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Nuclear physics activity in Institute for Nuclear Research and Nuclear Energy, Sofia

Nuclear physics activity in Institute for Nuclear Research and Nuclear Energy, Sofia. Ch. Protochristov, Ch. Stoyanov. Historical remarks. Prof. Dr. Elisabeth Kara – Michailova (1897-1968). obtained Ph.D at the Vienna University, Austria in 1923

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Nuclear physics activity in Institute for Nuclear Research and Nuclear Energy, Sofia

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  1. Nuclear physics activity inInstitute for Nuclear Research and Nuclear Energy,Sofia Ch. Protochristov, Ch. Stoyanov

  2. Historical remarks • Prof. Dr. Elisabeth Kara – Michailova (1897-1968) • obtained Ph.D at the Vienna University, Austria in 1923 • Nucl. Spectroscopy research at the Radium Institute Vienna • invited by Rutherford in Cavendish Laboratory in Cambridge, • important contributions in dosimetry • the first women, to become professor at the Sofia University • head of the newly established chair of Atomic Physics • introduced the photo emulsion method in cosmic-ray • investigations in Bulgaria

  3. Prof. Dr. sc. Zhelio Zhelev (1923-1988) • investigations of natural radioactivity in Bulgaria • postgraduated in Leningrad (St.Peterburg), Russia • experimental investigations of short-lived isotopes • headed the Department of Nuclear Spectroscopy • In 1969 he founded the International School on Nuclear Physics, Neutron Physics and Nuclear Energy

  4. Acad. Wenzeslav Andrejtscheff (1941-2001) • studied at the Technical University Dresden • developed the Generalized Centroid Shift Method (GCSM) • head of the Department of Nuclear Spectroscopy • professor in the University of New Brunswick, USA • member of the Bulgarian Academy of Sciences

  5. Head of the group JRSI (Nuclear & Roentgen Research) in the Department of Nuclear Spectroscopy(1966-1996); • Professor in the Physics Department of Sofia (1964-1996); • Member of the Bulgarian Academy of Sciences (1995); • Vice-director of the Laboratory of Nuclear Reactions, JINR - Dubna (1982-1986). He combined scientific investigations in theoretical nuclear physics and experimental nuclear spectroscopy. In the seventies some 30% of the data of lifetimes of high-spin states in deformed rare-earth nuclei have been generated by the group headed by acad. E. Nadjakov in close collaboration with JINR-Dubna. Often citated is his last work no nuclear charge radii. Acad. Emil G.Nadjakov (1929-1996)

  6. Joint Institute for Nuclear Research Dubna

  7. Present status The activity in the nuclear physics in INRNE is concentrated mainly in the Department of Nuclear Physics. There are 4 laboratories in the Department: • Laboratory of Nuclear Spectroscopy • Laboratory of Nuclear Reaction • Laboratory of Positron Spectroscopy • Laboratory of Semi-conductor Detectors • Laboratory of Theoretical Nuclear Physics does not belong to Department of Nuclear Physics but the activity of this Lab is mainly devoted to study the structure of atomic nuclei. • Altogether, INRNE is the leading and complex center for research and application of nuclear science in Bulgaria. More that 40 researchers are included in the activity connected with nuclear physics. Around half of them are less than 40 years old. Experimental physics: The basic facilities like accelerators are not available and the research reactor is under reconstruction. Because of that the main part of experimental work is done in collaboration with European research centers like CERN, GANIL, INFN, LNL-Legnaro, GSI-Darmstadt, IreS Strasbourg, JINR-Dubna etc.

