DOCSLIB.ORG

A Quantum Monte Carlo Study of Strangeness in Nuclear Structure and Nuclear Astrophysics

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A Quantum Monte Carlo Study of Strangeness in Nuclear Structure and Nuclear Astrophysics UNIVERSITÀ DEGLI STUDI DI TRENTO Facoltà di Scienze Matematiche, Fisiche e Naturali Dipartimento di Fisica Tesi di Dottorato di Ricerca in Fisica Ph.D. Thesis in Physics From Hypernuclei to Hypermatter: a Quantum Monte Carlo Study of Strangeness in Nuclear Structure and Nuclear Astrophysics Supervisor: Candidate: Prof. Francesco Pederiva Diego Lonardoni Dottorato di Ricerca in Fisica, XXVI ciclo Trento, November 8th, 2013 Tutta la materia di cui siamo fatti noi l’hanno costruita le stelle, tutti gli elementi dall’idrogeno all’uranio sono stati fatti nelle reazioni nucleari che avvengono nelle supernove, cioè queste stelle molto più grosse del Sole che alla fine della loro vita esplodono e sparpagliano nello spazio il risultato di tutte le reazioni nucleari avvenute al loro interno. Per cui noi siamo veramente figli delle stelle. Margherita Hack Intervista su Cortocircuito Il computer non è una macchina intelligente che aiuta le persone stupide, anzi, è una macchina stupida che funziona solo nelle mani delle persone intelligenti. Umberto Eco dalla prefazione a Claudio Pozzoli, Come scrivere una tesi di laurea con il personal computer, Rizzoli Contents Introduction xi 1 Strangeness in nuclear systems1 1.1 Hyperons in finite nuclei........................2 1.2 Hyperons in neutron stars.......................6 2 Hamiltonians 15 2.1 Interactions: nucleons......................... 19 2.1.1 Two-body NN potential.................... 19 2.1.2 Three-body NNN potential.................. 21 2.2 Interactions: hyperons and nucleons................. 25 2.2.1 Two-body ΛN potential.................... 25 2.2.2 Three-body ΛNN potential.................. 27 2.2.3 Two-body ΛΛ potential.................... 29 3 Method 31 3.1 Diffusion Monte Carlo......................... 32 3.1.1 Importance Sampling...................... 36 3.1.2 Sign Problem.......................... 38 3.1.3 Spin-isospin degrees of freedom................ 42 3.2 Auxiliary Field Diffusion Monte Carlo................ 44 3.2.1 Propagator for nucleons: σ, σ τ and τ terms....... 45 · 3.2.2 Propagator for neutrons: spin-orbit terms.......... 52 3.2.3 Propagator for neutrons: three-body terms......... 53 3.2.4 Wave functions......................... 55 3.2.5 Propagator for hypernuclear systems............. 61 v vi Table of Contents 4 Results: finite systems 69 4.1 Nuclei.................................. 70 4.2 Single Λ hypernuclei.......................... 77 4.2.1 Hyperon separation energies.................. 77 4.2.2 Single particle densities and radii............... 88 4.3 Double Λ hypernuclei.......................... 93 4.3.1 Hyperon separation energies.................. 93 4.3.2 Single particle densities and radii............... 94 5 Results: infinite systems 97 5.1 Neutron matter............................. 97 5.2 Λ neutron matter............................ 100 5.2.1 Test: fixed Λ fraction..................... 100 5.2.2 Λ threshold density and the equation of state........ 106 5.2.3 Mass-radius relation and the maximum mass........ 114 6 Conclusions 119 A AFDMC wave functions 121 A.1 Derivatives of the wave function: CM corrections.......... 121 A.2 Derivatives of a Slater determinant.................. 124 B ΛN space exchange potential 127 Bibliography 129 Acknowledgements 149 List of Figures i.1 Neutron star structure......................... xi 1.1 Strangeness producing reactions....................3 1.2 Λ hypernuclei accessible via different experimental reactions....4 1.3 Λ hypernuclear chart..........................5 1.4 Hyperon and nucleon chemical potentials...............9 1.5 Neutron star mass-radius relation: Schulze 2011........... 10 1.6 Neutron star mass-radius relation: Massot 2012........... 11 1.7 Neutron star mass-radius relation: Miyatsu 2012.......... 12 1.8 Neutron star mass-radius relation: Bednarek 2012.......... 