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Measurement of antideuteron and net-$\Lambda$ number fluctuations at the Large Hadron Collider

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ALICE Collaboration

Nuclear Experiment · Submitted 26 Oct 2026 · 25 references

Pith's verdict: First measurement of antideuteron-net-Lambda correlation: clean data, plausible interpretation, minor model-sensitivity concern.

T0 · AI review

How this review was made: An AI referee (deepseek/deepseek-v4-flash) read the paper on October 28, 2026 and answered a fixed list of questions about it. T0 is the starting level every paper gets. The levels describe how deeply Pith has checked the paper, never the authors.

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arXiv ID2610.36307 (version 1)
Pith ID25E7DWRQ, Pith's permanent record of this paper and its review
CitationALICE Collaboration. "Measurement of antideuteron and net-$\Lambda$ number fluctuations at the Large Hadron Collider." arXiv:2610.36307 (2026). https://pith.science/paper/25E7DWRQ
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The paper

The paper claims

The paper reports the first measurement of antideuteron–net-Λ number correlations in Pb–Pb collisions at the LHC, establishing that antideuteron correlations with non-nucleonic hadrons reflect the hadronization mechanism while those with…

The reading

This letter presents the first measurement of the Pearson correlation coefficient between antideuterons and net-Λ number ($\rho_{\bar{d}\Delta\Lambda}$) and the normalized second-order cumulant of net-Λ ($\kappa_2(\Lambda-\bar{\Lambda})/\langle\Lambda+\bar{\Lambda}\rangle$) in Pb–Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV with the ALICE detector. These observables are compared to the statistical hadronization model (SHM) implemented in Thermal-FIST, which describes hadron yields and fluctuations of light-flavor species using a canonical volume $V_c = 3.0~\mathrm{d}V/\mathrm{d}y$. The net-Λ cumulant and the antideuteron–net-Λ correlation are well described by this SHM (within $0.8\sigma$), consistent with a universal hadronization picture. In contrast, the previously published antideuteron–antiproton correlation ($\rho_{\bar{d}p}$) deviates from the same SHM by $3.9\sigma$ and is only described when a coalescence afterburner is added (agreement within $1.5\sigma$). This demonstrates that $\rho_{\bar{d}p}$ is sensitive to nucleosynthesis while $\rho_{\bar{d}\Delta\Lambda}$ probes the underlying quantum-number correlations from hadronization, thereby resolving a tension in earlier data and supporting a two-stage formation scenario where antideuterons are formed via coalescence of nucleons produced in a statistically equilibrated fireball.

What carries the argument

The analysis uses two event-by-event observables: the Pearson correlation coefficient $\rho_{ab}$ between species $a$ and $b$, and the normalized second-order cumulant $\kappa_2(a-\bar{a})/\langle a+\bar{a}\rangle$. The theoretical comparison relies on the Thermal-FIST implementation of the canonical-ensemble statistical hadronization model, which conserves quantum numbers exactly within a truncated fireball of size $V_c$ (the canonical volume, expressed in units of $\mathrm{d}V/\mathrm{d}y$). The coalescence afterburner uses the Wigner-function formalism with the Argonne $v_{18}$ nuclear potential and femtoscopic source parameters from p–p correlations to form antideuterons from pre-existing antinucleons in the same Thermal-FIST events. The key parameter is $V_c$: $V_c=3.0~\mathrm{d}V/\mathrm{d}y$ describes all light-flavor hadron fluctuations, while $V_c=1.6~\mathrm{d}V/\mathrm{d}y$ had been required to describe $\rho_{\bar{d}p}$ without coalescence. The new measurement of $\rho_{\bar{d}\Delta\Lambda}$ favors $V_c=3.0$, showing that the earlier discrepancy for $\rho_{\bar{d}p}$ is resolved by coalescence rather than by changing $V_c$.