  8. Laboratory of Nuclear Spectroscopy The new direction of the experimental activity of the Lab is connected with nuclear waist transmutation problems. Spalation neutrons, produced by bombardment of heavy targets such as Pb, Pb-Bi, Hg etc. are used for transmutation of long-lived radioactive waste. The special design of the transmutation facilities depends on the neutron spectra and on details of nuclear reactions induced by neutrons, which can be studied by high-resolution gamma-ray spectroscopy. Therefore spallation spectra from massive lead targets (20 cm), irradiated with 1 GeV protons from the NUCLOTRON accelerator, have been investigated. The gamma-ray spectra emitted by decaying of residual nuclei produced by spallation neutrons in (n,xn), (n,xnyp), (n,p) and (n,n) reactions with activation threshold detectors 209-215 Bi were measured in the Laboratory of Nuclear Problems (LNP), JINR Dubna. The corresponding gamma-ray spectra have been analyzed with specialized software and the cross sections for the different reactions have been obtained. • During the last years the activity of Laboratory of Nuclear Spectroscopy was concentrated on the traditional for the Lab fields – theoretical and experimental nuclear physics and some applications. The members of the Lab applied the method of high-resolution gamma-spectroscopy to study the environmental problems. The systematical investigations of the environmental radioactivity in the Bansko – Razlog region, carried out during the recent years, have been enlarged with investigations of Cs-137 concentration in soil, performed here for the first time. A total area of about 40 km2 has been investigated, by means of high-resolution gamma-ray spectroscopy, thereby the radio-nuclide content of the soil samples has been determined. The results gave us the opportunity to assess the total Cs-137 fallout in the region. The measured concentrations are compared with previous data obtained for other regions in Bulgaria. The Cs-137 fallout following the Chernobyl accident has been estimated and compared with the results obtained in other countries. The additional dose rate caused by this fallout has been estimated. `

  9. Lifetime Measurements in Nuclear Spectroscopy • The experimental techniques employed include the Recoil distance • Doppler-shift (RDDS) method, the Doppler-shift attenuation method (DSAM) • and the delayed-coincidence method. These techniques cover a range • from e.g. hundred nanoseconds (which is not an upper limit) down to • few fs. This range nearly exhausts most of the level lifetimes of interest for • Nuclear Spectroscopy. • Most important results: • For the first time it was possible to take into account precisely the time-velocity correlations in Doppler-shift coincidence measurements when the gate is set on a fraction of the line-shape. • For the first time taking into account of the finite stopping time of the recoils in the stopper in RDDS measurements led to a correction for the lifetimes typically from 20% to 70%, for lifetime values of about 1 ps and 0.3 ps, respectively. The knowledge of the lifetimes of excited nuclear states allows the derivation of absolute transition probabilities and of absolute values of reduced transition matrix elements. These experimental quantities represent a stringent test information for nuclear models because they are very sensitive to the wave functions of the initial and final states. Therefore the determination of lifetimes is of importance for the understanding of nuclear structure. Recently, some new topics are the focus of our collaboration as a possible new region of X(5) nuclei around mass A=180, the application of the theoretical supersymmetry scheme to 195Pt and the isospin purity in Z=N nuclei (e.g. Ref.[20]) as well as experimental developments with the aim to perform RDDS measurements with beams of relativistic ions in exotic nuclei. In this experimental field, since more than 20 years we have a collaboration with the Institute fuer Kernphysik of the University of Cologne, namely with the group of Prof. J. Jolie, Prof. P. von Brentano and Dr. A. Dewald. This collaboration resulted so far in more than 40 publications in refereed journals like Phys. Rev. C and Nucl. Phys. A.

