arXiv subjects

Atsushi Hosaka

Publications and source records attributed to Atsushi Hosaka.

At least 55 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

Model independent analysis of coupled-channel scattering: a deep learning approach

We develop a robust method to extract the pole configuration of a given partial-wave amplitude. In our approach, a deep neural network is constructed where the statistical errors of the experimental data are taken into account. The teaching dataset is constructed using a generic S-matrix parametrization, ensuring that all the poles produced are independent of each other. The inclusion of statistical error results into a noisy classification dataset which we should solve using the curriculum method. As an application, we use the elastic $πN$ amplitude in the $I(J^P)=1/2(1/2^{-})$ sector where $10^6$ amplitudes are produced by combining points in each error bar of the experimental data. We fed the amplitudes to the trained deep neural network and find that the enhancements in the $πN$ amplitude are caused by one pole in each nearby unphysical sheet and at most two poles in the distant sheet. Finally, we show that the extracted pole configurations are independent of the way points in each error bar are drawn and combined, demonstrating the statistical robustness of our method.

hep-ph↗

arXiv2021

Decay properties of Roper resonance in the holographic QCD

We investigate the one pion decay of the Roper resonance $N^*(1440)$$\to$$N$$π$ in the Sakai-Sugimoto model of the holographic QCD. The nucleon and Roper resonance emerge as ground and first excited states of the collective radial motion of the instanton in the four dimensional space with one extra dimension. It is found that the ratio of the $π$$NN^*$ and $π$$NN$ couplings, and hence the ratio of $g_A^{NN^*}$ and $g_A^{NN}$, is well reproduced in comparison with the experimental data. The mechanism of this result is due to the collective nature of excitations, which is very different from that of the single particle nature of the constituent quark model. Our results are obtained in the large-$N_c$ and large $λ$ ('t~Hooft coupling) limit which are useful to test how baryon resonances share what are expected in these limits.

hep-ph↗

arXiv2021

Photoproduction of $Λ^$ and $Σ^$ resonances with $J^P=1/2^-$ off the proton

We study the photoproduction of the $Λ(1405)$ and $Σ(1400)$ hyperon resonances, the latter of which is not a well established state. We evaluate the $s$-, $t$- and $u$-channel diagrams in the Born approximation by employing the effective Lagrangians. A new ingredient is the inclusion of a nucleon resonance $N^*(1895)$ that is dynamically generated with predictions for its coupling to the $KΛ(1405)$ and $KΣ(1400)$ channels. To extend the applicability of the model to energies beyond the threshold region, we consider a Regge model for the $t$-channel $K$- and $K^*$-exchanges. Our results are in good agreement with the CLAS data available on $Λ(1405)$, while for $Σ(1400)$ we predict observables for its production. We also provide polarization observables for both hyperon productions, which can be useful in future experimental investigations. The present study provides new information on the nucleon resonance $N^*(1895)$ which can be an alternative source for generating the hyperon resonances $Λ(1405)$ and $Σ(1400)$.

hep-ph↗

arXiv2020

Charmed baryon productions in proton-antiproton collisions in effective Lagrangian and Regge approaches

Strange and charmed baryon productions from proton-antiproton collisions are studied in the effective Lagrangian and Regge approaches. We include only the $t$-channel dynamics which is dominant for the diffractive region that is relevant in the present discussions. For strangeness productions, the coupling constants for $K$ meson are determined by $SU(3)$ relations while other unknown parameters for $K^{*}$ couplings and for form factors are fixed by existing observed data for strangeness productions. By extrapolating the amplitudes for strangeness productions to those for charm, we predict charm production cross sections. It turns out that the total cross sections are $10^{4}$ to $10^{5}$ smaller than those of strangeness productions, depending on the final states. By using the known total cross sections for strangeness, $\sim 10^{2} μb$ for $Λ\barΛ$ and, $\sim 10^{1} μb$ for $Σ\barΛ$ the total cross sections for charm productions are predicted to be $\sim 10^{-2} μb$ for $Λ_{c} \barΛ_c$, $\sim 10^{-3} μb$ for $Σ_{c} \barΛ_c$, and $\sim 10^{-4} μb$ for $Σ_{c} \barΣ_c$. Our results can be tested in the future experiments at $\bar{\text{P}}$ANDA.

