arXiv subjects

Sebastian Lahs

Publications and source records attributed to Sebastian Lahs.

5 recordsLinked to original sources

arXiv2025

Atomic Observables Induced by Cosmic Fields

The existence of cosmic fields made from yet unknown light bosons is predicted in many extensions to the Standard Model. They are especially of interest as possible constituents of dark matter. To detect such light and weakly interacting fields, atomic precision measurements offer one of the most sensitive platforms. In this work, we derive which atomic observables are sensitive to what kind of cosmic field couplings. For this we consider fields that couple either through scalar, pseudoscalar, vector, axial vector, or tensor couplings. We derive the corresponding non relativistic atomic potentials. Based on their symmetry properties, these can induce direct energy shifts or induce atomic electric dipole, magnetic dipole, electric quadrupole as well as nuclear Schiff and anapole moments.

hep-ph↗

arXiv2025

Demonstration of deuterium's enhanced sensitivity to symmetry violations governed by the Standard-Model Extension

We have performed hyperfine spectroscopy of two transitions in ground-state deuterium and searched for violations of CPT and Lorentz symmetry that would manifest as sidereal variations of the observed transition frequencies. Several nonrelativistic proton coefficients of the Standard-Model Extension framework have been addressed. The spin-independent coefficients with momentum power k=2,4 are constrained for the first time. Bounds on spin-dependent coefficients are improved by exploiting a sensitivity enhancement originating from the relative momenta of the nucleons in the deuteron. The best previous constraints by hydrogen maser measurements are surpassed by 4 and 14 orders of magnitude for coefficients with k=2 and 4, respectively.

hep-ex↗

arXiv2024

Polarizabilities as Probes for P, T, and PT Violation

Searches for violations of the fundamental symmetries of parity P and time reversal T in atomic and molecular systems provide a powerful tool for precise measurements of the physics of and beyond the standard model. In this work, we investigate how these symmetry violations affect the response of atoms and molecules to applied electric and magnetic fields. We recover well-known observables such as the P-odd, T-odd spin-electric field coupling that is used for searches of the electron electric dipole moment (eEDM) or the effect of P-odd, T-even optical rotation in atomic gases. Besides these, we obtain several other possible observables. This includes, in particular, effects that can only be seen when using oscillating or inhomogeneous fields.

physics.atom-ph↗

arXiv2024

CPT and Lorentz symmetry tests with hydrogen using a novel in-beam hyperfine spectroscopy method applicable to antihydrogen experiments

We present a Rabi-type measurement of two ground-state hydrogen hyperfine transitions performed in two opposite external magnetic field directions. This puts first constraints at the level of 2.3 10^-21 GeV on a set of coefficients of the Standard Model Extension, which were not measured by previous experiments. Moreover, we introduce a novel method, applicable to antihydrogen hyperfine spectroscopy in a beam, that determines the zero-field hyperfine transition frequency from the two transitions measured at the same magnetic field. Our value, nu_0 = 1.420 405 751 63(63) GHz, is in agreement with literature at a relative precision of 0.44 ppb. This is the highest precision achieved on hydrogen in a beam, improving over previous results by a factor of 6.

hep-ex↗

arXiv2023

Cesium atoms in cryogenic argon matrix

This paper presents both experimental and theoretical investigations into the spectroscopy of dilute cesium (Cs) atoms within a solid argon (Ar) matrix at cryogenic temperatures. This system is relevant for matrix isolation spectroscopy and in particular for recently proposed methods for investigating phenomena that extend beyond the standard model of particle physics. We record absorption spectra at various deposition temperatures and examine the evolution of these spectra post-deposition with respect to temperature changes. Taking advantage of Cs-Ar and Ar-Ar pairwise interaction potentials, we conduct a stability study of trapping sites, which indicates a preference for T$_{\rm d}$ (tetrahedral, 4 vacancies) and O$_{\rm h}$ (cubic, 6 vacancies) symmetries. By implementing a mean-field analysis of the long-range Cs(6s,6p)-Ar-Ar triple dipole interaction, combined with a temperature-dependent shift in zero point energy, we propose effective Cs(6s,6p)-Ar pairwise potentials. Upon integrating these pairwise potentials with spin-orbit coupling, we achieve a satisfactory agreement between the observed and simulated absorption line positions. The observed line broadening is reasonably well reproduced by a semi-classical thermal Monte Carlo approach based on Mulliken-type differences between excited and ground potential curves. Additionally, we develop a simple, first-order crystal field theory featuring only 6 interaction mode coordinates. It uses the reflection approximation and incorporates quantized (phonon) normal modes. This produces a narrow triplet structure but not the observed amount of splitting.

physics.atom-ph↗