arXiv subjects

S. Yasui

Publications and source records attributed to S. Yasui.

At least 19 recordsLinked to original sources

arXiv2024

Exploration of optimal hyperfine transitions for spin-wave storage in $^{167}$Er$^{3+}$:Y$_2$SiO$_5$

The dependence of the magnetic fluctuations and the spin coherence time $T_2^{\rm hyp}$ of the lowest Stark states $^4I_{15/2}\ (Z_1)$ in $^{167}$Er$^{3+}$:Y$_2$SiO$_5$ under zero magnetic field on Er concentration is numerically investigated in the range of 10 to 100 parts per million (ppm). We investigate two primary sources of magnetic fluctuation limiting spin coherence: a constant contribution from host Y nuclei and a concentration-dependent component from dipole-dipole interactions among Er ions. Due to these two components, the Er-concentration dependence of $T_2^{\rm hyp}$ at the zero first-order Zeeman (ZEFOZ) points saturates for crystals with Er concentration below 10 ppm and no extension of the $T_2^{\rm hyp}$ is expected without an external magnetic field. Under a magnetic field, the longest $T_2^{\rm hyp}$ at a particular ZEFOZ point is expected to be over 170 s (90 s) for site 1 (site 2), which is more than $10^4$ times longer than that at zero field for 10-ppm $^{167}$Er$^{3+}$:Y$_2$SiO$_5$. Remarkably, these optimal ZEFOZ points form striking geometric patterns: a line for site 1 and a plane for site 2. This trend, which is favorable for experiments, can be explained by the anisotropy of the effective spin Hamiltonian parameters. Finally, the tolerance of the ZEFOZ point at each site with the longest $T_2^{\rm hyp}$ against the errors in the applied magnetic field vector is evaluated.

quant-ph↗

arXiv2021

Dielectric response of BaTiO3 electronic states under AC fields via microsecond time-resolved X-ray absorption spectroscopy

For the first time, the dielectric response of a BaTiO3 thin film under an AC electric field is investigated using time-resolved X-ray absorption spectroscopy at the Ti K-edge to clarify correlated contributions of each constituent atom on the electronic states. Intensities of the pre-edge eg peak and shoulder structure just below the main edge increase with an increase in the amplitude of the applied electric field, whereas that of the main peak decreases in an opposite manner. Based on the multiple scattering theory, the increase and decrease of the eg and main peaks are simulated for different Ti off-center displacements. Our results indicate that these spectral features reflect the inter- and intra-atomic hybridization of Ti 3d with O 2p and Ti 4p, respectively. In contrast, the shoulder structure is not affected by changes in the Ti off-center displacement but is susceptible to the effect of the corner site Ba ions. This is the first experimental verification of the dynamic electronic contribution of Ba to polarization reversal.

cond-mat.mtrl-sci↗

arXiv2014

Spectroscopy of heavy baryons with breaking of heavy-quark symmetry

Transition decay widths by one-pion emissions for excited heavy-baryons with a single heavy (charm and bottom) quark are investigated by following the heavy-quark symmetry and its breaking effects at ${\cal O}(1/M)$ for a heavy-baryon mass $M$. Based on the heavy-baryon effective theory, interaction Lagrangian for the heavy baryons with axial-vector current induced by a pion is constructed. It is presented that the transition decay widths up to ${\cal O}(1/M)$ in several channels are constrained. The results will be useful in experimental study of excited heavy-baryons.

hep-ph↗

arXiv2014

Heavy quark symmetry in multi-hadron systems

We discuss the properties of hadronic systems containing one heavy quark in the heavy quark limit. The heavy quark symmetry guarantees the mass degeneracy of the states with total spin and parity $(j-1/2)^{P}$ and $(j+1/2)^{P}$ with $j \geq 1/2$, because the heavy-quark spin is decoupled from the total spin $j$ of the light components called brown muck. We apply this idea to heavy multi-hadron systems, and formulate the general framework to analyze their properties. We demonstrate explicitly the spin degeneracy and the decomposition of the wave functions in exotic heavy hadron systems generated by the one boson exchange potential. The masses of the brown muck can be extracted from theoretical and experimental hadron spectra, leading to the color non-singlet spectroscopy.

