arXiv subjects

Atsushi Hosaka

Publications and source records attributed to Atsushi Hosaka.

At least 73 records · Page 4Linked to original sources

arXiv2019

Vector and Axial-vector form factors in radiative kaon decay and flavor SU(3) symmetry breaking

We study the vector and axial-vector form factors of radiative kaon decay within the framework of the gauged nonlocal effective chiral action from the instanton vacuum, focusing on the effects of flavor SU(3) symmetry breaking. The general tendency of the results are rather similar to those of radiative pion decays: The nonlocal contributions make the results of the vector form factor increased by about $20\,\%$, whereas they reduce those of the axial-vector form factor by almost $30\,\%$. Suppressing the prefactors consisting of the kaon mass and the pion decay constant, we scrutinize how the kaon form factors undergo changes as the mass of the strange current quark is varied. Those related to the vector and second axial-vector form factors tend to decrease monotonically as the strange quark mass increases, whereas that for the axial-vector form factor decreases. When $K\to eνγ$ decay is considered, both the results of the vector and axial-vector form factors at the zero momentum transfer are in good agreement with the experimental data. The results are also compared with those from chiral perturbation theory to $p^6$ order.

hep-ph↗

arXiv2019

Identifying the $Ξ_{b}(6227)$ and $Σ_{b}(6097)$ as $P$-wave bottom baryons of $J^P = 3/2^-$

We use the method of QCD sum rules within the framework of heavy quark effective theory to study the mass spectrum of the $Σ_{b}(6097)^{\pm}$ and $Ξ_{b}(6227)^{-}$, and use the method of light-cone sum rules still within the heavy quark effective theory to study their decay properties. Our results suggest that they can be well interpreted as $P$-wave bottom baryons with the spin-parity $J^P = 3/2^-$. They belong to the baryon doublet $[\mathbf{6}_F, 2, 1, λ]$, where the total and spin angular momenta of the light degree of freedom are $j_l = 2$ and $s_l = 1$, and the orbital angular momentum is between the bottom quark and the two-light-quark system ($λ$-type). This doublet contains six bottom baryons, and we predict masses (mass differences) and decay widths of the other four states to be $M_{Ω_b(3/2^-)} = 6.46 \pm 0.12 {~\rm GeV}$, $Γ_{Ω_b(3/2^-)} = 58{^{+65}_{-33}} {~\rm MeV}$, $M_{Σ_b(5/2^-)}-M_{Σ_b(3/2^-)}= 13 \pm 5 {~\rm MeV}$, $M_{Ξ_b^{\prime}(5/2^-)}-M_{Ξ_b^{\prime}(3/2^-)} = 12 \pm 5 {~\rm MeV}$, and $M_{Ω_b(5/2^-)}-M_{Ω_b(3/2^-)} = 11 \pm 5 {~\rm MeV}$. We propose to search for them in further LHCb experiments.

hep-ph↗

arXiv2019

Search of QCD phase transition points in the canonical approach of the NJL model

We study the Lee-Yang zeros in the canonical approach to search phase transition points at finite temperature and density in the Nambu-Jona-Lasinio (NJL) model as an effective model of QCD. The canonical approach is a promising method to avoid the sign problem in lattice QCD at finite density. We find that a set of Lee-Yang zeros computed with finite degrees of freedom can be extrapolated to those with infinite degrees of freedom, providing the correct phase transition point. We propose the present method as a useful method for actual lattice simulations for QCD.

hep-lat↗

arXiv2019

Studies on photo- and electro-productions of $Λ(1405)$ via $γ^{()} p\to K^{+}π^0Σ^0$

We study the photo- and electro-productions of the vector kaon off the proton, i.e., $γ^{(*)}p\to K^{*+}π^0Σ^0$, and investigate the line shape of the $π^0Σ^0$ invariant mass in an effective Lagrangian approach with the inclusion of a $K^*NΛ^*$ interaction. Relevant electromagnetic form factors for the neutral hyperons and charged strange mesons are constructed by considering experimental and theoretical information. We find that the $Λ^*$ peak is clearly observed for the photo- and electro-productions with the finite $K^*NΛ^*$ interaction, whereas the clear peak signals survive only for the electro-production, when we ignore the interaction. These different behaviors can be understood by different $Q^2$ dependences in the $K^*$ electromagnetic and $K^*\toγK$ transition form factors. We suggest a photon-polarization asymmetry $Σ$ to extract information of the $K^*NΛ^*$ interaction. It turns out that $Σ$ near the $Λ^*$ peak region becomes negative with a finite $K^*NΛ^*$ interaction while positive without it for $Q^2 = 0$, due to the different naturalities of $K$ and $K^*$ exchanges. For $Q^2\ne 0$, we observe more obvious signals in the peak region due to the additional contribution of the longitudinal virtual photon for $Λ^*$.