13 2.1 Two-pion exchange processes in the NNN force........... 22 2.2 Three-pion exchange processes in the NNN force.......... 23 2.3 Short-range contribution in the NNN force............. 24 2.4 Meson exchange processes in the ΛN force.............. 25 2.5 Two-pion exchange processes in the ΛNN force........... 27 4.1 Binding energies: E vs. dτ for 4He, Argonnne V4’......... 72 4.2 Binding energies: E vs. dτ for 4He, Argonnne V6’......... 73 4.3 Binding energies: E vs. mixing parameter for 6He.......... 76 4.4 Λ separation energy vs. A: closed shell hypernuclei......... 80 4.5 Λ separation energy for 5 He vs. W C : 3D plot......... 81 Λ D − P 4.6 Λ separation energy for 5 He vs. W C : 2D plot......... 82 Λ D − P 4.7 Λ separation energy vs. A ....................... 83 2=3 4.8 Λ separation energy vs. A− ..................... 84 4 5 4.9 Single particle densities: N and Λ in He and ΛHe......... 90 4.10 Single particle densities: Λ in hypernuclei for 3 A 91 ...... 91 ≤ ≤ vii viii List of Figures 4 5 6 4.11 Single particle densities: N and Λ in He, ΛHe and ΛΛHe...... 95 5.1 Energy per particle vs. baryon density at fixed Λ fraction..... 103 3 5.2 Pair correlation functions at fixed Λ fraction: ρb = 0:16 fm− ... 104 3 5.3 Pair correlation functions at fixed Λ fraction: ρb = 0:40 fm− ... 105 5.4 YNM and PNM energy difference vs. Λ fraction........... 110 5.5 Hyperon symmetry energy vs. baryon density............ 111 5.6 xΛ(ρb) function and Λ threshold density............... 113 5.7 YNM equation of state......................... 114 5.8 YNM mass-radius relation....................... 116 5.9 YNM mass-central density relation.................. 117 List of Tables 1.1 Nucleon and hyperon properties....................1 2.1 Parameters of the ΛN and ΛNN interaction............. 29 2.2 Parameters of the ΛΛ interaction................... 30 4.1 Binding energies: nuclei, 2 A 1 90 ............... 75 ≤ − ≤ 5 17 4.2 Λ separation energies: ΛN + ΛNN set (I) for ΛHe and ΛO.... 78 4.3 Λ separation energies: Λ hypernuclei, 3 A 91 .......... 85 ≤ ≤ 4.4 Λ separation energies: A = 4 mirror hypernuclei........... 86 4.5 Λ separation energies: effect of the CSB potential.......... 87 4.6 Λ separation energies: effect of the ΛN exchange potential..... 88 4.7 Nucleon and hyperon radii in hypernuclei for 3 A 49 ...... 92 6 ≤ ≤ 4.8 Λ separation energies: ΛΛHe...................... 94 6 4.9 Nucleon and hyperon radii for ΛΛHe................. 94 5.1 Energy per particle: neutron matter................. 99 5.2 Energy per particle: Λ neutron matter................ 102 5.3 Baryon number and Λ fraction.................... 108 5.4 Coefficients of the hyperon symmetry energy fit........... 110 ix x List of Tables Introduction Neutron stars (NS) are among the densest objects in the Universe, with central 3 densities several times larger than the nuclear saturation density ρ0 = 0:16 fm− . As soon as the density significantly exceeds this value, the structure and composi- tion of the NS core become uncertain. Moving from the surface towards the interior of the star, the stellar matter undergoes a number of transitions, Fig. i.1. From electrons and neutron rich ions in the outer envelopes, the composition is supposed to change to the npeµ matter in the outer core, a degenerate gas of neutrons, pro- tons, electrons and muons. At densities larger than 2ρ0 the npeµ assumption can be invalid due to the appearance of new hadronic∼ degrees of freedom or exotic phases. 12 NEUTRON STARS Figure i.1: Schematic structure of a neutron star. Stellar parameters strongly Figuredepend 1.2. onSchematic the equation structure of state of a neutron of the core. star. StellarFigure parameters taken from strongly Ref. [1] depend on the EOS in a neutron star core. Some attempts to extract this informationxi from observations are described in Chapter 9. The atmosphere thickness varies from some ten centimeters in a 6 hot neutron star (with the effective surface temperature Ts 3 10 K) to a 5 ∼ × few millimeters in a cold one (Ts 3 10 K). Very cold or ultramagnetized neutron stars may have a solid or liquid∼ × surface. Neutron star atmospheres have been studied theoretically by many authors (see, e.g., Zavlin & Pavlov 2002 and references therein). Current atmosphere models, especially for neutron stars 6 11 with surface temperatures Ts ! 