arXiv subjects

Daiki Suenaga

Publications and source records attributed to Daiki Suenaga.

54 records · Page 3Linked to original sources

arXiv2021

Relativistic corrections to decays of heavy baryons in the quark model

We investigate relativistic corrections of order $1/m^{2}$, where $m$ is the constituent quark mass, to heavy baryon decays by emitting one pseudoscalar meson in the quark model. This work is motivated by shortcomings in the previous studies in the nonrelativistic quark model for decays of the Roper-like states such as $Λ_c(2765)$. We find that the relativistic corrections due to the internal motion of quarks are essential ingredients in improving their decay properties such that the decay widths are significantly increased. In addition, such corrections can explain a phenomenological suppression of the quark axial-vector coupling constant $g_A^q$ for the $Σ_c(2455)$ and $Σ_c(2520)$ decays.

hep-ph↗

arXiv2021

Spin-orbital magnetic response of relativistic fermions with band hybridization

Spins of relativistic fermions are related to their orbital degrees of freedom. In order to quantify the effect of hybridization between relativistic and nonrelativistic degrees of freedom on spin-orbit coupling, we focus on the spin-orbital (SO) crossed susceptibility arising from spin-orbit coupling. The SO crossed susceptibility is defined as the response function of their spin polarization to the "orbital" magnetic field, namely the effect of magnetic field on the orbital motion of particles as the vector potential. Once relativistic and nonrelativistic fermions are hybridized, their SO crossed susceptibility gets modified at the Fermi energy around the band hybridization point, leading to spin polarization of nonrelativistic fermions as well. These effects are enhanced under a dynamical magnetic field that violates thermal equilibrium, arising from the interband process permitted by the band hybridization. Its experimental realization is discussed for Dirac electrons in solids with slight breaking of crystalline symmetry or doping, and also for quark matter including dilute heavy quarks strongly hybridized with light quarks, arising in a relativistic heavy-ion collision process.

cond-mat.mes-hall↗

arXiv2021

Thermal quarks and gluon propagators in two-color dense QCD

We study Landau gauge gluon propagators in two-color QCD at finite quark chemical potential ($μ_q$) and temperature ($T$). We include medium polarization effects at one-loop by quarks into massive gluon propagators, and compared the analytic results with the available lattice data. We particularly focus on the high density phase of color-singlet diquark condensates whose critical temperature is $\sim 100$ MeV with weak dependence on $μ_q$. At zero temperature the color singlet condensates protect the IR limit of electric and magnetic gluon propagators from the medium screening effects. At finite temperature, this behavior remains true for the magnetic sector, but the electric screening mass should be generated by thermal, and hence gapless, particles which are unbound from the diquark condensates. Treating thermal excitations as quasi-quarks, we found that the electric screening develops too fast compared to the lattice results. Beyond the critical temperature for diquark condensates the analytic results are consistent with the lattice results.

hep-ph↗

arXiv2021

Two relativistic Kondo effects: Classification with particle and antiparticle impurities

We investigate two different types of relativistic Kondo effects, distinguished by heavy-impurity degrees of freedom, by focusing on the energy-momentum dispersion relations of the ground state with condensates composed of a light Dirac fermion and a nonrelativistic impurity fermion. Heavy fermion degrees of freedom are introduced in terms of two types of heavy-fermion effective theories, in other words, two heavy-fermion limits for the heavy Dirac fermion, which are known as the heavy-quark effective theories (HQETs) in high-energy physics. While the first one includes only the heavy-particle component, the second one contains both the heavy-particle and heavy-antiparticle components, which are opposite in their parity. From these theories, we obtain two types of Kondo effects, in which the dispersions near the Fermi surface are very similar, but they differ in the structure at low momentum. We also classify the possible forms of condensates in the two limits. The two Kondo effects will be examined by experiments with Dirac/Weyl semimetals or quark matter, lattice simulations, and cold-atom simulations.

hep-ph↗

arXiv2020

Chiral separation effect catalyzed by heavy impurities

We investigate the influence of Kondo effect, namely, the nonperturbative effect induced by heavy impurities, on the chiral separation effect (CSE) in quark matter. We employ a simple effective model incorporating the Kondo condensate made of a light quark and a heavy quark, and compute the response function of axial current to the magnetic field in static limit and dynamical limit. As a result, we find that the Kondo effect catalyzes the CSE in both the limits, and particularly the CSE in dynamical limit can be enhanced by a factor of approximately three. Our findings clearly show that the presence of heavy impurities in quark matter can play an important role in the transport phenomena of light quarks induced by a magnetic field.

