Cálculos para la interpretación de experimentos de reacciones nucleares con núcleos exóticos (CIERNEX)

Transcription

1 Cálculos para la interpretación de experimentos de reacciones nucleares con núcleos exóticos (CIERNEX) Calculations for the interpretation of nuclear reactions experiments with exotic nuclei (FPA ) Antonio Matías Moro Muñoz Universidad de Sevilla

2 Outline: Background: Nuclear Reactions with Exotic Nuclei at Seville Objectives of the project Participants Working program Requested budget Expected results and outcome.

3 The nuclear landscape

4 Studying exotic nuclei through nuclear reactions Information about structure comes mainly from reaction measurements. Interactions and reaction mechanisms are different from normal nuclei

5 Motivation of the project Considerable investment in European facilities devoted to Radioactive Nuclear Beams experiments: GSI/FAIR GANIL/SPIRAL2 CERN/ISOLDE Theoretical support is required to extract meaningful information from data. There is a clear lack of groups with expertise in these kind of studies. The Nucl. Phys. Group at Seville has been working in the field since the 1990's.

6 Exotic nuclei studies at Seville University

7 Previous projects (IP Joaquín GómezCamacho) FPA C04-04 FPA FPA c02-01 Theory (since ~1990s): Structure and Reaction Calculations of exotic nuclei. (effect of the Continuum). Experiments ( ): Elastic and break-up measurements in international radioactive beam facilities. Instrumentation ( ): Use of local facility (CNA Tandem). Contribution to FAIR project (Low Energy Beam Tracking).

8 Evolution of EJC ( ) Theory EJC Experiment

9 Present situation (2009) Big and well established experimental group based at the CNA: Local activities (experiments + instrumentation) Experiments in international facilities Experimental project coordinated by J. Gómez Camacho. Well established theory group, based at the Faculty of Physics of the U. of Seville (Department of Atomic, Molecular and Nuclear Physics. PRESENT PROJECT Modality A ( IP below 40)

10 Main objectives of the project Study of exotic nuclei: 1) Development of structure and reaction formalisms appropriate for exotic nuclei. 2) Applications of these formalisms to the understanding and interpretation of experiments. Collaboration with experimental groups.

11 Members of the project Member PhD Position EDP Antonio M. Moro Muñoz (IP) 2001 Assistant profesor (profesor contratado doctor) 1.0 Francisco Barranco Paulano 1986 Full professor (catedrático de escuela ) 0.5 María Victoria Andrés Martín 1987 Associate professor (profesora titular ) 0.5 Manuela Rodríguez Gallardo 2005 Researcher JAE-DOC 1.0-1st year Ph.D. student 1.0 José Antonio Lay Varela 4 EDP

12 ...and hopefully: Ph.D. fellow. Postdoctoral fellow:will work in one (or several) of the following: Reactions mechanisms at intermediate and high energies (eg. eikonal models) Reactions at astrophysical energies. Two-nucleon transfer reactions that incorporate three-body description of borromean nuclei.

13 Highlights of our recent research activities 1) Development of new formalisms for exotic nuclei. Structure: few-body, and correlation effects. Reactions: effect of the continuum in scattering observables. 2) Calculations to interpret reactions experiments.

14 Collaboration with experimental groups: Sevilla-Madrid-Huelva collaboration: scattering of exotic nuclei in international RNB facilities (Louvain-laNeuve, ISOLDE/CERN, TRIUMF) REX-ISOLDE (CERN): Low energy reactions with radioactive beams RIBRAS (Sao Paulo, Brasil) Notre Dame (USA)

15 Discretization of two-body continuum The scattering of weakly bound systems is strongly affected by the coupling to continuum states We have developed a discretization procedure to represent two-body continuum states using a Transformed Harmonic Oscillator (THO) basis: Successfully applied to deuteron and 8 B scattering. PRC73, (2006) PRC72, (2005) PRC65, (2002) (with J.Gómez Camacho, J.M. Arias, and F.Pérez-Bernal)

