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論文

Understanding the nature of $$Omega(2012)$$ in a coupled-channel approach

L$"u$, Q.-F.*; 永廣 秀子*; 保坂 淳

Physical Review D, 107(1), p.014025_1 - 014025_10, 2023/01

We perform a systematic analysis of the mass and strong decays of the $$Omega$$(2012) resonance in a coupled -channel approach of a bare three-quark state and a composite meson-baryon state. Besides the coupling of the bare state and $$Xi$$*$$overline{K}$$ channel, the effective meson-baryon interactions are also included. We find a pole with a mass of 2008 MeV by solving the Bethe-Salpeter equation. The calculated decay widths and its ratios of branching fractions $$R$$ $$Xi$$$$pi$$$$overline{K}$$/$$Xi$$$$overline{K}$$ agree well with the new experimental measurement by the Belle Collaboration. Our results suggest that both three-quark core and $$Xi$$*$$overline{K}$$ channel are essential for the description of the $$Omega$$(2012) resonance. We expect that present calculations can help us to better understand the nature of $$Omega$$(2012) resonance.

論文

Open charm and bottom meson-nucleon potentials $`a$ la the nuclear force

山口 康宏; 安井 繁宏*; 保坂 淳

Physical Review D, 106(9), p.094001_1 - 094001_16, 2022/11

We discuss the interaction of an open heavy meson ($$overline{D}$$ and $$overline{D}$$* for charm or $$B$$ and $$B$$* for bottom) and a nucleon ($$N$$) by considering the $$pi$$, $$sigma$$, $$rho$$, and $$omega$$ exchange potentials. We construct a potential model by respecting chiral symmetry for light quarks and spin symmetry for heavy quarks. Model parameters are adjusted by referring the phenomenological nuclear (CD-Bonn) potentials reproducing the low-energy $$NN$$ scatterings. We show that the resulting interaction may accommodate $$overline{D}N$$ and $$BN$$ bound states with quantum numbers $$I(J^{P})$$ = 0(1/2$$^{-}$$), and 1(1/2$$^{-}$$). We find that, in the present potential model, the $$pi$$ exchange potential plays an important role for the isosinglet channel, while the $$sigma$$ exchange potential does for the isotriplet one.

論文

Exotic properties of $$N^*(1895)$$ and its impact on photoproduction of light hyperons

Khemchandani, K. P.*; Mart$'i$nez Torres, A.*; Kim, S.-H.*; Nam, S.-I.*; 保坂 淳

Acta Physica Polonica A, 142(3), p.329 - 336, 2022/09

In this work, we outline the findings of our recent study of the properties of $$N^*(1895)$$ and its consequential impacts on the cross-sections of the photoproduction of $$Lambda$$(1405). Further, we discuss the possibility of the existence of an isovector state with a mass similar to $$Lambda$$(1405), which we refer to as $$Sigma$$(1400). With the idea of motivating experimental investigations of $$Sigma$$(1400), we have studied its photo-production process and determined the respective cross-sections and polarization observables. We have studied also the coupling of $$N^*(1895)$$ to $$K$$$$Sigma$$(1400) and found that it gives an important contribution to the cross-sections near the threshold. In the process, we have determined the branching ratios of the decay of $$N^*(1895)$$ to the final states involving $$Lambda$$(1405) and $$Sigma$$(1400) to be in the range of 6-7 MeV. Our findings can motivate the consideration of alternative processes in partial wave analyses of experimental data when studying the properties of $$N^*(1895)$$.