hep-ph↗

arXiv2020

Kondo effect driven by chirality imbalance

We propose a novel mechanism of the Kondo effect driven by a chirality imbalance (or chiral chemical potential) of relativistic light fermions. This effect is realized by the mixing between a right- or left-handed fermion and a heavy impurity in the chirality imbalanced matter even at zero density. This is different from the usual Kondo effect induced by finite density. We derive the Kondo effect from both a perturbative calculation and a mean-field approach. We also discuss the temperature dependence of the Kondo effect. The Kondo effect at nonzero chiral chemical potential can be tested by future lattice simulations.

hep-ph↗

arXiv2020

QCD Kondo excitons

The quantum chromodynamics (QCD) Kondo effect is a quantum phenomenon in which heavy quarks ($c$, $b$) exist as impurity particles in quark matter composed of light quarks ($u$, $d$, $s$) at extremely high density. This is analogous to the famous Kondo effect in condensed matter physics. In the present paper, we show theoretically the existence of the "QCD Kondo excitons", i.e., the bound states of light quarks and heavy quarks, as the lowest-excitation modes above the ground state of the quark matter governed by the QCD Kondo effect. These are neutral for color and electric charges, similarly to the Kondo excitons in condensed matter, and they are new type of quasiparticles absent in the normal phase of quark matter. The QCD Kondo excitons have various masses and quantum numbers, i.e., flavors and spin parities (scalar, pseudoscalar, vector, and axialvector). The QCD Kondo excitons lead to the emergence of the neutral currents in transport phenomena, which are measurable in lattice QCD simulations. The study of the QCD Kondo excitons will provide us with understanding of new universal properties shared by quark matter and condensed matter.

nucl-th↗

arXiv2020

Comprehensive study of mass modifications of light mesons in nuclear matter in the three-flavor extended Linear Sigma Model

We present a comprehensive study of mass modifications of scalar, pseudo-scalar, vector, and axial-vector mesons in nuclear matter using the three-flavor extended Linear Sigma Model (eLSM) and the two-flavor Parity Doublet Model (PDM). The meson masses in nuclear matter are determined by calculating the one-loop nucleon corrections to the meson mean fields. As a result, we find all spin-$0$ meson masses except those of the pion, kaon, and the lightest scalar-isoscalar mesons decrease at finite baryon density. For spin-$1$ mesons, masses of all axial-vector mesons decrease in medium, and the density dependences of the $ρ$ and $ω$ meson masses strongly depend on the value of chiral invariant mass ($M_0$). Also, our results suggest $M_0\approx0.8\, {\rm GeV}$ is preferable.

nucl-th↗

arXiv2019

Gluon propagator in two-color dense QCD: Massive Yang-Mills approach at one-loop

We study the Landau gauge gluon propagators in dense two-color QCD at quark chemical potential, $μ_q$, in the range from 0.5 to 1.0 GeV not reachable by the perturbative method at weak coupling. In order to take into account the non-perturbative effects, at tree level we use a massive Yang-Mills model for the Yang-Mills theory (or the Curci-Ferrari model) which has successfully described the lattice results of the gluon and ghost propagators in the Landau gauge. We couple quarks to this theory and compute the one-loop polarization effects in medium. The presence of the gluon mass significantly tempers the medium effects and uncertainties associated with the strong coupling constant $α_s$. The diquark condensate in two-color QCD is color-singlet, for which neither electric nor magnetic screening masses should appear at the scale less than the diquark gap. The presence of the gap helps to explain the lattice results which are not very sensitive to the quark density. Meanwhile we also found the limitation of the one-loop estimate as well as the lack of some physics in perturbative medium corrections.

