arXiv subjects

Minoru Tanaka

Publications and source records attributed to Minoru Tanaka.

At least 19 recordsLinked to original sources

arXiv2026

Precision Isotope-Shift Measurement of the ${}^1S_0 \leftrightarrow {}^3P_2$ Transition and a Multi-Transition King-Plot Consistency Test

We present precision spectroscopy and isotope shift measurement of the ${}^1S_0 \leftrightarrow {}^3P_2$ clock transition in neutral ytterbium ($\mathrm{Yb}$) atoms. By revealing a magic wavelength at $905.4(2)$ nm, we successfully achieve the atomic spectrum narrower than $100$ Hz. The interleaved clock operation between isotopes allows us to determine isotope shifts of four bosonic isotope pairs at Hz-level uncertainties, which is combined with those of other four ultra-narrow transitions in $\mathrm{Yb}$ and $\mathrm{Yb}^+$ to construct the King plot. We show that a rich dataset spanning multiple transitions enables a test of a restricted isotope-shift ansatz comprising the leading mass and field shifts, one effective factorized higher-order Standard Model contribution, and a new-particle contribution. Within this ansatz, the five-transition data are inconsistent with the new-particle contribution serving as the sole additional contribution over the mass ranges $m_ϕ\leq 6.5$ keV and $18$ keV $\leq m_ϕ< 100$ keV, while the previous works rely on another bound set by the neutron scattering and $(g-2)_e$ measurements. This work paves the way for the effective use of precision isotope shift data in the King plot analysis and stimulates further measurements in Yb and other elements.

physics.atom-ph↗

arXiv2026

Orders-of-magnitude improvement in precision spectroscopy of an inner-shell orbital clock transition in neutral ytterbium

An inner-shell orbital clock transition $^1S_0 \leftrightarrow 4f^{13}5d6s^2 \: (J=2)$ in neutral ytterbium atoms has attracted much attention as a new optical frequency standard as well as a highly sensitive probe for several new physics phenomena, such as ultralight dark matter, violation of local Lorentz invariance, and a new Yukawa potential between electrons and neutrons. Here, we demonstrate almost two-orders-of-magnitude improvement in precision spectroscopy over the previous reports on this transition, achieved by trapping atoms in a three-dimensional magic-wavelength optical lattice. In particular, we successfully observe the coherent Rabi oscillation, the relaxation dynamics of the excited state and the interorbital Feshbach resonance. To highlight the high precision of our spectroscopy, we carry out precise isotope shift measurements between five stable bosonic isotopes well below 10 Hz uncertainties, successfully setting bounds for a hypothetical boson mediating a force between electrons and neutrons. These results open up the way for various new physics search experiments and a wide range of applications to quantum science with this clock transition.

physics.atom-ph↗

arXiv2024

Measurement of cesium $8\,^2P_{J}\rightarrow 6\,^2P_{J'}$ electric quadrupole transition probabilities using fluorescence spectroscopy

Fluorescence spectra of the $8P_{J} \rightarrow 6P_{J'}$ ($J$ and $J'$ = 3/2, 1/2) electric quadrupole transition of cesium atoms have been observed with a heated cesium vapor cell. We determined the ratio of the transition probabilities of $8P_{J}\rightarrow6P_{J'}$ to $8P_{J}\rightarrow5D_{3/2}$ by comparing their respective photon emission rates. The results are in good agreement with our theoretical calculations. These measurements provide crucial parameters for tests of coherent amplification method and improve knowledge of cesium properties which are essential to dark matter detection through atomic transitions.

physics.atom-ph↗

arXiv2024

Delta-convex structure of the singular set of distance functions

For the distance function from any closed subset of any complete Finsler manifold, we prove that the singular set is equal to a countable union of delta-convex hypersurfaces up to an exceptional set of codimension two. In addition, in dimension two, the whole singular set is equal to a countable union of delta-convex Jordan arcs up to isolated points. These results are new even in the standard Euclidean space and shown to be optimal in view of regularity.

math.AP↗

arXiv2023

Rare Leptonic Processes Induced by Massless Dark Photon

We introduce a dark photon considering a U(1) gauge extension of the standard model in particle physics. Provided that the extra U(1) symmetry is unbroken, the dark photon is massless and has no coupling to the standard electromagnetic current. Higher-dimensional operators describe interactions of the massless dark photon with particles in the standard model. We investigate the interactions of the massless dark photon with charged leptons via dipole operators, mainly focusing on the lepton family-violating processes. We present an improved constraint in the polarized two-body muon decay and a set of new bounds in tau decays. We also examine possible lepton family-violating signals of the massless dark photon in future lepton colliders.

hep-ph↗

arXiv2022

Generalized von Mangoldt surfaces of revolution and asymmetric two-spheres of revolution with simple cut locus structure