論文

Electromagnetic transition amplitude for Roper resonance from holographic QCD

藤井 大輔; 岩中 章紘*; 保坂 淳*

Physical Review D, 106(1), p.014010_1 - 014010_6, 2022/07

核子の第一励起状態であるローパー共鳴は、最もよく確立されたバリオン共鳴の一つである。しかし、その性質は非相対論的クォーク模型のようなQCDの有効模型では一貫して説明できていない。本論文では、QCDのホログラフィック模型の一つである酒井・杉本模型における別のアプローチを提案する。本論文では、QCDのホログラフィック模型の一つである・酒井杉本模型において、特に、't Hooft結合$$1/lambda$$のleadingにおける電磁遷移のヘリシティ振幅を解析する。このモデルは、長距離のメソンクラウドに囲まれた、近距離の非線形メソン場によってバリオンを取り扱う。CLASで最近観測されたデータがこのアプローチで説明できることを示す。

論文

Strong decays of multistrangeness baryon resonances in the quark model

Arifi, A. J.*; 末永 大輝*; 保坂 淳; Oh, Y. S.*

Physical Review D, 105(9), p.094006_1 - 094006_17, 2022/05

Decay properties of multistrangeness $$Xi$$ and $$Omega$$ baryon resonances are investigated within the constituent quark model by including relativistic corrections. The strong decay widths of various $$Xi$$ and $$Omega$$ resonances are computed and tested for internal quark configurations to pin down their spin-parity ($$J$$$$^{P}$$) quantum numbers and internal structures. We found that the Roper-like resonances in the multistrangeness sector have large decay widths bearing resemblances to their siblings in light and heavy baryon sectors. In addition, we obtained the decay ratio for the $$Omega$$(2012) as $$Gamma$$($$Omega$$ $$rightarrow$$ $$Xi$$$$overline{K}$$$$pi$$)/$$Gamma$$($$Omega$$ $$rightarrow$$ $$Xi$$$$overline{K}$$) = 4.5%, which is consistent with the experimental data when $$J$$$$^{P}$$ = 3/2$$^{-}$$ is assigned. This observation holds the possibility that the $$Omega$$(2012) could naturally be explained as a three-quark state in the quark model. The decays of other low-lying $$Xi$$ and $$Omega$$ resonances are systematically analyzed, which would be useful to unveil the structure of these resonances in future experiments.

論文

Decays of Roper-like singly heavy baryons in a chiral model

末永 大輝*; 保坂 淳

Physical Review D, 105(7), p.074036_1 - 074036_13, 2022/04

We present a chiral model describing decays of the Roper-like $$Lambda$$$$_{c}$$(2765) and $$Xi$$$$_{c}$$(2970) as well as those of the heavy quark spin-doublet ${ $Sigma$$_{c}$(2455), $Sigma$$_{c}$(2520)}$ and ${ $Xi$$_{c}$', $Xi$$_{c}$(2645)}$, by focusing on chiral representations of diquarks inside the heavy baryons. Based on our chiral model together with the heavy quark spin symmetry, we derive a relation satisfied by axial charges of the heavy baryons that controls the magnitude of their one pion (kaon) decays. Besides, it is shown that the large decay widths of the Roperlike $$Lambda$$$$_{c}$$(2765) and $$Xi$$$$_{c}$$(2970), which cannot be implemented by conventional nonrelativistic quark models, are explained by reasonable values of the axial charges. In addition, we apply the chiral model to bottom baryons and predict decay widths of the undiscovered Roper-like $$Xi$$$$_{b}$$. We expect that our present investigation leads to elucidation of dynamical properties of the excited heavy baryons from the viewpoint of chiral symmetry.

論文

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

Sangkhakrit, T.*; Shim, S.-I.*; Yan, Y.*; 保坂 淳

European Physical Journal A, 58(2), p.32_1 - 32_11, 2022/02

Strange and charmed baryon pair productions in proton-antiproton collisions are studied in the effective Lagrangian and Regge approaches. Unknown parameters of both models are determined from the comparison with the existing data for strangeness productions. Then, we predict charm production cross sections by extrapolating the amplitudes for strangeness productions to those for charm. As a result, the total cross sections are about 10$$^{-4}$$ to 10$$^{-5}$$ times smaller than those of strangeness productions, depending on the final states. By using the known total cross sections for strangeness, similar to 10$$^{2}$$ $$mu$$b for $$Lambda$$ $$overline{Lambda}$$ and, similar to 10$$^{1}$$ $$mu$$b for $$Sigma$$ $$overline{Lambda}$$, the total cross sections for charm productions are predicted to be similar to 10$$^{-2}$$ $$mu$$b for $$Lambda$$$$_{c}$$ $$overline{Lambda}$$$$_{c}$$, similar to 10$$^{-3}$$ $$mu$$b for $$Sigma$$$$_{c}$$ $$overline{Lambda}$$$$_{c}$$, and similar to 10$$^{-4}$$ $$mu$$b for $$Sigma$$$$_{c}$$ $$overline{Sigma}$$$$_{c}$$. Our results can be tested in the future experiments at $$overline{rm P}$$ANDA.

