## PAPERS [The theoretical basis of EPOS4](#basis) [New concepts in EPOS4: A pedagogical presentation](#concepts) [The EPOS4HQ project](#eposhq) [Applications based on EPOS4](#applications) [Selected Papers on earlier EPOS versions, NEXUS, and VENUS](#selected) In EPOS4, one distinguishes between primary and secondary interactions. The former refer to the multiple parallel scatterings happening (at high energies) instantaneously and which result in complex configurations composed of many strings, whereas the latter refer to subsequent interactions of the string decay products, which amounts to first a core-corona separation based on the string segments, and then the fluid formation, evolution, and decay of the core part. The discussion of primary interactions covers two topics, namely the parallel scattering formalismn, developed in terms of abstract objects for single scatterings called "Pomerons", and the internal structure of the Pomerons, showing how the Pomeron is related to parton-parton cross sections expressed in terms of QCD diagrams. ### The theoretical basis of EPOS4 *The following series of four basic papers should be cited when using EPOS4* * **EPOS4 overview\:** "Revealing a deep connection between factorization and saturation: New insight into modeling high-energy proton-proton and nucleus-nucleus scattering in the EPOS4 framework"; [K. Werner, Phys. Rev. C 108, 064903 (2023)](https://link.aps.org/doi/10.1103/PhysRevC.108.064903) and [arXiv:2301.12517](https://arxiv.org/pdf/2301.12517.pdf) * **Internal Pomeron structure in terms of QCD (link between the multiple scattering formalism and QCD)\:** "Perturbative QCD concerning light and heavy flavor in the EPOS4 framework"; [K. Werner and B. Guiot, Phys. Rev. C 108, 034904 (2023)](https://link.aps.org/doi/10.1103/PhysRevC.108.034904) and [arXiv:2306.02396](https://arxiv.org/pdf/2306.02396.pdf) * **Detailed and rigorous treatment of the multiple scattering formalism based on Pomerons\:** "Parallel scattering, saturation, and generalized Abramovskii-Gribov-Kancheli (AGK) theorem in the EPOS4 framework, with applications for heavy-ion collisions at $\sqrt{s_{NN}}$ of 5.02 TeV and 200 GeV"; [K. Werner, Phys. Rev. C 109, 034918 (2024)](https://link.aps.org/doi/10.1103/PhysRevC.109.034918) and [arXiv:2310.09380](https://arxiv.org/pdf/2310.09380.pdf) * **Core-corona procedure and microcanonical hadronization in EPOS4\:** "Core-corona procedure and microcanonical hadronization to understand strangeness enhancement in proton-proton and heavy ion collisions in the EPOS4 framework"; [K. Werner, Phys. Rev. C 109, 014910 (2024)](https://link.aps.org/doi/10.1103/PhysRevC.109.014910) and [arXiv:2306.10277](https://arxiv.org/pdf/2306.10277.pdf) ### New concepts in EPOS4: A pedagogical presentation * **EPOS4 in short: Understanding the new concepts\:** "EPOS4: New theoretical concepts for modeling proton-proton and ion-ion scattering at very high energies"; [arXiv:2410.09955](https://arxiv.org/pdf/2410.09955) ### The EPOS4HQ project * **Does charm flow, even in small systems?** "Heavy flavor as a probe of hot QCD matter produced in proton-proton collisions"; [J. Zhao, J. Aichelin, P.B. Gossiaux, and K. Werner, Phys. Rev. D 109, 054011 (2024)](https://journals.aps.org/prd/pdf/10.1103/PhysRevD.109.054011) and [arXiv:2310.08684](https://arxiv.org/pdf/2310.08684.pdf) * **Systematic comparison of open heavy flavor data with EPOS4HQ simulations\:** "Heavy flavour hadron production in relativistic heavy ion collisions at RHIC and LHC in EPOS4HQ"; [J. Zhao, J. Aichelin, P.B. Gossiaux, V. Ozvenchuk, and K. Werner, Phys. Rev. C 110, 024909 (2024)](https://journals.aps.org/prc/pdf/10.1103/PhysRevC.110.024909) and [arXiv:2401.17096](https://arxiv.org/abs/2401.17096) * **Comparing pp and central O-O, Ar-Ar, Kr-Kr, and Pb-Pb reactions at LHC energies\:** "System-size dependence of energy loss and correlations of heavy mesons at energies available at the CERN Large Hadron Collider"; [J. Zhao, J. Aichelin, P.B. Gossiaux, and K. Werner, Phys. Rev. C 111, 014907 (2025)](https://journals.aps.org/prc/abstract/10.1103/PhysRevC.111.014907) and [arXiv:2407.20919](https://arxiv.org/pdf/2407.20919) ### Applications based on EPOS4 * **Studying RHIC energies\:** "Heavy ion collisions from $\sqrt{s_{NN}}$ of 62.4 GeV down to 7.7 GeV in the EPOS4 framework"; [K. Werner, J. Jahan, I. Karpenko, T. Pierog, M. Stefaniak, and D. Vintache, Phys. Rev. C 111, 014903 (2025)](https://journals.aps.org/prc/abstract/10.1103/PhysRevC.111.014903) and [arXiv:2401.11275](https://arxiv.org/pdf/2401.11275.pdf) * **Studying second order cumulants of conserved charges in heavy-ion collisions\:** "New proxies for second-order cumulants of conserved charges in heavy-ion collisions within the EPOS4 framework"; [Johannes Jahan, Claudia Ratti, Maria Stefaniak, and Klaus Werner, Phys. Rev. C 110, 035201 (2024)](https://journals.aps.org/prc/abstract/10.1103/PhysRevC.110.035201) and [arXiv:2403.02306](https://arxiv.org/pdf/2403.02306.pdf) ### Selected Papers on earlier EPOS versions, NEXUS, and VENUS * **First detailed publication on EPOS 3, 2014** Analysing radial flow features in p-Pb and p-p collisions at several TeV by studying identified particle production in EPOS3 K. Werner, B. Guiot, Iu. Karpenko, T. Pierog [arXiv:1312.1233](https://arxiv.org/pdf/1312.1233.pdf) Published in Phys.Rev. C89 (2014) 064903. Publication details and [Citations](https://scholar.google.com/citations?view_op=view_citation&hl=fr&user=qpOtG7gAAAAJ&citation_for_view=qpOtG7gAAAAJ:wvYxNZNCP7wC) * **First detailed publication on EPOS LHC, 2013** EPOS LHC: Test of collective hadronization with data measured at the CERN Large Hadron Collider T Pierog, I Karpenko, JM Katzy, E Yatsenko, K Werner [arXiv:1306.0121](https://arxiv.org/pdf/1306.0121.pdf) Published in Physical Review C 92 (2015) 034906 Publication details and [Citations](https://scholar.google.com/citations?view_op=view_citation&hl=fr&user=qpOtG7gAAAAJ&citation_for_view=qpOtG7gAAAAJ:htyGaKyDgHMC) * **First detailed publication on EPOS + hydro, 2010** Event-by-Event Simulation of the Three-Dimensional Hydrodynamic Evolution from Flux Tube Initial Conditions in Ultrarelativistic Heavy Ion Collisions K. Werner, Iu. Karpenko, T. Pierog, M. Bleicher, K. Mikhailov [arXiv:1004.0805](https://arxiv.org/pdf/1004.0805.pdf) Published in Phys.Rev. C82 (2010) 044904 Publication details and [Citations](https://scholar.google.com/citations?view_op=view_citation&hl=fr&user=qpOtG7gAAAAJ&citation_for_view=qpOtG7gAAAAJ:JWITY9-sCbMC) * **First publication on the core-corona procedure in EPOS, 2007** Core-corona separation in ultra-relativistic heavy ion collisions Klaus Werner [arXiv:0704.1270](https://arxiv.org/pdf/0704.1270.pdf) Published in Phys. Rev. Lett. 98 (2007) 152301 Publication details and [Citations](https://scholar.google.com/citations?view_op=view_citation&hl=fr&user=qpOtG7gAAAAJ&citation_for_view=qpOtG7gAAAAJ:5Ul4iDaHHb8C) * **First major publication on saturation in NEXUS/EPOS, 2006** Parton ladder splitting and the rapidity dependence of transverse momentum spectra in deuteron-gold collisions at the BNL Relativistic Heavy Ion Collider K Werner, FM Liu, T Pierog [hep-ph/0506232](https://arxiv.org/pdf/hep-ph/0506232.pdf) Published in Physical Review C 74 (4), 044902 Publication details and [Citations](https://scholar.google.com/citations?view_op=view_citation&hl=fr&user=qpOtG7gAAAAJ&citation_for_view=qpOtG7gAAAAJ:_axFR9aDTf0C) * **Theoretical basis of NEXUS/EPOS, 2001** Parton based Gribov-Regge theory H.J. Drescher, M. Hladik, S. Ostapchenko, T. Pierog, K. Werner. [hep-ph/0007198](https://arxiv.org/pdf/1004.0805.pdf) Published in Phys.Rept. 350 (2001) 93-289. Publication details and [Citations](https://scholar.google.com/citations?view_op=view_citation&hl=fr&user=qpOtG7gAAAAJ&citation_for_view=qpOtG7gAAAAJ:hEXC_dOfxuUC) * **The main VENUS publication, 1993** Strings, pomerons and the VENUS model of hadronic interactions at ultrarelativistic energies K Werner Physics Reports 232 (2-5), 87-299 Publication details and [Citations](https://scholar.google.com/citations?view_op=view_citation&hl=fr&user=qpOtG7gAAAAJ&citation_for_view=qpOtG7gAAAAJ:k8Z6L05lTy4C)