arXiv subjects

Natsumi Ikeno

Publications and source records attributed to Natsumi Ikeno.

At least 19 recordsLinked to original sources

arXiv2026

Line shapes of $Ω(2012)$ production in the $Ξ\bar K $ and $Ξπ\bar K$ decay channels

We theoretically study the line shape of the experiment for $Ω(2012)$ production in the $Ξ^- π^+ K^-$ and $Ξ^0 K^-$ decay modes, reflecting the $Ξ^* \bar K$ and $Ξ\bar K$ decay modes, from the perspective that the $Ω(2012)$ is a molecular state dynamically generated from the interaction of the $Ξ^* \bar K $ and $Ωη$, coupled channels with $Ξ\bar K$ as a decay channel. We show the consistency of the picture with the experimental mass distributions, giving support to the molecular picture for the $Ω(2012)$ state. We also call the attention to the sensitivity of the results to the cut imposed on the $πΞ$ invariant mass, and suggest a different method to obtain the ratio $R^{Ξπ\bar K}_{Ξ\bar K}$ of the three-body to two-body decay widths used so far as a test of the molecular picture. We stress that the direct comparison with the experimental mass distributions done here is a more stringent test of the molecular nature of the $Ω(2012)$ state than the comparison of the ratio $R^{Ξπ\bar K}_{Ξ\bar K}$ which has been so far obtained using different criteria.

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arXiv2026

$Λ(1670)$ production in the $ψ(3686) \to Λ\bar Λη$ reaction

We perform a calculation of the invariant mass distributions in the $ψ(3686) \to Λ\bar Λη$ reaction, where a neat peak for the excitation of the $Λ(1670)$ and $\bar Λ(1670)$ in the $ηΛ$ and $η\bar Λ$ mass distributions, respectively, is observed. Our approach uses the fact that the $ψ(3686)$, a $c \bar c$ state, is a singlet of SU(3) in the $u,d,s$ quarks and constructs the two flavor structures allowed with a pseudoscalar meson, a baryon and an antibaryon. The resonance peaks come from the final state interaction of meson baryon pairs, which generate the $ Λ(1670)$ in our approach. With a reasonable relative weight of the two flavor structures, the only free parameter of the theory, we are able to get the three mass distributions in good agreement with experiment, giving extra support to the molecular structure of the $ Λ(1670)$ resonance. The agreement with data improves with an extra resonant contribution with mass around 2200 MeV, possibly accounting for some resonances.

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arXiv2026

Feasibility of the observation of $η^{\prime}$ mesic nuclei in the semi-exclusive $^{12}$C($p, dp$) reaction

We study theoretically the feasibility of the semi-exclusive $^{12}$C($p,dp$)$X$ reaction for the observation of $η^\prime$ mesic nuclei using the microscopic transport model JAM. The semi-exclusive measurements of the ($p,d$) reaction with protons from $η^\prime$ absorption are found to be significant for the observation of the $η^\prime$ bound states. Especially, the measurements of the energetic protons from $η^\prime$ non-mesic two-body absorption ($η^\prime NN \to NN$) are considered to be critically important. The Green's function method is used to calculate the expected spectrum of forward going deuterons corresponding to the excitation energy spectrum of the $η^\prime \otimes {}^{11}$C system in the semi-exclusive measurement. The semi-exclusive measurements are shown to be important in general for the $η^\prime$ mesic nucleus observation.

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arXiv2025

Correlation function for the $n \bar{D}_{s0}^*(2317)$ interaction and the issue of elastic unitarity

We study the interaction of a neutron with the $\bar D_{s0}^*(2317)$ resonance and look at the amplitude below threshold and close above threshold. The study is done from the perspective that the $D_{s0}^*(2317)$ resonance is a molecular state of $DK$ in $I=0$. To study this interaction, we use the Fixed Center Approximation to Faddeev equations that considers the $DK$ molecule as the cluster and the neutron as the external particle. We improve the Fixed Center approach to implement elastic unitarity around threshold, which is needed to obtain scattering parameters and to evaluate the $n \bar D_{s0}^*(2317)$ correlation function that we determine here. One interesting result of the study is the appearance of a resonant state below threshold with a binding of about 130 MeV and a width of about 80 MeV, which we suggest to look at in reactions measuring the invariant mass of $πΣ\bar D$. The ALICE collaboration has initiated studies of this type, by looking at the $p f_1(1285)$ correlation function, and we can only encourage work in this direction which should provide much valuable information on the nature of many resonant states.

