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PreprintCC BY 4.0arXiv

Multiplicity and transverse density as ordering variables of the Λ/K0S ratio in oxygen-oxygen collisions at the LHC

  • Neeraj
  • Amal Sarkar
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Abstract

Baryon-to-meson enhancements are commonly compared across collision systems at equal multiplicity. Using published data only, we test whether the pT dependence of the CMS Λ/K0S ratio in minimum-bias O-O collisions at √(sNN)=5.36 TeV can be obtained from CMS multiplicity-differential p-Pb and Pb-Pb measurements weighted with the O-O multiplicity distribution. The prediction from p-Pb collisions of equal multiplicity is harder than the data, with a tilt of +0.35±0.04 in ln(prediction/data) versus ln pT, whereas that from peripheral Pb-Pb collisions is consistent with the data. In a Glauber model calibrated on O-O data, O-O and peripheral Pb-Pb collisions of equal multiplicity have similar transverse densities ρ=⟨(dNch/dη)/S⊥⟩, about half of that in p-Pb. Matching the p-Pb reference in ρ instead of multiplicity reduces the tilt by about 60%, to +0.14±0.04, with nucleons as sources; the tension is fully removed (−0.02±0.04) only when sub-nucleonic structure is included (three constituents per nucleon), so the conclusion depends on the modeled size of high-multiplicity p-Pb collisions. The published blast-wave velocities of p-Pb and Pb-Pb collisions, which differ at equal multiplicity, are close at equal ρ. Multiplicity alone thus does not determine the Λ/K0S shape across systems; the data are consistent with a radial boost governed by the transverse density, as expected from hydrodynamics. The same pattern is found in EPOS4, which has a hydrodynamic core, but not in PYTHIA Angantyr. For Ne-Ne collisions, which have the transverse density of O-O at equal multiplicity, the minimum-bias ratio is predicted to agree with O-O within 3-5%, as EPOS4 also predicts.

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Cite

BibTeXRIS
BibTeX
@misc{neeraj2026multiplicity,
  title = {{Multiplicity and transverse density as ordering variables of the $Λ/K^0_S$ ratio in oxygen-oxygen collisions at the LHC}},
  author = {Neeraj and Amal Sarkar},
  howpublished = {arXiv},
  year = {2026},
  month = nov,
  doi = {10.48550/arxiv.2611.04865},
  eprint = {2611.04865},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2611.04865},
  note = {CC BY 4.0},
}
RIS
TY  - UNPB
TI  - Multiplicity and transverse density as ordering variables of the Λ/K^0_S ratio in oxygen-oxygen collisions at the LHC
AU  - Neeraj
AU  - Amal Sarkar
PY  - 2026
DA  - 2026/11/03
PB  - arXiv
DO  - 10.48550/arxiv.2611.04865
UR  - https://arxiv.org/abs/2611.04865
AB  - Baryon-to-meson enhancements are commonly compared across collision systems at equal multiplicity. Using published data only, we test whether the p_T dependence of the CMS Λ/K^0_S ratio in minimum-bias O-O collisions at √(s_NN)=5.36 TeV can be obtained from CMS multiplicity-differential p-Pb and Pb-Pb measurements weighted with the O-O multiplicity distribution. The prediction from p-Pb collisions of equal multiplicity is harder than the data, with a tilt of +0.35±0.04 in ln(prediction/data) versus ln p_T, whereas that from peripheral Pb-Pb collisions is consistent with the data. In a Glauber model calibrated on O-O data, O-O and peripheral Pb-Pb collisions of equal multiplicity have similar transverse densities ρ=⟨(dN_ch/dη)/S_⊥⟩, about half of that in p-Pb. Matching the p-Pb reference in ρ instead of multiplicity reduces the tilt by about 60%, to +0.14±0.04, with nucleons as sources; the tension is fully removed (−0.02±0.04) only when sub-nucleonic structure is included (three constituents per nucleon), so the conclusion depends on the modeled size of high-multiplicity p-Pb collisions. The published blast-wave velocities of p-Pb and Pb-Pb collisions, which differ at equal multiplicity, are close at equal ρ. Multiplicity alone thus does not determine the Λ/K^0_S shape across systems; the data are consistent with a radial boost governed by the transverse density, as expected from hydrodynamics. The same pattern is found in EPOS4, which has a hydrodynamic core, but not in PYTHIA Angantyr. For Ne-Ne collisions, which have the transverse density of O-O at equal multiplicity, the minimum-bias ratio is predicted to agree with O-O within 3-5%, as EPOS4 also predicts.
ER  -