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Reconstructing sources of rare particles by femtoscopic correlations

Liang Zhang (张良)^1,2, Song Zhang (张松)^1,3,*, Kai-Jia Sun (孙开佳)^1,3,†, and Yu-Gang Ma (马余刚)^1,3,4,‡

¹Key Laboratory of Nuclear Physics and Ion-Beam Application (MOE), Institute of Modern Physics, Fudan University, Shanghai 200433, China
²Shanghai Institute of Applied Physics (SINAP), Shanghai, China
³Shanghai Research Center for Theoretical Nuclear Physics, NSFC and Fudan University, Shanghai 200438, China
⁴School of Physics, East China Normal University, Shanghai 200241, China

^*Contact author: song_zhang@fudan.edu.cn
^†Contact author: kjsun@fudan.edu.cn
^‡Contact author: mayugang@fudan.edu.cn

Phys. Rev. C 113, 064907 – Published 22 June, 2026

DOI: https://doi.org/10.1103/kpdh-t7hs

Abstract

Measurement of particle emission source is a fundamental objective of femtoscopy in high-energy nuclear collisions. Conventional analyses rely on Gaussian parametrizations of pair emission sources, which makes the extraction of single-particle emission sources challenging, particularly for rare particles. Here, we introduce a novel statistical reconstruction method that allows extracting information of the target source relative to a data-constrained reference source instead of the Gaussian assumption. The correlation function is expressed as an ensemble average over the single-particle-conditioned correlation kernel, defined as the particle-by-particle contribution to the correlation function conditioned by the target particles. For particles with rare yields, the particle-by-particle distribution of this kernel can be transformed into event-by-event extraction and becomes experimentally accessible, enabling a direct statistical reconstruction of the emission source of single particles, instead of inferring a pair source. We apply this method to reconstruct $J / ψ$ source via $p − J / ψ$ correlations, using HAL QCD-derived $N J / ψ$ potentials in $\sqrt{s} = 13.6$ TeV $p p$ collisions simulated with EPOS4HQ. The reconstructed source reproduces the key characteristics and this new approach achieves a systematic uncertainty of approximately $13 %$ based on EPOS4 simulation.

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Phys. Rev. C 113, 064907– Published 22 June, 2026

Vol. 113, Iss. 6 — June 2026

Received 7 March 2026
Revised 9 April 2026
Accepted 20 May 2026

DOI: https://doi.org/10.1103/kpdh-t7hs

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP³.

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Reconstructing sources of rare particles by femtoscopic correlations

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