arXiv subjects

Masayuki Matsuzaki

Publications and source records attributed to Masayuki Matsuzaki.

At least 19 recordsLinked to original sources

arXiv2024

The consistent analyses for determination of the point-nucleon distributions by electron and proton scatterings

Electron scattering cross section, as well as proton scattering cross section, observes the point-proton and the point-neutron distributions, but both cross sections are not able to determine them separately. If they are analyzed consistently with each other, there is a possibility to determine them with less ambiguity.The consistency can be examined through the moments of the charge distribution, which linearly depend on the moments of the point-proton and -neutron distributions.

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arXiv2022

Neutron skin of 48Ca deduced from interaction cross section

The neutron skin thickness of 48Ca was deduced from the interaction cross section by adopting a microscopic optical potential. The optical potential used was constructed by folding a chiral g matrix and the Skyrme mean-field densities renormalized by considering the information of the interaction cross section. The result was R_skin = 0.139 \pm 0.058 fm.

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arXiv2021

Neutron skin thickness of $^{208}$Pb, $^{116,120,124}$Sn, and $^{40}$Ca determined from reaction cross sections of $^{4}$He scattering

[Background] We constructed the Kyushu chiral $g$-matrix and confirmed its reliability at $30 \lesssim E_{\rm in} \lesssim 100 $~MeV and $250 \lesssim E_{\rm in} \lesssim 400$~MeV for $^{12}$C scattering. Reaction cross section data of $^{4}$He scattering are available for some nuclides including $^{208}$Pb. PREX II collaboration reported a thick neutron skin for $^{208}$Pb. [Purpose] Our purpose is to deduce neutron skin thicknesses of $^{208}$Pb and some other nuclides from reaction cross sections calculated in terms of the double folding model with the $g$-matrix. [Methods] We fold the $g$-matrix and densities given by mean field calculations. In order to remedy less-constrainedness of the neutron sector, we renormalize densities so as to reproduce the observed cross sections. [Results] We found that a 3.4~$\%$ renormalization is necessary for $^{208}$Pb. The neutron density obtained from renormalization results in $R_{\rm skin}=$ 0.416$\pm$0.146 fm by confronting the precision proton radius. [Conclusions] Our result is consistent with PREX II and therefore supports larger slope parameter $L$. Results for $^{40}$Ca and $^{124}$Sn are also consistent with $R_{\rm skin}$ deduced from other experiments. For $^{116,120}$Sn the present method gives thicker skins.

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arXiv2020

Multiparameter quantum estimation under dephasing noise

Simultaneous quantum estimation of multiple parameters has recently become essential in quantum metrology. Although the ultimate sensitivity of a multiparameter quantum estimation in noiseless environments can beat the standard quantum limit that every classical sensor is bounded by, it is unclear whether the quantum sensor has an advantage over the classical one under realistic noise. In this work, we present a framework of the simultaneous estimation of multiple parameters with quantum sensors in a certain noisy environment. Our multiple parameters to be estimated are three components of an external magnetic field, and we consider the noise that causes only dephasing. We show that there is an optimal sensing time in the noisy environment and the sensitivity can beat the standard quantum limit when the noisy environment is non-Markovian.

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arXiv2020

Nuclear Magnetic Resonance model of an entangled sensor under noise

Entangled sensors have been attracting a lot of attention recently because they can achieve the sensitivity beyond that of the classical sensors. To exploit entanglement as a resource, it is important to understand the effect of noise because the entangled state is fragile against noise. Here, we provide a Nuclear Magnetic Resonance (NMR) model of an entangled sensor under engineered noise: one can implement an entangled sensor under various noisy environments. In particular, we experimentally investigate the performance of the entangled sensor under the effect of time-inhomogeneous noisy environment with which the entangled sensor holds potential to beat the classical sensors. Our "entangled sensor" consists of a multi-spin molecule solved in isotropic liquid, and we can perform the quantum sensing by using NMR techniques.

