arXiv subjects

J. Yamagata-Sekihara

Publications and source records attributed to J. Yamagata-Sekihara.

At least 19 recordsLinked to original sources

arXiv2025

Excitation Spectra of the ${}^{12}{\rm C}(p,d)$ Reaction near the $η'$-Meson Emission Threshold Measured in Coincidence with High-Momentum Protons

The missing mass of the ${}^{12}{\rm C}(p,d)$ reaction has been measured near the $η'$-meson emission threshold in coincidence with a high-momentum proton to selectively collect $η'$-${}^{11}{\rm C}$ mesic nucleus formation events at GSI, Germany. A 2.5 GeV proton excites a carbon nucleus to form an $η'$-mesic nucleus emitting a deuteron forward with an energy of $\sim 1.6$ GeV. The deuteron is momentum-analyzed by the Fragment Separator used as a high-resolution spectrometer to deduce the excitation energy of the residual system. The large-acceptance detector WASA surrounding the target identifies high-momentum protons emitted in the decay of the $η'$-mesic nucleus. The measured semi-exclusive spectrum exhibits structures below the threshold though the statistical significance is limited. The spectrum is fitted by theoretically calculated spectra varying optical-potential parameters of the $η'$-nucleus interaction. The analysis results indicate $η'$-mesic nuclei formation for the real potential depth of $\sim -61$ MeV with a local statistical significance of $3.5 σ$ and, taking into account the look-elsewhere effect, a global significance of $2.1 σ$.

nucl-ex↗

arXiv2024

Investigation of kaonic atom optical potential by the high precision data of kaonic $^3$He and $^4$He atoms

We theoretically investigate kaonic atom states based on the latest high precision data of the $2p$ states of the kaonic atoms in $^3$He and $^4$He (J-PARC E62). We consider the phenomenological form for the optical potential proportional to the nuclear density distributions and determine the potential parameters by the latest data. We find two sets of potential parameters for each of $K^--^3$He and $K^--^4$He that reproduce the data. We then extract the potential parameters consistent with the data of $^3$He and $^4$He atoms simultaneously. Using the potential, we investigate the structure of the kaonic atoms and kaonic nuclei for various nuclei up to Sn. We also report the optical potential parameters suited for the global description of the atomic data, the possible strong isospin dependence of the potential, and the different strength of the data of $K^--^3$He and $K^--^4$He in the restrictions on the potential parameters. In addition, we find that the study of the $1s$ states of the kaonic helium atom is very interesting as a next step, and the determination of the orbital angular momenta of the kaonic nuclear states is helpful for the unified understandings of the atomic and nuclear bound states of kaon because of the mutual influence between the atomic and the nuclear states of kaon with the same orbital angular momentum.

nucl-th↗

arXiv2024

Mini-Proceedings of the "Fourth International Workshop on the Extension Project for the J-PARC Hadron Experimental Facility (HEF-ex 2024)"

The mini proceedings of the "Fourth International Workshop on the Extension Project for the J-PARC Hadron Experimental Facility (HEF-ex 2024) [https://kds.kek.jp/event/46965]" held at J-PARC, February 19-21, 2024, are presented. The workshop was devoted to discussing the physics case that connects both the present and the future Hadron Experimental Facility at J-PARC, covering a wide range of topics in flavor, hadron, and nuclear physics related to both experimental and theoretical activities being conducted at the facility.

nucl-ex↗

arXiv2016

First application of superconducting transition-edge-sensor microcalorimeters to hadronic-atom x-ray spectroscopy

High-resolution pionic-atom x-ray spectroscopy was performed with an x-ray spectrometer based on a 240-pixel array of superconducting transition-edge-sensor (TES) microcalorimeters at the piM1 beam line of the Paul Scherrer Institute. X-rays emitted by pionic carbon via the 4f->3d transition and the parallel 4d->3p transition were observed with a full-width-at-half-maximum energy resolution of 6.8 eV at 6.4 keV. Measured x-ray energies are consistent with calculated electromagnetic values which considered the strong-interaction effect assessed via the Seki-Masutani potential for the 3p energy level, and favor the electronic population of two filled 1s electrons in the K-shell. Absolute energy calibration with an uncertainty of 0.1 eV was demonstrated under a high-rate hadron beam condition of 1.45 MHz. This is the first application of a TES spectrometer to hadronic-atom x-ray spectroscopy and is an important milestone towards next-generation high-resolution kaonic-atom x-ray spectroscopy.

physics.ins-det↗

arXiv2015

Formation spectra of charmed meson--nucleus systems using an antiproton beam

We investigate the structure and formation of charmed meson--nucleus systems, with the aim of understanding the charmed meson--nucleon interactions and the properties of the charmed mesons in the nuclear medium. The $\bar{D}$ mesic nuclei are of special interest, since they have tiny decay widths due to the absence of strong decays for the $\bar{D} N$ pair. Employing an effective model for the $\bar{D} N$ and $D N$ interactions and solving the Klein--Gordon equation for $\bar{D}$ and $D$ in finite nuclei, we find that the $D^{-}$-${}^{11}\rm{B}$ system has $1 s$ and $2p$ mesic nuclear states and that the $D^{0}$-${}^{11}\rm{B}$ system binds in a $1s$ state. In view of the forthcoming experiments by the PANDA and CBM Collaborations at the future FAIR facility and the J-PARC upgrade, we calculate the formation spectra of the $[D^{-}$-${}^{11}\rm{B}]$ and $[D^{0}$-${}^{11}\rm{B}]$ mesic nuclei for an antiproton beam on a ${}^{12} \rm{C}$ target. Our results suggest that it is possible to observe the $2 p$ $D^{-}$ mesic nuclear state with an appropriate experimental setup.

