arXiv subjects

Ayut Limphirat

Publications and source records attributed to Ayut Limphirat.

At least 19 recordsLinked to original sources

arXiv2026

Separating Equation-of-State Dynamics from Hadronic Rescattering in Low-Mass Dileptons

We investigate low-mass dilepton emission as a probe of the QCD equation of state and phase structure within non-equilibrium chiral fluid dynamics, comparing first-order phase-transition and crossover scenarios at $\sqrt{s_{\rm NN}}=2.20-6.20$~GeV. To disentangle effects of the macroscopic equation-of-state dynamics from conventional hadronic in-medium modifications, the $ρ$ and $ω$ meson self-energies are calculated from the same resonance-driven forward-scattering amplitudes in both scenarios. We find two temporally distinct signatures of the first-order phase transition: an early enhancement in the vector-meson pole region associated with the non-equilibrium evolution through the phase transition, and a later enhancement of the low-mass continuum driven by reheating and the prolonged fireball evolution. Both effects survive integration over the complete space-time evolution, with the pole-mass region retaining the strongest sensitivity to the phase structure. Across the investigated beam energies, the pole-mass excitation function retains a pronounced sensitivity to first-order transition dynamics at low collision energies, identifying this mass region as a promising target for future dilepton beam-energy scans.

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arXiv2026

Hypernucleus production in p+Au reactions at the FAIR facility

We explore the production of hypernuclei in p+Au reactions using the UrQMD model accompanied by a standard phase space coalescence model. We focus on the proton beam energy range of $E_{\rm lab}= 5 - 30$ GeV as this energy range will be investigated by the CBM-experiment at the upcoming FAIR facility. Starting from proton, $Λ$, $Σ$, $Ξ$ and $Ω$ production, we predict the yields, rapidity and transverse momentum distributions of $^{3}_ΛH$, $^{4}_ΛH$, $Ξ$N and $Ξ$NN hypernuclei. We conclude that the production rates of novel multi-strange hypernuclei are well within the reach of the CBM-experiment.

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arXiv2026

Study of $1^{--}$ P wave charmoniumlike and bottomoniumlike tetraquark spectroscopy

The masses of $1^{--}$ P-wave charmonium-like and bottomonium-like tetraquark states are calculated in a constituent quark model (CQM) where the Cornell-like potential and Breit-Fermi interaction are employed. All model parameters were imported from previous work, and predetermined by studying the low-lying conventional S- and P-wave light, charmed, bottom, charmonium, and bottomonium meson mass spectra. The lowest $1^{--}$ tetraquark mass is predicted to be around 4.15 GeV. The decay widths of $1^{--}$ P-wave tetraquark states are calculated for possible two-body strong decay channels within the rearrangement mechanism, including $ωχ_{cJ}$ and $ηJ/ψ$ for charmonium-like tetraquarks, and $ωχ_{bJ}$ for bottomonium-like tetraquarks. The theoretical results are compared with the selected exotic states, also known as Y states, and tentative assignments are suggested. This study suggests that $ψ(4230)$, $ψ(4360)$, $ψ(4660)$, and $Υ$(10753) may be P-wave tetraquark states and that multiple states might exist around 4.36 GeV.

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arXiv2026

Systematic study of exotic $1^{-+}$ tetraquark spectroscopy

The masses of exotic quantum-number $1^{-+}$ compact tetraquark states are calculated in a constituent quark model, where a Cornell-like potential is employed as the central potential, spin-spin and spin-orbit coupling derived from the Breit-Fermi interaction are treated as hyperfine corrections, and model parameters are taken from previous works. The ground state $1^{-+}$ P-wave tetraquarks are predicted at 1.9, 4.2, and 6.6~GeV for the light, charmonium-like, and fully-charm sectors, respectively. The decay width ratios of $1^{-+}$ tetraquark states are calculated for two-body strong decay channels within the rearrangement mechanism, including $ωh_1$ and $ηf_1$ for isospin $I=0$ light tetraquarks, $ρh_1$ and $πf_1$ for isospin $I=1$ light tetraquarks, $π/η+χ_{c1}$ and $ρ/ω+ h_c$ for charmonium-like tetraquarks, and $η_c χ_{c1}$ and $J/ψh_c$ for fully-charm tetraquarks. The theoretical results are compared with the observed exotic $1^{-+}$ states, and promising search channels for $1^{-+}$ tetraquarks are discussed. The work suggests that $η_1(1855)$ is unlikely to be a compact tetraquark state.