It was known that if the Gaussian curvature function along each meridian on a surface of revolution $(R^2, dr^2+m(r)^2dθ^2)$ is decreasing, then the cut locus of each point of $θ^{-1}(0)$ is empty or a subarc of the opposite meridian $θ^{-1}(π).$ Such a surface is called a von Mangoldt's surface of revolution. A surface of revolution $(R^2, dr^2+m(r)^2dθ^2)$ is called a generalized von Mangoldt surface of revolution if the cut locus of each point of $θ^{-1}(0)$ is empty or a subarc of the opposite meridian $θ^{-1}(π).$ For example, the surface of revolution $(R^2, dr^2+m_0(r)^2dθ^2),$ where $m_0(x):=x/(1+x^2),$ has the same cut locus structure as above and the cut locus of each point in $r^{-1}( (0, \infty ) )$ is nonempty. Note that the Gaussian curvature function is not decreasing along a meridian for this surface. In this article, we give sufficient conditions for a surface of revolution $(R^2, dr^2+m(r)^2dθ^2)$ to be a generalized von Mangoldt surface of revolution. Moreover, we prove that for any surface of revolution with finite total curvature $c,$ there exists a generalized von Mangoldt surface of revolution with the same total curvature $c$ such that the Gaussian curvature function along a meridian is not monotone on $[a,\infty)$ for any $a>0.$

math.DG↗

arXiv2022

Generation of Twisted Gamma-Rays via Two-Photon Transition

We present a new and efficient method of generating twisted gamma rays utilizing highly accelerated helium-like ions; they are excited to a chosen state by irradiating two optical lasers and emit a photon with orbital angular momentum in the deexcitation process. We study its emission rate together with other properties such as background and photo-ionization processes.

hep-ph↗

arXiv2022

Observation of non-linearity of generalized King plot in the search for new boson

We measure isotope shifts for neutral Yb isotopes on an ultranarrow optical clock transition $^{1}\text{S}_{0}-^{3}\text{P}_{0}$ with an accuracy of a few Hz. The part-per-billion precise measurement was possible by loading the ultracold atoms into a three-dimensional magic-wavelength optical lattice and alternately interrogating the isotope pairs, thus minimizing the effects due to the optical lattice light-shift and inter-atomic interaction as well as the drifts of a clock laser frequency and a magnetic field. The determined isotope shifts, combined with one of the recently reported isotope-shift measurements of Yb$^+$ on two optical transitions, allow us to construct the King plots. Extremely large nonlinearity with the corresponding $χ^2$ on the order of $10^4$ is revealed, and is not explained by a quadratic field shift. We further carry out the generalized King plot for three optical transitions so that we can eliminate the contribution arising from a higher-order effect within the Standard Model which might explain the observed nonlinearity of King plots for two transitions. Our analysis of the generalized King plot shows a deviation from linearity at the 3$σ$ level, indicating that there exist at least two higher order contributions in the measured isotope shifts. Then, under the reasonable assumption to attribute them to higher-order field shifts within the Standard Model, we obtain the upper bound of the product of the couplings for a new boson mediating a force between electrons, and neutrons $|y_ey_n|/(\hbar c)< 1\times10^{-10}$ for the mass less than 1 keV with the 95% confidence level is derived, providing an important step towards probing new physics via isotope-shift spectroscopy.

physics.atom-ph↗

arXiv2021

Alternative method of generating gamma rays with orbital angular momentum

We propose a new method of generating gamma rays with orbital angular momentum (OAM). Accelerated partially-stripped ions are used as an energy up-converter. Irradiating an optical laser beam with OAM on ultrarelativistic ions, they are excited to a state of large angular momentum. Gamma rays with OAM are emitted in their deexcitation process. We examine the excitation cross section and deexcitation rate.

hep-ph↗

arXiv2021

A new family of latitudinally corrugated two-spheres of revolution with simple cut locus

There are not so many kinds of surface of revolution whose cut locus structure have been determined, although the cut locus structures of very familiar surfaces of revolution (in Euclidean space) such as ellipsoids, 2-sheeted hyperboloids, paraboloids, and tori are now known. Except for tori, the known cut locus structures are very simple, i.e., a single point or an arc. In this article, a new family {M_n}_n of 2-spheres of revolution with simple cut locus structure is introduced. This family is also new in the sense that the number of points on each meridian which assume a local minimum or maximum of the Gaussian curvature function on the meridian goes to infinity as n goes to infinity.

math.DG↗

arXiv2020

Relativistic effects in search for new intra-atomic force with isotope shifts

Isotope shift of atomic spectra is considered as a probe of new interaction between electrons and neutrons in atoms. We employ the method of seeking a breakdown of King's linearity in the isotope shifts of two atomic transitions. In the present work, we evaluate the magnitudes of the nonlinearity using relativistic wave functions and the result is compared with that of nonrelativistic wave functions in our previous work. It turns out that the nonrelativistic calculation underestimates the nonlinearity owing to the new interaction in the mass range of the mediator greater than 1 MeV. Further, we find that the nonlinearity within the standard model of particle physics is significantly magnified by the relativistic effect in the $\text{p}_{1/2}$ state. To get rid of this obstacle in the new physics search, we suggest to avoid $\text{p}_{1/2}$, and use $\text{p}_{3/2}$ instead for example.