10 K and strong magnetic fields B " 10 G, are far from being complete. The most serious problems consist in calculating the EOS, ionization equilibrium, and spectral opacity of the atmospheric plasma (Chapters 2 and 4). If the radiation flux is too strong, the radiative force exceeds the gravitational one and makes the atmosphere unstable with respect to a plasma outflow. In a hot nonmagnetized atmosphere, where the radiative force is produced by Thomson scattering, this happens whenever the stellar luminosity L exceeds the Eddington limit 38 1 LEdd =4πcGMmp/σT 1.3 10 (M/M )ergs− , (1.3) ≈ × ! where σT is the Thomson scattering cross section and mp the proton mass. The outer crust (the outer envelope) extends from the atmosphere bottom 11 3 to the layer of the density ρ = ρND 4 10 gcm− . Its thickness is some hundred meters (Chapter 6). Its matter≈ × consists of ions Z and electrons e (Chapters 2 and 3). A very thin surface layer (up to few meters in a hot star) contains a non-degenerate electron gas. In deeper layers the electrons constitute xii Introduction In the pioneering work of 1960 [2], Ambartsumyan and Saakyan reported the first theoretical evidence of hyperons in the core of a NS. Contrary to terrestrial conditions, where hyperons are unstable and decay into nucleons through the weak interaction, the equilibrium conditions in a NS can make the inverse process hap- pen. At densities of the order 2 3ρ0, the nucleon chemical potential is large enough to make the conversion of÷ nucleons into hyperons energetically favorable. This conversion reduces the Fermi pressure exerted by the baryons, and makes the equation of state (EoS) softer. As a consequence, the maximum mass of the star is typically reduced. Nowadays many different approaches of hyperonic matter are available, but there is no general agreement among the predicted results for the EoS and the maximum mass of a NS including hyperons.
Load more

Recommended publications
  • Structure of Hypernuclei in Relativistic Approaches 3
    June21,2021 12:22 WorldScientificBook-9inx6in ch7 page1 Chapter 7 Structure of hypernuclei in relativistic approaches K. Hagino1,2 and J. M. Yao1,3 1Department of Physics, Tohoku University, Sendai 980-8578, Japan 2Research Center for Electron Photon Science, Tohoku University, 1-2-1 Mikamine, Sendai 982-0826, Japan 3 School of Physical Science and Technology, Southwest University, Chongqing 400715, China 7.1 Introduction Hypernuclei consist of neutrons, protons, and one or more hyperons such as Λ, Σ, and Ξ. In Table 7.1, we summarize properties of those hyperons. The most extensively studied hypernuclei are single-Λ hypernuclei, which contain one Λ particle inside ordinary nuclei. Since the first discovery of Λ hypernucleus by Danysz and Pniewski in 1953 [Danysz and Pniewski (1953)] (see also Ref. [Wroblewski (2004)]), more than thirty Λ hypernuclei 3 208 ranging from ΛH up to Λ Pb have been produced. Several properties of hypernuclei, such as the mass number dependence of Λ binding energy, spin- orbit splittings, and electromagnetic transitions, have been revealed using reaction spectroscopy with (K−, π−), (π+,K+), and (e,e′K+) reactions arXiv:1410.7531v1 [nucl-th] 28 Oct 2014 as well as γ-ray spectroscopy [Hashimoto and Tamura (2006a)]. Decay properties of hypernuclei have also been studied [Alberico and Garbarino (2002); Bando et al. (1990)]. An important motivation to study hypernuclei is to extract information on baryon-baryon interactions including the strangeness degrees of freedom. Such information is crucial in order to understand neutron stars, in which hyperons may emerge in the inner part [Vidana (2013); Schaffner-Bielich 1 June21,2021 12:22 WorldScientificBook-9inx6in ch7 page2 2 Book Title (2008)], since the first hyperon to appear may be different depending on the properties of baryon-baryon interaction.