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arXiv2026

$f_0(980)$ production from $K\bar{K}$ coalescence in pp collisions at $\sqrt{s}=5.02$ TeV within UrQMD

We investigate the production of the scalar meson $f_0(980)$ in proton--proton collisions at $\sqrt{s}=5.02$~TeV using the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) transport model supplemented with a $K\bar{K}$ coalescence afterburner. After conservatively tuning the UrQMD string-fragmentation parameters, the model reproduces the bulk charged-kaon production in the low-to-intermediate transverse-momentum region, providing the kaon phase-space distribution used as input for the coalescence calculation. In the present implementation, both charged and neutral kaon--antikaon pairs are considered, and each accepted $K\bar{K}$ pair is assigned to the isoscalar $f_0(980)$ and isovector $a_0(980)$ channels with an equal Monte Carlo probability. Using the updated integration analysis, we find that $Δp=0.4$~GeV/$c$ gives the best directly simulated agreement with the ALICE $p_T$ spectrum and integrated yield, while a linear interpolation between the neighboring points at $Δp=0.3$ and $0.4$~GeV/$c$ yields an interpolated optimum of $Δp^{\ast}\approx0.365$~GeV/$c$. Within this constrained hadronic coalescence framework, the measured $f_0(980)$ production is reasonably described, and the results are consistent with interpreting the $f_0(980)$ as a late-stage $K\bar{K}$ molecular configuration formed near kinetic freeze-out in small collision systems.

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arXiv2026

Charmed nuclei and exotic charmed meson production at CBM@FAIR and ALICE@LHC

We make predictions for the expected multiplicities of exotic charmed hadrons and charmed nuclei in Au+Au collisions at SIS100 and LHC beam energies, using input on light hadron and charm production from the UrQMD transport model, and applying the Thermal-FIST model. We demonstrate that the CBM experiment has the capability to explore these states with production rates of one per 3 seconds for $χ_{c0}(1P)$ and $χ_{c1}(1P)$, and one every 3 minutes for $X(3872)$ at the expected data taking rates. Due to the higher baryon density at CBM compared to the LHC, charmed nuclei, if they exist, will be equally abundant at CBM as at the LHC, even though the total charm production at CBM is much lower.

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arXiv2025

Helicity amplitudes of $N(1520)$ and $N(1535)$ including pentaquark components

We investigate the helicity amplitudes of the $N(1520)$ and $N(1535)$ resonances in the electromagnetic transition process $γ^*p\to N^*$, where the $N(1520)$ and $N(1535)$ are assumed to include both the $L=1$ three-quark and $L=0$ spatial symmetric $q^4\bar q$ pentaquark components. The helicity transition amplitudes $A_{1/2}$, $A_{3/2}$ (for spin 3/2 states) and $S_{1/2}$ are computed within the constituent quark model. The inclusion of the $q^4 \bar q$ pentaquark components via the $γ^*\to q\bar q$ diagram significantly improves the theoretical description of the helicity amplitudes for both $N(1520)$ and $N(1535)$, yielding a closer agreement with experimental data compared to the pure three-quark picture. The work reveals that the $N(1520)$ and $N(1535)$ resonances may contain a considerable pentaquark components.

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arXiv2025

Electromagnetic probes as signatures for a first-order QCD phase transition

We investigate dimuon production in the context of a first-order phase transition in QCD matter using a chiral fluid dynamics model. This approach incorporates non-equilibrium effects such as entropy production and reheating, which emerge during the dynamical evolution through a first-order phase transition. By comparing equilibrium and non-equilibrium scenarios across a range of beam energies ($\sqrt{s_{NN}}=2.2-6.2$~GeV), we analyze the resulting invariant mass spectra. Our results reveal a substantial enhancement of dilepton yields in the non-equilibrium scenario, particularly pronounced at lower beam energies, where reheating leads to a prolonged lifetime of the fireball and increased emission. The enhancement persists even after normalizing to pion multiplicities, indicating sensitivity beyond effects of entropy production.