hep-ph↗

arXiv2019

QED background against atomic neutrino process with initial spatial phase

Atomic deexcitation emitting a neutrino pair and a photon is expected to provide a novel method of neutrino physics if it is enhanced by quantum coherence in a macroscopic target. However, the same enhancement mechanism may also lead to a serious problem of enhanced QED background process. We show that the QED background can be suppressed enough in the photonic crystal waveguide by using the spatial phase that is imprinted in the process of initial coherence generation in the target at excitation.

hep-ph↗

arXiv2019

Differentiable sphere theorems whose comparison spaces are standard spheres or exotic ones

We show that for an arbitrarily given closed Riemannian manifold $M$ admitting a point $p \in M$ with a single cut point, every closed Riemannian manifold $N$ admitting a point $q \in N$ with a single cut point is diffeomorphic to $M$ if the radial curvatures of $N$ at $q$ are sufficiently close in the sense of $L^1$-norm to those of $M$ at $p$. Our result hence not only produces a weak version of the Cartan--Ambrose--Hicks theorem in the case where underlying manifolds admit a point with a single cut point, but also is a kind of a weak version of the Blaschke conjecture for spheres proved by Berger. In particular that result generalizes one of theorems in Cheeger's Ph.D. Thesis in that case. Remark that every exotic sphere of dimension $> 4$ admits a metric such that there is a point whose cut locus consists of a single point.

math.DG↗

arXiv2018

Testing leptoquark models in $\bar B \to D^{(*)} τ\barν$

We study potential New Physics effects in the $\bar B \to D^{(*)} τ\barν$ decays. As a particular example of New Physics models we consider the class of leptoquark models and put the constraints on the leptoquark couplings using the recently measured ratios $R(D^{(*)})=BR(\bar B \to D^{(*)} τ\barν)/BR(\bar B \to D^{(*)} μ\barν)$. For consistency, some of the constraints are compared with the ones coming from the current experimental bound on $BR(B \to X_s ν\barν)$. In order to discriminate various New Physics scenarios, we examine the correlations between different observables that can be measured in future.

hep-ph↗

arXiv2018

The Singular Locus of an Almost Distance Function

The aim of this article is to generalize the notion of the cut locus and to get the structure theorem for it. For this purpose, we first introduce a class of 1-Lipschitz functions, each member of which is called an {\it almost distance function}. Typical examples of an almost distance function are the distance function from a point and the Busemann function on a complete Riemannian manifold. The generalized notion of the cut locus in this paper is called the {\it singular locus} of an almost distance function. The singular locus consists of the upper one and the lower one. The upper singular locus coincides with the cut locus of a point for the distance function from the point, and the lower singular locus coincides with the set of all copoints of a ray when the almost distance function is the Busman function of the ray. Therefore, it is possible to treat the cut locus of a closed subset and the set of copoints of a ray in a unified way by introducing the singular locus for the almost distance function. In this article, we obtain the structure theorem (Theorem B) for the singular locus of an almost distance function on a 2-dimensional Finsler manifold that contains both structure theorems ([S], Theorem B) and [Sa,Theorem 2.13]) for the cut locus and the set of copoints of a ray as a corollary.

math.DG↗

arXiv2018

Tomography by neutrino pair beam

We consider tomography of the Earth's interior using the neutrino pair beam which has recently been proposed. The beam produces a large amount of neutrino and antineutrino pairs from the circulating partially stripped ions and provides the possibility to measure precisely the energy spectrum of neutrino oscillation probability together with a sufficiently large detector. It is shown that the pair beam gives a better sensitivity to probe the Earth's crust compared with the neutrino sources at present. In addition we present a method to reconstruct a matter density profile by means of the analytic formula of the oscillation probability in which the matter effect is included perturbatively to the second order.

hep-ph↗

arXiv2017

Effects of initial spatial phase in radiative neutrino pair emission

We study radiative neutrino pair emission in deexcitation process of atoms taking into account coherence effect in a macroscopic target system. In the course of preparing the coherent initial state to enhance the rate, a spatial phase factor is imprinted in the macroscopic target. It is shown that this initial spatial phase changes the kinematics of the radiative neutrino pair emission. We investigate effects of the initial spatial phase in the photon spectrum of the process. It turns out that the initial spatial phase provides us significant improvements in exploring neutrino physics such as the Dirac-Majorana distinction and the cosmic neutrino background.

hep-ph↗

arXiv2017

Probing new intra-atomic force with isotope shifts

In the development of atomic clocks, some atomic transition frequencies are measured with remarkable precision. These measured spectra may include effects of a new force mediated by a weakly interacting boson. Such effects might be distilled out from possible violation of a linear relation in isotope shifts between two transitions, as known as King's linearity, with relatively suppressed theoretical uncertainties. We discuss the experimental sensitivity to a new force in the test of the linearity as well as the linearity violation owing to higher order effects within the Standard Model. The sensitivity to new physics is limited by such effects. We have found that for Yb$^+$, the higher order effect is in the reach of future experiments. The sensitivity to a heavy mediator is also discussed. It is analytically clarified that the sensitivity becomes weaker than that in the literature. Our numerical results of the sensitivity are compared with other weak force search experiments.

hep-ph↗