    [Show full text]
  • Pos(STORI11)020 Hyperons
    Production of Ξ− hyperons in the storage ring HESR in PANDA PoS(STORI11)020 Felice Iazzi∗ Politecnico di Torino and INFN-Torino E-mail: [email protected] Riccardo Introzzi Politecnico di Torino and INFN-Torino E-mail: [email protected] Andrea Lavagno Politecnico di Torino and INFN-Torino E-mail: [email protected] Hannan Younis Politecnico di Torino and INFN-Torino E-mail: [email protected] The Ξ− hyperon is the basic tool to produce all systems containing double strangeness. These systems allow to investigate the hyperon-nucleon and hyperon-hyperon strong interaction. More- over the non mesonic decays, in particular the hyperon induced decay of ΛΛ hypernuclei, give information about their weak interaction. In spite of the great interest of these topics, data are scarce at present, due to the difficulty in producing and stopping the short living Ξ− hyperons. The techniques exploited up to now to produce doubly strange systems are here shortly reviewed, toghether with the related physics items. Then the proposal of PANDA Collaboration to use an- tiprotons for the hyperon production and the design of the innovative system of two separated targets is briefly described. Finally the problems arising from the interacion of the solid target, inserted in the ring and the antiproton beam are illustrated and the possible solutions for getting high rates of stopped Ξ−’s are indicated. 8th International Conference on Nuclear Physics at Storage Rings-Stori11, October 9-14, 2011 Laboratori Nazionali di Frascati dell’INFN, Italy ∗Speaker. c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
    [Show full text]
  • Study of Light Hypernuclei by Pionic Decay at Jlab
    Study of Light Hypernuclei by Pionic Decay at JLab M. Christy, C. Keppel, M. Kohl, Liguang Tang (spokesperson), L. Yuan (spokesperson), L. Zhu Department of Physics, Hampton University, VA 23668, U.S.A. N. Grigoryan, S. Knyazyan, A. Margaryan (spokesperson), L. Parlakyan, S. Zhamkochyan, H. Vardanyan Yerevan Physics Institute, 375036 Yerevan, Armenia O. Hashimoto, S.N. Nakamura (spokesperson) Department of Physics, Tohoku University, Sendai, 98-77, Japan P. Baturin, W. Boeglin, P. Markowitz, J. Reinhold (spokesperson) Department of Physics, Florida International University, Miami, FL , U.S.A. P. Bosted, K. de Jager, R. Ent, H. Fenker, D. Gaskell, T. Horn, M. Jones, J. LeRose (spokesperson), G. Smith, W. Vulcan, S.A. Wood Thomas Jefferson National Accelerator Facility, Newport News, VA 23606, USA E. Cisbani, F. Cusanno, S. Frullani, F. Garibaldi (spokesperson), M.L. Magliozzi Istituto Nazionale di Fisica Nucleare, Sezione di Roma, Gr. Coll. Sanita', Viale Regina Elena 299, Rome, Italy Ed.V. Hungerford Department of Physics, University of Houston, Houston, TX 77204, U.S.A. L. Majling Nuclear Physics Institute, Academy of Sciences of the Czech Republic, Prague, Czech Republic B. Gibson Los Alamos National Laboratory, Los Alamos, U.S.A. T. Motoba Laboratory of Physics, Osaka Electro-Comm. University, Osaka, Japan B. Hu, J. Shen, W. Wang, X. Zhang, Y. Zhang Nuclear Physics Institute, Lanzhou University, China D. Androic, M. Furic, T. Petkovic, T. Seva Departments of Physics & Applied Physics, University of Zagreb, Croatia A. Ahmidouch, S. Danagoulian, A. Gasparian Department of Physics, North Carolina A&T State University, Greensboro, NC 27411, U.S.A. G. Niculescu, I.