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arXiv2025

Radiative decay of $χ_{c1}$ states in effective Lagrangian approach

The $χ_{c1}(3872)$ state, first observed by the Belle collaboration with its quantum numbers identified as $J^{PC} = 1^{++}$, has been the subject of extensive research due to its intriguing properties. Several theoretical interpretations have been proposed to explain its unique characteristics, including the $χ_{c1}(2P)$ assignment, a molecular $\bar{D}^{*}D/\bar{D}D^{*}$ configuration, a coupled-channel framework incorporating $c\bar{c}$ and di-meson degrees of freedom, and the compact tetraquark hypothesis. However, challenges remain in reconciling its mass coincidence with the threshold and the observed isospin violation within both the pure $c\bar{c}$ and compact tetraquark models. In this study, we examine the radiative decays of the $χ_{c1}(1P)$ and $χ_{c1}(3872)$ states in an effective field theory framework, incorporating triangle loops of $D$ and $D^{*}$ mesons. The model parameters are calibrated based on the observed branching fraction of the radiative decay mode $χ_{c1}(1P) \to J/ψγ$. Utilizing these fixed parameters, we predict the branching fractions $R_{χ_{c1}(3872) \to J/ψγ} \sim 10^{-1}$ and $R_{χ_{c1}(3872) \to ψ(2S) γ} \sim 10^{-2}$, and the relative fraction $\mathcal{R}_{Ψγ} \approx 0.109$. The work supports the argument that the $χ_{c1}(3872)$ is unlikely a $c\bar{c}$ state.

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arXiv2025

The structure of the f_0(980) from system size dependent hadronic resonance ratios in p+p, p+Pb, and Pb+Pb collisions at the LHC

It is shown that the hadronic phase in ultra-relativistic heavy ion collisions can be used to understand the properties of the $f_0(980)$ resonance. In particular it is shown that the centrality dependence of the $f_0(980)/π$ and $f_0(980)/ϕ$ ratios depends strongly on the $f_0(980)\rightarrow \overline{K}+K$ branching ratio and whether the $f_0(980)$ is produced as a $\left | \overline{q}q \right \rangle$ or $\left | \overline{s}s \right \rangle$ state. These conclusions are drawn from calculations within the partial chemical equilibrium of the HRG model within Thermal-FIST as well as with the fully non-equilibrium hybrid-transport approach UrQMD. Our findings show how the hadronic phase in heavy ion collisions can be used for studies of exotic hadron properties otherwise possible only in dedicated experiments such as PANDA.

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arXiv2024

The time evolution of light nuclei cumulants and ratios with a first-order phase transition in the UrQMD transport model

The UrQMD model with a density dependent equation of state, including a first-order phase transition, is used to study the time dependence of baryon number and proton number susceptibilities up to third order in heavy ion reactions of $E_{\mathrm{lab}}=2-3 A$ GeV. A significant deviation from the Gaussian fluctuations of the baryon number fluctuation in coordinate space is observed. The proton number fluctuations are always suppressed as they constitute only a small fraction of the total baryon number during the dense phase of the collision. It is found that the only measurable, but small, signal would be an enhancement of the third order (or higher) proton cumulant in a finite rapidity window $Δy$ that is larger than one unit of rapidity. In addition, it is found that the coordinate fluctuations will lead to an enhancement of cluster production due to the correlations in coordinate space. However, this enhancement is small and mainly occurs during the dense part of the collision before the system actually freezes out.

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arXiv2024

Determining the Meson Cloud Contribution of Nucleon Electromagnetic Form Factor Using Dispersion Relation

We explore the meson cloud contribution to nucleon electromagnetic form factors in dispersion relation approach. In our calculations, experimental data on transition amplitudes for pion-nucleon scatterings are taken directly as inputs, with the assumption that the photon-pion interaction dominates over other meson-photon couplings. Combining with the quark core contribution evaluated in quark model, the proton electromagnetic form factors are well reproduced in the work. The resulting mean-square charge radius of the proton agrees well with experimental data, and the quark core radius is reasonable.