16 Extension of THO method to 3-body projectiles: 6He case He is a 3-body Borromean nucleus and requires a 3-body description of the bound and unbound states. 6 We have extended the THO method to describe the 3-body continuum using HH expansion of 3-body WF's. - Ph.D thesis of Manuela Rodríguez Gallardo (U. Sevilla, 2005) - M.R.G. et al, PRC72, (2005), PRC77, (2008)

17 PH189 experiment: 6He + 208Pb at Coulomb barrier energies (Seville-Huelva-Madrid-LLN collaboration)

18 Application of the 3-body discretization method to interpret 6He elastic data. We have implemented our THO discretization method into the Continuum Discretized Coupled Channels (CDCC) reaction formalism to interpret the elastic data. Four-body scattering calculation! Inclusion of 3-body continuum states essential to describe the data!

19 Analysis of transfer/breakup reactions: the transfer to the continuum method Breakup reactions can be interpreted as excitation-like processes ( direct breakup picture) but also using a transfer to the continuum (TC) picture:. We have developed a transfer to the continuum formalism combining: Continuum discretization of final states. CCBA reaction formalism. F.M. Nunes and A.M. Moro, NPA767, 138 (2006)

20 Application to transfer to the continuum model to 8 Li+208Pb 7Li +X inclusive reaction (Notre Dame) 7 Li from 33 MeV Transfer to the continuum - A.M.M. et al, PRC68, (2004) - PhD thesis of Homero García (ININ, Mexico).

21 Application of TC method to the inclusive reaction 6 He + 208Pb at Coulomb barrier energies (PH189) What is the mechanism producing particles? (data from PH189 experiment)

22 Application of TC method to the inclusive reaction 6 He + 208Pb at Coulomb barrier energies (PH189) Angular and energy distribution of particles consistent with 2n-neutron transfer to the low energy continuum in the target - D. Escrig et al, NPA792, 2 (2007) - Thesis of Diego Escrig (UCM, to be defended in september 2009).

23 Application of TC to 10Li spectroscopy: 9 Li(d,p)10Li transfer ISOLDE IS367 (B. Jonson): Experiment performed at REX-ISOLDE (CERN) in 2002 by the ISOLDE collaboration to study the properties of 10Li continuum using the transfer reaction 9Li(d,p)10Li. 00 Excitation energy spectrum of 10Li

24 10 Li spectroscopy from 9Li(d,p)10Li transfer reaction. Transfer to the continuum calculations: Two-body model of 10Li=9Li+n CDCC continuum discretization for 10Li states CCBA formalism for reaction mechanism. Clear identification a pwave resonance and s-wave virtual state Jeppesen et al, Phys. Lett. B 642, 449 (2006)

25 First applications of Faddeev equations to nuclear reactions with weakly bound nuclei The exact solution of a 3-body scattering problem is formally provided by Faddeev equations. Faddeev includes elastic, transfer and breakup consistently. We are collaborating with the Nuclear Physics group at the University of Lisbon to apply for the first time Faddeev equations to reactions with exotic nuclei.

26 First applications of Faddeev equations to nuclear reactions with weakly bound nuclei We are performing benchamark calculations comparing the accuracy of transfer/breakup nuclear reaction models with Faddeev. These comparison will establish the validity of approximate methods used in nuclear reactions, such as as the CDCC..

27 Planned activities for the next 3 years

28 New methods for continuum discretization of 3-body systems THEORY: More efficient methods for continuum discretization: (Faddeev expansions, S-matrix eigenstates...) COLLABORATION WITH EXPERIMENTS: Keep existing collaborations New collaborations GANIL/SPIRAL2

29 New methods for continuum discretization of 3-body systems We are working in more efficient discretization methods: Analytical transformations of the HO basis: identification of resonant structures Adiabatic expansion of Faddeev equations (collaboration with Aarhus group) Eigenstates of the 3-body S-matrix

30 Interpretation of fragmentation experiments involving coincidence measurements of outgoing fragments. Leading facilities (eg. GANIL) are starting to measure correlations between fragments produced after breakup. We plan to develop the appropriate formalisms to calculate these observables from our four-body CDCC calculations. (PhD thesis of J.A. Lay)