論文

Doubly heavy tetraquark resonant states

Meng, Q.*; 原田 正康*; 肥山 詠美子; 保坂 淳; 岡 眞

Physics Letters B, 824, p.136800_1 - 136800_5, 2022/01

 被引用回数:10 パーセンタイル:97.68(Astronomy & Astrophysics)

ダブルヘビーテトラクォークのスペクトルを計算した。

論文

Prediction of Double-heavy Tetraquarks Bound States in Quark Model

Meng, Q.*; 肥山 詠美子; 保坂 淳; 岡 眞; Gubler, P.; Can, K. U.*; 高橋 徹*; Zong, H. S.*

Few-Body Systems, 62(4), p.79_1 - 79_5, 2021/12

 被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)

Bound states of double-heavy tetraquarks are studied in a constituent quark model. Two bound states are found for isospin and spin-parity $$I(J^P) = 0(1^+)$$ in the $$bbbar{u}bar{d}$$ channel. One is deeply bound and compact made of colored diquarks, while the other is shallow and extended as a $$BB^{ast}$$ molecule. The former agrees well with lattice QCD results. A systematic decrease in the binding energy is seen by replacing one of the heavy quarks to a lighter one. Altogether we find ten bound states. It is shown for the first time that hadrons with totally different natures emerge from a single Hamiltonian.

論文

$$P_c(4312)^+$$ and $$P_c(4337)^+$$ as interfering $$Sigma_cbar{D}$$ and $$Lambda_cbar{D}^*$$ threshold cusps

中村 聡*; 保坂 淳; 山口 康宏

Physical Review D, 104(9), p.L091503_1 - L091503_8, 2021/11

The recent LHCb data on $$B$$$$_s^{0}$$ $$rightarrow$$ $$J$$/$$psi$$$$p$$$$bar{p}$$ revealed a new pentaquark-like $$P$$$$_{c}$$(4337)$$^{+}$$ structure, while finding no evidence for $$P$$$$_{c}$$(4312)$$^{+}$$ discovered earlier in $$Lambda$$$$_b^{0}$$ $$rightarrow$$ $$J$$/$$psi$$$$pK^{-}$$. Though puzzling, the data actually offer an important hint to understand the nature of the pentaquark candidates. We develop a model to analyze the $$B$$$$_s^{0}$$ $$rightarrow$$ $$J$$/$$psi$$$$p$$$$bar{p}$$ data. We find that a $$Sigma$$$$_{c}$$$$bar{D}$$ over bar over bar one-loop mechanism causes a threshold cusp that fits well the $$P$$$$_{c}$$(4337)$$^{+}$$ peak. Also, the $$Sigma$$$$_{c}$$$$bar{D}$$ over bar over bar and $$Lambda$$$$_c$$$$bar{D}$$* threshold cusps interfere with each other to reproduce an oscillating behavior in the proton helicity angle distribution. These results combined with our earlier analysis on $$Lambda$$$$_b^{0}$$ $$rightarrow$$ $$J$$/$$psi$$$$pK^{-}$$ indicate that $$P$$$$_{c}$$(4312)$$^{+}$$ and $$P$$$$_{c}$$(4337)$$^{+}$$ are created by different interference patterns between the $$Sigma$$$$_{c}$$$$bar{D}$$ and $$Lambda$$$$_c$$$$bar{D}$$* (anomalous) threshold cusps. The proposed scenario consistently explains why the $$P$$$$_{c}$$(4312)$$^{+}$$ and $$P$$$$_{c}$$(4337)$$^{+}$$ peaks appear in $$Lambda$$$$_b^{0}$$ $$rightarrow$$ $$J$$/$$psi$$$$pK^{-}$$ and $$B$$$$_s^{0}$$ $$rightarrow$$ $$J$$/$$psi$$$$p$$$$bar{p}$$ over bar over bar , respectively, but not vice versa or both.