hep-ph↗

arXiv2019

$D$ mesons as a probe of Casimir effect for chiral symmetry breaking

We propose $D$ mesons as probes to investigate finite-volume effects for chiral symmetry breaking at zero and finite temperature. By using the $2+1$-flavor linear-sigma model with constituent light quarks, we analyze the Casimir effects for the $σ$ mean fields: The chiral symmetry is rapidly restored by the antiperiodic boundary for light quarks, and the chiral symmetry breaking is catalyzed by the periodic boundary. We also show the phase diagram of the $σ$ mean fields on the volume and temperature plane. For $D$ mesons, we employ an effective model based on the chiral-partner structure, where the volume dependence of $D$ mesons is induced by the $σ$ mean fields. We find that $D_s$ mesons are less sensitive to finite volume than $D$ mesons, which is caused by the insensitivity of $σ_s$ mean fields. An anomalous mass shift of $D$ mesons at high temperature with the periodic boundary will be useful in examinations with lattice QCD simulations. The dependence on the number of compactified spatial dimensions is also studied.

hep-ph↗

arXiv2018

Spectral function for $\bar{D}_{0}^{\ast}$ $(0^+)$ meson in isospin asymmetric nuclear matter with chiral partner structure

We study a spectral function for $\bar{D}_0^*$ $(0^+)$ meson in symmetric and neutron-rich asymmetric nuclear matter from the viewpoint of the partial restoration of chiral symmetry. Nuclear matter is constructed by a parity doublet model with hidden local symmetry which can reproduce properties at normal nuclear matter density as well as those in the vacuum. $\bar{D}$ mesons are introduced by the chiral partner structure. Our results show that a mass of $\bar{D}$ ($0^-$) meson increases while a mass of $\bar{D}_0^*$ meson decreases at mean field level as we increase the baryon density, reflecting the partial restoration of chiral symmetry. In the spectral function for $\bar{D}_0^*$ meson, we find a threshold enhancement is remarkably enhanced which indicates this peak is an appropriate probe to observe the partial restoration of chiral symmetry in nuclear matter. We also find a resonance of $\bar{D}_0^*$ meson revives at higher density due to a narrowing of the phase space. In the spectral function in neutron-rich asymmetric nuclear matter, we observe the threshold enhancement in negatively-charged $\bar{D}_0^*$ meson channel stands at higher energy and its height is more enhanced compared to neutral $\bar{D}_0^*$ meson channel, due to the violation of isospin symmetry. On the other hand, the resonance of negatively-charged $\bar{D}_0^*$ meson is slightly suppressed compared to the neutral one.

nucl-th↗

arXiv2018

Examination of $N^*(1535)$ as a probe to observe the partial restoration of chiral symmetry in nuclear matter

We investigate modifications of mass and decay width of $N^*(1535)$ in nuclear matter in a chiral symmetric way. The nucleon and $N^*(1535)$ are introduced by a parity doublet model, and nuclear matter is constructed by one-loop diagrams of the nucleon and $N^*(1535)$. The decay width of $N^*(1535)$ is studied respecting chiral symmetry. Our calculations show that the partial width of $Γ_{N^*\to Nπ}$ is slightly broadened by a collisional broadening, and that of $Γ_{N^*\to Nη}$ is drastically suppressed at density. As a result, the total decay width $Γ_{\rm tot}$ gets small at density. These modifications, especially the drastic narrowing of partial width of $Γ_{N^*\to Nη}$, together with the dropping of mass of $N^*(1535)$ provide experiments for observing the partial restoration of chiral symmetry in nuclear matter by means of $N^*(1535)$ resonance with useful information.

nucl-th↗

arXiv2017

Relation between the mass modification of the heavy-light mesons and the chiral symmetry structure in dense matter

We point out that the study of the density dependences of the masses of heavy-light mesons give some clues to the chiral symmetry structure in nuclear matter. We include the omega meson effect as well as the sigma meson effect at mean field level on the density dependence of the masses of heavy-light mesons with chiral partner structure. It is found that the omega meson affects the masses of the heavy-light mesons and their antiparticles in the opposite way, while it affects the masses of chiral partners in the same way. This is because the omega meson is sensitive to the baryon number of the light degrees included in the heavy-light mesons. We also show that the mass difference between chiral partners is proportional to the mean field of sigma, reflecting the partial restoration of chiral symmetry in the nuclear matter. In addition to the general illustration of the density dependence of the heavy-light meson masses, we consider two concrete models for nuclear matter, the parity doublet model and skyrmion crystal model in the sense of mean field approximation.

hep-ph↗

arXiv2017

Spectral functions for $\bar{D}$ meson and $\bar{D}_0^*$ meson in nuclear matter with partial restoration of chiral symmetry

