arXiv subjects

N. Ikeno

Publications and source records attributed to N. Ikeno.

At least 19 recordsLinked to original sources

arXiv2025

Impact of the in-medium cross section on cluster spectra in ${}^{40,48}\mathrm{Ca}+{}^{58,64}\mathrm{Ni}$ collisions at $56$ and $140$ $\mathbf{\mathrm{MeV}}/\mathrm{\mathbf{nucleon}}$

Although significant efforts have been made to investigate the density dependence of the nuclear symmetry energy, the influence of the in-medium cross section on particle production in transport models is not well constrained. The in-medium cross section reflects the dynamic situation of the medium such as a nontrivial phase space distribution. In this study, we analyze the transverse momentum spectra of $p$, $d$, $t$, ${}^3{\mathrm{He}}$ and $\alpha$ particles emitted near mid-rapidity in central $^{40,48}\mathrm{Ca}$ + $^{58, 64}\mathrm{Ni}$ reactions at $56$ and $140$ $\mathrm{MeV}/\mathrm{nucleon}$. The Antisymmetrized Molecular Dynamics ($\mathrm{AMD}$) model is chosen as the transport model for data comparison. Central events are selected based on charged-particle multiplicity in both the experimental data and AMD calculations after applying an experimental filter. Our results show that the in-medium nucleon-nucleon scattering cross-sections are more strongly reduced at $56$ $\mathrm{MeV}/\mathrm{nucleon}$ than at $140$ $\mathrm{MeV}/\mathrm{nucleon}$ incident energy.

nucl-th↗

arXiv2025

Excitation Spectra of the ${}^{12}{\rm C}(p,d)$ Reaction near the $\eta'$-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 $\eta'$-meson emission threshold in coincidence with a high-momentum proton to selectively collect $\eta'$-${}^{11}{\rm C}$ mesic nucleus formation events at GSI, Germany. A 2.5 GeV proton excites a carbon nucleus to form an $\eta'$-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 $\eta'$-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 $\eta'$-nucleus interaction. The analysis results indicate $\eta'$-mesic nuclei formation for the real potential depth of $\sim -61$ MeV with a local statistical significance of $3.5 \sigma$ and, taking into account the look-elsewhere effect, a global significance of $2.1 \sigma$.

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.

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arXiv2023

Molecular states of $ D^* D^* \bar{K}^*$ nature

We study the interaction of two $ D^* $ and a $\bar{K}^{*}$ by using the Fixed Center Approximation to the Faddeev equations to search for bound states of the three body system. Since the $ D^* D^* $ interaction is attractive and gives a bound state, and so is the case of the $D^* \bar{K}^{*}$ interaction, where the $J^{P}=0^{+}$ bound state is identified with the $X_0 (2900)$, the $ D^* D^* \bar{K}^{*}$ system leads to manifestly exotic bound states with $ccs$ open quarks. We obtain bound states of isospin $I=1/2$, negative parity and total spin $J=0,1,2$. For $J=0$ we obtain one state, and for $J=1,2$ we obtain two states in each case. The binding energies range from $56$ MeV to $151$ MeV and the widths from $80$ MeV to $100$ MeV.

hep-ph↗

arXiv2023

Sequential single pion production explaining the dibaryon "$d^*(2380)$" peak

We study the two step sequential one pion production mechanism, $np(I=0)\to π^-pp$, followed by the fusion reaction $pp\to π^+d$, in order to describe the $np\to π^+π^-d$ reaction with $π^+π^-$ in $I=0$, where a narrow peak, so far identified with a "$d(2380)$" dibaryon, has been observed. We find that the second step $pp\to π^+d$ is driven by a triangle singularity that determines the position of the peak of the reaction and the large strength of the cross section. The combined cross section of these two mechanisms produce a narrow peak with the position, width and strength compatible with the experimental observation within the approximations done. This novel interpretation of the peak without invoking a dibaryon explains why the peak is not observed in other reactions where it has been searched for.

nucl-th↗

arXiv2023

Predictions of super-exotic heavy mesons from $K^{}B^{}B^{*}$ interactions

We make a theoretical study of the three-body system composed of ${\bar K^*}{\bar B^*}{\bar B^*}$ to look for possible bound states, which could be associated to mesonic resonances of very exotic nature, containing open strange and double-bottom flavours. The three-body interaction is evaluated by using the fixed center approach to the Faddeev equations where the ${\bar B^*}{\bar B^*}$ is bound forming an $I(J^P)=0(1^+)$ state, as it was found in previous works, and the third particle, the ${\bar B^*}$, of much smaller mass, interacts with the components of the cluster. We obtain bound states for all the channels considered: spin $J=0$, 1 and 2, all of them with isospin $I=1/2$ and negative parity.