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arXiv2025

The $η^\prime N$ interaction from the $η^\prime p$ correlation function

We evaluate for the first time the $η^\prime p$ femtoscopic correlation function to study the $η^\prime N$ interaction. We find it extremely sensitive to the value of the $η^\prime p$ scattering length, for which at present there exists only very limited information, not even knowing its sign. The measurement of this correlation function would provide much valuable information on the $η^\prime N$ interaction, which could then also be used to settle the issue of possible $η^\prime$ nucleus bound states, an issue attracting much attention in the nuclear physics community.

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arXiv2025

The role of the $f_0(1710)$ and $a_0(1710)$ resonances in the $D^0 \to ρ^0 ϕ$, $ωϕ$ decays

We study the $D^0 \to ρ^0 ϕ$, $ωϕ$ decays which proceed in a direct mode via internal emission with equal rates. Yet, the experimental branching ratio for the $ρ^0 ϕ$ mode is twice as big as that for the $ωϕ$ mode. We find a natural explanation based on the extra indirect mechanism where $K^{*+} K^{*-}$ is produced via external emission and that channel undergoes final state interaction with other vector--vector channels to lead to the $ρ^0 ϕ$, $ωϕ$ final states, with transition amplitudes dominated by the $a_0(1710)$ resonance, recently discovered, and $f_0(1710)$ respectively. The large coupling of the $a_0(1710)$ to the $ρ^0 ϕ$ channel is mostly responsible for this large ratio of the production rates.

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arXiv2025

On the determination of the $D$ meson width in the nuclear medium with the transparency ratio

We have studied the feasibility of the experimental determination of the width of a $D$ meson in a nuclear medium by using the method of the nuclear transparency. The cross section for inclusive production of a $D^+$ in different nuclei is evaluated, taking care of the $D^+$ absorption in the nucleus, or equivalently, the survival probability of the $D^+$ in its way out of the nucleus from the point of production. We use present values of the in medium width of $D$ mesons and calculate ratios of the cross sections for different nuclei to the $^{12} \text{C} $ nucleus as reference. We find ratios of the order of $0.6$ for heavy nuclei, a large deviation from unity, which indicates that the method proposed is adequate to measure this relevant magnitude, so far only known theoretically.

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arXiv2024

Comparing pion production in transport simulations of heavy-ion collisions at $270A$ MeV under controlled conditions

Within the TMEP, we present a detailed study of the performance of different transport models in Sn+Sn collisions at $270A$ MeV, and put particular emphasis on the production of pions and $Δ$ resonances, which have been used as probes of the nuclear symmetry energy. We prescribe a common and rather simple physics model, and follow in detail the results of 4 BUU models and 6 QMD models. The nucleonic evolution of the collision and the nucleonic observables in these codes do not completely converge, but the differences among the codes can be understood as being due to several reasons: the basic differences between BUU and QMD models in the representation of the phase-space distributions, computational differences in the mean-field evaluation, and differences in the adopted strategies for the Pauli blocking in the collision integrals. For pionic observables, we find that a higher maximum density leads to an enhanced pion yield and a reduced $π^-/π^+$ yield ratio, while a more effective Pauli blocking generally leads to a slightly suppressed pion yield and an enhanced $π^-/π^+$ yield ratio. We specifically investigate the effect of the Coulomb force, and find that it increases the total $π^-/π^+$ yield ratio but reduces the ratio at high pion energies, although differences in its implementations do not have a dominating role in the differences among the codes. Taking into account only the results of codes that strictly follow the homework specifications, we find a convergence of the codes in the final charged pion yield ratio to a $1σ$ deviation of about $5\%$. However, the uncertainty is expected to be reduced to about $1.6\%$ if the same or similar strategies and ingredients, i.e., an improved Pauli blocking and calculation of the non-linear term in the mean-field potential, are similarly used in all codes.