nucl-th↗

arXiv2015

Exotic atoms and exotic nuclei

We briefly review the study of the exotic atoms and exotic nuclei, and report recent research activities of eta-mesic nucleus and kaonic atoms in this article.

nucl-th↗

arXiv2013

MesonNet 2013 International Workshop. Mini-proceedings

The mini-proceedings of the MesonNet 2013 International Workshop held in Prague from June 17th to 19th, 2013, are presented. MesonNet is a research network within EU HadronPhysics3 project (1/2012 -- 12/2014). The web page of the conference, which contains all talks, can be found at http://ipnp.mff.cuni.cz/mesonnet13

hep-ph↗

arXiv2013

Production of hyperon resonances induced by kaon on a deuteron target

The $K^- d \to πYN$reaction is theoretically studied so as to investigate the $K^{-}$-induced production of the hyperon resonances $Σ(1385)$ and $Λ(1405)$. For this purpose we take into account the p-wave amplitudes for the meson-baryon two-body scatterings as well as the s-wave amplitudes. Due to the fact that the hyperon resonances are selectively produced from the $\bar{K} N$ channel in this reaction, the $Λ(1405)$ peak appears at 1420 MeV, which implies that $Λ(1405)$ and $Σ(1385)$ could be separately seen in the missing mass spectrum of the emitted nucleon in the $K^{-} d \to n X$ reaction. The $πY$ invariant mass spectrum in this study is consistent with experimental data both for $Σ(1385)$ and $Λ(1405)$. The pion exchange contributions are also included and are found to give smooth background without distorting the peak structure of the hyperon resonances.

nucl-th↗

arXiv2012

Nuclear density probed by Kaon-Nucleus systems and Kaon-Nucleus interaction

Effective nuclear densities probed by kaon- and anti-kaon-nucleus systems are studied theoretically both for bound and low energy scattering states. As for the anti-kaon bound states, we investigate kaonic atoms. We find that the effective density depends on the atomic states significantly and we have the possibility to obtain the anti-kaon properties at various nuclear densities by observing the several kaonic atom states. We also find the energy dependence of the probed density by kaon and anti-kaon scattering states. We find that the study of the effective nuclear density will help to find the proper systems to investigate the meson properties at various nuclear densities.

nucl-th↗

arXiv2012

A new perspective on the Faddeev equations and the $\bar{K}NN$ system from chiral dynamics and unitarity in coupled channels

We review recent work concerning the $\bar{K}N$ interaction and Faddeev equations with chiral dynamics which allow us to look at the $\bar{K}NN$ from a different perspective and pay attention to problems that have been posed in previous studies on the subject. We show results which provide extra experimental evidence on the existence of two $Λ(1405)$ states. We then show the findings of a recent approach to Faddeev equations using chiral unitary dynamics, where an explicit cancellation of the two body off shell amplitude with three body forces stemming from the same chiral Lagrangians takes place. This removal of the unphysical off shell part of the amplitudes is most welcome and renders the approach unambiguous, showing that only on shell two body amplitudes need to be used. With this information in mind we use an approximation to the Faddeev equations within the fixed center approximation to study the $\bar{K}NN$ system, providing answers within this approximation to questions that have been brought before and evaluating binding energies and widths of this three body system. As a novelty with respect to recent work on the topic we find a bound state of the system with spin S=1, like a bound state of $\bar{K}$-deuteron, less bound that the one of S=0, where all recent efforts have been devoted. The width is relatively large in this case, suggesting problems in a possible experimental observation.

hep-ph↗

arXiv2011

Formation of Heavy Meson Bound States by Two Nucleon Pick-up Reactions

We develop a model to evaluate the formation rate of the heavy mesic nuclei in the two nucleon pick-up reactions, and apply it to the $^6$Li target cases for the formation of heavy meson-$α$ bound states, as examples. The existence of the quasi-deuteron in the target nucleus is assumed in this model. It is found that the mesic nuclei formation in the recoilless kinematics is possible even for heavier mesons than nucleon in the two nucleon pick-up reactions. We find the formation rate of the meson-$α$ bound states can be around half of the elementary cross sections at the recoilless kinematics with small distortions.

