Research

Parity violation in ytterbium

This project aims to establish a platform for fundamental tests in nuclear and particle physics, based on detecting isotopic variation of atomic parity violation.

Atomic probes in tabletop experiments offer a unique approach to testing fundamental physics, complementary to high-energy experiments. In particular, atomic parity violation (APV) provides a window into the effects of weak interaction in atoms. Our recent observations on how the APV effect varies among a chain of ytterbium (Yb) isotopes [1,2] motivate the use of this method as a versatile probe of nuclear and particle physics. More specifically, comparing the APV effect in different isotopes of the same atomic species is a sensitive tool to study the distribution of neutrons in the nucleus, which in turn is closely related to the structure and size of neutron stars. The method is also a probe of additional vector bosons, beyond the Standard Model of particle physics. Finally, the study of nuclear-spin-dependent contributions to the APV effect in isotopes with nuclear spin is a sensitive way to investigate intranuclear weak interactions, which are currently poorly understood. 

The objective of the project is to expand existing approaches to probing isotopic APV variation and to establish the method as a powerful tool at the interdisciplinary junction between atomic, nuclear and particle physics. Towards this goal, we will i) employ high-precision measurements of isotopic variation of the APV effect in Yb to probe the neutron distribution in the Yb nucleus and thus help answer questions regarding the size of neutron-rich nuclei and neutron stars;  ii) make use of the isotopic comparison method to explore electron–nucleon interactions mediated by potential additional Z bosons; and iii) undertake studies of spin-dependent APV to advance the fundamental understanding of intranuclear weak forces. 

The project is funded by the European Research Council (ERC) via the Starting Grant “Tests Of Fundamental Physics With Atomic Parity Violation in Ytterbium” (project acronym YbFUN). 

[1] D. Antypas, A. Fabricant, J. E. Stalnaker, K. Tsigutkin, V. V. Flambaum, and D. Budker, Isotopic variation of parity violation in atomic  ytterbium. Nature Physics 15, 120 (2019). 

[2] D. Antypas, A. Fabricant, J. E. Stalnaker, K. Tsigutkin, V. V. Flambaum, and D. Budker, Isotopic variation of parity violation in atomic ytterbium: Description of the measurement method and analysis of systematic effects.  Physical Review A 100 012503  , (2019). 

Fundamental constant oscillations

There is multiple direct observational evidence about the existence of Dark Matter (DM) in the Universe, a form of matter that is known to have an abundance that is significantly greater than that of matter. After decades of focused efforts to elucidate its origin and composition,  DM still remains a mystery.

 Within one of the most prominent scenarios, DM consists of light bosonic particles, that have small interactions with matter.  A number of such possibilities are being investigated including scenarios that predict DM-induced oscillations in the fundamental constants (FC) of nature.  If such oscillations were present, they would induce, in turn, oscillations to the frequencies of a variety of "oscillator" systems,  such as the frequencies of electronic or hyperfine transitions in atoms, vibrational transition frequencies in molecules, mechanical resonance frequencies, such as the resonance frequency of an optical resonator, or that of a quartz clock, etc.

Within this framework, we have looked in the last few years for FC oscillations in frequency comparisons of several of the above mentioned "oscillators" [1, 2, 3, 4]. These experiments have yielded null results, but have provided, however, important constraints on possible DM couplings to several FCs, such as the fine-structure constant, the electron mass, and the strong-force coupling constant. 

We are planning to carry out improved sensitivity experiments in search for FC oscillations. One such work involves developing  a high sensitivity Rb hyperfine clock, whose frequency will be compared to that of a state-of-the-art optical resonator, via conversion of the optical frequency down to the microwave regime with a frequency comb. 

[1] X. Zhang, A. Banerjee, M. Leyser, G. Perez, S. Schiller, D. Budker, and D. Antypas. Search for Ultralight Dark Matter with Spectroscopy of Radio-Frequency Atomic Transitions. Physical Review Letters 130, 251002 (2023).

[2] O. Tretiak,  X. Zhang, N.L.  Figueroa, D. Antypas, A. Brogna, A. Banerjee, G. Perez, and D. Budker.  Improved bounds on ultralight scalar dark matter in the radio-frequency range. Physical Review Letters 129, 031301 (2022).

[3] R.  Oswald, V. Vogt, A. Nevsky, N. L. Figueroa, O. Tretiak, K. Zhang, A. Banerjee, D. Antypas, G. Perez, D. Budker, and S. Schiller.  Search for oscillations of fundamental constants using molecular spectroscopy. Physical. Review Letters 129, 031302 (2022).

[4] D. Antypas, O. Tretiak, A. Garcon, R. Ozeri, G. Perez, and D. Budker, Scalar dark matter in the radio-frequency band: Atomic-spectroscopy search results. Physical Review Letters 123, 141102 (2019).