  10. Investigation of chiral symmetry in nuclear systems. • collaboration: • Laboratori Nazionali di Legnaro, Italy • Publications related to this subject: • 1. D. Tonev, G. de Angelis, P. Petkov, A. Dewald, S. Brant,S. Frauendorf, D. L. Balabanski, P. Pejovic, D. Bazzacco, P. Bednarczyk, F. Camera, A. Fitzler, A. Gadea, S. Lenzi, S. Lunardi, N. Marginean, O. M\"oller, D. R. Napoli, A. Paleni, C. M. Petrache, G. Prete, K. O. Zell, Y. H. Zhang, Jing-ye Zhang, Q. Zhong, and D. Curien, • "Transition probabilities in 134Pr: A test for chirality in nuclear • systems", Phys. Rev. Lett. 96 (2006) 052501. • 2. D. Tonev, G. de Angelis, P. Petkov, A. Dewald, A. Gadea, P. Pejovic, D. L. Balabanski, P. Bednarczyk, F. Camera, A. Fitzler, O. Moller, N. Marginean, A. Paleni, C. Petrache, K. O. Zell, Y. H. Zhang, • "Check for chirality in real nuclei", • Eur. Phys. J. A 25 Suppl. 1, (2005) 447 Since few years, we have also a fruitful collaboration with the group of G. de Angelis from the Laboratori Nazionali di Legnaro, Italy, where operates the multidetector array GASP. The main topic studied within this collaboration is chirality in nuclear physics, concentrating on RDDS and DSAM data for 134Pr, which was considered to be the best example where the broken symmetry is realized. It was found that in this nucleus chirality exists only in a dynamical context.

  11. Investigation of critical points of shape/phase transitions in nuclei. • collaborations: • University of Cologne • Publications related to this subject: • D. Tonev, A. Dewald, T. Klug, P. Petkov, J. Jolie, A. Fitzler, O. Moller, S. Heinze, P. von Brentano and R. F. Casten, • "Transition probabilities in 154Gd: Evidence for X(5) critical point symmetry", • Phys. Rev. C 69 (2004) 034334. • A. Dewald, O. Moller, D. Tonev, A. Fitzler, B. Saha, K. Jessen, S. Heinze, A. Linnemann, J. Jolie, K. O. Zell, P. von Brentano,P.Petkov, R. F. Casten, M. Caprio, J. R. Cooper, R. Krucken, V. Zamfir, D. Bazzacco, S. Lunardi, C. Rossi-Alvarez, F. Brandolini, C. Ur, G. De Angelis, D. R. Napoli, E. Farnea, N. Marginean, T. Martinez, M. Axiotis, • "Shape changes and test of the critical point symmetry X(5) in N=90 nuclei", • European Physical Journal A 20 (2004) 173. • O. Mőller, A. Dewald, P. Petkov, B. Saha, A. Fitzler, K. Jessen,D. Tonev, T. Klug, S. Heinze, J. Jolie, P. von Brentano, D. Bazzacco,C. Ur, E. Farnea, M. Axiotis, S. Lunardi, G. de Angelis, D.R. Napoli,N. Marginean, T. Martinez, M. Caprio, and R.F. Casten, • "Electromagnetic transition strengths in 156Dy", • Phys. Rev. C 74 (2006) 024313. Lifetime measurements in 154Gd were performed by means of the Recoil Distance Doppler-shift method. Excited states of 154Gd were populated via Coulomb excitation with a 32S beam at 110 MeV delivered by the FN tandem accelerator of the University of Cologne. The data show that 154Gd is one of the good examples of the realization of the X(5) dynamical symmetry. In addition, the experimental data are compared to fits in the framework of the IBA and the General Collective Model (GCM). A comparison of the model predictions and experimental data are shown in Fig. 2.

  12. The activity of Laboratory of Nuclear Spectroscopy Several theoretical results have been obtained: MICROSCOPIC DESCRIPTION OF THE STRUCTURE OF EXCITED STATES Dipole excitations

  13. Dipole excitations • COLLABORATIONS • Institut für Theoretische Physik, Universität Giessen, Germany • Institute de Physique Theorique, Univeriste Paris-Sud XI, France • Bogolyubov Laboratory of Theoretical Physics, Dubna, Russia • SOME RECENT PUBLICATIONS: • N. Tsoneva, H. Lenske, Ch. Stoyanov. • Pygmy Dipole Resonances as a Manifestation of the Structure of the Neutron Rich Nuclei . • Nucl. Phys. A731(2004) pp. 273 - 280 • N. Tsoneva, H. Lenske, Ch. Stoyanov. • Probing the nuclear skin by low-energy dipole modes. • Phys. Lett. B586 (2004) pp. 213 - 218 • Dipole excitations below the neutron threshold in neutron-rich Sn isotopes are studied theoretically in the Quasiparticle-Phonon Model with Hartree-Fock-Bogoliubov single-particle input. Of special interest are the low-lying two-phonon 1-states and Pygmy Dipole Resonance (PDR). The evolution of low-energy dipole excitations with neutron excess are investigated over the Sn isotopic chain including the experimentally unknown region close to 132 Sn. A dependence of the PDR strengths and centroid energies on the neutron skin thickness is found. Despite significant multi-phonon contributions to mean energies and transition strengths, the PDR states retain their one-phonon character. The fragmentation pattern is reduced with increasing neutron excess towards the N=82 shell closure which will be of advantage for the future experimental work.