    [Show full text]
  • 10 May 2008 Hypernucleus Production by A(P, Pk )ΛB Reactions
    + Hypernucleus Production by A(p,pK )ΛB Reactions Hantao Jing1,6, Pengnian Shen5,1,3,4, Huanching Chiang1,2 1Institute of High Energy Physics, Chinese Academy of Sciences, P.O.Box 918(4), Beijing 100049, P.R.China 2South-west University, Chongqing 400715, China 3Department of Physics, Guangxi Normal University, Guilin 541004, China 4Institute of Theoretical Physics, Chinese Academy of Sciences, P.O.Box 2735, P.R.China 5Center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Accelerator, Lanzhou 730000, P.R.China 6Graduate School of the Chinese Academy of Sciences, Beijing 100049, P.R.China Abstract + The Λ-hypernucleus production by A(p,pK )ΛB reactions is investigated within the framework of the distorted wave impulse approximation(DWIA). The amplitude for the elementary process is evaluated in a fully covariant two-nucleon model based on the effec- tive Lagrangian. The reaction cross sections for Λ-hypernucleus productions on 6Li, 12C and 16O targets are calculated. It is found that the distortion effects tend to reduce the cross sections by a factor of 3 10. Various differential cross sections (DCS) and double ∼ differential cross sections (DDCS) are presented. It is shown that for the s wave hy- Λ− pernucleus production, the DCS is decreased with increasing nuclear mass, and the DCS for the p wave hypernucleus production is normally higher than that for the s wave Λ− Λ− hypernucleus production. As a reference, the DDCS with respect to the momenta of the outgoing proton and kaon is also demonstrated. Finally, the missing mass spectra of the inclusive reaction p + A p + K+ + X for 6Li, 12C and 16O targets are presented, from → which the masses of hypernuclei can accurately be extracted.
    [Show full text]
  • The Physics of Hypernuclei
    FEATURES nuclei (with new quantum numbers), in direction ofother exotic nuclear systems (charmed nuclei and so on). The physics of A hypernucleus is generally indicated with the symbol ofthe parent nucleus with the suffix A, indicating that a A particle has replaced a neutron. ~ C means a nuclear system composed of6 hypernuclei protons, 5 neutrons and one A particle. Three events ofdouble hypernucleiwere observed, inwhich 2 nucleons are substitutedby Aldo Zenoni, Universitii di Brescia and INFN Sezione di Pavia, 2 A particles. One example is ,J. He, a system composed of2 pro­ Brescia, Italy tons, 2 neutrons and 2 A particles. Paola Gianotti, INFN Laboratori Nazionali di Frascati, Frascati, The concept ofhypernuclei can be extended to nuclei where a Italy nucleon is replaced by hyperons other than the A one. Experi­ mental evidence was claimed oftheexistence ofE-hypernuclei,in which a nucleon is replaced by a L hyperon. This is rather sur­ ypernuclear physics was born 50 years ago, in 1953, when prising since, in nuclear matter, the L can decay through a strong H the Polish physicists M.Danysz and J. Pniewski [1] observed, interaction process (L + N ~ A + N) givingverylargewidths for in a stack ofphotographic emulsions exposed to cosmic rays at the hypernuclear states, unless a strongsuppression mechanism is around 26 km above the ground, the event shown in Figure 1. A at work. However, the experimental evidence ofthe existence of high energy proton, colliding with a nucleus ofthe emulsion, narrow L-hypernuclei is rather controversial and only the case of breaks it in several fragments forming a star.