Extended reading notes

Core claim

The ALICE Collaboration measures, for the first time, the event-by-event correlation between antideuterons and net-Λ number ($\rho_{\bar{d}\Delta\Lambda}$) and the normalized second-order cumulant of net-Λ ($\kappa_2(\Lambda-\bar{\Lambda})/\langle\Lambda+\bar{\Lambda}\rangle$) in Pb–Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV. Both observables are consistent with the canonical-ensemble statistical hadronization model implemented in Thermal-FIST using a canonical volume $V_c = 3.0~\mathrm{d}V/\mathrm{d}y$ — the same value that describes yields and fluctuations of other light-flavor hadrons. The significance of the agreement is $0.8\sigma$ for $\rho_{\bar{d}\Delta\Lambda}$ across centralities. In contrast, the antideuteron–antiproton correlation ($\rho_{\bar{d}p}$), measured with increased precision from combined 2015+2018 data, shows a $3.9\sigma$ deviation from the same SHM baseline. However, when a coalescence afterburner based on the Wigner formalism (using the Argonne $v_{18}$ wave function and femtoscopic source parameters) is added to the same SHM event generator, $\rho_{\bar{d}p}$ is reproduced within $1.5\sigma$. This discrepancy is specific to $\rho_{\bar{d}p}$; all other observables (including $\kappa_2(\Lambda-\bar{\Lambda})/\langle\Lambda+\bar{\Lambda}\rangle$, $\kappa_2(p-\bar{p})/\langle p+\bar{p}\rangle$, and $\rho_{\Delta\Xi\Delta K}$) are unaffected by coalescence and follow the $V_c=3.0$ predictions. The results establish that the antideuteron–net-Λ correlation is driven by baryon-number conservation during hadronization, while the antideuteron–antiproton correlation carries an additional signal from antinucleosynthesis via coalescence.

Load-bearing premise

The conclusion that a single canonical volume $V_c=3.0~\mathrm{d}V/\mathrm{d}y$ consistently describes all light-flavor hadron fluctuations relies on the box-approximation implementation of quantum-number conservation in Thermal-FIST; a different implementation (e.g., with explicit rapidity correlations) could modify the required $V_c$ and potentially affect the agreement for $\rho_{\bar{d}\Delta\Lambda}$.

Editorial extensions

If this is right

  • If the coalescence picture is correct, the production of heavier nuclear clusters (e.g., $A=3$ hypernuclei) in heavy-ion collisions should also show correlation signals that require a coalescence afterburner beyond the SHM baseline.
  • The consistent value of $V_c=3.0~\mathrm{d}V/\mathrm{d}y$ across light-flavor hadrons and antideuteron–net-Λ correlations supports a universal rapidity correlation length for baryon-number and strangeness conservation, enabling more precise tests of local conservation laws.
  • The measurement provides a baseline for future studies of antideuteron correlations in smaller systems (pp, p–Pb) at higher LHC luminosities, where the coalescence and SHM predictions diverge more strongly.
  • The combined analysis of $\rho_{\bar{d}p}$ and $\rho_{\bar{d}\Delta\Lambda}$ demonstrates a method to separate hadronization from nucleosynthesis, which can be applied to other composite objects such as hypertritons and $\bar{\Lambda}\bar{\Lambda}$ correlations.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • The result resolves a previous tension where $\rho_{\bar{d}p}$ appeared to require a smaller $V_c$ than other species; now the data are consistent with a single $V_c$ once coalescence is included, strengthening the statistical hadronization picture as the description of the primordial fireball.
  • The fact that volume fluctuations affect $\rho_{\bar{d}p}$ significantly but $\rho_{\bar{d}\Delta\Lambda}$ negligibly suggests that net-Λ cumulants are robust against such systematics; this property could be exploited to test volume fluctuation models.
  • The success of the coalescence afterburner with a source size from p–p femtoscopy implies a consistent picture of antideuteron formation at kinetic freeze-out; future measurements of $\rho_{\bar{d}p}$ with better precision could constrain the antideuteron wave function and the emitting source geometry.
Original abstract

The recent measurements of event-by-event correlations between the antideuteron and antiproton numbers in Pb$-$Pb collisions at the LHC deviate from the statistical hadronization model parameterizations that describe the yields and fluctuations of light-flavored hadrons. This discrepancy may stem from nucleosynthesis processes involved in the formation of composite states like antideuterons. In this letter, we present the first measurement of the antideuteron$-$net-$\Lambda$ number correlation obtained in Pb$-$Pb collisions with the ALICE detector. This quantity is mostly sensitive to the quantum-number correlations induced by the hadronization process, as $\Lambda$ hyperons are not constituents of antideuterons. Both the antideuteron$-$net-$\Lambda$ number correlation and the normalized second-order cumulant of the net-$\Lambda$ number are well described by the statistical hadronization model implemented in Thermal-FIST. This establishes strong evidence that the antideuteron$-$antiproton correlation is driven by the nucleosynthesis processes, while the correlation between antideuterons and non-nucleonic hadrons is primarily sensitive to the hadronization mechanism.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-10-28: 1 request, 5,153 input tokens.