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arXiv2018

Study of Open Systems with Molecules in Isotropic Liquids

We are interested in dynamics of a system in an environment, or an open system. Such phenomena like {\it crossover} from Markovian to non-Markovian relaxation and {\it thermal equilibration} are of our interest. Open systems have experimentally been studied with ultra cold atoms, ions in traps, optics, and cold electric circuits because well isolated systems can be prepared here and thus the effects of environments can be controlled. We point out that some molecules solved in isotropic liquid are well isolated and thus they can also be employed for studying open systems in Nuclear Magnetic Resonance (NMR) experiments. First, we provide a short review on related phenomena of open systems that helps readers to understand our motivation. We, then, present two experiments as examples of our approach with molecules in isotropic liquids. Crossover from Markovian to non-Markovian relaxation was realized in one NMR experiment, while relaxation like phenomena were observed in approximately isolated systems in the other.

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arXiv2016

Quantal rotation and its coupling to intrinsic motion in nuclei

Symmetry breaking is an importance concept in nuclear physics and other fields of physics. Self-consistent coupling between the mean-field potential and the single-particle motion is a key ingredient in the unified model of Bohr and Mottelson, which could lead to a deformed nucleus as a consequence of spontaneous breaking of the rotational symmetry. Some remarks on the finite-size quantum effects are given. In finite nuclei, the deformation inevitably introduces the rotation as a symmetry-restoring collective motion (Anderson-Nambu-Goldstone mode), and the rotation affects the intrinsic motion. In order to investigate the interplay between the rotational and intrinsic motions in a variety of collective phenomena, we use the cranking prescription together with the quasiparticle random phase approximation. At low spin, the coupling effect can be seen in the generalized intensity relation. A feasible quantization of the cranking model is presented, which provides a microscopic approach to the higher-order intensity relation. At high spin, the semiclassical cranking prescription works well. We discuss properties of collective vibrational motions under rapid rotation and/or large deformation. The superdeformed shell structure plays a key role in emergence of a new soft mode which could lead to instability toward the $K^π=1^-$ octupole shape. A wobbling mode of excitation, which is a clear signature of the triviality, is discussed in terms of a microscopic point of view. A crucial role played by the quasiparticle alignment is presented.

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arXiv2016

Quadrupole and monopole transition properties of $0^+_2$ in Gd isotopes

The longstanding problem of characterization of the $0^+_2$ states in Gd isotopes is revisited by adopting the Nilsson$+$BCS mean field and the random-phase approximation. The interband electric quadrupole transition strengths varying almost two orders of magnitude are nicely reproduced at the same time as other observables. These results indicate that the $0^+_2$ states, in particular, those in lighter isotopes are well described as $β$ vibrations excited on top of deformed ground states without recourse to the shape-coexistence picture.

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arXiv2014

Changes in rotational characters of one- and two-phonon $γ$-vibrational bands in $^{105}$Mo

The $γ$ vibration is the most typical low-lying collective motion prevailing the nuclear chart. But only few one-phonon rotational bands in odd-$A$ nuclei have been known. Furthermore, two-phonon states, even the band head, have been observed in a very limited number of nuclides not only of odd-$A$ but even-even. Among them, that in $^{105}$Mo is unique in that Coriolis effects are expected to be stronger than in $^{103}$Nb and $^{105}$Nb on which theoretical studies were reported. Then the purpose of the present work is to study $^{105}$Mo paying attention to rotational character change of the one-phonon and two-phonon bands. The particle-vibration coupling model based on the cranking model and the random-phase approximation is used to calculate the vibrational states in rotating odd-$A$ nuclei. The present model reproduces the observed yrast zero-phonon and one-phonon bands well. Emerging general features of the rotational character change from low spin to high spin are elucidated. In particular, the reason why the one-phonon band does not exhibit signature splitting is clarified. The calculated collectivity of the two-phonon states, however, is located higher than observed.

