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

Phacharatouch Chaimongkon, Krittaporn Anukulkitch, Pornrad Srisawad, Natthaphat Thongyoo, Sukanya Sombun, Ayut Limphirat, Yu-Peng Yan

Abstract

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.

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

Abstract

We investigate the production of the scalar meson in proton--proton collisions at ~TeV using the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) transport model supplemented with a 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 pair is assigned to the isoscalar and isovector channels with an equal Monte Carlo probability. Using the updated integration analysis, we find that ~GeV/ gives the best directly simulated agreement with the ALICE spectrum and integrated yield, while a linear interpolation between the neighboring points at and ~GeV/ yields an interpolated optimum of ~GeV/. Within this constrained hadronic coalescence framework, the measured production is reasonably described, and the results are consistent with interpreting the as a late-stage molecular configuration formed near kinetic freeze-out in small collision systems.

Paper Structure

This paper contains 6 sections, 2 equations, 2 figures, 2 tables.

Table of Contents

  1. Introduction
  2. $f_{0}(980)$ in Molecular Picture in UrQMD
  3. RESULTS AND DISCUSSION
  4. Charged-Kaon Production in pp Collisions
  5. Production of $f_0(980)$ in Proton--Proton Collisions
  6. Summary

Figures (2)

  • Figure 1: Transverse-momentum spectra of charged kaons, $K^+ + K^-$, in proton--proton collisions at $\sqrt{s}=5.02$ TeV within $|y|<0.5$. Black squares represent the ALICE data from Ref. Acharya2020, and the blue dashed line denotes the tuned UrQMD result.
  • Figure 2: Transverse-momentum spectra of $f_0(980)$ derived in $pp$ collisions at $\sqrt{s}=5.02$ TeV within $|y|<0.5$. Solid black circles represent the ALICE data from Ref. Acharya:2023plb846137644, while colored symbols stand for the UrQMD coalescence results for $\Delta p=0.2$, $0.3$, $0.4$, and $0.5$ GeV/$c$, respectively. The red diamonds highlight the best directly simulated results at $\Delta p=0.4$ GeV/$c$.