31 Preliminary results for n-n correlations after 6He fragmentation on a heavy target. (unpublished data courtesy of GANIL/Orsay collaboration)

32 Two-neutron transfer of Borromean nuclei Two-neutron transfer mechanism proven to be very important in reactions induced by 6He, 11Li, etc We want to implement a realistic 3-body description of the 6He or Li nucleus into the DWBA reaction formalism (PostDoc). 11 (with Gregory Pottel from Univ. of Milan)

33 Collaboration with GANIL/SPIRAL2

34 Collaboration with REX-ISOLDE Spectroscopic studies of light exotic nuclei using lowenergy transfer reactions: IS430 experiment (K. Riisager, H. Jeppesen, 2005): Study of Neutron-Rich Be Isotopes with REX-ISOLDE 2.25 MeV/u: 11Be(d,d*), 11Be(d,p)12Be,11Be(d,t)10Be IS446 experiment (H. Jeppesen, 2005): 3.15 MeV/u: 8Li(d,p)9Li, 8Li(d,t)7Li

35 Bound and unbound states in 3-body systems 1) We want to extend the methods developed for 6He to other 3-body systems (11Li, 12Be, 16Ne, etc). 2) Our short-term goal is the 11Li nucleus: 11 TRIUMF (E1104): Sevilla/Huelva/Madrid collaboration 11 TRIUMF: GANIL/TRIUMF collaboration

36 Li+208Pb reaction at Coulomb barrier energies (Sevilla-Madrid-Huelva-Chalmers collaboration) 11 Li 11 9 Li What is the mechanism producing 9Li? Preliminary calculations using a simple 11Li two-body model suggest a direct breakup mechanism

37 Requested budget (3 years) Concept Equipment (computing resources) Travel Post Doc (2 years) Spendable ( fungible ) Other TOTAL (DIRECT COSTS) INDIRECT COSTS Amount (EUR)

38 Expected outcomes: Reinforce the theoretical studies of Nuclear Reactions with exotic nuclei Seville. Become a reference group giving support to experimental collaborations in the interpretation of nuclear reactions experiments with exotic beams. Extend our collaboration to other experimental groups.

39 THE END...

40 Summary of ongoing collaborations We plan to keep a close collaboration with experimental groups to provide theoretical support in the interpretation of their measurements: REX-ISOLDE (CERN) 11Be+p 8Li+p GANIL 11Li+p 8He+208Pb (approved) RIBRAS (Sao Paulo) 6He + 120Sn, 6He+ 27Al 8Li + 12C TRIUMF 11Li + 208Pb, 11Li+p These experiments have been already performed,and the theoretical analysis is under our responsibility.

41 Collaboration with RIBRAS (Brazil) - RIBRAS: Radioactive nuclear beams facility at Brazil - Low energy experiments with RIB He+120Sn (R. Litchtenthaler, K. Cezaretto): Transfer/breakup 6 Li+12C (V. Guimaraes) Elastic, inelastic, transfer 8

42 First applications of Faddeev equations to nuclear reactions with weakly bound nuclei Collaboration with nuclear physics group at Lisbon University

43 Reaction mechanism Models Elastic scattering Optical model Inelastic, CC Two-body breakup 3-body CDCC High energy fragmentation CDCC Eikonal Fusion Statistical models 2-nucleon transfer DWBA, CCBA

44 Extension of THO method to 3-body projectiles Borromean nuclei, such as 6He or 11Li, require a 3-body description of the bound and unbound states. We have developed two methods to discretize the 3-body continuum: Transformed harmonic oscillator (THO) method Binning method

45 Continuum discretization in terms of eigenstates of the 3body S-matrix Eigenstates of the 3-body S-matrix found to provide an efficient way of characterizing continuum structures. B(E2) response 2+ phase shifts (with J. Gómez Camacho, J.M. Arias, and I.J. Thompson)