We investigate the in-medium masses of a $\bar{D} (0^-)$ meson and a $\bar{D}_0^* (0^+)$ meson and spectral functions for $\bar{D}$ and $\bar{D}_0^*$ meson channels in nuclear matter. These mesons are introduced as chiral partner in the chiral symmetry broken vacuum, hence they are useful to explore the partial restoration of the broken chiral symmetry in nuclear matter. We consider the linear sigma model to describe the chiral symmetry breaking. Our study shows that the loop corrections to $\bar{D}$ and $\bar{D}_0^*$ meson masses provide a smaller mass splitting at finite density than that in vacuum, whose result indicates a tendency of the restoration of the chiral symmetry. We investigate also the spectral function for $\bar{D}_0^*$ meson channel, and find three peaks. The first peak which corresponds to the resonance of $\bar{D}_0^*$ meson is broadened by collisions with nucleons in medium, and the peak position shifts to lower mass due to the partial restoration of chiral symmetry as the density increases. The second peak is identified as a threshold enhancement which shows a remarkable enhancement as the density increase. The third peak is Landau damping. The obtained properties of $\bar{D}$ and $\bar{D}_0^*$ mesons in nuclear matter will provide useful information for experiments.

nucl-th↗

arXiv2016

Coupled channel analysis of molecule picture of $P_{c}(4380)$

We construct a potential obtained by one-pion exchange for the coupled channel $Σ_c^\ast$$\bar{D}$-$Σ_c$$\bar{D}^\ast$, and solve the coupled Schrödinger equations to determine the binding energy. We find that there exists one or two bound states with the binding energy of several MeV below the threshold of $Σ_c^\ast$ and $\bar{D}$, dominantly made from a $Σ_c^\ast$ baryon and a $\bar{D}$ meson, with the size of about $1.5$fm for wide parameter region. We also study the pentaquark states including a $b$ quark and/or an anti-$b$ quark. We show that there exist pentaquarks including $c\bar{b}$, $b\bar{c}$ and $b\bar{b}$, all of which lie at about $10$MeV below the corresponding threshold and have size of about $1.5$fm.

hep-ph↗

arXiv2016

Appearance of novel modes of $\bar{D}$ mesons in the Dual Chiral Density Wave

We calculate dispersion relations for $\bar{D}(0^-)$, $\bar{D}^*(1^-)$, $\bar{D}_0^*(0^+)$ and $\bar{D}_1(1^+)$ mesons in the Dual Chiral Density Wave (DCDW) where the chiral symmetry is spontaneously broken by inhomogeneous chiral condensate. Employing the Bloch's theorem, we show that all the modes have opposite group velocity to the momentum in the low-momentum region and the energy is minimized at non-zero momentum. Furthermore, the magnitude of momentum which realizes the minimum energy is equal to the wave number of the density wave.

hep-ph↗

arXiv2014

Mass degeneracy of the heavy-light mesons with chiral partner structure in the half-skyrmion phase

We explore the mass splitting of the heavy-light mesons with chiral partner structure in nuclear matter. In our calculation, we employed the heavy hadron chiral perturbation theory with chiral partner structure and the nuclear matter is constructed by putting skyrmions from the standard Skyrme model onto the face-centered cubic crystal and regarding the skyrmion matter as nuclear matter. We find that, although the masses of the heavy-light mesons with chiral partner structure are splitted in the matter-free space and skyrmion phase, they are degenerated in the half-skyrmion phase in which the chiral symmetry is restored globally. This observation suggests that the magnitude of the mass splitting of the heavy-light mesons with chiral partner structure can be used as a probe of the phase structure of the nuclear matter.

hep-ph↗

arXiv2014

$D$ and $D^{\ast}$ meson mixing in spin-isospin correlated cold nuclear matter

We propose to study the mass spectrum of the heavy-light mesons to probe the structure of the spin-isospin correlation in the nuclear medium. We point out that the spin-isospin correlation in the nuclear medium generates a mixing among the heavy-light mesons carrying different spins and isospins such as $D^+$, $D^0$, $D^{\ast +}$, and $D^{\ast 0}$ mesons. We use two types of correlations motivated by the skyrmion crystal and the chiral density wave as typical examples to obtain the mass splitting caused by the mixing. Our result shows that the structure of the mixing reflects the pattern of the correlation, i.e., the remaining symmetry. Furthermore, the magnitude of the mass modification provides information of the strength of the correlation.

hep-ph↗