    [Show full text]
  • Hyperon-Nucleon Interaction, Hypernuclei & Hyperonic Matter
    Hyperon-nucleon interaction, hypernuclei & hyperonic matter Isaac Vidaña Universidade de Coimbra “Interaction forte dans la matière nucléaire: nouvelles tendaces” Ecole Internationale Joliot-Curie, 27 Sept.- 3 Oct. 2009, Lacanau (France) Plan of the Lecture Introduction & Historical Overview Birth, Life & Death of Hypernuclei Hyperon-Nucleon Interaction Hypernuclear Matter & Neutron Star Properties What is a hyperon ? A hyperon is a baryon made of one , two or three strange quarks Hyperon Quarks I(JP) Mass (MeV) Λ uds 0(1/2+) 1115 Σ+ uus 1(1/2+) 1189 Σ0 uds 1(1/2+) 1193 Σ- dds 1(1/2+) 1197 Ξ0 uss 1/2(1/2+) 1315 Ξ- dss 1/2(1/2+) 1321 Ω- sss 0(3/2+) 1672 What is a hypernucleus ? A hypernucleus is a bound system of nucleons with one or more strange baryons (Λ,Σ,Ξ,Ω- hyperons). H. Bando, PARITY 1, 54 (1986) In a simple single-particle model: protons, neutrons and hyperons are considered distinguishable particles placed in independent effective potential wells in which 12 Pauli exclusion principle is applied. Simple s.p. model of " C ! Since hyperons are distinguishable from nucleons, they are privileged probes to explore states deep inside the nucleus, extending our knowledge of conventional to flavored nuclear physics. ΛΛ Hyperons can change the nuclear nuclear structure. For instance the glue-like role of the Λ hyperon can facilitate the existance of neutron-rich hypernuclei, being a more suitable framework to study matter with extreme n/p ratios as compared to ordinary nuclei. A hypernucleus is a “laboratory” to study hyperon-nucleon (YN) and hyperon-hyperon (YY) interactions.
    [Show full text]
  • Essence of Hypernuclear Physics
    INSTITUTE FOR NUCLEAR STUDY UNIVERSITY OF TOKYO INS-PT-31 Tanashi, Tokyo 188 September, 19 8 2 Japan Essence of Hypernuclear Physics H. BANDO INS-PT-31 September, 19 82 Essence of Hypernuclear Physics* H. BANDO Division of Mathematical Physics, Fukui University, Fukui, Japan *Lecture talk given in December, 19 81 at the Institute for Nuclear Study, Tokyo University Contents §1. Introduction l § 2 . Hyperons and hypernuclei l §3. Hyperon-nucleon interaction -empirical and theoretical- 3 §4. Binding energies of a A particle in hypernuclei 10 §5. (K TT ) hypernuclear production reactions 14 §6. Single particle potential for A in hypernuclei 22 §7. Collective excitations of A-hypernuclei 29 §8. Hypernuclear y spectroscopy 34 § 9 . Z-hypernuclei 37 § 10. E-hypernuclei 41 § 11. Multi-hyper nuclei- 44 §12. Production of multi-hyper nuclei by high energy heavy-ion collisions 54 § 13. Decays of A-hypernuclei 58 §14. Flavour nuclei 64 §15. Concluding remarks 68 §1. Introduction Hypernuclear physics is to investigate the baryon many-body system containing hyperons in addition to nucleons. Recent developments of experiments are disclosing dynamical structures of A- and E-hypernuclei. It is attractive to extend our consideration to H-hypernuclei, multi-hypernuclei, flavour nuclei and so forth. Such extension of this field in future will highly depend on how far the experimental works can go actually. This lecture is to briefly survey the present status of hypernuclear physics so that one can have a gross picture on what have been done and what should be done. §2. Hyperons and hypernuclei Baryons with non-zero strangeness quantum number are generally called hyperons (hereafter denoted as Y), of which the A, E and E particles together with the nucleon (N) constitute the baryon octet (Fig.l) based on the SU(3) classification for the u,d and s quarks.