What the abstract itself states, as probabilities: claims first 0.95 · states limitation 0.13 · human participants 0.01 · controlled comparison 0.18 · randomized assignment 0.01 · states quantitative result 0.20 · compares with prior results 0.94 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; .

The recent measurements of event-by-event correlations between the antideuteron and antiproton numbers in Pb$-$Pb collisions at the LHC deviate from the statistical hadronization model parameterizations that describe the yields and fluctuations of light-flavored hadrons. This discrepancy may stem from nucleosynthesis processes involved in the formation of composite states like antideuterons. In this letter, we present the first measurement of the antideuteron$-$net-$\Lambda$ number correlation obtained in Pb$-$Pb collisions with the ALICE detector. This quantity is mostly sensitive to the quantum-number correlations induced by the hadronization process, as $\Lambda$ hyperons are not constituents of antideuterons. Both the antideuteron$-$net-$\Lambda$ number correlation and the normalized second-order cumulant of the net-$\Lambda$ number are well described by the statistical hadronization model implemented in Thermal-FIST. This establishes strong evidence that the antideuteron$-$antiproton correlation is driven by the nucleosynthesis processes, while the correlation between antideuterons and non-nucleonic hadrons is primarily sensitive to the hadronization mechanism.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 The recent measurements of event-by-event correlations between the antideuteron and antiproton numbers in Pb$-$Pb collisions at the LHC deviate from the statistical hadronization model parameterizations that describe the yields and fluctuations of light-flavored hadrons. background 0.99 0.10 0.04 asserted 1.00
s1 This discrepancy may stem from nucleosynthesis processes involved in the formation of composite states like antideuterons. interpretation 0.62 0.06 0.04 hedged possibility 1.00
s2 In this letter, we present the first measurement of the antideuteron$-$net-$\Lambda$ number correlation obtained in Pb$-$Pb collisions with the ALICE detector. contribution 1.00 0.97 0.05 asserted 1.00
s3 This quantity is mostly sensitive to the quantum-number correlations induced by the hadronization process, as $\Lambda$ hyperons are not constituents of antideuterons. interpretation 0.78 0.17 0.05 asserted 0.96
s4 Both the antideuteron$-$net-$\Lambda$ number correlation and the normalized second-order cumulant of the net-$\Lambda$ number are well described by the statistical hadronization model implemented in Thermal-FIST. result 1.00 0.88 0.15 asserted 1.00
s5 This establishes strong evidence that the antideuteron$-$antiproton correlation is driven by the nucleosynthesis processes, while the correlation between antideuterons and non-nucleonic hadrons is primarily sensitive to the hadronization mechanism. interpretation 1.00 0.84 0.92 asserted 1.00

What kind of paper the classifier reports this is: empirical study 1.00 · evidence from observation or experiment 0.98.

What was examined, and what was not

sources read
  • arXiv listing abstract v1
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures
Figure 1. Upper panels: normalized second-order cumulants κ2(p − p)/⟨p + p⟩ [23], κ2(Λ − Λ)/⟨Λ + Λ⟩, and κ2(Ξ + − Ξ −)/⟨Ξ + + Ξ −⟩ [24]. Lower panels: Pearson correlation coefficients ρdp [18], ρd¯∆Λ, and ρ∆Ξ∆K [24]. The results of the analysis described in this Letter are shown in panels (b), (d), and (e): (b) and (e) are obtained from the 2018 data, while (d) is obtained with the combined 2015+2018 data. The observables are measured as a function of centrality in Pb–Pb collisions at √ sNN = 5.02 TeV. The error bars and boxes show the statistical and systematic uncertainties, respectively

Figures reproduced from arXiv:2610.36307 by the authors.

References

Discussion

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