論文

Heavy hadronic molecules coupled with multiquark states

山口 康宏; Garc$'i$a-Tecocoatzi, H.*; Giachino, A.*; 保坂 淳; Santopinto, E.*; 竹内 幸子*; 瀧澤 誠*

Few-Body Systems, 62(3), p.33_1 - 33_7, 2021/09

 被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)

本研究では$$Lambda_cbar{D}^{(ast)}-Sigma_c^{(ast)}bar{D}^{(ast)}$$ハドロン分子にコンパクトな$$uudcbar{c}$$コアが結合したハイブリット状態としての$$P_c$$ペンタクォーク状態の理論解析が行われた。相互作用としてヘビークォーク対称性とカイラル対称性を尊重したものが用いられ、結果、$$P_c^+(4312)$$$$P_c^+(4440)$$, $$P_c^+(4457)$$の質量と崩壊幅の実験データを説明することができた。その時、スピン-パリティは$$J^P=1/2^-$$, $$3/2^-$$, $$1/2^-$$と求まった。この解析で、エネルギー順位の構造にはコンパクト状態との結合より導かれたハドロン間相互作用が支配的な働きをしていることが得られ、一方、崩壊幅の決定にはパイオン交換力のテンソル項が重要な働きをしていることが得られた。

論文

Novel pentaquark picture for singly heavy baryons from chiral symmetry

末永 大輝*; 保坂 淳

Physical Review D, 104(3), p.034009_1 - 034009_7, 2021/08

We propose a new type of structure for singly heavy baryons of $$Qqq$$$$bar{q}$$$$q$$ in addition to the conventional one of $$Qqq$$. Based on chiral symmetry of the light quarks, we show that the $$Qqq$$$$bar{q}$$$$q$$ baryon offers a novel picture for heavy-quark spin-singlet and flavor-antisymmetric baryons. By making use of the effective Lagrangian approach, we find that $$Lambda$$$$_{c}$$(2765) and $$Xi$$$$_{c}$$(2967) are mostly $$Qqq$$$$bar{q}$$$$q$$, while $$Lambda$$$$_{c}$$(2286) and $$Xi$$$$_{c}$$(2470) are mostly $$Qqq$$. The masses of negative-parity baryons are predicted. We also derive a sum rule and the extended Goldberger-Treiman relation that the masses of the baryons satisfy. Furthermore, a mass degeneracy of parity partners of the baryons with the restoration of chiral symmetry is discussed. These are the unique features that the conventional picture of radial excitation in the quark model does not accommodate. Our findings provide useful information not only for future experiments but also for future lattice simulations on diquarks.

論文

Model independent analysis of coupled-channel scattering; A Deep learning approach

Sombillo, D. L. B.*; 池田 陽一*; 佐藤 透*; 保坂 淳

Physical Review D, 104(3), p.036001_1 - 036001_12, 2021/08

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 $$pi$$$$N$$ 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 $$pi$$$$N$$ 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.

論文

Decay properties of Roper resonance in the holographic QCD

藤井 大輔*; 保坂 淳

Physical Review D, 104(1), p.014022_1 - 014022_6, 2021/07

We investigate the one pion decay of the Roper resonance $$N$$*(1440) $$rightarrow$$ $$N$$$$pi$$ 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 $$pi$$$$NN$$* and $$pi$$$$NN$$ 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 $$lambda$$ ('t Hooft coupling) limit which are useful to test how baryon resonances share what are expected in these limits.

