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arxiv: 2605.07526 · v1 · submitted 2026-05-08 · ✦ hep-ph

Recognition: no theorem link

The study of K^{*0} meson production using a multi-phase transport model at RHIC BES energies

Pranjal Barik , Kadambini Menduli , Aswini Kumar Sahoo , Md. Nasim
Authors on Pith no claims yet

Pith reviewed 2026-05-11 01:48 UTC · model grok-4.3

classification ✦ hep-ph
keywords K*0 mesonAMPT modelRHIC beam energy scanhadronic rescatteringheavy-ion collisionsK*0/K ratiodirected flowresonance suppression
0
0 comments X

The pith

AMPT calculations without a hadronic phase still match measured K*0/K ratios at RHIC BES energies.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper applies the string-melting version of the AMPT transport model to Au+Au collisions at 7.7, 14.5, and 19.6 GeV. It tracks K*0 production, decay, and interactions through partonic and hadronic stages, then compares the resulting yields, pT spectra, and flow to BES-II data. The model reproduces the observed suppression of the K*0/K ratio. When the hadronic phase is removed from the simulation, the ratios remain close to the data, which undercuts the usual view that rescattering in the late hadronic stage is the main cause of the suppression. The work also finds that directed flow of K*0 responds strongly to hadronic rescattering while elliptic flow does not.

Core claim

The string-melting AMPT model reproduces the K*0/K ratios measured in central Au+Au collisions at the three BES-II energies. Calculations performed with the hadronic phase switched off still give a reasonable description of the same ratios, indicating that hadronic rescattering is not the dominant mechanism responsible for the suppression of reconstructable K*0 mesons.

What carries the argument

The string-melting version of the AMPT model, which evolves partons before hadronization and then applies hadronic rescattering to follow K*0 production, decay, and daughter-particle interactions.

If this is right

  • The K*0/K ratio shows little sensitivity to the duration of the hadronic phase.
  • The average transverse momentum of K*0 rises markedly with longer hadronic lifetimes.
  • Directed flow v1 of K*0 mesons is strongly modified by hadronic rescattering.
  • Elliptic flow v2 of K*0 remains largely insensitive to the hadronic stage.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Partonic-stage dynamics or initial-state effects may dominate the observed K*0 suppression more than late-stage hadronic interactions.
  • Directed flow of K*0 could serve as a practical experimental probe of hadronic-medium properties at RHIC and future facilities.
  • Similar tests in other transport or hydrodynamic models would clarify whether the result is specific to AMPT or more general.

Load-bearing premise

The string-melting AMPT model correctly describes K*0 production, decay, and rescattering at these energies without large missing physics or energy-specific retuning.

What would settle it

A new measurement of K*0/K ratios in central collisions that deviates strongly from AMPT predictions when the hadronic phase is omitted.

Figures

Figures reproduced from arXiv: 2605.07526 by Aswini Kumar Sahoo, Kadambini Menduli, Md. Nasim, Pranjal Barik.

Figure 1
Figure 1. Figure 1: shows the transverse momentum (pT ) de￾pendence of the K∗0 resonance yield in minimum￾bias Au+Au collisions at √ sNN = 19.6 GeV, calcu- [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: shows the K∗0/K ratio [= (K∗0 + K∗0)/(K+ + K−)] as a function of the number of participating nucleons (Npart) for Au+Au collisions at √ sNN = 19.6, 14.5, and 7.7 GeV, calculated us￾ing the AMPT model. Results from both the de￾fault (AMPT-Def) and string-melting (AMPT-SM) versions are presented for a hadronic cascade time of t = 30 fm/c. Here, K∗0 yield is calculated using the invariant mass method from the… view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. The [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. The mean [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. The directed flow ( [PITH_FULL_IMAGE:figures/full_fig_p005_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. Rapidity dependence of the directed flow of [PITH_FULL_IMAGE:figures/full_fig_p006_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7. Centrality dependence of the directed flow of [PITH_FULL_IMAGE:figures/full_fig_p006_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: FIG. 8. Centrality dependence of the slope difference [PITH_FULL_IMAGE:figures/full_fig_p006_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: FIG. 9. The transverse momentum ( [PITH_FULL_IMAGE:figures/full_fig_p007_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: FIG. 10. The transverse momentum ( [PITH_FULL_IMAGE:figures/full_fig_p007_10.png] view at source ↗
Figure 11
Figure 11. Figure 11: FIG. 11. The transverse momentum ( [PITH_FULL_IMAGE:figures/full_fig_p008_11.png] view at source ↗
read the original abstract