hep-ph↗

arXiv2013

Spin degeneracy in multi-hadron systems with a heavy quark

We study multi-hadron systems with a single heavy quark (charm or bottom) in the limit of heavy quark mass. The spin degeneracy of the states with quantum numbers $(j+1/2)^{P}$ and $(j-1/2)^{P}$ for $j \neq 0$, known in a normal hadron, can be generalized to multi-hadron systems. The spin degeneracy is the universal phenomena for any multi-hadron systems with a single heavy quark, irrespective of their internal structures, including compact multi-quarks, hadronic molecules and exotic nuclei. We demonstrate the spin degeneracy in the hadronic systems formed by a heavy hadron effective theory; $P^{(\ast)}N$ states with a $P^{(\ast)}=\bar{D}^{(\ast)}$, $B^{(\ast)}$ meson and a nucleon $N$, and a $P^{(\ast)}$ meson in nuclear matter.

hep-ph↗

arXiv2013

Probing gluon dynamics by charm and bottom mesons in nuclear medium from heavy meson effective theory with 1/M-corrections

We consider heavy mesons with charm and bottom in nuclear medium. We construct the effective Lagrangian with axial-vector coupling including 1/M-corrections for the heavy meson mass $M$ by following the velocity-rearrangement invariance. As an application, we consider heavy mesons, $\bar{\mathrm{D}}$ and $\bar{\mathrm{D}}^{\ast}$ mesons for charm and $\mathrm{B}$ and $\mathrm{B}^{\ast}$ mesons for bottom, bound in nuclear matter, and we discuss their in-medium masses modified by the interaction with nucleons via pion exchanges including the 1/M-corrections. The mass modifications are affected by the gluon dynamics in nuclear medium. By comparison with the heavy quark effective theory, we find that the effects of scale anomaly become suppressed in nuclear medium. We also find that the contributions from the chromoelectric gluon are enhanced in nuclear medium, while those from the chromomagnetic gluon are reduced. We propose to use heavy mesons as probes to research the gluon fields in nuclear medium in experimental studies.

hep-ph↗

arXiv2013

Heavy quark dynamics for charm and bottom flavor on Fermi surface at zero temperature

We discuss the dynamics in finite density medium including a heavy impurity particle (hadron or quark) with a heavy flavor, charm and bottom, at zero temperature. As a system, we consider a $\bar{D}$ ($B$) meson embedded in nuclear matter as a heavy impurity boson with SU(2) isospin symmetry. As another system, we also consider a charm (bottom) quark embedded in quark matter as a heavy impurity fermion with SU(3) color symmetry. We suppose a vector current interaction with SU($n$) symmetry ($n \ge 2$) for the fermion composing the Fermi surface and the embedded heavy impurity particle, and calculate the scattering amplitude perturbatively for the small coupling constant up to one-loop level. We obtain that the scattering amplitude has a logarithmic enhancement in the large mass limit of the heavy impurity particle, and show that the perturbative calculation breaks down for any small coupling constant in this limit.

hep-ph↗

arXiv2013

Exotic hadrons and hadron-hadron interactions in heavy ion collisions

We discuss the exotic hadron structure and hadron-hadron interactions in view of heavy ion collisions. First, we demonstrate that a hadronic molecule with a large spatial size would be produced more abundantly in the coalescence model compared with the statistical model result. Secondly, we constrain the Lambda-Lambda interaction by using the recently measured Lambda-Lambda correlation data. We find that the RHIC-STAR data favor the Lambda-Lambda scattering parameters in the range 1/a_0 <= -0.8 fm^{-1} and r_{eff} >= 3 fm.