46 Ongoing work: 11Li+208Pb TRIUMF (Sevilla-Madrid-Huelva-Chalmers collaboration)

47 Study of 6He + 208Pb at Coulomb barrier energies (Seville-Huelva-Madrid(CSIC)-LLN collaboration) He+208Pb 6

48 Example: 11Li+208Pb TRIUMF (2008) (Sevilla-Madrid-Huelva-Chalmers collaboration) 9 Li Li 11 What is the mechanism producing 9Li? Preliminary calculations suggest a direct breakup mechanism

49 Pairing effects and particle-vibration couplings in the description of drip-line nuclei The structure of nuclei close to drip line is very sensitive to residual interactions: Pairing Coupling between single-particle and collective modes. Recent publications: Eur. Phys. Jour. A11, 385 (2001) Phys. Rev. C 69, (2004). Phys. Rev. C 78, (2008).

50 Participants in previous projects: THEORY EXPERIMENTS + INSTRUMENTATION Manuela Rodríguez Juan Antonio Caballero Carlos Dasso Francisco Barranco Gregory Potel (Milan) Antonio Moro Joaquín Gómez Camacho María Victoria Andrés Marcos Alvarez Jose Manuel Espino Navas Ivan Mukha

51 Analysis of 6He + 208Pb at Coulomb barrier energies (Seville-Huelva-Madrid(CSIC)-LLN collaboration) Elastic scattering Phenomenological analysis of 6He elastic scattering shows a wild departure from Fresnel-type scattering due to the presence of longrange coupling effects

52 TNET recommendations The new experimental facilities being planned and built will cover experimental reaction studies for a wide range of energies with exotic nuclei far off stability, with emphasis on nuclear structure and dynamics, and astrophysical aspects. The new projects will demand, with their versatile experimental arrangements, many different kinds of reaction mechanisms with radioactive beams. New experimental results of high accuracy and completeness; e.g. quasi-elastic scattering experiments in reverse kinematics detecting all outgoing reaction products including the recoil protons from the target. This requires the development of reaction theory to the same accuracy that is currently achieved for dedicated light-nucleus few-body dynamics, and theoretical support is essential for the extraction of structure information from the details of the reaction mechanisms and outcomes.

53 Application to the interpretation of the 6He + 208Pb elastic scattering at Coulomb barrier energies (Seville-Huelva-Madrid(CSIC)-LLN collaboration)

54 Discretization of two-body and three-body continuum We applied the THO discretization method to Coulomb breakup of the halo nucleus 8B: 8 B+58Ni 7Be+p+58Ni PRC73, (2006)

55 1) Development of structure and reaction formalisms appropriate for exotic nuclei. Description of the structure of exotic nuclei: bound and unbound states. Eg: Borromean systems (6He, 11Li, 14Be, etc) Effect of the continuum in scattering observables. Calculation of correlations between fragments following breakup. Application of Faddeev-AGS equations to the scattering of light exotic nuclei. Treatment of two-neutron transfer in reactions induced by Borromean nuclei. Collective excitations.

56 2) Applications of these formalisms to the understanding and interpretation of experimental results Theoretical support to CNA activities at Seville. Extract global properties of nucleus-nucleus interaction from the analysis of elastic, transfer and breakup experiments performed in RNB facilities (GANIL, TRIUMF, ISOLDE, Sao Paulo). Extraction of spectroscopic information from transfer and breakup experiments (eg. ISOLDE/CERN) Physic cases for future experiments to be performed at the new European facilities (GANIL/SPIRAL2, GSI/FAIR).

57 Collaborations THEORY Instituto Superior Técnico (Lisbon, Portugal) EXPERIMENTS University of Lisbon (Lisbon, Portugal) Michigan State University (USA) Surrey University (UK) Warsaw University (Poland) INFN Division of Catania Andrzej Soltan Institute for Nuclear Studies (Poland) GANIL Aarhus University (Denmark) University of Sao Paulo (Brasil) Univerity of Orsay (France) Göteborg University (Sweden) Univerity of Orsay (France) University of Milan. Padova University (Italy) Instituto de Estructura de la Materia (CSIC, Madrid) Aarhus University (Denmark) University of Huelva (Spain)