Pre-equilibrium Emission in formation of 46 Ti*

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1 3 rd year of PhD Admission Exam Pre-equilibrium Emission in formation of 46 Ti* Magda Cicerchia Dipartimento di Fisica e Astronomia Università di Padova Laboratori Nazionali di Legnaro INFN

2 Outline Clustering & Pre-equilibrium in Light Nuclei The Experiment The Statistical Code: GEMINI++ The Dynamical Codes: TWINGO and AMD Preliminary Results 2

3 Nuclear Clustering 1968: Ikeda a-cluster structure observed in 2N=2Z nuclei at E* close to the a-decay threshold {W. Von Oertzen et al. Phys. Rep. 432 (2006) 43 M. Freer et al., Rep. Progr. Phys. 70 (2007) 2149 J. P. Ebran te al., Nature 487 (2012) 341 P.E. Hodgson, E. Běták, Phys. Rep. 374 (2003) 1-89} Renewed interest in nuclear clustering due to the study of neutron-rich and exotic weaklybound nuclei In light nuclei at drip-lines, clustering might be the preferred structural mode 3

4 How to study the Clustering effects on reaction dynamics? α-cluster pre-formed inside nuclear matter formed in dynamical part of the reaction Search for cluster structure effects studying the Pre-equilibrium Particles Emission {E. Běták EPJ Web of Conf. 21 (2012) 09004} E CM > B C σ reaz = σ reaz l = π k 2 l 0 (2l + 1) T l Central Reaction Termalizzation CN Formation {Pre-equilibrium Emission} CN Decay l evap 4

5 The Experiment: Reactions Main Characteristics LCP identification Entrance channel E beam, lab θ grazing CN Mass Asymm σ fus E* Lab. Vel. E.R. Distrib. θ lab Beam + Target Me V MeV/ u 16 O + 30 Si ,8 46 Ti 0,30 16 O + 30 Si ,1 46 Ti 0,30 18 O + 28 Si ,0 46 Ti 0,22 19 F + 27 Al ,9 46 Ti 0,17 deg mb MeV cm/ns deg ,4 1, ,0 1, ,5 1, ,5 1, RESIDUE identification same beam velocity same CN Excitation Energy same pre-equilibrium component same statistical component 5

6 Target Contamination Gemini Simulation Plot: 30 Si target Inclusive Experimental Plot Gemini Simulation Plot: 16 O target TARGETS of F.CAMERA 6

7 Good Events Selection Correlation between the laboratory energy and charge Correlation between the longitudinal momentum and total charge 7

8 Good Events Selection Correlation between the laboratory energy and charge Correlation between the longitudinal momentum and total charge q z q beam <1.3 Z tot > 70% Z p +Z T 7

9 Residue Selection 7 MeV/u 8

10 Residue Distribution p and α multiplicities in 4π vs. geo The Statistical Code: GEMINI++ Simulate the decay of hot nuclei formed in fusion/quasi-fusion reaction. Hauser-Feshbach Model W β ඵ l T l ρ B E B, J B dε b dφ Weisskopf Evaporative Theory Quantum Description of Angular Momentum l = 2l + 1 Standalone when a good selection of central events can be performed; R. J. Charity, Phys Rev C 82 (2010) Afterburner (after a dynamical code) to produce secondary particles distributions from primary fragments -> to be compared with exp data. Effect of the Experimental filter on different systems 9

11 The Dynamical Codes TWINGO based on the Stochastic Mean Field Approximation {M. Colonna et al., Nucl. Phys. A 642, 449 (1998)} TEST PARTICLE METHOD describe each nucleons as TEST PARTICLES subject to a mean field in a phase-space lattice 16O MeV AMD describes the cluster structure of the interacting particles. {A. Ono, Phys. Rev. C59, 853 (1999)} based on a Stochastic equation of motion for the Gaussian wave-packets representing the colliding nucleons takes into account the particle-particle correlations. 16O MeV 10

12 Preliminary Results 11

13 Preliminary Results 11

14 Preliminary Results 11

15 Preliminary Results Multiplicity 11

16 Summary and Perspective Looking at the α-decay channel where (in a quasi-inclusive mode) the proton and alpha spectra have a quasistatistical shape, only some little differences are evidenced between the four systems due to the interplay between evaporative and fast emission channels. Starting point to NEW EXPERIMENTS at HIGHER ENERGIES Study on particle-particle correlations will be performed, selecting specific decay channels (1α, 2α, 3α ) to get a better insight on the reaction interplay. The AMD calculations are still in progress: further calculations are ongoing for all systems, changing same important parameter, as clustering preformation parameter. From the multiplicity spectra differences are observed, which make it interesting to study in a more detailed way some specific decay channel, comparing them for the four systems and to their relative model predictions. To better disentangle the pre-equilibrium emission, it is planned to use the Moscow Pre-equilibrium Model based on the Hybrid model. This model takes into account a pre-equilibrium stage before a second thermalized emission stage. In an upgrade version it is also possible to take into account possible clusters preformation in the colliding partners (especially the projectile). {O. V. Fotina et al., Phys. Atom. Nucl. 73 (2010) 1317c.} 12

17 Thank you!

18 NUCL-EX Collaboration M. Cicerchia 1,2, T. Marchi 3, F. Gramegna 1, M. Cinausero 1, J. Mabiala 1, D. Fabris 4, A. Caciolli 2,4, G. Collazzuol 2,4, D. Mengoni 2,4, M. Degerlier 5, L. Morelli 6, M. Bruno 6, M. D Agostino 6, S. Barlini 7, M. Bini 7, G. Pasquali 7, S. Piantelli 7, G. Casini 7, G. Pastore 7, D. Gruyer 7, P. Ottanelli 7, S.Valdré 7, N. Gelli 7, A. Olmi 7, G.Poggi 7, E. Vardaci 8, I. Lombardo 8, D. Dell Aquila 8, S. Leoni 9, N. Cieplicka 9, B. Fornal 10. ¹INFN Laboratori Nazionali di Legnaro, Legnaro (PD), Italia. 2 Dipartimento di Fisica e Astronomia, Univ. di Padova, Padova, Italia. 3 KU Leuven, Department of Physics and Astronomy Instituut voor Kern- en Stralingsfysica, 3001 Leuven, Belgium. 4 INFN Sezione di Padova, Padova, Italia. 5 Science and Art Faculty, Physics Department, Nevsehir Haci Bektas Veli Univ., Nevsehir, Turkey. 6 INFN Sezione di Bologna e Dipartimento di Fisica e Astronomia, Univ. di Bologna, Bologna, Italia. 7 INFN Sezione di Firenze e Dipartimento di Fisica e Astronomia, Univ. di Firenze, Firenze, Italia. 8 INFN Sezione di Napoli e Dipartimento di Fisica, Univ. Federico II Napoli, Napoli, Italia. 9 INFN Sezione di Milano e Dipartimento di Fisica, Univ. di Milano, Milano, Italia. 10 Institute of Nuclear Physics, Polish Academy of Sciences Krakow, Poland. 18