hep-ph↗

arXiv2019

Strange and charmed baryon productions with an instanton interaction

We study strange and charmed baryon productions, ${π+ p \rightarrow K(D) + Y(Y_c)}$, where ${Y(Y_c)}$ is a strange(charmed) baryon of a ground or an excited state. We propose a new production mechanism where two quarks in the baryon participate in the reaction (two-quark process), which enables excitation of both $λ$- and $ρ$-modes of the baryons. To deal with the two-quark process, we consider the 't Hooft six-quark interaction from the instanton model. We study production rates in relation with the structure of charmed baryons for the forward angle scattering.

hep-ph↗

arXiv2018

Baryon fields with $U_{L}(3)\times U_{R}(3)$ chiral symmetry V: Pion-Nucleon and Kaon-Nucleon $Σ$ Terms

We have previously calculated the pion-nucleon $Σ_{πN}$ term in the chiral mixing approach with $u,d$ flavors only, and found the lower bound $Σ_{πN} \geq \left(1 + \frac{16}{3} \sin^2 θ\right){3 \over 2} \left(m_{u}^{0} + m_{d}^{0}\right)$. The mixing angle $θ$ can be calculated as $\sin^2θ= \frac{3}{8}\left(g_A^{(0)} + g_A^{(3)}\right)$. With presently accepted values of current quark masses, this leads to $Σ_{πN} \geq 58.0 \pm 4.5 \begin{array}{l} +11.4 \\ -6.5 \end{array}$ MeV, which is in agreement with the values extracted from experiments, and substantially higher than most previous two-flavour calculations. The causes of this enhancement are: 1) the large, ($\frac{16}{3}\simeq 5.3$), purely $SU_L(2) \times SU_R(2)$ algebraic factor, 2) the admixture of the $[(\mathbf{1},\mathbf{\frac12})\oplus (\mathbf{\frac12},\mathbf{1})]$ chiral multiplet component in the nucleon, whose presence has been known for some time, but that had not been properly taken into account, yet. We have now extended these calculations of $Σ_{πN}$ to three light flavours, i.e., to $SU_L(3) \times SU_R(3)$ multiplet mixing. Phenomenology of chiral $SU_L(3) \times SU_R(3)$ multiplet mixing demands the presence of three chiral $SU_L(3) \times SU_R(3)$ multiplets in order to successfully reproduce the baryons' flavor-octet and flavor-singlet axial currents, as well as the baryon anomalous magnetic moments. The physical significance of these results lies in the fact that they show no need for $q^4 {\bar q}$ components, and in particular, no need for an $s \bar s$ component in the nucleon, in order to explain the large "observed" $Σ_{πN}$ value. We also predict the experimentally unknown kaon-nucleon sigma term $Σ_{K N}$.

hep-ph↗

arXiv2018

Exotic triple-charm deuteron-like hexaquarks

Adopting the one-boson-exchange model, we perform a systematic investigation of interactions between a doubly charmed baryon $(Ξ_{cc})$ and an $S$-wave charmed baryon ($Λ_c$, $Σ_c^{(*)}$, and $Ξ_c^{(\prime,*)}$). Both the $S$-$D$ mixing effect and coupled-channel effect are considered in this work. Our results suggest that there may exist several possible triple-charm deuteron-like hexaquarks. Meanwhile, we further study the interactions between a doubly charmed baryon and an $S$-wave anticharmed baryon. We find that a doubly charmed baryon and an $S$-wave anticharmed baryon can be easily bound together to form shallow molecular hexaquarks. These heavy flavor hexaquarks predicted here can be accessible at future experiment like LHCb.

hep-ph↗

arXiv2018

Quark model estimate of hidden-charm pentaquark resonances

A quark model, which reproduces the ground-state mesons and baryons, i.e., the threshold energies, is applied to the $qqqc\bar c$ configurations, where $q$ is a light quark and~$c$ the charmed quark. In the calculation, several open channels are explicitly included such as $\Jpsi +N$, $η_c+N$, $Λ_c +D$, etc. To distinguish genuine resonances and estimate their width, we employ Gaussian Expansion Method supplemented by the real scaling method (stabilization). No resonance is found at the energies of the $P_c(4380)$ and $P_c(4450)$ pentaquarks. On the other hand, there is a sharp resonant state at 4690\,MeV with $J=1/2^-$ state and another one at 4920\,MeV with $J=3/2^-$ state, which have a compact structure.

nucl-th↗

arXiv2018

Searching for possible $Ω_c-$like molecular states from $Ξ_{c}^{}\bar{K}/Ξ_c\bar{K}^/Ξ_c'\bar{K}^*$ interaction