hep-ph↗

arXiv2020

Classifying Pole of Amplitude Using Deep Neural Network

Most of exotic resonances observed in the past decade appear as peak structure near some threshold. These near-threshold phenomena can be interpreted as genuine resonant states or enhanced threshold cusps. Apparently, there is no straightforward way of distinguishing the two structures. In this work, we employ the strength of deep feed-forward neural network in classifying objects with almost similar features. We construct a neural network model with scattering amplitude as input and nature of pole causing the enhancement as output. The training data is generated by an S-matrix satisfying the unitarity and analyticity requirements. Using the separable potential model, we generate a validation data set to measure the network's predictive power. We find that our trained neural network model gives high accuracy when the cut-off parameter of the validation data is within $400$-$800\mbox{ MeV}$. As a final test, we use the Nijmegen partial wave and potential models for nucleon-nucleon scattering and show that the network gives the correct nature of pole.

hep-ph↗

arXiv2020

Lambda(1405) as a K-bar N Feshbach resonance in the Skyrme model

We describe the Lambda(1405) hyperon as a Feshbach resonance of a bar-KN quasi-bound state coupled by a decaying channel of pi Sigma in the Skyrme model. A weakly bound bar-KN state is generated in the laboratory frame, while the Sigma hyperon as a strongly bound state of bar-KN in the intrinsic frame. We obtain a coupling of bar-KN and pi Sigma channels by computing a baryon matrix element of the axial current. This coupling enables the decay of the bar-KN bound state to pi-Sigma . It is shown that the Skyrme model supports the Lambda(1405) as a narrow Feshbach resonance.

hep-ph↗

arXiv2020

Heavy hadronic molecules with pion exchange and quark core couplings: a guide for practitioners

We discuss selected and important features of hadronic molecules as one of promising forms of exotic hadrons near thresholds. Using examples of $D \bar D^*$ systems such as $X(3872)$ and $Z_c$, emphasis is put on the roles of the one pion exchange interaction between them and their coupling to intrinsic quark states. Thus hadronic molecules emerge as admixtures of the dominant long-range hadron structure and short-range quark structure. For the pion exchange interaction, properties of the tensor force are analyzed in detail. More coupled channels supply more attractions, and heavier constituents suppress kinetic energies, providing more chances to form hadronic molecules of heavy hadrons. Throughout this article, we show details of basic ideas and methods.

hep-ph↗

arXiv2020

Regge behaviors in orbitally excited spectroscopy of charmed and bottom baryons

Stimulated by recent progress made by the LHCb Collaboration in discoveries of new bottom baryons, e.g., the $Ξ_{b}(6227)^{-}$ and the $Σ_{b}(6097)^{\pm}$, we re-examine the orbitally excited spectrum of the charmed and bottom baryons using Regge approach in the heavy quark-diquark picture. The results indicate that the spin-averaged mass spectrum of the orbitally-excited charmed and bottom baryons can be described by a linear Regge relation, which is derived from the rotating QCD string model. By giving further mass-splitting analysis of spin-dependent interactions, we explain the baryons $Ξ_{b}(6227)^{-}$ and the $Σ_{b}(6097)^{\pm}$,and the $Σ_{c}(2800)$ and $Ξ_{c}^{\prime }(2930)$ to be the $1P$%-wave baryons, all with the spin-parity $J^{P}=3/2^{-}$ preferably. Mass prediction of the bottom baryon $Ξ_{b}$ in its P- and D-waves are presented, providing clues for the coming experiments like the LHCb to find them.

hep-ph↗

arXiv2020

Excited $Ω_b$ baryons and fine structure of strong interaction

The heavy baryon system bounded by the strong interaction has a rich internal structure, so its mass spectra can have the fine structure similar to the line spectra of atom bounded by the electromagnetic interaction. We systematically study the internal structure of $P$-wave $Ω_b$ baryons and calculate their $D$-wave decay properties. The present study, together with our previous studies on their mass spectra and $S$-wave decay properties, suggest that all the four excited $Ω_b$ baryons recently discovered by LHCb can be well explained as $P$-wave $Ω_b$ baryons, and their beautiful fine structure is directly related to the rich internal structure of $P$-wave $Ω_b$ baryons.