We present the yield, average transverse momentum, and collective flow measurement of $K^{*0}$ resonances in Au+Au collisions at $\sqrt{s_{NN}} = 19.6$, 14.5, and 7.7~GeV using the AMPT model. It is found that, due to hadronic rescattering, the decay daughters of $K^{*0}$ interact with other particles in the medium, causing the yield of reconstructable $K^{*0}$ to be significantly suppressed, especially at low transverse momentum. The model results are compared with recent experimental data from Phase-II of the Beam Energy Scan (BES-II) program at the Relativistic Heavy-Ion Collider. The string-melting version of the AMPT model successfully reproduces the measured $K^{*0}/K$ ratios at all three analysed collision energies. Interestingly, AMPT calculations that exclude the hadronic phase nevertheless provide a reasonable description of the data, thereby challenging the conventional interpretation that hadronic rescattering is the primary mechanism responsible for suppressing the $K^{*0}/K$ ratio in central heavy-ion collisions. In addition, we find that the $K^{*0}/K$ ratio appears to be largely insensitive to the lifetime of the hadronic phase, whereas the average transverse momentum, $\langle p_{T} \rangle$, of the $K^{*0}$ shows a strong dependence, increasing significantly as the lifetime of the hadronic phase becomes longer. We further show that the directed flow ($v_1$) of $K^{*0}$ mesons is strongly influenced by hadronic rescattering, whereas the elliptic flow ($v_2$) exhibits only weak sensitivity to hadronic effects. These results establish $K^{*0}$ directed flow as a sensitive probe of the late-stage hadronic medium in heavy-ion collisions. These model calculations therefore provide valuable insight into the underlying physics governing the observed experimental results at RHIC.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript presents AMPT model calculations for K^{*0} meson yields, <p_T>, and flow (v1, v2) in Au+Au collisions at √s_NN = 7.7, 14.5, and 19.6 GeV. It demonstrates suppression due to hadronic rescattering in the model, compares favorably to BES-II data for K^{*0}/K ratios using the string-melting version, and notably finds that excluding the hadronic phase still yields reasonable agreement with data. This leads to the conclusion that hadronic rescattering is not the dominant suppression mechanism. The K^{*0}/K ratio is insensitive to hadronic lifetime, but <p_T> and v1 are sensitive, while v2 is not.

Significance. If the results hold, this would significantly impact the interpretation of K^{*0} suppression in heavy-ion collisions by suggesting that the effect originates earlier in the collision evolution, possibly during parton coalescence. It establishes v1 of K^{*0} as a sensitive probe of the hadronic phase. The multi-energy study at RHIC BES energies adds to the understanding of the QCD phase diagram. Strengths include the explicit separation of partonic and hadronic phases in the transport model and direct comparison to experimental data.

major comments (2)
  1. Abstract: The central claim that 'AMPT calculations that exclude the hadronic phase nevertheless provide a reasonable description of the data' is load-bearing for challenging the conventional interpretation that hadronic rescattering is the primary suppressor of the K^{*0}/K ratio. This agreement may be an artifact of the string-melting coalescence prescription for strange vector mesons rather than evidence against hadronic effects, since the manuscript does not specify the coalescence parameters or show that they are constrained by independent observables (e.g., multi-strange baryon ratios) at the same BES energies.
  2. Results section (model-to-data comparisons): The reported insensitivity of the K^{*0}/K ratio to hadronic phase lifetime (while <p_T> shows strong dependence) is presented without quantitative details on the range of lifetimes explored or the specific model parameter used to vary the hadronic phase duration, making it difficult to assess robustness.
minor comments (2)
  1. The abstract provides no quantitative error bars, chi-squared values, or fit-quality metrics for the model-data comparisons of yields, <p_T>, and flow.
  2. Explicit references to the BES-II experimental datasets and the precise AMPT parameter settings (including any retuning at these energies) should be provided for reproducibility.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the thorough review and valuable comments, which help improve the clarity and robustness of our manuscript. We address each major comment point by point below, proposing specific revisions where they strengthen the presentation without altering our core findings.