Stimulated by the observations of recent observation of $Ω_c$ as well as former one of $P_c(4380)$ and $P_c(4450)$, we perform a coupled channel analysis of $Ξ_c^*\bar{K}/Ω_cη/Ω_c^*η/Ξ_c\bar{K}^*/Ξ_c'\bar{K}^*/Ω_cω$ systems to search for possible $Ω_c-$like molecular states by using a one-boson-exchange potential. Our results suggest there exists a loosely bound molecular state, a $Ξ_c^*\bar{K}/Ω_cη/Ω_c^*η/Ξ_c\bar{K}^*/Ξ_c'\bar{K}^*/Ω_cω$ with $I(J^P)=0(3/2^-)$, it is mainly composed of the $Ξ_c^*\bar{K}$ system. Two-body strong decay width is also studied, where we find that $Ξ_c'\bar{K}$ is the dominant decay channel.

hep-ph↗

arXiv2018

Hidden-charm and bottom meson-baryon molecules coupled with five-quark states

In this paper, we investigate the hidden-charm pentaquarks as $\bar{D}^{(\ast)}Λ_{\rm c}$ and $\bar{D}^{(\ast)}Σ^{(\ast)}_{\rm c}$ molecules coupled to the five-quark states. Furthermore, we extend our calculations to the hidden-bottom sector. The coupling to the five-quark states is treated as the short range potential, where the relative strength for the meson-baryon channels is determined by the structure of the five-quark states. We found that resonant and/or bound states appear in both the charm and bottom sectors. The five-quark state potential turned out to be attractive and, for this reason, it plays an important role to produce these states. In the charm sector, we need the five-quark potential in addition to the pion exchange potential in producing bound and resonant states, whereas, in the bottom sector, the pion exchange interaction is strong enough to produce states. Thus, from this investigation, it emerges that the hidden-bottom pentaquarks are more likely to form than their hidden-charm counterparts; for this reason, we suggest that the experimentalists should look for states in the bottom sector.

hep-ph↗

arXiv2017

Heavy molecules and one-$σ/ω$-exchange model

In the framework of the one-boson-exchange model, we explore whether the intermediate and short-range forces from $σ/ω$-exchange can be strong enough to bind heavy molecular states. $Λ_cD(\bar{D})$, and $Λ_cΛ_c(\barΛ_c)$ systems have been studied and compared. We find that the force from $σ$-exchange is attractive and dominant, whereas the $ω$-exchange force not. As a consequence, the S-wave $Λ_cD$, $Λ_cΛ_c$, and $Λ_c\barΛ_c$ can be possible molecular candidates. We further indicate that one hadron-hadron system with more light quarks $(u,d)$ can be easier to form a bound state. As a byproduct, by studying the heavy-quark mass dependence for the $Λ_cD(\bar{D})$-like and $Λ_cΛ_c(\barΛ_c)$-like systems, we find that the charm/bottom sector can easily accommodates molecular states. Finally, the $Λ_cN(\bar{N})$ and $Λ_bN(\bar{N})$ systems are investigated. Our results indicate that they are also likely to form bound states. By including one-$π$-exchange forces providing additional attraction when coupled channels are included, we expect many molecular states in heavy quark sectors.

hep-ph↗

arXiv2017

Prediction of triple-charm molecular pentaquarks

In a one-boson-exchange model, we study molecular states of double-charm baryon ($Ξ_{cc}(3621)$) and a charmed meson ($D$ and $D^*$). Our model indicates that there exist two possible triple-charm molecular pentaquarks, a $Ξ_{cc}D$ state with $I(J^P)=0(1/2^-)$ and a $Ξ_{cc}D^*$ state with $I(J^P)=0(3/2^-)$. In addition, we also extend our formula to explore $Ξ_{cc}\bar{B}^{(*)}$, $Ξ_{cc}\bar{D}^{(*)}$, and $Ξ_{cc}B^{(*)}$ systems, and find more possible heavy flavor molecular pentaquarks, a $Ξ_{cc}\bar{B}$ state with $I(J^P)=0(1/2^-)$, a $Ξ_{cc}\bar{B}^*$ state with $I(J^P)=0(3/2^-)$, and $Ξ_{cc}\bar{D}^*/Ξ_{cc}B^*$ states with $I(J^P)=0(1/2^-)$. Experimental search for these predicted triple-charm molecular pentaquarks is encouraged.

hep-ph↗

arXiv2017

Mass Formula for Light Nonstrange Mesons and Regge Trajectories in Quark Model

We study the Regge-like spectra of light mesons in a relativized quark model. An analytical mass formula is presented for the light unflavored mesons with the help of auxiliary field method, by which a quasi-linear Regge-Chew-Frautschi plot is predicted for the orbitally excited states. We show that the trajectory slope is proportional to the inverse confining parameter $1/a$ up to a factor depending on the strong coupling $α_{s}$ when the orbital quantum number $L$ is large. The result is tested against the experimental data of the spectra of the meson families $π/b$,$ρ/a$,$η/h$ and $ω/f$ in the ($L$,$M^{2}$) planes, with the fitted parameters consistent with that in the literatures.

