contribution is calculated to be especially large at low energies, which leads to a high discovery potential for GAPS. The theoretically predicted antideuteron flux resulting from secondary interactions of primary cosmic rays, e.g. protons, with the interstellar medium is very low. Furthermore, the search for antihelium-3 and antihelium-4 promises an even lower secondary background. As the cosmic-ray experiment AMS-02 has recently identified a few antihelium candidates in their higher-energy data, it is crucial to perform an independent search with a different experimental technique in a lower energy range. GAPS is designed to achieve its goals via a series of long duration balloon flights at high altitude in Antarctica starting from 2020.
The presentation will review the theoretical status, introduce the GAPS experiment, and report on the status of the different GAPS subdetectors as well as on the development of the simulation and analysis tools. |
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