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Studies of collisions of light systems, like O–O, are planned at the LHC [1]. In particular, the translation of initial collision geometry with alpha-clustering in O-16 to triangular modulation of elliptic flow is discussed [2,3]. To date there were no measurements, even at lower collision energies, which demonstrated such fine effects of radial flow. However, numerous measurements of fragmentation of relativistic O-16 were already performed, see, in particular [4]. Therefore, the clustering of O-16 can be revealed by comparing these data to calculations with and without clustering. In the present work we model the fragmentation of O-16 in collisions with light and heavy nuclei by means of a new version of Abrasion-Ablation Monte Carlo for Colliders (AAMCC) model [5] with accounting for pre-equilibrium clustering of spectator matter. AAMCC model is based on Glauber Monte Carlo model [6] in calculating the numbers of participant and spectator nucleons in colliding nuclei. Because of a half-moon shape of spectator matter, it instantaneously dissociates into several independent hot systems defined by minimum spanning tree (MST) clustering algorithm. It is assumed that the excitation energy of each system correlates with its volume and its decays are simulated by means of Fermi break-up model from the Geant4 toolkit [7]. A small contribution to production of forward fragments from electromagnetic dissociation of O-16 is also calculated with RELDIS model [8]. It is demonstrated that in contrast to Pb–Pb collisions, neutron and proton Zero Degree Calorimeters in the ALICE experiment at the LHC will be less effective in triggering hadronic and electromagnetic interactions of O-16 because of a large number of neutrons and protons remaining in undetected nuclear fragments. As found, the measured production of Li, Be, B and N fragments [4] is described by AAMCC, but the production of carbon is underestimated. At the same time, channels with a single He-4 are overestimated with respect to data [4], but the rates of simultaneous production of two and three He-4 are underestimated. This all indicates that alpha-clustering effects in initial O-16, which give preference to He-4 as fragmentation products of relatively cold spectator matter, have to be taken into account in AAMCC in addition to the considered pre-equilibrium MST clustering.

The work has been carried out with financial support of RFBR within the

project 18-02-40035-mega.

[1] Z. Citron et al., CERN Yellow Rep. Monogr. 7 (2019) 1159

[2] W. Broniowsky et al., Nucl. Phys. A 1005 (2021) 121763

[3] S.H. Lim et al., Phys. Rev. C 99 (2019) 044904

[4] M. El-Nagdy et al., J. Phys. Comm. 2 (2018) 035010

[5] A. Svetlichnyi, I. Pshenichnov, Bull. RAS:Physics 84 (2020) 911

[6] C. Loizides et al., Phys. Rev. C 97 (2018) 054910

[7] J.M. Quesada et al., Prog. Nucl. Sci. Tech. 2 (2011) 936

[8] I.A.Pshenichnov, Phys. Part. Nucl. 42 (2011) 215

aleksandr.svetlichnyy@phystech.edu | |

First author | Svetlichnyi Aleksandr |

Collaboration / Activity | Nuclear fragmentation |