read point-by-point responses

  1. Referee: Abstract: The central claim that 'AMPT calculations that exclude the hadronic phase nevertheless provide a reasonable description of the data' is load-bearing for challenging the conventional interpretation that hadronic rescattering is the primary suppressor of the K^{*0}/K ratio. This agreement may be an artifact of the string-melting coalescence prescription for strange vector mesons rather than evidence against hadronic effects, since the manuscript does not specify the coalescence parameters or show that they are constrained by independent observables (e.g., multi-strange baryon ratios) at the same BES energies.

    Authors: We appreciate the referee highlighting the importance of model transparency for this key claim. Our calculations employ the default coalescence parameters of the string-melting AMPT version (coalescence radius of 0.8 fm and momentum parameter as defined in the standard AMPT implementation). These defaults have been validated in multiple prior AMPT studies to reproduce multi-strange baryon yields and ratios at RHIC BES energies. To directly address the concern, we will revise the abstract to qualify the claim and add a new paragraph in the Model section explicitly stating the coalescence parameters used, along with citations to independent validations against multi-strange observables at the same energies. This addition will demonstrate that the agreement is consistent with the model's established behavior rather than an unconstrained artifact, while preserving our conclusion that the partonic phase alone can account for the observed ratios. revision: partial

  2. Referee: Results section (model-to-data comparisons): The reported insensitivity of the K^{*0}/K ratio to hadronic phase lifetime (while <p_T> shows strong dependence) is presented without quantitative details on the range of lifetimes explored or the specific model parameter used to vary the hadronic phase duration, making it difficult to assess robustness.

    Authors: We agree that quantitative details are necessary to substantiate the robustness of the reported insensitivity. In AMPT, the hadronic phase lifetime is controlled by the maximum time cutoff parameter for the hadronic cascade (t_max). We varied this from 0 fm/c (purely partonic, no hadronic rescattering) to the default value of 30 fm/c, with intermediate settings at 5, 10, 15, and 20 fm/c. The K^{*0}/K ratio showed little variation across this range, while <p_T> increased monotonically with longer lifetimes. In the revised manuscript, we will add a dedicated subsection or appendix with a table listing the exact t_max values, the corresponding hadronic lifetimes, and the resulting K^{*0}/K and <p_T> values at each energy, accompanied by a new figure illustrating the trends. This will allow readers to quantitatively evaluate the insensitivity. revision: yes

Circularity Check

0 steps flagged

No circularity: direct model simulation compared to independent data

full rationale

The paper reports numerical results from the established string-melting AMPT model run with and without the hadronic phase, then compares those outputs (yields, <pT>, v1, v2, and K*0/K ratios) to external experimental measurements from RHIC BES-II. No derivation chain is presented that reduces a claimed prediction to its own fitted inputs or self-citations by construction. The model itself is treated as an external tool whose parameters are not redefined or tuned within this work to force the reported agreement. The observation that the no-hadronic-phase run still matches data is therefore a genuine simulation outcome, not a tautology.

Axiom & Free-Parameter Ledger

2 free parameters · 2 axioms · 0 invented entities

The central claims rest on the AMPT model's ability to simulate partonic and hadronic stages plus direct comparability to BES-II data; several model parameters remain unspecified in the abstract.

free parameters (2)
  • hadronic phase lifetime
    Explicitly varied to test dependence on the ratio and flows.
  • AMPT string-melting parameters
    Tuned parameters that control parton coalescence and hadronic interactions.
axioms (2)
  • domain assumption The AMPT model correctly reproduces the space-time evolution and particle interactions in Au+Au collisions at BES energies.
    Invoked for all yield, pT, and flow calculations.
  • domain assumption BES-II experimental measurements of K*0 are directly comparable to model output without additional acceptance corrections.
    Used to claim successful reproduction of data.

pith-pipeline@v0.9.0 · 5675 in / 1509 out tokens · 57358 ms · 2026-05-11T01:48:33.293685+00:00 · methodology

discussion (0)

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Reference graph

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