nucl-th↗

arXiv2011

The $\bar{K}NN$ system with chiral dynamics

We have performed a calculation of the scattering amplitude for the three body system $\bar{K}NN$ assuming $\bar{K}$ scattering against a $NN$ cluster, using the Fixed Center approximation to the Faddeev equations. The $\bar{K}N$ amplitudes, which we take from chiral unitary dynamics, govern the reaction and we find a $\bar{K}NN$ amplitude that peaks around 40 MeV below the $\bar{K}NN$ threshold, with a width in $|T|^2$ of the order of 50 MeV for spin 0 and has another peak around 27 MeV with similar width for spin 1. The results are in line with those obtained using different methods but implementing chiral dynamics. The simplicity of the approach allows one to see the important ingredients responsible for the results. In particular we show the effects from the reduction of the size of the $NN$ cluster due to the interaction with the $\bar{K}$ and those from the explicit considiration of the $ πΣN $ channel in the three body equations.

hep-ph↗

arXiv2011

Selected topics on Hadrons in Nuclei

In this talk we report on selected topics on hadrons in nuclei. The first topic is the renormalization of the width of the $Λ(1520)$ in a nuclear medium. This is followed by a short update of the situation of the $ω$ in the medium. The investigation of the properties of $\bar{K}$ in the nuclear medium from the study of the $(K_{flight},p)$ reaction is also addressed, as well as properties of X,Y,Z charmed and hidden charm resonances in a nuclear medium. Finally we address the novel issue of multimeson states.

nucl-th↗

arXiv2011

Couplings in coupled channels versus wave functions in the case of resonances: application to the two $Λ(1405)$ states

In this paper we develop a formalism to evaluate wave functions in momentum and coordinate space for the resonant states dynamically generated in a unitary coupled channel approach. The on shell approach for the scattering matrix, commonly used, is also obtained in Quantum Mechanics with a separable potential, which allows one to write wave functions in a trivial way. We develop useful relationships among the couplings of the dynamically generated resonances to the different channels and the wave functions at the origin. The formalism provides an intuitive picture of the resonances in the coupled channel approach, as bound states of one bound channel, which decays into open ones. It also provides an insight and practical rules for evaluating couplings of the resonances to external sources and how to deal with final state interaction in production processes. As an application of the formalism we evaluate the wave functions of the two $Λ(1405)$ states in the $πΣ$, $\bar{K} N$ and other coupled channels.

hep-ph↗

arXiv2010

Latest results for the antikaon-nucleon optical potential

The key question of this letter is whether the K-nucleus optical potential is deep, as it is prefered by the phenomenological fits to kaonic atoms data, or shallow, as it comes out from unitary chiral model calculations. The current experimental situation is reviewed.

nucl-th↗

arXiv2010

Wave functions for dynamically generated resonances; the two $Λ(1405)$ and $Λ(1670)$

In this work we develop a formalism to evaluate wave functions in momentum and coordinate space for the resonant states dynamically generated in a unitary coupled channel approach. The on shell approach for the scattering matrix, commonly used, is also obtained in Quantum Mechanics with a separable potential, which allows one to write wave functions in a trivial way. We develop useful relationships among the couplings of the dynamically generated resonances to the different channels and the wave functions at the origin. The formalism provides an intuitive picture of the resonances in the coupled channel approach, as bound states of one bound channel, which decays into open ones. It also provides an insight and practical rules for evaluating couplings of the resonances to external sources and how to deal with final state interaction in production processes. As an application of the formalism we evaluate the wave functions of the two $Λ(1405)$ states in the $πΣ$, $\bar{K} N$ and other coupled channels. It also offers a practical way to study three body systems when two of them cluster into a resonance.

hep-ph↗

arXiv2010

Experimental status of deeply bound kaonic states in nuclei

We review recent claims of the existence of deeply bound kaonic states in nuclei. Also we study in details the (K-,p) reaction on C12 with 1 GeV/c momentum kaon beam, based on which a deep kaon nucleus optical potential was claimed in [1]. In our Monte Carlo simulation of this reaction we include not only the quasi-elastic K- p scattering, as in [1], but also K- absorption by one and two nucleons followed by the decay of the hyperon in pi N, which can also produce strength in the region of interest. The final state interactions in terms of multiple scattering of the K-, p and all other primary particles on their way out of the nucleus is also considered. We will show that all these additional mechanisms allow us to explain the observed spectrum with a "standard" shallow kaon nucleus optical potential obtained in chiral models. [1] T. Kishimoto et al., Prog. Theor. Phys. 118, 181 (2007).

nucl-th↗

arXiv2010

On the nature of the K2(1430), K3(1780), K4(2045), K5(2380) and K6 as K--multi-rho states

We show that the $K^*_2(1430)$, $K^*_3(1780)$, $K^*_4(2045)$, $K^*_5(2380)$ and a not yet discovered $K_6^*$ resonance are basically molecules made of an increasing number of $ρ(770)$ and one $K^*(892)$ mesons. The idea relies on the fact that the vector-vector interaction in s-wave with spins aligned is very strong both for $ρρ$ and $K^*ρ$. We extend a recent work, where several resonances showed up as multi-$ρ(770)$ molecules, to the strange sector including the $K^*(892)$ into the system. The resonant structures show up in the multi-body scattering amplitudes, which are evaluated in terms of the unitary two-body vector-vector scattering amplitudes by using the fixed center approximation to the Faddeev equations.

hep-ph↗