hep-ph↗

arXiv2020

Feasibility study of the $K^{+} d \to K^{0} p p$ reaction for the "$Θ^{+}$" pentaquark

We investigate theoretically the $K^{0} p$ invariant mass spectrum of the $K^{+} d \to K^{0} p p$ reaction and scrutinize how the signal of the "$Θ^{+}$" pentaquark, if it exists, emerges in the $K^{0} p$ spectrum. The most prominent advantage of this reaction is that we can clearly judge whether the "$Θ^{+}$" exists or not as a direct-formation production without significant backgrounds, in contrast to other reactions such as photoproduction and $π$-induced productions. We show that while the impulse or single-step scattering process can cover the "$Θ^{+}$" energy region with an initial kaon momentum $k_{\mathrm{lab}} \approx 0.40\, \mathrm{GeV} / c$ in the laboratory frame, the contributions from double-step processes may have a potential possibility to reach the "$Θ^{+}$" energy region with a higher kaon momentum $k_{\mathrm{lab}} \sim 1 \, \mathrm{GeV} / c$. Assuming that the full decay width of the "$Θ^{+}$" is around $0.5\, \mathrm{MeV}$, we predict that the magnitude of the peak corresponding to the "$Θ^+$" is around a few hundred $μ\mathrm{b}$ to $1\, \mathrm{mb}$ with the momentum of the kaon beam $k_{\mathrm{lab}} \approx 0.40\, \mathrm{GeV} / c$ while it is around $\lesssim 1\, μ\mathrm{b}$ with $k_{\mathrm{lab}} \approx 0.85\, \mathrm{GeV} / c$. Thus, the "$Θ^+$" peak is more likely to be seen at $k_{\mathrm{lab}} \approx 0.40\, \mathrm{GeV} / c$ than at $k_{\mathrm{lab}} \approx 0.85 \,\mathrm{GeV} / c$.

hep-ph↗

arXiv2020

Heavy baryons in holographic QCD with higher dimensional degrees of freedom

We try to introduce heavy flavors to Sakai-Sugimoto model by regarding higher dimensional components of gauge fields as heavy mesons. Using the Forgács and Manton approach, we obtain a theory composed of heavy mesons and the instanton of light flavors. Applying the collective coordinate quantization method, we derived a mass formula of heavy baryons. In the leading order of $1/m_{H}$ expansion ($m_{H}$ the mass of a heavy quark), we find singlet and doublet states in the heavy quark symmetry (HQS). Also, we obtain the degenerate Roper like and odd parity excitations. By virtue of heavy meson degrees of freedom, our mass formula reproduces the mass ordering of $Σ^*_c$ and $Λ_c^*$ correctly.

hep-ph↗

arXiv2020

The use of the canonical approach in effective models of QCD

We clarify regions where the canonical approach works well at the finite temperature and density in the Nambu-Jona-Lasinio (NJL) and Polyakov-NJL (PNJL) models. The canonical approach is a useful method for avoiding the sign problem in lattice QCD simulations at finite density, but it involves some parameters. We find that number densities computed from the canonical approach are consistent with exact values in most of the confinement phase within the parameters, which are applicable in lattice QCD.

hep-ph↗

arXiv2020

$P_c$ pentaquarks with chiral tensor and quark dynamics

We investigate the hidden-charm pentaquarks as superpositions of $Λ_c \bar{D}^{(*)}$ and $Σ_c^{(*)} \bar{D}^{(*)}$ (isospin $I = 1/2$) meson-baryon channels coupled to a $uudc\bar{c}$ compact core by employing an interaction satisfying the heavy quark and chiral symmetries. Our model can consistently explain the masses and decay widths of $P_c^+(4312)$, $P_c^+(4440)$ and $P_c^+(4457)$ with the dominant components of $Σ_c \bar D$ and $Σ_c \bar D^\ast$ with spin parity assignments $J^P = 1/2^{-}, 3/2^{-}$ and $1/2^{-}$, respectively. We analyze basic properties of the $P_c$'s such as masses and decay widths, and find that the mass ordering is dominantly determined by the quark dynamics while the decay widths by the tensor force of the one-pion exchange.