    [Show full text]
  • Hypernuclei (And Strange Particles) — How It All Began?∗
    Vol. 35 (2004) ACTA PHYSICA POLONICA B No 3 HYPERNUCLEI (AND STRANGE PARTICLES) — HOW IT ALL BEGAN?∗ Andrzej K. Wróblewski Physics Department, Warsaw University Hoża 69, 00-681 Warszawa, Poland e-mail: [email protected] (Received January 20, 2004) The first hypernucleus was discovered in Warsaw in September 1952 by Marian Danysz and Jerzy Pniewski. It happened during a time of con- fusion concerning the newly detected heavy unstable particles. The study of hypernuclei was of considerable help in understanding the properties of strange particles. An account is given of the early history of strange particles and hypernuclear physics. PACS numbers: 01.65.+g Elementary particle physics began in the 1930s as an outgrowth of ex- perimental studies of nuclear and cosmic ray physics. It started to develop rapidly after the discoveries of the pion and the strange particles in 1947. Its beginnings and development have already been documented in a num- ber of books [1–4]. The discovery of hypernuclei has also been described by one of its authors [5]. The present article contains previously unpublished material pertaining to this discovery, and also statistical data on the first decade of hypernuclear physics. The early efforts to understand the nature and properties of new unstable particles set a stage (see Fig. 1) on which hypernuclei appeared and provided an important piece to solve the jigsaw puzzle. ∗ Invited talk presented at the XXVIII Mazurian Lakes School of Physics, Krzyże, Poland, August 31–September 7, 2003 and at the XXXIII International Symposium on Multiparticle Dynamics, Kraków, Poland, September 5–11, 2003.
    [Show full text]
  • A Study of Lambda Hypernuclei Within the Skyrme-Hartree-Fock Model
    A study of Λ hypernuclei within the Skyrme-Hartree-Fock Model Neelam Guleriaa, Shashi K. Dhimana,b, Radhey Shyamc,d aDepartment of Physics, H. P. University, Shimla 171005, India bUniversity Institute of Natural Sciences and Interface Technologies, Himachal Pradesh Technical University, Hamirpur 177001, India cSaha Institute of Nuclear Physics, AF/1, Bidhan Nagar, Kolkata 700064,India dCentre for the Subatomic Structure of Matter (CSSM), School of Chemistry and Physics, University of Adelaide, SA 5005, Australia Abstract We investigate the properties of the single Λ hypernuclei within a Skyrme-Hartree- Fock (SHF) model. The parameters of the Skyrme type effective lambda-nucleon (ΛN) interaction are obtained by fitting to the experimental Λ binding energies of hypernuclei with masses spanning a wide range of the periodic table. Alternative parameter sets are also obtained by omitting nuclei below mass number 16 from the fitting procedure. The SHF calculations are performed for the binding energies of the Λ single-particle states over a full mass range using the best fit parameter sets obtained in these fitting procedures and the results are compared with the available experimental data. The data show some sensitivity to the parameter sets obtained with or without including the nuclei below mass 16. The radii of the Λ orbits in the hypernuclear ground states and the Λ effective mass in nuclear matter show some dependence on different parameter sets. We present results for the total binding energy per baryon of the hypernuclei over a large mass region to elucidate their stability as a function of the baryon number. We have also employed the our best fit ΛN parameter sets to investigate the role of hyperons in some key properties of neutron stars.
    [Show full text]
  • 1. Introduction. Nuclei with a Neutron Halo
    PRODUCTION AND IDENTIFICATION OF THE SUPERHEAVY HYDROGEN HYPERNUCLEUS ~H 1 2 1 1 1 3 3 L. Majling • t, Yu. Batusov , J. Lukstins , A. Parfenov , M. Solar and B. Sopko (1) Joint Institute for Nuclear Research, Dubna, Russia (2) Nuclear Physics Institute, GAS, Rei, Czech Republic (3) Czech Technical University, Prague, Czech Republic t E-mail: [email protected] Abstract The hypernucleus ~H, existence of which has been suggested recently, could be identified unambiguously in experiments with light relativistic hypernuclei prepared for Nuclotron. Key-words: relativistic hypernuclei, exotic nuclei 1. Introduction. Nuclei with a Neutron Halo In the last twenty years a new branch of nuclear physics, namely physics of nuclei in the vicinity of the neutron drip line has been constituted [l]. The dripline is the limit of the nuclear landscape, where additional neutrons can no longer be kept in the nucleus. This dripline has been really reached for light nuclei (Z :::; 6), see Fig. 1. One can see irregularities at the border of neutron stability. There is considerable interest in unbound nuclear systems close to the driplines, both in themselves and as subsystem of Borromean halo nuclei. The term Borromean was coined in ref. [2] to denote a bound three-body system (core + n + n) for which no binary subsystem is bound. In Fig. 1, the /3-stable isotopes are marked by ( E9) and the type of neutron halo is also given. The short range of the nuclear force and the low separation energy of the valence nucleons results, in some cases, in considerable tunneling into the classical forbidden region and more or less pronounced halo may be formed.