hep-ph↗

arXiv2022

Isoscaling in central Sn+Sn collisions at 270 MeV/u

Experimental information on fragment emissions is important in understanding the dynamics of nuclear collisions and in the development of transport model simulating heavy-ion collisions. The composition of complex fragments emitted in the heavy-ion collisions can be explained by statistical models, which assume that thermal equilibrium is achieved at collision energies below 100 MeV/u. Our new experimental data together with theoretical analyses for light particles from Sn+Sn collisions at 270 MeV/u, suggest that the hypothesis of thermal equilibrium breaks down for particles emitted with high transfer momentum. To inspect the system's properties in such limit, the scaling features of the yield ratios of particles from two systems, a neutron-rich system of ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ and a nearly symmetric system of ${}^{108}\mathrm{Sn}+{}^{112}\mathrm{Sn}$, are examined in the framework of the statistical multifragmentation model and the antisymmetrized molecular dynamics model. The isoscaling from low energy particles agree with both models. However the observed breakdown of isoscaling for particles with high transverse momentum cannot be explained by the antisymmetrized molecular dynamics model.

nucl-ex↗

arXiv2020

Analysis of the $ψ(4040)$ and $ψ(4160)$ decay into $D^{(\ast)} \bar D^{(\ast)}$, $D_s^{(\ast)}\bar D_s^{(\ast)}$

We have performed an analysis of the $e^+ e^- \to D^{(*)} \bar D^{(*)}$ data in the region of the $ψ(4040)$ and $ψ(4160)$ resonances which have a substantial overlap and require special care. By using the $^3 P_0$ model to relate the different $D^{(*)} \bar D^{(*)}$ production modes, we make predictions for production of these channels and compare with experiment and other theoretical approaches. As a side effect we find that these resonances qualify largely as $c \bar c$ states and the weight of the meson-meson components in the wave function is very small.

hep-ph↗

arXiv2018

Spectroscopy of pionic atoms in $\mathbf{{}^{122}{\textbf Sn}({\textit d},{}^3{\textbf He})}$ reaction and angular dependence of the formation cross sections

We observed the atomic $1s$ and $2p$ states of $π^-$ bound to ${}^{121}{\rm Sn}$ nuclei as distinct peak structures in the missing mass spectra of the ${}^{122}{\rm Sn}(d,{}^3{\rm He})$ nuclear reaction. A very intense deuteron beam and a spectrometer with a large angular acceptance let us achieve potential of discovery, which includes capability of determining the angle-dependent cross sections with high statistics. The $2p$ state in a Sn nucleus was observed for the first time. The binding energies and widths of the pionic states are determined and found to be consistent with previous experimental results of other Sn isotopes. The spectrum is measured at finite reaction angles for the first time. The formation cross sections at the reaction angles between 0 and $2^\circ$ are determined. The observed reaction-angle dependence of each state is reproduced by theoretical calculations. However, the quantitative comparison with our high-precision data reveals a significant discrepancy between the measured and calculated formation cross sections of the pionic $1s$ state.

nucl-ex↗

arXiv2018

Constraining the optical potential in the search for eta-mesic 4He

A consistent description of the $ d d \rightarrow$ $^{4}\hspace{-0.03cm}\mbox{He} η$ and $ d d \rightarrow$ ($^4$He$η$)$_{bound} \rightarrow X $ cross sections was recently proposed with a broad range of real ($V_{0}$) and imaginary (W0), $η$-$^4$He optical potential parameters leading to a good agreement with the d d -> 4He eta data. Here we compare the predictions of the model below the $η$ production threshold, with the WASA-at-COSY excitation functions for the dd -> 3He N pi reactions to put stronger constraints on (V0, W0). The allowed parameter space (with |V_0| < \sim 60 MeV and |W_0| < \sim 7 MeV estimated at 90% CL ) excludes most optical model predictions of eta-4He nuclei except for some loosely bound narrow states.

nucl-ex↗

arXiv2018

Missing-mass spectroscopy of the ${}^{12}{\rm C}(p,d)$ reaction near the $η^\prime$-meson production threshold