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arXiv2024

$D^+ \to K_s^0 π^+ η$ reaction and $a_0(980)^+$

We study the $D^+ \to \bar K^0 π^+ η$ reaction where the $a_0(980)$ excitation plays a dominant role. We consider mechanisms of external and internal emission at the quark level, hadronize the $q \bar q$ components into two mesons and allow these mesons to undergo final state interaction where the $a_0(980)$ state is generated. While the $a_0(980)$ production is the dominant term, we also find other terms in the reaction that interfere with this production mode and, through interference with it, lead to a shape of the $a_0(980)$ significantly different from the one observed in other experiments, with an apparently much larger width.

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arXiv2024

Dense Nuclear Matter Equation of State from Heavy-Ion Collisions

The nuclear equation of state (EOS) is at the center of numerous theoretical and experimental efforts in nuclear physics. With advances in microscopic theories for nuclear interactions, the availability of experiments probing nuclear matter under conditions not reached before, endeavors to develop sophisticated and reliable transport simulations to interpret these experiments, and the advent of multi-messenger astronomy, the next decade will bring new opportunities for determining the nuclear matter EOS, elucidating its dependence on density, temperature, and isospin asymmetry. Among controlled terrestrial experiments, collisions of heavy nuclei at intermediate beam energies (from a few tens of MeV/nucleon to about 25 GeV/nucleon in the fixed-target frame) probe the widest ranges of baryon density and temperature, enabling studies of nuclear matter from a few tenths to about 5 times the nuclear saturation density and for temperatures from a few to well above a hundred MeV, respectively. Collisions of neutron-rich isotopes further bring the opportunity to probe effects due to the isospin asymmetry. However, capitalizing on the enormous scientific effort aimed at uncovering the dense nuclear matter EOS, both at RHIC and at FRIB as well as at other international facilities, depends on the continued development of state-of-the-art hadronic transport simulations. This white paper highlights the essential role that heavy-ion collision experiments and hadronic transport simulations play in understanding strong interactions in dense nuclear matter, with an emphasis on how these efforts can be used together with microscopic approaches and neutron star studies to uncover the nuclear EOS.

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arXiv2024

On the molecular nature of the $Ω_c(3120)$ and its analogy with the $Ω(2012)$

We make a study of the $Ω_c(3120)$, one of the five $Ω_c$ states observed by the LHCb collaboration, which is well reproduced as a molecular state from the $Ξ^*_c \bar K$ and $Ω^*_c η$ channels mostly. The state with $J^P = 3/2^-$ decays to $Ξ_c \bar K$ in $D$-wave and we include this decay channel in our approach, as well as the effect of the $Ξ^*_c$ width. With all these ingredients, we determine the fraction of the $Ω_c(3120)$ width that goes into $Ξ_c π\bar K$, which could be a measure of the $Ξ^*_c \bar K$ molecular component, but due to a relatively big binding, compared to its analogous $Ω(2012)$ state, we find only a small fraction of about 3%, which makes this measurement difficult with present statistics. As an alternative, we evaluate the scattering length and effective range of the $Ξ^*_c \bar K$ and $Ω^*_c η$ channels which together with the binding and width of the $Ω_c(3120)$ state, could give us an answer to the issue of the compositeness of this state when these magnitudes are determined experimentally, something feasible nowadays, for instance, measuring correlation functions.

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arXiv2023

Collision integral with momentum-dependent potentials and its impact on pion production in heavy-ion collisions