論文

Photoproduction of $$Lambda^*$$ and $$Sigma^*$$ resonances with $$J^P=1/2^-$$ off the proton

Kim, S.-H.*; Khemchandani, K. P.*; Mart$'i$nez Torres, A.*; Nam, S.-I.*; 保坂 淳

Physical Review D, 103(11), p.114017_1 - 114017_12, 2021/06

We study the photoproduction of the $$Lambda$$(1405) and $$Sigma$$(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 $$K$$$$Sigma$$(1405) and $$K$$$$Sigma$$(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 $$Lambda$$(1405), while for $$Sigma$$(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 $$Lambda$$(1405) and $$Sigma$$(1400).

論文

Relativistic corrections to decays of heavy baryons in the quark model

Arifi, A. J.*; 末永 大輝*; 保坂 淳

Physical Review D, 103(9), p.094003_1 - 094003_6, 2021/05

We investigate relativistic corrections of an 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 $$Lambda$$$$_{c}$$(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 $$Sigma$$$$_{c}$$(2455) and $$Sigma$$$$_{c}$$(2520) decays.

論文

Stable double-heavy tetraquarks; Spectrum and structure

Meng, Q.*; 肥山 詠美子*; 保坂 淳; 岡 眞; Gubler, P.; Can, K. U.*; 高橋 徹*; Zong, H. S.*

Physics Letters B, 814, p.136095_1 - 136095_6, 2021/03

 被引用回数:29 パーセンタイル:98.89(Astronomy & Astrophysics)

Bound states of double-heavy tetraquarks are studied in a constituent quark model. Two bound states are found for isospin and spin-parity $$I(J^P) = 0(1^+)$$ in the $$bbbar{u}bar{d}$$ channel. One is deeply bound and compact made of colored diquarks, while the other is shallow and extended as a $$BB^{ast}$$ molecule. The former agrees well with lattice QCD results. A systematic decrease in the binding energy is seen by replacing one of the heavy quarks to a lighter one. Altogether we find ten bound states. It is shown for the first time that hadrons with totally different natures emerge from a single Hamiltonian.

論文

Use of the canonical approach in effective models of QCD

若山 将征*; Nam, S.-I.*; 保坂 淳

Physical Review D, 102(3), p.034035_1 - 034035_9, 2020/08

We discuss the canonical approach for the study of QCD phase at finite densities and temperatures in the confinement phase. The canonical approach, which is a method to extrapolate observables calculated at pure imaginary chemical potentials to those at real chemical potentials, is useful to overcome the sign problem in lattice QCD simulations at finite density. To validate the applicability of the approach, we employ the Nambu-Jona-Lasinio (NJL) and Polyakov-NJL (PNJL) models where exact solutions for the number density are available, which is the basic input of the fugacity expansion and can be compared with those of the canonical approach. We fmd that the number densities computed from the canonical approach are consistent with the exact solutions in most of the confinement phase. The results in the present study are applicable to the study of lattice QCD.

論文

$$Lambda(1405)$$ as a $$bar{K}N$$ Feshbach resonance in the Skyrme model

江添 貴之*; 保坂 淳

Physical Review D, 102(1), p.014046_1 - 014046_9, 2020/07

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

論文

Roper-like resonances with various flavor contents and their two-pion emission decays

Arifi, A. J.*; 永廣 秀子*; 保坂 淳; 谷田 聖

Physical Review D, 101(11), p.111502_1 - 111502_5, 2020/06

 被引用回数:13 パーセンタイル:71.01(Astronomy & Astrophysics)

We study the three-body decay of the newly observed bottom baryon $$Lambda_b^*(6072)$$ by LHCb; $$Lambda_b^*(6072) to Lambda_b pi pi$$. Its mass about 500 MeV above the ground state $$Lambda_b$$ and a broad width imply that the state could be an analogue of the Roper resonance of the nucleon $$N(1440)$$. In terms of sequential processes going through $$Sigma_b$$ and $$Sigma_b^*$$, we find that the observed invariant mass distribution is reproduced assuming its spin and parity $$J^P = 1/2^+$$. We discuss that the ratio of the two sequential processes and angular correlation of two pions are useful for the determination of spin and parity. We suggest further studies for the Roper resonance analogue in various flavor contents, raising an interesting and important question in baryon spectroscopy.

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