Excitation-energy spectra of $^{11}$C nuclei near the $η^\prime$-meson production threshold have been measured by missing-mass spectroscopy using the $^{12}$C($p$,$d$) reaction. A carbon target has been irradiated with a 2.5 GeV proton beam supplied by the synchrotron SIS-18 at GSI to produce $η^\prime$ meson bound states in $^{11}$C nuclei. Deuterons emitted at $0^\circ$ in the reaction have been momentum-analyzed by the fragment separator (FRS) used as a high-resolution spectrometer. No distinct structure due to the formation of $η^\prime$-mesic states is observed although a high statistical sensitivity is achieved in the experimental spectra. Upper limits on the formation cross sections of $η^\prime$-mesic states are determined, and thereby a constraint imposed on the $η^\prime$-nucleus interaction is discussed.

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arXiv2017

$η$-nucleus interaction from the $d+d$ reaction around the $η$ production threshold

The $η$ mesic nucleus is considered to be one of the interesting exotic many body systems and has been studied since 1980's theoretically and experimentally. Recently, the formation of the $η$ mesic nucleus in the fusion reactions of the light nuclei such as $d + d \rightarrow (η+ α) \rightarrow X$ has been proposed and the experiments have been performed by WASA-at-COSY. We develop a theoretical model to evaluate the formation rate of the $η$ mesic nucleus in the fusion reactions and show the calculated results. We find that the $η$ bound states could be observed in the reactions in cases with the strong attractive and small absorptive $η$-nucleus interactions. We compare our results with existing data of the $d + d \rightarrow η+ α$ and the $d + d \rightarrow {^3 \rm He} + N + π$ reactions. We find that the analyses by our theoretical model with the existing data can provide new information on the $η$-nucleus interaction.

nucl-th↗

arXiv2016

Measurement of excitation spectra in the ${}^{12}$C$(p,d)$ reaction near the $η'$ emission threshold

Excitation spectra of $^{11}$C were measured in the $^{12}$C$(p,d)$ reaction near the $η'$ emission threshold. A proton beam extracted from the synchrotron SIS-18 at GSI with an incident energy of 2.5 GeV impinged on a carbon target. The momenta of deuterons emitted at 0 degrees were precisely measured with the fragment separator FRS operated as a spectrometer. In contrast to theoretical predictions on the possible existence of deeply bound $η'$ mesic states in carbon nuclei, no distinct structures were observed associated with the formation of bound states. The spectra were analyzed to set stringent constraints on the formation cross section and on the hitherto barely-known $η'$-nucleus interaction.

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↗

arXiv2016

Formation of eta'(958) Meson Bound States by the 6Li(gamma,d) reaction

We have investigated the 6Li(gamma,d) reaction theoretically for the formation of the eta'(958) mesic nucleus close to the recoilless kinematics. We have developed the theoretical formula and reported the quantitative results of the formation spectra for various cases in this article. We have found that the formation cross sections are reduced by the effects of the fragile deuteron form factor.

nucl-th↗

arXiv2015

Semileptonic $Λ_c$ decay to $νl^+$ and $Λ(1405)$

We study the semileptonic decay of $Λ_c$ to $νl^+$ and $Λ(1405)$, where the $Λ(1405)$ is seen in the invariant mass distribution of $πΣ$. We perform the hadronization of the quarks produced in the reaction in order to have a meson baryon pair in the final state and then let these hadron pairs undergo final state interaction from where the $Λ(1405)$ is dynamically generated. The reaction is particularly suited to study this resonance because we show that it filters I=0. It is also free of tree level $πΣ$ production, which leads to a clean signal of the resonance with no background. This same feature has as a consequence that one populates the state of the $Λ(1405)$ with higher mass around 1420 MeV, predicted by the chiral unitary approach. We make absolute predictions for the invariant mass distributions and find them within measurable range in present facilities. The implementation of this reaction would allow us to gain insight into the existence of the predicted two $Λ(1405)$ states and their nature as molecular states.

hep-ph↗

arXiv2015

Spectroscopy of $η'$-nucleus bound states at GSI and FAIR --- very preliminary results and future prospects ---

The possible existence of η'-nucleus bound states has been put forward through theoretical and experimental studies. It is strongly related to the η' mass at finite density, which is expected to be reduced because of the interplay between the $U_A(1)$ anomaly and partial restoration of chiral symmetry. The investigation of the C(p,d) reaction at GSI and FAIR, as well as an overview of the experimental program at GSI and future plans at FAIR are discussed.

nucl-ex↗

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↗