https://doi.org/10.1140/epja/s10050-024-01350-2
Regular Article–Theoretical Physics
Collision energy dependence of source sizes for primary and secondary pions at energies available at the JINR nuclotron-based ion collider facility from Lévy fits
1
Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70-543, CdMx 04510, Mexico
2
Facultad de Ciencias Físico-Matemáticas, Universidad Autónoma de Sinaloa, Avenida de las Américas y Boulevard Universitarios, 80000, Ciudad Universitaria, Culiacán, Mexico
3
Joint Institute for Nuclear Research, 141980, Dubna, Russia
4
Facultad de Ciencias-CUICBAS, Universidad de Colima, Bernal Díaz del Castillo No. 340, Colonia Villas San Sebastián, 28045, Colima, Mexico
b
santiago.bernal@correo.nucleares.unam.mx
Received:
6
March
2024
Accepted:
23
May
2024
Published online:
20
June
2024
We study the evolution of the two-pion correlation function parameters with collision energy in the context of relativistic heavy-ion collisions within the NICA energy range. To this end, we perform UrQMD simulations in the cascade mode to produce samples of pions from 
Bi+Bi collisions for each of the studied energies. The effects of the quantum-statistical correlations are introduced using the correlation afterburner code CRAB. We fit the correlation function using Gaussian, exponential and symmetric Lévy shapes and show that for all collision energies the latter provides the best fit. We separate the sample into pions coming from primary processes and pions originating from the decay of long-lived resonances, and show that the source size for the latter is significantly larger than for the former. The source size for the secondaries, is similar but in general larger than the size for the whole pion sample. To further characterize the pion source, we also simulate the effects of a non-ideal detector introducing a momentum smearing parameter, representing the minimum pair momentum and thus a maximum source size that can be resolved. The values of the correlation function intercept parameter are therefore modified from the values they attain for the perfect detector case. Using the core-halo picture of the source, we show that the values of the intercept parameter are influenced by the presence of a significant fraction of core pions coming from the decay of long-lived but slow-moving resonances. These findings serve as a benchmark to compare with future Monte Carlo studies that consider an Equation of State and thus allow for a phase transition within the studied energy domain.
© The Author(s) 2024
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