  14. The activity of Laboratory of Nuclear Spectroscopy Several theoretical results have been obtained: MICROSCOPIC DESCRIPTION OF THE STRUCTURE OF EXCITED STATES Dipole excitations High-lying states

  15. High-lying states • Highly excited single-particle states in nuclei are coupled with the excitations of more complex character, first of all with collective phononlike modes of the core. In the framework of the quasiparticle-phonon model, the structure of resulting complex configurations is considered, using 1k17/2 orbital in 209 Pb as an example. Although, on the level of one- and two-phonon admixtures, the fully chaotic Gaussian orthogonal ensemble regime is not reach, the eigenstates of the model carry a significant degree of complexity that can be quantified with the aid of correlated invariant entropy. Artificially enhanced particle-core coulping, the system undergoes the doubling phase transition with the quasiparticle strength concemtrated in two repelling peaks. This phase transition is clearly detected by correlational entropy COLLABORATIONS Department of Physics and Astronomy, Michigan State University, National Superconducting Cyclotron Laboratory and East Lansing, Michigan SOME RECENT PUBLICATIONS: Ch. Stoyanov, V. Zelevinsky. High-lying single-particle modes, chaos, correlational entropy, and doubling phase transition. Phys. Rev. C v. 70 (2004) p. 014302, 7p.

  16. The activity of Laboratory of Nuclear Spectroscopy Several theoretical results have been obtained: MICROSCOPIC DESCRIPTION OF THE STRUCTURE OF EXCITED STATES Dipole excitations High-lying states Mixed symmetry states

  17. Mixed symmetry states • COLLABORATIONS • Dipartimento di Scienze Fisiche , • Universita di Napoli Federico II and • Istituto Nazionale di Fisica Nucleare, sezione di Napoli Complesso Monte S. Angelo, via Cintia I-80126, Napoli • SOME RECENT PUBLICATIONS: • N. Lo Iudice, Ch. Stoyanov, Microscopic description of newly discovered mixed symmetry states. • Phys. Rev. C, v. 62 (2000) pp. 047302, 4p. • N. Lo Iudice, Ch. Stoyanov, Mroscopic Study of the Proton-Neutron Symmetry and Phonon Structure of the Low-Lying States in 92Zr., • Phys. Rev. C, v. 69 (2004) p. 044312, 6p. • Within the microscopic multiphonon approach the proton-neutron symmetry symmetry and phonon structure of some low-lying states in 92 Zr is studied. The breaking of F-spin symmetry is confirmed, but the breaking mechanism is more complex than one suggested in the original shell model analysis of the data. The new intriguing features of the spectrum, such as a pronounced multiphonon fragmentation of the states and a tentative evidence of three-phonon mixed-symmetry state is found .

  18. High-spin states in the neutron-rich nuclei with 80 < A < 150 produced as fission fragments (FF) by heavy ion reactions collaboration betweenCNRS/Franceand BAS: Contracts No 2937, 8198, 12531, 16946. IPN Orsay; IreS Strasbourg; CEA/DSM/DAPNIA/SPhN Gif-sur-Yvette; IPNL, Uni Claude Bernard, Villeurbanne; IPN Lyon, France; Dep. of Phys., Dep.Phys.Astronomy University of Manchester, Manchester