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arXiv2014

Single-phonon and multi-phonon excitations of the $γ$ vibration in rotating odd-$A$ nuclei

Multi-phonon excitations in atomic nuclei were observed very rarely although collective motions in quantum many-body systems are described as bosonic excitations. In particular, the first two-phonon $γ$ vibrational ($2γ$) excitation in odd-$A$ nuclei was reported in 2006 and only a few have been known. Quite recently, conspicuously enhanced $B(E2)$s feeding $2γ$ states were observed in $^{105}$Nb and conjectured that their parent states are candidates of $3γ$ states. In the present work, the model space is enlarged from the present author's previous calculation for $^{103}$Nb. The purpose is twofold: One is to see how the description of $2γ$ states is improved, and the other is to examine the existence of collective $3γ$ states, and when they exist, study their collectivity through calculating interband $B(E2)$s. The particle-vibration coupling model based on the cranking model and the random-phase approximation is used to calculate the vibrational states in rotating odd-$A$ nuclei. Interband $B(E2)$s are calculated by adopting the method of the generalized intensity relation. The present calculation reproduces the observed spectra of $0γ$ - $2γ$ states well and gives collective $3γ$ states with enhanced $B(E2)$s to $2γ$ states in $^{103}$Nb and $^{105}$Nb. The most collective $3γ$ state with the highest $K$ at zero rotation is thought to be the main component of the observed band.

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arXiv2014

Recursion Method for Deriving Energy-Independent Effective Interaction

The effective-interaction theory has been one of the useful and practical methods for solving nuclear many-body problems based on the shell model. Various approaches have been proposed which are constructed in terms of the so-called $\widehat{Q}$ box and its energy derivatives introduced by Kuo {\it et al}. In order to find out a method of calculating them we make decomposition of a full Hilbert space into subspaces (the Krylov subspaces) and transform a Hamiltonian to a block-tridiagonal form. This transformation brings about much simplification of the calculation of the $\widehat{Q}$ box. In the previous work a recursion method has been derived for calculating the $\widehat{Q}$ box analytically on the basis of such transformation of the Hamiltonian. In the present study, by extending the recursion method for the $\widehat{Q}$ box, we derive another recursion relation to calculate the derivatives of the $\widehat{Q}$ box of arbitrary order. With the $\widehat{Q}$ box and its derivatives thus determined we apply them to the calculation of the $E$-independent effective interaction given in the so-called Lee-Suzuki (LS) method for a system with a degenerate unperturbed energy. We show that the recursion method can also be applied to the generalized LS scheme for a system with non-degenerate unperturbed energies. If the Hilbert space is taken to be sufficiently large, the theory provides an exact way of calculating the $\widehat{Q}$ box and its derivatives. This approach enables us to perform recursive calculations for the effective interaction to arbitrary order for both systems with degenerate and non-degenerate unperturbed energies.

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arXiv2013

Formulation of effective interaction in terms of renormalized vertices and propagators

One of the useful and practical methods for solving quantum-mechanical many-body systems is to recast the full problem into a form of the effective interaction acting within a model space of tractable size. Many of the effective-interaction theories in nuclear physics have been formulated by use of the so called $\hatQ$ box introduced by Kuo et.al. It has been one of the central problems how to calculate the $\hatQ$ box accurately and efficiently. We first show that, introducing new basis states, the Hamiltonian is transformed to a block-tridiagonal form in terms of submatrices with small dimension. With this transformed Hamiltonian, we next prove that the $\hatQ$ box can be expressed in two ways: One is a form of continued fraction and the other is a simple series expansion up to second order with respect to renormalized vertices and propagators. This procedure ensures to derive an exact $\hatQ$ box, if the calculation converges as the dimension of the Hilbert space tends to infinity. The $\hatQ$ box given in this study corresponds to a non-perturbative solution for the energy-dependent effective interaction which is often referred to as the Bloch-Horowitz or the Feshbach form. By applying the $\hatZ$-box approach based on the $\hatQ$ box proposed previously, we introduce a graphical method for solving the eigenvalue problem of the Hamiltonian. The present approach has a possibility of resolving many of the difficulties encountered in the effective-interaction theory.