hep-ph↗

arXiv2017

$D$-wave heavy baryons of the $SU(3)$ flavor $\mathbf{6}_F$

We use the method of QCD sum rules to study the $D$-wave charmed and bottom baryons of the $SU(3)$ flavor $\mathbf{6}_F$, and calculate their masses up to the order $\mathcal{O}(1/m_Q)$ with $m_Q$ the heavy quark mass. Our results suggest that the $Ξ_c(3123)$ can be well interpreted as a $D$-wave $Ξ_c^\prime(\mathbf{6}_F)$ state, and it probably has a partner state close to it. Our results also suggest that there may exist as many as four $D$-wave $Ω_c$ states in the energy region $3.3\sim3.5$ GeV, and we propose to search for them in the further LHCb and BelleII experiments.

hep-ph↗

arXiv2017

Heavy Hadrons in Nuclear Matter

Current studies on heavy hadrons in nuclear medium are reviewed with a summary of the basic theoretical concepts of QCD, namely chiral symmetry, heavy quark spin symmetry, and the effective Lagrangian approach. The nuclear matter is an interesting place to study the properties of heavy hadrons from many different points of view. We emphasize the importance of the following topics: (i) charm/bottom hadron-nucleon interaction, (ii) structure of charm/bottom nuclei, and (iii) QCD vacuum properties and hadron modifications in nuclear medium. We pick up three different groups of heavy hadrons, quarkonia ($J/ψ$, $Υ$), heavy-light mesons ($D$/$\bar{D}$, $\bar{B}$/$B$) and heavy baryons ($Λ_{c}$, $Λ_{b}$). The modifications of those hadrons in nuclear matter provide us with important information to investigate the essential properties of heavy hadrons. We also give the discussions about the heavy hadrons, not only in nuclear matter with infinite volume, but also in atomic nuclei with finite baryon numbers, to serve future experiments.

hep-ph↗

arXiv2017

Decay properties of $P$-wave charmed baryons from light-cone QCD sum rules

We study decay properties of the $P$-wave charmed baryons using the method of light-cone QCD sum rules, including the $S$-wave decays of the flavor $\mathbf{\bar 3}_F$ $P$-wave charmed baryons into ground-state charmed baryons accompanied by a pseudoscalar meson ($π$ or $K$) or a vector meson ($ρ$ or $K^*$), and the $S$-wave decays of the flavor $\mathbf{6}_F$ $P$-wave charmed baryons into ground-state charmed baryons accompanied by a pseudoscalar meson ($π$ or $K$). We study both two-body and three-body decays which are kinematically allowed. We find two mixing solutions from internal $ρ$- and $λ$-mode excitations, which can well describe both masses and decay properties of the $Λ_c(2595)$, $Λ_c(2625)$, $Ξ_c(2790)$ and $Ξ_c(2815)$. We also discuss the possible interpretations of $P$-wave charmed baryons for the $Σ_c(2800)$, $Ξ_c(2930)$, $Ξ_c(2980)$, and the recently observed $Ω_c(3000)$, $Ω_c(3050)$, $Ω_c(3066)$, $Ω_c(3090)$, and $Ω_c(3119)$.

hep-ph↗

arXiv2017

Effect of the final state interaction of $η' N$ on the $η'$ photoproduction off nucleon

We investigate the $η'$ photoproduction off the nucleon with a particular interest in the effect of the final-state interaction (FSI) of the $η'$ meson and nucleon $(η'N)$ based on three-flavor linear sigma model. We find an enhancement in the cross section of the $η'$ photoproduction near the $η'N$-threshold energy owing to the $η'N$ FSI. With the $η'$ meson at forward angles, the energy dependence near the $η'N$ threshold is well reproduced with the $η'N$ FSI. The cross section at backward angles can also be a good probe to investigate the strength of the $η'N$ interaction.

nucl-th↗

arXiv2017

Kaon-Nucleon scattering states and potentials in the Skyrme model

We study the (anti)kaon nucleon interaction in the Skyrme model. The kaon field is introduced as a fluctuation around the rotating Skyrmion for the nucleon. As an extension of our previous work, we study scattering states and examine phase shifts in various kaon-nucleon channels. Then we study the interaction, where we find that it consists of central and spin-orbit components for isospin channels, $I = 0, 1$, with energy dependence and nonlocality. The interaction is then fitted to a Shrödinger equivalent local potential for s- and p-waves.

hep-ph↗