nucl-th↗

arXiv2012

Exotic mesons with hidden charm and bottom near thresholds

We study heavy hadron spectroscopy near heavy meson thresholds. We employ heavy pseudoscalar meson P and heavy vector meson P* as effective degrees of freedom and consider meson exchange potentials between them. All possible composite states which can be constructed from the P and P* mesons are studied up to the total angular momentum J <= 2. We consider, as exotic states, isosinglet states with exotic J^{PC} quantum numbers and isotriplet states. We solve numerically the Schrödinger equation with channel-couplings for each state. We found B(*)barB(*) molecule states for I^G(J^{PC}) = 1^+(1^{+-}) correspond to the masses of twin resonances Zb(10610) and Zb(10650). We predict several possible B(*)barB(*) bound and/or resonant states in other channels. On the other hand, there are no B(*)barB(*) bound and/or resonant states whose quantum numbers are exotic.

hep-ph↗

arXiv2012

$\bar{\mathrm{D}}$ and $\mathrm{B}$ mesons in nuclear medium

We discuss the mass modifications of $\bar{\mathrm{D}}$ and $\bar{\mathrm{D}}^{\ast}$ ($\mathrm{B}$ and $\mathrm{B}^{\ast}$) mesons in nuclear medium. The heavy quark symmetry for $\bar{\mathrm{D}}$ and $\bar{\mathrm{D}}^{\ast}$ ($\mathrm{B}$ and $\mathrm{B}^{\ast}$) mesons is adopted, and the interaction between a $\bar{\mathrm{D}}$ or $\bar{\mathrm{D}}^{\ast}$ ($\mathrm{B}$ or $\mathrm{B}^{\ast}$) meson and a nucleon is supplied from the pion exchange. We find the negative mass shifts for $\bar{\mathrm{D}}$ meson and $\mathrm{B}$ meson, and hence that the $\bar{\mathrm{D}}$ and $\mathrm{B}$ mesons are bound in the nuclear medium. As applications, we consider the atomic nuclei with a $\bar{\mathrm{D}}$ meson, $^{40}_{\bar{\mathrm{D}}}\mathrm{Ca}$ and $^{208}_{\bar{\mathrm{D}}}\mathrm{Pb}$, and investigate the energy levels of the $\bar{\mathrm{D}}$ meson in each nucleus. We also discuss the mass shifts in the isospin asymmetric nuclear medium, and present the possible phenomenon about distribution of isospin density around a $\bar{\mathrm{D}}$ or $\mathrm{B}$ meson in nuclear medium. We find that the mass shifts of $\bar{\mathrm{D}}^{\ast}$ and $\mathrm{B}^{\ast}$ mesons have large imaginary parts, which would prevent precise study of the energy levels of $\bar{\mathrm{D}}^{\ast}$ and $\mathrm{B}^{\ast}$ mesons in nuclei.

hep-ph↗

arXiv2008

Studying Diquark Structure of Heavy Baryons in Relativistic Heavy Ion Collisions

We propose the enhancement of $Λ_c$ yield in heavy ion collisions at RHIC and LHC as a novel signal for the existence of diquarks in the strongly coupled quark-gluon plasma produced in these collisions as well as in the $Λ_c$. Assuming that stable bound diquarks can exist in the quark-gluon plasma, we argue that the yield of $Λ_c$ would be increased by two-body collisions between $ud$ diquarks and $c$ quarks, in addition to normal three-body collisions among $u$, $d$ and $c$ quarks. A quantitative study of this effect based on the coalescence model shows that including the contribution of diquarks to $Λ_c$ production indeed leads to a substantial enhancement of the $Λ_c/D$ ratio in heavy ion collisions.

nucl-th↗

arXiv2007

Λ^{\ast}-hypernuclei in phenomenological nuclear forces

The $Λ^{\ast}$-hypernuclei, which are bound states of $Λ(1405)$ and nuclei, are discussed as a possible interpretation of the $\bar{K}$-nuclei. The Bonn and Nijmegen potentials are extended and used as a phenomenological potential between $Λ^{\ast}$ and $N$. The $K$-exchange potential is also considered in the $Λ^{\ast}$ and $N$ interaction. The two-body ($Λ^{\ast}N$) and three-body ($Λ^{\ast}NN$) systems are solved by a variational method. It is shown that the spin and isospin of the ground states are assigned as $Λ^{\ast}N(S=1, I=1/2)$ and $Λ^{\ast}NN(S=3/2, I=0)$, respectively. The binding energies of the $Λ^{\ast}$-hypernuclei are discussed in comparison with experiment.