The momentum dependence of the nucleon mean-field potential in a wide momentum range can be an important factor to determine the $Δ$ resonance and pion production in intermediate-energy heavy-ion collisions. In particular, in neutron-rich systems such as ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ collisions, we need to carefully treat the momentum dependence because the neutron and proton potentials can have different momentum dependence, as characterized at low momenta by effective masses. In the present work, we rigorously calculate the collision terms of $NN \leftrightarrow N Δ$ and $Δ\leftrightarrow N π$ processes with the precise conservation of energy and momentum under the presence of momentum-dependent potentials for the initial and final particles of the process. The potentials affect not only the threshold condition for the process but also the cross section in general as a function of the momenta of the initial particles, which is treated in a natural way in the present work. Calculations are performed by combining the nucleon dynamics obtained by the antisymmetrized molecular dynamics (AMD) model with a newly developed transport code which we call sJAM. The calculated results for central ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ collisions at 270 MeV/nucleon clearly show that the momentum dependence of the neutron and proton potentials has a significant impact on the $NN \to N Δ$ process, and this information is strongly reflected in the charged pion ratio ($π^-/π^+$). We also investigate the effects of the high-density symmetry energy and the isovector part of the potential of $Δ$ resonances on pion production, which we find are relatively small compared to the effect of the momentum dependence of the neutron and proton potentials.

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arXiv2023

Chiral symmetry restoration at high matter density observed in pionic atoms

Modern theories of physics tell that the vacuum is not an empty space. Hidden in the vacuum is a structure of anti-quarks $\bar{q}$ and quarks $q$. The $\bar{q}$ and $q$ pair has the same quantum number as the vacuum and condensates in it since the strong interaction of the quantum chromodynamics (QCD) is too strong to leave it empty. The $\bar{q}q$ condensation breaks the chiral symmetry of the vacuum. The expectation value $<\bar{q}q>$ is an order parameter. For higher temperature or higher matter-density, $|<\bar{q}q>|$ decreases reflecting the restoration of the symmetry. In contrast to these clear-cut arguments, experimental evidence is so far limited. First of all, the $\bar{q}q$ is nothing but the vacuum itself. It is neither visible nor perceptible. In this article, we unravel this invisible existence by high precision measurement of pionic atoms, $π^-$-meson-nucleus bound systems. Using the $π^-$ as a probe, we demonstrate that $|<\bar{q}q>|$ is reduced in the nucleus at 58% of the normal nuclear density by a factor of 77 $\pm$ 2% compared with that in the vacuum. This reduction indicates that the chiral symmetry is partially restored due to the extremely high density of the nucleus. The present experimental result clearly exhibits the existence of the hidden structure, the chiral condensate, in the vacuum.

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arXiv2023

Model independent analysis of femtoscopic correlation functions: An application to the $D_{s0}^*(2317)$

We face the inverse problem of obtaining the interaction between coupled channels from the correlation functions of these channels. We apply the method to the interaction of the $D^0 K^+$, $D^+ K^0$, and $D^+_s η$ channels, from where the $D^*_{s0}(2317)$ state emerges. We use synthetic data extracted from an interaction model based on the local hidden gauge approach and find that the inverse problem can determine the existence of a bound state of the system with a precision of about 20 MeV. At the same time, we can determine the isospin nature of the bound state and its compositeness in terms of the channels. Furthermore, we evaluate the scattering length and effective range of all three channels, as well as the couplings of the bound state found to all the components. Lastly, the size parameter of the source function, $R$, which in principle should be a magnitude provided by the experimental teams, can be obtained from a fit to the data with relatively high accuracy. These findings show the value of the correlation function to learn about the meson-meson interaction for systems which are difficult to access in other present facilities.

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arXiv2023

Role of $f_0(980)$ and $a_0(980)$ in the $B^- \to π^- K^+ K^- $ and $B^- \to π^- K^0 \bar K^0 $ reactions

In this work we study the role of the $f_0(980)$ and $a_0(980)$ resonances in the low $ K ^{+} K^{-} $ and $K^0 \bar K^0 $ invariant-mass region of the $B^- \to π^- K^+ K^- $ and $B^- \to π^- K^0 \bar K^0 $ reactions. The amplitudes are calculated by using the chiral unitary $\rm SU(3)$ formalism, in which these two resonances are dynamically generated from the unitary pseudocalar-pseudoscalar coupled-channel approach. The amplitudes are then used as input in the evaluation of the mass distributions with respect to the $ K^{+}K^{-} $ and $ K^{0}\bar K^{0} $ invariant-masses, where the contributions coming from the $I=0$ and $I=1$ components are explicitly assessed. Furthermore, the contribution of the $ K^{\ast }(892)^0 K^- $ production and its influence on the $ π^{-} K^+ $ and $ K^{+} K^- $ systems are also evaluated, showing that there is no significant strength for small $ K^{+} K^- $ invariant mass. Lastly, the final distributions of $ M_{\rm inv}^2( K^{\pm}K^{\mp} ) $ for the $B^{\mp} \to π^{\mp} K^{\pm}K^{\mp} $ reactions are estimated and compared with the LHCb data. Our results indicate that the $I=0$ component tied to the $f_0(980)$ excitation generates the dominant contribution in the range of low $ K ^{+} K^{-} $ invariant-mass.