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arXiv2011

Two-phonon $γ$-vibrational states in rotating triaxial odd-$A$ nuclei

Distribution of the two phonon $γ$ vibrational collectivity in the rotating triaxial odd-$A$ nucleus, $^{103}$Nb, that is one of the three nuclides for which experimental data were reported recently, is calculated in the framework of the particle vibration coupling model based on the cranked shell model plus random phase approximation. This framework was previously utilized for analyses of the zero and one phonon bands in other mass region and is applied to the two phonon band for the first time. In the present calculation, three sequences of two phonon bands share collectivity almost equally at finite rotation whereas the $K=Ω+4$ state is the purest at zero rotation.

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arXiv2010

Pionic BEC--BCS crossover at finite isospin chemical potential

We study the character change of the pionic condensation at finite isospin chemical potential μ_\mathrm{I} by adopting the linear sigma model as a non-local interaction between quarks. At low |μ_\mathrm{I}| the condensation is purely bosonic, then the Cooper pairing around the Fermi surface grows gradually as |μ_\mathrm{I}| increases. This q-\bar q pairing is weakly coupled in comparison with the case of the q-q pairing that leads to color superconductivity.

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arXiv2009

Correlations among discontinuities in QCD phase diagram

We show, in general, that when a discontinuity of either zeroth-order or first-order takes place in an order parameter such as the chiral condensate, discontinuities of the same order emerge in other order parameters such as the Polyakov loop. A condition for the coexistence theorem to be valid is clarified. Consequently, only when the condition breaks down, zeroth-order and first-order discontinuities can coexist on a phase boundary. We show with the Polyakov-loop extended Nambu--Jona-Lasinio model that such a type of coexistence is realized in the imaginary chemical potential region of the QCD phase diagram. We also present examples of coexistence of the same-order discontinuities in the real chemical potential region.

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arXiv2009

Meson mass at real and imaginary chemical potentials

The chemical-potential dependence of pi and sigma meson masses is analyzed at both real and imaginary chemical potentials, $μ_\mathrm{R}$ and $μ_\mathrm{I}$, by using the Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model that possesses both the extended ${\mathbb Z}_3$ symmetry and the chiral symmetry. In the $μ_\mathrm{I}$ region, the meson masses have the Roberge-Weiss periodicity. Assuming that the meson masses will be measured at finite $μ_\mathrm{I}$ by lattice QCD in future, we simulate how meson masses at finite $μ_\mathrm{R}$ are extracted from those at finite $μ_\mathrm{I}$, and propose a reliable extraction method.

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arXiv2009

Determination of QCD phase diagram from the imaginary chemical potential region

We test the reliability of the the Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model, comparing the model result with the lattice data at nonzero imaginary chemical potential. The PNJL model with the vector-type four-quark and scalar-type eight-quark interactions reproduces the lattice data on the pseudocritical temperatures of the deconfinement and chiral phase transitions. The QCD phase diagram in the real chemical potential region is predicted by the PNJL model. The critical endpoint survives, even if the vector-type four-quark interaction is taken into account.

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arXiv2008

Vector-type four-quark interaction and its impact on QCD phase structure

Effects of the vector-type four-quark interaction on QCD phase structure are investigated in the imaginary chemical potential region, by using the Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model with the extended Z3 symmetry. In the course to this end, we clarify analytically the Roberge-Weiss periodicity and symmetry properties of various quantities under the existence of a vector-type four-quark interaction. In the imaginary chemical potential region, the chiral condensate and the quark number density are sensitive to the strength of the interaction. Based on this result, we propose a possibility to determine the strength of the vector-type interaction, which largely affects QCD phase structure in the real chemical potential region, by comparing the results of lattice simulations and effective model calculations in the imaginary chemical potential region.

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