nucl-th↗

arXiv2007

Quark condensates in the chiral bag with the NJL interaction

We discuss the quark condensate of the vacuum inside the baryon. We analyze the 1+1 dimensional chiral bag in analogy with the realistic 3+1 dimensional one. The Nambu--Jona-Lasinio (NJL) type interaction is used to investigate the quark condensate in the chiral bag. Considering the strong meson-quark coupling, we solve the mean field solution to the scalar and pseudoscalar channels by including the chiral Casimir effects. The self-consistent equation allows a finite value of the quark condensate and hence a finite dynamical quark mass inside the bag. It is shown that an approximate Cheshire Cat picture holds for massive quarks.

hep-ph↗

arXiv2007

Management of localized energy in discrete nonlinear transmission lines

The manipulation of locked intrinsic localized modes/discrete breathers is studied experimentally in nonlinear electric transmission line arrays. Introducing a static lattice impurity in the form of a capacitor, resistor or inductor has been used both to seed or destroy and attract or repel these localized excitations. In a nonlinear di-element array counter propagating short electrical pulses traveling in the acoustic branch are used to generate a stationary intrinsic localized mode in the optic branch at any particular lattice site. By changing the pulse polarity the same localized excitation can be eliminated demonstrating that the dynamical impurity associated with the propagating electrical pulse in the acoustic branch can trigger optical localized mode behavior.

nlin.PS↗

arXiv2007

Triquark structure and isospin symmetry breaking in exotic Ds mesons

The color anti-triplet triquark $q\bar{q}\bar{q}$ is considered as a compact component in the tetraquark structure $cq\bar{q}\bar{q}$ of exotic $D_{s}$ mesons. We discuss the mass spectrum and the flavor mixing of the triquarks by using the instanton induced interaction and the one-gluon exchange potentials. As a characteristic property of the triquark, we investigate the isospin violation. It is shown that the flavor $\bar{\bf 3}$ (isosinglet) and $\bf 6$ (isotriplet) states may be strongly mixed and then are identified with $D_{s}(2632)$.

hep-ph↗

arXiv2006

Chiral symmetry breaking and vacuum polarization in a bag

We study the effects of a finite quark mass in the hedgehog configuration in the two phase chiral bag model. We discuss the chiral properties, such as the fractional baryon number and the chiral Casimir energy, by using the Debye expansion for the analytical calculation and the Strutinsky's smearing method for the numerical computation. It is shown that the fractional baryon number carried by massive quarks in the vacuum is canceled by that in the meson sector. A finite term of the chiral Casimir energy is obtained with subtraction of the logarithmic divergence term.

hep-ph↗

arXiv2006

Quark droplets with chiral symmetry in the Nambu--Jona-Lasinio model

We discuss the stability of strangelets by considering dynamical chiral symmetry breaking. For quark droplets of finite volume, we formulate the Nambu--Jona-Lasinio model with a basis set of the quark wave functions in the chiral bag model. Chiral symmetry breaking for the finite volume bag is discussed in a mean field approximation. Effects of the pion cloud including the chiral Casimir effect are investigated. Physical quantities of the quark droplets such as masses and radii are obtained for quark droplets of baryon numbers up to five. We also apply our model setting to the nucleon and discuss the stability of the quark droplets against nuclei.

hep-ph↗

arXiv2006

Chiral symmetry breaking and stability of quark droplets

We discuss the stability of strangelets -- quark droplets with strangeness -- in the Nambu--Jona-Lasinio model supplemented by a boundary condition for quark confinement. Effects of dynamical chiral symmetry breaking are considered properly inside quark droplets of arbitrary baryon number. We obtain the energy per baryon number of quark droplets with baryon number from one to thousands. It is shown that strangelets are not the ground states as compared with nuclei, though they can be locally stable.

hep-ph↗