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arXiv2023

Pion-nucleon sigma term $σ_{πN}$ and deeply bound pionic atoms

We investigate the possibility to determine the value of the pion-nucleon sigma term $σ_{πN}$ precisely by the experimental observables of the deeply bound pionic atoms. We discuss the sensitivity of the observables to $σ_{πN}$ and take into account the typical errors of the up-to-date experiments of the deeply bound pionic atoms. We find that the gap of the binding energies and the width of the deeply bound pionic states are good observables for the $σ_{πN}$ value determination by the experimental data. We also discuss the expected difficulties for the accurate determination of the value of $σ_{πN}$ due to the correlation between the $σ$ term and the potential parameter in the pion-nucleus optical potential.

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arXiv2022

Interpretation of the $Ω_c \to π^+ Ω(2012) \to π^+(\bar{K} Ξ)$ relative to $Ω_c \to π^+\bar{K} Ξ$ from the $Ω(2012)$ molecular perspective

We present a mechanism for $Ω_c \to π^+ Ω(2012)$ production through an external emission Cabibbo favored weak decay mode, where the $Ω(2012)$ is dynamically generated from the interaction of $\bar{K}Ξ^*(1530)$, $ηΩ$, with $\bar{K}Ξ$ as the main decay channel. The $Ω(2012)$ decays later to $\bar{K}Ξ$ in this picture, with results compatible with Belle data. The picture has as a consequence that one can evaluate the direct decay $Ω_c^0 \to π^+K^- Ξ^0$ and the decay $Ω_c^0 \to π^+\bar{K} Ξ^*$, $π^+ηΩ$ with direct coupling of $\bar{K}Ξ^*$ and $ηΩ$ to $K^- Ξ^0$. We show that, within uncertainties and using data from a recent Belle measurement, all these three channels account for about (12-20)\% of the total $Ω_c \to π^+K^- Ξ^0$ decay rate. The consistency of the molecular picture with all the data is established by showing that $Ω_c \to Ξ^0 \bar{K}^{*0} \to Ξ^0K^- π^+$ together with $Ω_c \to π^+ Ω^* \to π^+K^- Ξ^0 $ account for about 85\% of the total $Ω_c \to π^+K^- Ξ^0 $.

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arXiv2022

Transport Model Comparison Studies of Intermediate-Energy Heavy-Ion Collisions

Transport models are the main method to obtain physics information from low to relativistic-energy heavy-ion collisions. The Transport Model Evaluation Project (TMEP) has been pursued to test the robustness of transport model predictions in reaching consistent conclusions from the same type of physical model. Calculations under controlled conditions of physical input and set-up were performed with various participating codes. These included both calculations of nuclear matter in a box with periodic boundary conditions, and more realistic calculations of heavy-ion collisions. In this intermediate review, we summarize and discuss the present status of the project. We also provide condensed descriptions of the 26 participating codes, which contributed to some part of the project. These include the major codes in use today. We review the main results of the studies completed so far. They show, that in box calculations the differences between the codes can be well understood and a convergence of the results can be reached. These studies also highlight the systematic differences between the two families of transport codes, known as BUU and QMD type codes. However, when the codes were compared in full heavy-ion collisions using different physical models, as recently for pion production, they still yielded substantially different results. This calls for further comparisons of heavy-ion collisions with controlled models and of box comparisons of important ingredients, like momentum-dependent fields, which are currently underway. We often indicate improved strategies in performing transport simulations and thus provide guidance to code developers. Results of transport simulations of heavy-ion collisions from a given code will have more significance if the code can be validated against benchmark calculations such as the ones summarized in this review.

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