Experimental study of isospin transport with $^{40,48}$Ca+ $^{40,48}$Ca reactions at 35 MeV/nucleon

Q. Fable (1) , A. Chbihi (2) , J.D. Frankland (2) , P. Napolitani (3) , G. Verde (1, 4) , E. Bonnet (5) , B. Borderie (3) , R. Bougault (6) , Emmanuelle Galichet (3, 7) , T. Génard (2) , Diego D. Gruyer (6) , M. Henri (2) , Marco La Commara (8) , A. Le Fèvre (9) , J. Lemarié (2) , Nicolas Le Neindre (6) , Olivier Lopez (6) , M. Pârlog (6) , A. Rebillard-Soulié (6) , E. Vient (6) , M. Vigilante (10, 11)

1 L2IT - Laboratoire des deux Infinis de Toulouse
2 GANIL - Grand Accélérateur National d'Ions Lourds
3 IJCLab - Laboratoire de Physique des 2 Infinis Irène Joliot-Curie
4 INFN - Istituto Nazionale di Fisica Nucleare, Sezione di Catania
5 SUBATECH - Laboratoire de physique subatomique et des technologies associées
6 LPCC - Laboratoire de physique corpusculaire de Caen
7 CNAM - Conservatoire National des Arts et Métiers [CNAM]
8 University of Naples Federico II = Università degli studi di Napoli Federico II
9 GSI - GSI Helmholtzzentrum für Schwerionenforschung
10 Dipartimento di Matematica e Fisica, Seconda Università degli Studi di Napoli
11 INFN, Sezione di Napoli - Istituto Nazionale di Fisica Nucleare, Sezione di Napoli

We investigate the isospin transport with 40,48 Ca+ 40,48 Ca reactions at 35 MeV/nucleon, measured with the coupling of the VAMOS high acceptance spectrometer and the INDRA charged particle multidetector. Using the quasi-projectile remnant measured with VAMOS and carefully selected light-charged-particles measured in coincidence with INDRA, a reconstruction method is applied to estimate the excited quasi-projectile (QP) on an event-by-event basis. The isospin diffusion is investigated using the isospin transport ratio with the asymmetry δ = (N − Z)/A of the projectile as an isospin-sensitive observable and the total transverse energy of Z ≤ 2 nuclei for experimental centrality sorting. The experimental isospin transport ratios present, for both the reconstructed QP and its remnant, a clear evolution towards isospin equilibration with increasing dissipation of the collision while the full equilibration is not reached. A smoother evolution with less discrepancies between the two mixed systems in the case of the reconstructed QP is also observed. The isospin migration is investigated using the neutron-to-proton ratio of the light-charged-clusters and the velocity of the QP remnant as a sorting parameter. More particularly, we focused on an angular region centered around the mid-rapidity of the reaction so as to characterize the low-density neck emissions. A systematic neutron-enrichment is observed and interpreted as a consequence of isospin migration, more particularly for the symmetric systems which present no isospin gradient between the projectile and the target. We also noticed that the ^{2}H and ^{4}He particles exhibit very close multiplicities independently of the sorting variable for the symmetric systems.

Mots clés: numbers: 21.65.Ef; 25.70.-z; 25.70.Lm; 25.70.Mn; 25.70.Pq

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique des accélérateurs [physics.acc-ph]

Q. Fable, A. Chbihi, J.D. Frankland, P. Napolitani, G. Verde, et al.. Experimental study of isospin transport with $^{40,48}$Ca+ $^{40,48}$Ca reactions at 35 MeV/nucleon. Physical Review C, 2023, 107 (1), pp.014604. ⟨10.1103/PhysRevC.107.014604⟩. ⟨in2p3-03832816v2⟩