Stringent Constraints on New Pseudoscalar and Vector Bosons from Precision Hyperfine Splitting Measurements.

Area of Science:

• Atomic Physics
• Particle Physics
• Quantum Electrodynamics (QED)

Background:

• Axionlike particles (ALPs) and new bosons can mediate novel spin-dependent forces.
• These forces affect atomic and ionic systems, particularly their hyperfine structure.
• Understanding these interactions is crucial for probing physics beyond the Standard Model.

Purpose of the Study:

• To investigate the sensitivity of hyperfine structure measurements to axionlike particles and new bosons.
• To establish constraints on pseudoscalar and vector couplings using atomic spectroscopy data.
• To assess the future discovery potential of these measurements for new fundamental forces.

Main Methods:

• Analysis of hyperfine structure splittings in hydrogenlike and lithiumlike ions.
• Utilizing differences in splittings to mitigate nuclear uncertainties in calculations and measurements.
• Comparison of experimental data with theoretical predictions for various coupling scenarios.

Main Results:

• Existing measurements on Beryllium (Be) ions provide competitive limits for pseudoscalar couplings around m_ϕ ≳ 100 keV.
• These limits confirm or improve existing constraints by up to a factor of 2, depending on nuclear models.
• Future measurements on Cesium (Cs) show potential for 2-2.5 times improved discovery of pseudoscalars and an order of magnitude for vector bosons.

Conclusions:

• Hyperfine structure measurements in specific atomic charge states serve as a powerful probe for new spin-dependent forces.
• Atomic spectroscopy experiments, like those on Be, already place stringent limits on ALPs and related new bosons.
• Upcoming experiments, particularly on Cs, offer significant prospects for discovering new fundamental particles and interactions.