Speaker
Description
The study of nuclear reactions across different energy domains provides
valuable insights into nuclear structure, dynamics, and the equation of state of
nuclear matter. At low energies, reactions are dominated by mean-field effects,
whereas at very high energies, nucleon–nucleon collisions can produce
quark–gluon plasma. In the intermediate energy regime (20 MeV/nucleon to 2
GeV/nucleon), mean-field and nucleon–nucleon collisions compete, and nuclear
multifragmentation emerges as the dominant reaction process [1,2]. Experimental
studies of multifragmentation and nuclear liquid-gas phase transition around the
Fermi energy domain have been pursued for decades at major heavy-ion facilities
worldwide, with significant contributions from JINR, Dubna [3]. In India, such
experimental studies are recently initiated at the K=500 superconducting cyclotron
at VECC, Kolkata [4]. Theoretical models have been developed to understand the
complex reaction mechanism and interpret experimental data, broadly classified
into dynamical [5,6] and statistical [7,8] models. Based on dynamical
(BUU@VECC-McGill) and statistical (CTM) model studies, this presentation
addresses three key topics: (i) The evolution of fragment mass distributions,
including intermediate-mass fragments (IMF) and neutron-rich nuclei, reflecting the
transition from fission at low excitation to multifragmentation at moderate excitation
and eventual breakup into numerous small, neutron-rich fragments at higher
temperatures [9]. (ii) Signatures of the nuclear liquid–gas phase transition [10],
highlighted by the derivative of fragment multiplicity with respect to temperature
[11] as an experimentally accessible observable that is identical to specific heat
behavior and has been recently confirmed experimentally. (iii) Constraints on the
nuclear symmetry energy at sub-saturation densities, derived from isoscaling [4]
and isospin transport studies [12] at Fermi energies, which are highly sensitive to
the density dependence of the symmetry energy and provide critical input to the
nuclear equation of state relevant for nuclear physics and astrophysics.
References: [1] S. Das Gupta, S. Mallik and G. Chaudhuri, “Heavy ion reaction at
intermediate energies: Theoretical Models”, World Scientific Publishers (2019). [2]
Bao-An Li and Wolf-Udo Schroder, Isospin Physics in Heavy-Ion Collisions at
Intermediate Energies, Nova Science Pub. Inc. (2001). [3] V. A. Karnaukhov, H.
Oeschler, S. P. Avdeyev et. al., Nucl. Phys. A 749, 65 (2005) . [4] P. Karmakar, S.
Kundu, T.K. Rana, S. Mallik, S. Manna et. al., Phys. Rev. C 112, 024614 (2025).
[5]G. F. Bertsch and S. Das Gupta, Phys. Rep 160, 189 (1988). [6] J. Aichelin,
Phys. Rep. 202, 233 (1991). [7]J.P. Bondorf, A.S. Botvina, A.S. Iljinov, I.N.Mushustin, K. Sneppen , Phys. Rep. 257, 133(1995). [8] C. B. Das, S. Das Gupta,
W.G. Lynch, A.Z. Mekjian and M.B. Tsang, Phys. Rep. 406, 1 (2005). [9] S. Mallik,
Phys. Rev. C 107, 054605 (2023). [10] B. Borderie and J. D. Frankland, Prog. Part.
Nucl. Phys. 105, 82 (2019). [11] S. Mallik, G. Chaudhuri, P. Das and S. Das Gupta,
Phys. Rev. C 95, 061601 (2017)(R). [12] C. Ciampi, S. Mallik, F. Gulminelli, D.
Gruyer et. al, Phys. Lett. B 868,139815 (2025).