  19. Fission Fragments (FF) 106,107,108,109,110,111,112,113Rh (Z=45), 110,112,114,116Ag (Z=47), 115,117,119,121In (Z=49),121,123,125,127Sb (Z=51), 140Ba (Z=56),142,143,145,147Ce (Z=58),147,149Nd(Z=60)

  20. 1. Ts.Venkova, M.-G.Porquet, M.Houry, R.Lucas, Ch.Theisen, J.Durell and A.Roach “A new high-spin level scheme for 149Nd from a fusion-fission reaction” Eur. Phys. J. A28, 147 (2006) • 2. Ts.Venkova, M.-G.Porquet, A.Astier, I.Deloncle, P.Petkov, A.Prevost, F.Azaiez, A.Bogachev, A.Buta, D.Curien, O.Dorvaux, G.Duchene, J.Durell, B.J.P.Gall, M.Houry, F.Khalfallah, R.Lucas, M.Meyer, I.Piqueras, N.Redon, A.Roach, M.Rousseau, O.Stezowski, and Ch.Theisen “New high-spin states of 147Nd and 145Ce: Octupole correlation in the N = 87 isotones” Eur.Phys. J. A 26, 315 (2005) • 3. M.-G. Porquet, Ts.Venkova, R.Lucas, A.Astier, A.Bauchet, I.Deloncle, A.Prevost, F.Azaiez, G.Barreau, A.Bogachev, N.Buforn, A.Buta, D.Curien, T.P.Doan, L.Donadille, O.Dorvaux, G.Duchene, J.Durell, Th. Ethvignot, B.J.P.Gall, M.Houry, Ch.Theisen, D.Grimwood, W.Korten, , S.Lalkovski, Y.Le Coz, M.Meyer, A.Minkova, I.Piqueras, N.Redon, A.Roach, M.Rousseau, N.Schulz, A.G.Smith, O.Stezowski, Ch.Theisen, and B.J.Varley High-spin structure of 121,123,125,127Sb nuclei: single proton and core-coupled states” Eur. Phys. J. A 24, 39 (2005)

  21. 4. R.Lucas, M.-G. Porquet, Ts.Venkova,I.Deloncle, M.Houry, Ch.Theisen, A.Astier, A.Bauchet, S.Lalkovski, G.Barreau, N.Buforn, T.P.Doan, L.Donadille, O.Dorvaux, J.Durell, Th. Ethvignot, B.J.P.Gall, D.Grimwood, W.Korten, Y.Le Coz, M.Meyer, A.Minkova, A.Prevost, N.Redon, A.Roach, N.Schulz, A.G.Smith, O.Stezowski, B.J.Varley “High-spin study of odd-A49In isotopes beyond the neutron mid-shell” Eur. Phys. J. A 15, 315 (2002) • 5.M.-G. Porquet, Ts.Venkova, A.Astier, A.Bauchet, I.Deloncle, N.Buforn, L.Donadille, O.Dorvaux, B.J.P.Gall, S.Lalkovski, R.Lucas, M.Meyer, A.Minkova, A.Prevost, N.Redon, N.Schulz, O.Stezowski “Evolution of the π g 9/2 ν h11/2 configuration in the neutron-rich 110,112Rh and 114,116Ag isotopes” Eur. Phys. J. A 18, 25 (2003) • 6. M.-G.Porquet, Ts.Venkova, P.Petkov, A.Bauchet, I.Deloncle, A.Astier, N.Buforn, J.Duprat, B.J.P.Gall, C.Gautherin, E.Gueorgieva, F.Hoellinger, T.Kutsarova, R.Lucas, M.Meyer, A.Minkova, N.Redon, N.Schulz, H.Sergolle, A.Wilson “High-spin structure of the neutron-rich odd-odd 106,108Rh and 110,112 Ag isotopes” Eur. Phys. J. A 15, 463 (2002)

