pre-equilibrium emission in formation of ti* · pre-equilibrium emission in formation of 46ti* ......

Pre-equilibrium Emissionin formation of 46Ti*

Magda CicerchiaDipartimento di Fisica e Astronomia – Università di PadovaLaboratori Nazionali di Legnaro – INFN

3rd year of PhD Admission Exam

Outline

• Clustering & Pre-equilibrium in Light Nuclei

• The Experiment

• The Statistical Code: GEMINI++

• The Dynamical Codes: TWINGO and AMD

• Preliminary Results

2Magda Cicerchia – 103° Congresso Nazionale della SIF – Trento 11-15/09/2017

Nuclear Clustering1968: 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}

In light nuclei at drip-lines, clustering mightbe the preferred structural mode

Renewed interest in nuclear clustering due to the study of neutron-rich and exotic weakly-

bound nuclei


Magda Cicerchia – 103° Congresso Nazionale della SIF – Trento 11-15/09/2017

How to study the Clustering effects on reaction dynamics?

{E. Běták EPJ Web of Conf. 21 (2012) 09004}Search for cluster structure effects

studying the Pre-equilibrium Particles Emission

α-cluster

pre-formed inside nuclear matter formed in dynamical part of the reaction

Central Reaction

levap

𝐸𝐶𝑀 > 𝐵𝐶 ⟹ 𝜎𝑟𝑒𝑎𝑧 =

ℓ

𝜎𝑟𝑒𝑎𝑧 ℓ =𝜋

𝑘2

0

∞

(2ℓ + 1)𝑇ℓ

Termalizzation

{Pre-equilibrium Emission}

4

CN Formation

CN Decay

The Experiment: Reactions Main Characteristics

Entrance channel

Ebeam, lab 𝜽𝒈𝒓𝒂𝒛𝒊𝒏𝒈 CNMass

Asymm𝝈𝒇𝒖𝒔 E* Lab. Vel.

E.R. Distrib.

𝜽𝒍𝒂𝒃

Beam + Target

MeV

MeV/u

deg mb MeV cm/ns deg

16O + 30Si 128 8 8,8 46Ti 0,30107

098,4 1,37 0 – 30

16O + 30Si 111 7 10,1 46Ti 0,30108

188,0 1,28 0 – 30

18O + 28Si 126 7 9,0 46Ti 0,22111

098,5 1,44 0 – 28

19F + 27Al 133 7 8,9 46Ti 0,17110

0130,5 1,52 0 – 28

same beam velocity


same pre-equilibrium component

RESIDUE identification

LCP identification

same CN Excitation Energy same statistical component


Target Contamination

TAR

GETS o

f F.CA

MER

A

Inclusive Experimental

Plot

Gemini Simulation Plot: 30Si target Gemini Simulation Plot: 16O target

6

Good Events Selection

Correlation between the longitudinal momentum and total charge

Correlation between the laboratory energy and charge


Good Events Selection

Correlation between the longitudinal momentum and total charge

Ztot > 70% Zp+ZT

𝒒𝒛

𝒒𝒃𝒆𝒂𝒎

<1.3

Correlation between the laboratory energy and charge


Residue Selection7 MeV/u


The Statistical Code: GEMINI++Simulate the decay of hot nuclei formed in fusion/quasi-fusion reaction.

Hauser-Feshbach ModelWeisskopf Evaporative Theory

Quantum Description of Angular Momentum

𝑊𝛽 ∝ඵ ෨ℓ𝑇ℓ𝜌𝐵 𝐸∗𝐵, 𝐽𝐵 𝑑𝜀𝑏𝑑𝜙

R. J. Charity, Phys Rev C 82 (2010) 014610

෨ℓ = 2ℓ + 1

• Standalone when a good selection of central events can be performed;

• 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

p a

nd

αm

ult

iplic

itie

sin

4π

vs. g

eo

Re

sid

ue

Dis

trib

uti

on


The Dynamical CodesTWINGO→ based on the Stochastic Mean Field Approximation {M. Colonna et al., Nucl. Phys. A 642, 449 (1998)}


TEST PARTICLE METHOD → describeeach nucleons as TEST PARTICLES subjectto a mean field in a phase-space lattice

16O

+3

0Si @ 1

11

MeV

AMD→ describes the cluster structure of the interacting particles. {A. Ono, Phys. Rev. C59, 853 (1999)}

16O

+3

0Si @ 1

11

MeV

takes into account the particle-particle correlations.

based on a Stochastic equation of motion for the Gaussian

wave-packets representing the colliding nucleons


Preliminary Results

11


Preliminary Results

11

Multiplicity

Summary and Perspective• Looking at the α-decay channel where

(in a quasi-inclusive mode) the proton and alpha spectra have a quasi-statistical 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

• 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.

➢ Study on particle-particle correlations will beperformed, selecting specific decay channels (1α,2α, 3α …) to get a better insight on the reactioninterplay.

➢ The AMD calculations are still in progress: furthercalculations are ongoing for all systems, changingsame important parameter, as clustering pre-formation parameter.

➢ To better disentangle the pre-equilibrium emission,it is planned to use the Moscow Pre-equilibriumModel based on the Hybrid model.

This model takes into account a pre-equilibrium stage before asecond thermalized emission stage. In an upgrade version it isalso possible to take into account possible clusters pre-formation in the colliding partners (especially the projectile).

{O. V. Fotina et al., Phys. Atom. Nucl. 73 (2010) 1317c.}12Magda Cicerchia – 103° Congresso Nazionale della SIF – Trento 11-15/09/2017

Thank you!

NUCL-EX CollaborationM. Cicerchia1,2, T. Marchi3, F. Gramegna1, M. Cinausero1, J. Mabiala1, D. Fabris4, A. Caciolli2,4,G. Collazzuol2,4, D. Mengoni2,4, M. Degerlier5, L. Morelli6, M. Bruno6, M. D’Agostino6, S. Barlini7,M. Bini7, G. Pasquali7, S. Piantelli7, G. Casini7, G. Pastore7, D. Gruyer7, P. Ottanelli7, S.Valdré7, N. Gelli7,A. Olmi7, G.Poggi7, E. Vardaci8, I. Lombardo8, D. Dell’Aquila8, S. Leoni9, N. Cieplicka9, B. Fornal10.

¹INFN Laboratori Nazionali di Legnaro, Legnaro (PD), Italia.2Dipartimento di Fisica e Astronomia, Univ. di Padova, Padova, Italia.

3KU Leuven, Department of Physics and Astronomy Instituut voor Kern- en Stralingsfysica, 3001 Leuven, Belgium.

4INFN Sezione di Padova, Padova, Italia.5Science and Art Faculty, Physics Department, Nevsehir Haci Bektas Veli Univ., Nevsehir, Turkey.

6INFN Sezione di Bologna e Dipartimento di Fisica e Astronomia, Univ. di Bologna, Bologna, Italia.7INFN 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.9INFN Sezione di Milano e Dipartimento di Fisica, Univ. di Milano, Milano, Italia.

10Institute of Nuclear Physics, Polish Academy of Sciences Krakow, Poland.

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pre-equilibrium emission in formation of ti* · pre-equilibrium emission in formation of 46ti* ......

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