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arXiv2024

Production of nuclei and hypernuclei in pion-induced reactions near threshold energies

The Ultra-relativistic Quantum Molecular Dynamics model is employed to simulate $π^-+\mathrm{C}$ and $π^-+\mathrm{W}$ collisions at p$_\mathrm{lab}=1.7$ GeV motivated by the recent HADES results. By comparing the proton and $Λ$ transverse momentum spectra, it was observed that the data and transport model calculation show a good agreement, if cluster formation is included to obtain the free proton spectra. Predictions of light cluster ($d$, $t$, $^3$He, $^4$He, as well as ${}^{3}_Λ$H and $Ξ$N) multiplicities and spectra are made using a coalescence mechanism. The resulting multiplicities suggest that the pion beam experiment can produce a substantial amount of ${}^{3}_Λ$H, especially in $π^-+\mathrm{W}$ collisions due to the stopping of the $Λ$ inside the large tungsten nucleus. The findings are supplemented by a statistical multi-fragmentation analysis suggesting that even larger hyper-fragments are produced copiously. It is suggested that even double strange hypernuclei are in reach and might be studied in more detail using a slightly higher pion beam momentum.

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arXiv2024

Mass spectrum of $1^{--}$ heavy quarkonium

We calculate the masses and leptonic decay widths of the bottomonium $b\bar b$ and charmonium $c\bar c$ states in a constituent quark model where the Cornell-like potential and spin-dependent interaction are employed, with all model parameters predetermined by studying ground and first radial excited states of S- and P-wave heavy quarkonium mesons. By comparing the theoretical predictions for $J^{PC}=1^{--}$ quarkonium states with experimental data and considering possible mixtures of $nS$ and $(n-1)D$ states, we provide tentative assignments for all observed $J^{PC}=1^{--}$ heavy quarkonia. The work suggests that the $Υ$(10860) and $Υ$(11020) are $b\bar b$ $5S-4D$ mixture states, and the $ψ$(4360) and $ψ$(4415) are largely $4S$ and $3D$ $c\bar c$ states respectively. The $ψ$(4260) may not be accommodated with the conventional meson picture in the present work.

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arXiv2023

$P_c$ states in the mixture of molecular and pentaquark pictures

We systematically study hidden charm pentaquark states in the constituent quark model with a general Hamiltonian for multiquark systems, considering the coupling between the $Σ_c^{(*)}\bar{D}^{(*)}$ molecular states and the $q^3c\bar c$ compact pentaquark states by the one-gluon exchange hyperfine interaction. The ground state hidden-charm pentaquark mass spectra and the strong decay widths are calculated. This work suggests that $P_c(4312)$, $P_c(4457)$ and $P_c(4380)$ resonances might be mainly $Σ_c \bar D$, $Σ_c \bar D^*$ and $Σ_c^* \bar D$ hadronic molecules respectively, and $P_c(4440)$ might include sizable pentaquark components.

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arXiv2023

Investigating the cluster production mechanism with isospin triggering: Thermal models versus coalescence models

Isospin triggering allows to distinguish coalescence from thermal production of light clusters in heavy ion collisions. Triggering on $Y(π^-) - Y(π^+)$ allows to select very neutron or proton rich final states. The deuteron (cluster) production with coalescence ($d \propto n \cdot p$) leads then to an inverse parabolic dependence of the deuteron yield on $ΔY_π$. In contrast, in a thermal model, cluster production is independent on $ΔY_π$. The observation of a maximum deuteron (cluster) yield as function of $ΔY_π$ provides confirmation of the coalescence mechanism.

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arXiv2023

Determination of parameters of a potential model for tetraquark study by studying all S-wave mesons

The masses of low-lying S-wave mesons are evaluated in a constituent quark model (CQM) where the Cornell-like potential and one-gluon exchange spin-spin interaction are employed. To make the model applicable to both the light and heavy quark sectors, we introduce mass-dependent coupling coefficients. There are four free parameters in the model, which are determined by comparing the theoretical results with experimental data. The established model with one set of parameters may be applied to study higher excited meson states as well as multiquark systems in both the light and heavy quark sectors.

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arXiv2023

Study of light tetraquark spectroscopy

We calculate the masses of the $qq\bar q\bar q$ tetraquark ground state and first radial excited state in a constituent quark model where the Cornell-like potential and one-gluon exchange spin-spin coupling are employed. The three coupling parameters for the Cornell-like potential and one-gluon exchange spin-spin coupling are proposed mass-dependent in accordance with Lattice QCD data, and all model parameters are predetermined by studying light, charmed and bottom mesons. The theoretical predictions for light tetraquarks are compared with the observed exotic meson states in the light-unflavored meson sector, and tentative assignments are suggested. The work suggests that the $f_0(1500)$ and $f_0(1710)$ might be ground light tetraquark states with $J=0$.

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