Collaborative Research: Precision Tests of Physics Beyond the Standard Model with Antihydrogen

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The goal of this research, part of the ALPHA Collaboration, is to search for differences between the properties of hydrogen and antihydrogen, the antimatter counterpart to hydrogen. According to very general principles that underlie our mathematical description of the physical world, the atomic physics of antihydrogen should be identical to that of hydrogen. Any differences in the atomic physics or gravitational dynamics between antihydrogen and hydrogen would challenge the very basis of established mathematical descriptions of the world around us. The collaboration's high-precision measurements may shed light on one of the most important questions in physics, known as the baryon asymmetry, which is the preponderance of matter over antimatter in the observable universe. This award is made under the NSF/DOE Partnership in Basic Plasma Science and Engineering and will support the collaboration's effort at Purdue University and an undergraduate student at University of California, Berkeley as complementary to a DOE award made under the joint program. The goal of this research, part of the ALPHA Collaboration, is to search for differences between the properties of hydrogen and antihydrogen; such differences could only result from Charge-Parity-Time (CPT) or Weak Equivalence Principle violation. The ALPHA collaboration at CERN has progressed from trapping antihydrogen to measuring its positron spin flip frequency, somewhat crudely its gravitational properties, its charge neutrality, its 1S-2S spectrum, and its hyperfine spectrum. Significant improvement in the precision of all these measurements is expected during the duration of this funding period. In the near term, ALPHA is constructing, and is expected to install, a new vertical experimental apparatus, ALPHAg, to conduct an up/down gravity measurement. In parallel, it will continue measurements on the optical and hyperfine spectra of antihydrogen. During the upcoming two-year CERN shutdown, ALPHA will fully prepare ALPHAg and will build a new atomic spectrum trap, ALPHA-III. During the final two years of funding, plans call for carrying out high-precision measurements utilizing fine scale magnetometry for gravity measurements at the 1% level; and applying laser and adiabatic cooling for high-precision measurements of the Lamb shift, the anti-Rydberg constant, charge neutrality, and the hyperfine spectrum. Moreover, unlike many CPT tests, ALPHA's tests are model-independent and do not presume a particular CPT breaking mechanismThis award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.