  22. 7. Ts.Venkova, M.-G.Porquet, A.Astier, A.Bauchet, I.Deloncle, S.Lalkovski, N.Buforn, L.Donadille, O.Dorvaux, B.J.P.Gall, R.Lucas, M.Meyer, A.Minkova, A.Prevost, N.Redon, N.Schulz, O.Stezowski “High-spin structure of the neutron-rich 109,111,113Rh isotopes” Eur.Phys. J. A 15, 429 (2002) • 8. M.-G.Porquet, Ts. Venkova,A.Astier, I.Deloncle, A.Prevost, F.Azaiez, A.Buta, D.Curien, G.Duchene, B.J.P.Gall, F.Khalfallah, I.Piqueras, M.Rousseau, N.Redon, M.Meyer, O.Stezowski, R.Lucas, A. Bogachev ”Beyond the N = 50 shell closure: High-spin excitations of 87Kr isotope and ground state spin of 87Br” Eur. Phys. J. A 28, 153 (2006)

  23. Laboratory of Theoretical Nuclear Physics SUPERSCALING ANALYSIS OF INCLUSIVE ELECTRON SCATTERING AND ITS EXTENSION TO CHARGE- AND NEUTRAL-CURRENT NEUTRINO-NUCLEUS SCATTERING BEYOND THE RELATIVISTIC FERMI GAS MODEL

  24. SUPERSCALING ANALYSIS OF INCLUSIVE ELECTRON SCATTERING AND ITS EXTENSION TO CHARGE- AND NEUTRAL-CURRENT NEUTRINO-NUCLEUS SCATTERING BEYOND THE RELATIVISTIC FERMI GAS MODEL • COLLABORATIONS • The Institute of the structure of matter, CSIC, and the Complutense University, Madrid, E-28040 Madrid, Spain (Prof. Elvira Moya de Guerra and • Prof. J.M. Udias); • The University of Sevilla, Spain (Prof. J.A. Caballero) • The University of Torino, Italy (Prof. M.B. Barbaro) • SOME RECENT PUBLICATIONS: • A. N. Antonov, M. V. Ivanov, M. K. Gaidarov, E. Moya de Guerra, • P. Sarriguren, and J. M. Udias, Phys. Rev. C 73, 047302 (2005). • A. N. Antonov, M. V. Ivanov, M. K. Gaidarov, E. Moya de Guerra, J. A. Caballero, M. B. Barbaro, J. M. Udias, and P. Sarriguren, Phys. Rev. C 74, 054603 (2006). • A. N. Antonov, M. V. Ivanov, M. K. Gaidarov, E. Moya de Guerra, • nucl-th/0703003,Phys. Rev. C 75 (April 2007). • The superscaling analysis of inclusive electron scattering from nuclei in the quasielastic and delta-region is extended to calculate and to predict charge-changing neutrino (antineutrino) scattering [(νμ,μ-) and (νμ,μ+)] as well as of neutral current neutrino (antineutrino) scattering [(ν,N) and (ν,N)] on 12C at incident energies from 1 to 2 GeV. The calculations are performed using scaling function f(ψ') obtained in approaches beyond the Relativistic Fermi Gas model and mean-field approximation, such as Coherent Density Fluctuation Model and the Light-Front Dynamics Method. The analyses account for the nucleon-nucleon correlations in nuclei. It is found that the behavior of f(ψ') for ψ'<-1 depends on the particular form of the general power-low asymptotics of the momentum distribution n(k)~1/k4+m at large k. The best agreement with the experimental scaling function found for m≈4.5 gives a link to a corresponding particular behavior of the in medium NN forces around the core: VNN(r) goes to infinity for r→0 as 1/r or softer.

