arXiv subjects

C. Lyu

Publications and source records attributed to C. Lyu.

4 recordsLinked to original sources

arXiv2024

Nonlinear calcium King plot constrains new bosons and nuclear properties

Nonlinearities in King plots (KP) of isotope shifts (IS) can reveal the existence of beyond-Standard-Model (BSM) interactions that couple electrons and neutrons. However, it is crucial to distinguish higher-order Standard Model (SM) effects from BSM physics. We measure the IS of the transitions ${{}^{3}P_{0}~\rightarrow~{}^{3}P_{1}}$ in $\mathrm{Ca}^{14+}$ and ${{}^{2}S_{1/2} \rightarrow {}^{2}D_{5/2}}$ in $\mathrm{Ca}^{+}$ with sub-Hz precision as well as the nuclear mass ratios with relative uncertainties below $4\times10^{-11}$ for the five stable, even isotopes of calcium (${}^{40,42,44,46,48}\mathrm{Ca}$). Combined, these measurements yield a calcium KP nonlinearity with a significance of $\sim 900 \sigma$. Precision calculations show that the nonlinearity cannot be fully accounted for by the expected largest higher-order SM effect, the second-order mass shift, and identify the little-studied nuclear polarization as the only remaining SM contribution that may be large enough to explain it. Despite the observed nonlinearity, we improve existing KP-based constraints on a hypothetical Yukawa interaction for most of the new boson masses between $10~\mathrm{eV/c^2}$ and $10^7~\mathrm{eV/c^2}$.

physics.atom-ph↗

arXiv2024

Short-period pulsating hot-subdwarf stars observed by TESS II. Northern ecliptic hemisphere

We present results of a continuation of our Transiting Exoplanet Survey Satellite (TESS) search for short-period pulsations in compact stellar objects observed during Years 2 and 4 of the TESS mission that targeted the northern ecliptic hemisphere. For many of the targets, we exploit unpublished spectroscopic data to confirm or determine the object's spectral classification. From the TESS photometry, we identify 50 short-period hot-subdwarf pulsators, including 35 sdB and 15 sdOB stars. The sample contains 26 pulsators not known before the TESS mission. Nine stars show signals at both low and high frequencies, and are therefore ``hybrid'' pulsators. For each pulsator, we report the list of prewhitened frequencies and we show amplitude spectra calculated from the TESS data. We attempt to identify possible multiplets caused by stellar rotation, and we report five candidates with rotation periods between 11 and 46d. Having the search for p-mode pulsating hot subdwarfs in TESS Sectors 1 - 60 done, we discuss the completeness of the study, as well as instability strip and the evolutionary status of the stars we found. We also compare the distribution of pulsation periods as a function of effective temperature and surface gravity with theoretical predictions.

astro-ph.SR↗

arXiv2023

Stringent test of QED with hydrogenlike tin

Inner-shell electrons naturally sense the electric field close to the nucleus, which can reach extreme values beyond $10^{15}\,\text{V}/\text{cm}$ for the innermost electrons. Especially in few-electron highly charged ions, the interaction with the electromagnetic fields can be accurately calculated within quantum electrodynamics (QED), rendering these ions good candidates to test the validity of QED in strong fields. Consequently, their Lamb shifts were intensively studied in the last decades. Another approach is the measurement of $g$ factors in highly charged ions. However, so far, either experimental accuracy or small field strength in low-$Z$ ions limited the stringency of these QED tests. Here, we report on our high-precision, high-field test of QED in hydrogenlike $^{118}$Sn$^{49+}$. The highly charged ions were produced with the Heidelberg-EBIT (electron beam ion trap) and injected into the ALPHATRAP Penning-trap setup, where the bound-electron $g$ factor was measured with a precision of 0.5 parts-per-billion. For comparison, we present state-of-the-art theory calculations, which together test the underlying QED to about $0.012\,\%$, yielding a stringent test in the strong-field regime. With this measurement, we challenge the best tests via the Lamb shift and, with anticipated advances in the $g$-factor theory, surpass them by more than an order of magnitude.

physics.atom-ph↗

arXiv2021

$\text{Direct}~Q\text{-Value Determination of the}~\beta^-~\text{Decay of} ~^{187}\text{Re}$

The cyclotron frequency ratio of $^{187}\mathrm{Os}^{29+}$ to $^{187}\mathrm{Re}^{29+}$ ions was measured with the Penning-trap mass spectrometer PENTATRAP. The achieved result of $R=1.000\:000\:013\:882(5)$ is to date the most precise such measurement performed on ions. Furthermore, the total binding-energy difference of the 29 missing electrons in Re and Os was calculated by relativistic multiconfiguration methods, yielding the value of $\Delta E = 53.5(10)$ eV. Finally, using the achieved results, the mass difference between neutral $^{187}$Re and $^{187}$Os, i.e., the $Q$ value of the $\beta^-$ decay of $^{187}$Re, is determined to be 2470.9(13) eV.

nucl-ex↗