hep-ph↗

arXiv2020

Heavy baryon production with an instanton interaction

We propose a new reaction mechanism for the study of strange and charmed baryon productions. In this mechanism we consider the correlation of two quarks in baryons, so it can be called the two-quark process. As in the previously studied one-quark process, we find large production rates for charmed baryons in comparison with strange baryons. Moreover, the new mechanism causes the excitation of both the $ρ$ mode and the $λ$ mode. Using the wave functions for baryons from a quark model, we compute the production rates of various baryon states. We find that the production rates reflect the structure of the wave functions that imply the usefulness of the reactions for the study of baryon structures.

hep-ph↗

arXiv2020

Decay properties of $P$-wave heavy baryons accompanied by vector mesons within light-cone sum rules

We use the method of light-cone sum rules to study decay properties of $P$-wave bottom baryons belonging to the $SU(3)$ flavor $\mathbf{6}_F$ representation. In Ref.~\cite{Cui:2019dzj} we have studied their mass spectrum and pionic decays, and found that the $Σ_{b}(6097)$ and $Ξ_{b}(6227)$ can be well interpreted as $P$-wave bottom baryons of $J^P = 3/2^-$. In this paper we further study their decays into ground-state bottom baryons and vector mesons. We propose to search for a new state $Ξ_b({5/2}^-)$, that is the $J^P = 5/2^-$ partner state of the $Ξ_{b}(6227)$, in the $Ξ_b({5/2}^-) \to Ξ_b^{*}ρ\to Ξ_b^{*}ππ$ decay process. Its mass is $12 \pm 5$~MeV larger than that of the $Ξ_{b}(6227)$.

hep-ph↗

arXiv2019

Compact $sssc\bar{c}$ pentaquark states predicted by a quark model

Several compact $sssc\bar c$ pentaquark resonances are predicted in a potential quark model. The Hamiltonian is the best available one, which reproduces the masses of the low-lying charmed and strange hadrons well. Full five-body calculations are carried out by the use of the Gaussian expansion method, and the relevant baryon-meson thresholds are taken into account explicitly. Employing the real scaling method, we predict four sharp resonances, $J^P=1/2^-$ ($E=5180$ MeV, $Γ=20$ MeV), $5/2^-$ (5645 MeV, 30 MeV), $5/2^-$ (5670 MeV, 50 MeV), and $1/2^+$ (5360 MeV, 80 MeV). These are the candidates of compact pentaquark resonance states from the current best quark model, which should be confirmed either by experiments or lattice QCD calculations.

nucl-th↗

arXiv2019

Emergence of a complete heavy-quark spin symmetry multiplet: seven molecular pentaquarks in light of the latest LHCb analysis

A recent analysis by the LHCb collaboration suggests the existence of three narrow pentaquark-like states --- the $P_c(4312)$,$P_c(4440)$ and $P_c(4457)$ --- instead of just one in the previous analysis (the $P_c(4450)$). The closeness of the $P_c(4312)$ to the $\bar{D} Σ_c$ threshold and the $P_c(4440)$/$P_c(4457)$ to the $\bar{D}^* Σ_c$ one suggests a molecular interpretation of these resonances. We show that these three pentaquark-like resonances can be naturally accommodated in a contact-range effective field theory description that incorporates heavy-quark spin symmetry. This description leads to the prediction of all the seven possible S-wave heavy antimeson-baryon molecules (that is, there should be four additional molecular pentaquarks in addition to the $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$), providing the first example of a heavy-quark spin symmetry molecular multiplet that is complete. If this is confirmed, it will not only give us an impressive example of the application of heavy-quark symmetries and effective field theories in hadron physics: it will also uncover a clear and powerful ordering principle for the molecular spectrum, reminiscent of the SU(3)-flavor multiplets to which the light hadron spectrum conforms.

hep-ph↗