    [Show full text]
  • High-Resolution Search for Θ Pentaquark in Π
    Proposal for J-PARC 50 GeV Proton Synchrotron High-resolution Search for Θ+ Pentaquark in π−p K−X Reactions ! M. Naruki (contact person) RIKEN, Japan S. Ishimoto, T. Maruta, Y. Sato, S. Sawada, M. Sekimoto, H. Takahashi, T. Takahashi and A. Toyoda High Energy Accelerator Research Organization (KEK), Japan S. Dairaku, H. Fujimura, K. Imai, K. Miwa, Y. Nakatsugawa, N. Saito and K. Tanida Kyoto University, Japan S. Ajimura Osaka University M. Niiyama Research Center for Nuclear Physics (RCNP), Osaka University, Japan H. Tamura Tohoku University, Japan H.Fujioka, D.Nakajima and T.N.Takahashi University of Tokyo, Japan Abstract We propose an experimental search for the Θ+pentaquark resonance by the p(π−;K−) reaction at the J-PARC K1.8 beamline. This experiment is a natural expansion of KEK-PS E522. Compared to E522, where the same reaction was employed, we will accumulate 100 times more statistics with five times better mass resolution ( 2.5 MeV FWHM) and 2-10 times better S/N ratio. With those improvements∼ combined, the expected sensitivity will be 75 nb/sr for a narrow Θ+ (Γ < 2 MeV), and 150 nb/sr for Γ = 10 MeV. Also, if a Θ+ peak is found, we can determine its width down to 2 MeV. 1 1 Physics Motivation The first report on the evidence of the Θ+ baryon with positive strangeness S = +1 [1] has been immediately supported by several collaborations [2, 3, 4, 5, 6, 7, 8, 9, 10]. However the statistics of all experiments were not sufficient to claim a clear observation and better statistics is needed.
    [Show full text]
  • From "Super-Hypernuclei" to Strange Stars
    EG0600173 21"1 Conference on Nuclear and Particle Physics, 13 -17 Nov. 1999, Cairo, Egypt From "Super-Hypernuclei" to Strange Stars Hidezumi Terazawa Institute of Particle and Nuclear Studies, HEARO (Tanashi) Midori-cho, Tanashi, Tokyo 188-8501, Japan Abstract Both theoretical investigations of and experimental searches for not only super-hypernuclei (or "long lived hyperstrange multiquark droplets", "strangelets ", or "strange quark matter") consisting of roughly equal numbers of up, down, and strange quarks, but also super-hypernuclear matter in bulk (or "quark nuggets" or "strange matter") (in the early Universe or inside neutron stars) and strange stars made of super-hypernuclear matter are reviewed and discussed in some detail. The contents include: I. Introduction II. Quark-Shell Model of Nuclei III. Nuclear Mass Formula in the Quark-Shell Model IV. Mass Spectrum of Super-Hypernuclei V. Charge-to-Mass-Number Ratio of Super-Hypernuclei VI. Super-Hypernuclei or Other Exotic Nuclei in Cosmic Rays VII. Strange Stars in the Universe VIII. Conclusion, Further Discussions, and Future Prospects. 28 I. Introduction A "super-hypernucleus" is a nucleus which consists of many strange quarks as well as up and down quarks. In 1979 [1], I proposed the quark-shell model of nuclei in quantum chromodynamics (QCD) [2], presented the effective two-body potential be- tween quarks in a nucleus, pointed out violent breakdown of isospin-invariance and importance of U-spin invariance in superheavy nuclei, and predicted possible creation of super-hypernuclei in heavy-ion collisions at high energies, based on the natural expectation that not only the Fermi energy but also the Coulomb repulsive energy is reduced in such nuclei.
    [Show full text]