  25. Laboratory of Theoretical Nuclear Physics EFFECTS OF NUCLEON CORRELATIONS ON CHARACTERISTICS OF NUCLEAR STRUCTURE AND REACTIONS MODELS OF COMPLEX DEFORMED NUCLEI, SYMMETRIES AND FINE STRUCTURE OF NUCLEAR SPECTRA

  26. MODELS OF COMPLEX DEFORMED NUCLEI, SYMMETRIES AND FINE STRUCTURE OF NUCLEAR SPECTRA • Collective model approaches are proposed for description of rotation and rotation-vibration motion of nuclei with quadrupole and octupole degrees of freedom. They are applied to study the fine structure of energy spectra, E1, E2, E3 transition probabilities and complex shape deformations in different nuclear regions. COLLABORATIONS D. Bonatsos (Athens), W. Scheid (Giessen), R. Jolos (Dubna) SOME RECENT PUBLICATIONS: N. Minkov, P. Yotov, S. Drenska and W. Scheid, J. Phys. G: Nucl. Part. Phys. 32, 497-509 (2006) N. Minkov, P. Yotov, S. Drenska, W. Scheid, D. Bonatsos, D. Lenis and D. Petrellis, Phys. Rev. C  73, 044315 (2006) N. Minkov, P. Yotov, R. V. Jolos and W. Scheid, J. Phys. G: Nucl. Part. Phys. 34 299-313 (2007)

  27. Coherent quadrupole octupole modes in nuclei • Quadrupole-octupole potential, octupole band levels, B(E1) and B(E2)’s in 152Sm

  28. Laboratory of Theoretical Nuclear Physics EFFECTS OF NUCLEON CORRELATIONS ON CHARACTERISTICS OF NUCLEAR STRUCTURE AND REACTIONS MODELS OF COMPLEX DEFORMED NUCLEI, SYMMETRIES AND FINE STRUCTURE OF NUCLEAR SPECTRA APPLICATION OF THE ALGEBRAIC AND GEOMETRICAL ASPECTS OF DYNAMICAL SYMMETRIES IN THE DESCRIPTION OF CRITICAL PHENOMENA IN THE DEVELOPMENT OF NUCLEAR COLLECTIVITY.

  29. APPLICATION OF THEALGEBRAIC AND GEOMETRICAL ASPECTS OF DYNAMICAL SYMMETRIES IN THE DESCRIPTION OF CRITICAL PHENOMENA IN THE DEVELOPMENT OF NUCLEAR COLLECTIVITY. • The symplectic extensions of the boson and fermion representations of the convenient unitary algebras and their deformations are used to classify the basis states that correspond to different types of experimentally observed collective spectra. In the framework of the so developed dynamical symmetries exact analytic solutions are obtained for the respective Hamiltonians that describe the mixed mode collective spectra, even at the critical points of phase/shape transitions.

  30. COLLABORATIONS • Prof. J.P. Draayer, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA70803 • SOME RECENT PUBLICATIONS: • K. D. Sviratcheva, C. Bahri, A. I. Georgieva, and J. P. Draayer, Physical Significance of q-Deformation and Many-Body Interactions in Nuclei, Phys. Rev. Lett. 93, 152501 (2004). • H. G. Ganev, A. I. Georgieva, and J. P. Draayer, • Six-dimensional Davidson potential as a dynamical symmetry of the symplectic interacting vector boson model, Phys. Rev. C 72, 014314 (2005).

  31. 400 300 n 200 i 1.5 A=56 1 (n, i) 20 1f5/2 2p1/2 2p3/2 1g9/2 0.5 100 15 0 0 10 5 10 5 -10 -5 5 10 15 20 0 N– -100 N+ -200 Sp(4) model and its q-deformed extension Non-negligiblehigher-order many-body interactions (q) in regions of dominant pairing correlations • two-body interactions • common nuclear properties • Two-proton drip line • N=Z irregularities • Pairing gaps • Staggering behavior Local non-linear effects (within individual nucleus) Microscopic description of pairing-governed 0+ states in even A nuclei Smooth dependence on nuclear characteristics

  32. U(2)  U(3) U(6) InteractingVector Boson Model • Application of new dynamical symmetries arising in the symplectic extension of the model for the description of the Negative and possitive parity bands States withfixedL Sp(12,R) Sp(4,R)  SO(3) 6-D Davidson potential O(6)  U(1,1) SUpn(3) O(2)  mixing of collective modes in the heavy even-even nuclei

  33. Thank You For Your Atention

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