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Träfflista för sökning "WFRF:(Jonson Björn) srt2:(2005-2009);pers:(Alcorta M.)"

Sökning: WFRF:(Jonson Björn) > (2005-2009) > Alcorta M.

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1.
  • Alcorta, M., et al. (författare)
  • Nuclear Structure of C-12 from Break-up Studies in Complete Kinematics
  • 2009
  • Ingår i: Nuclear Structure and Dynamics '09. - 0094-243X. ; 1165, s. 27-30461
  • Konferensbidrag (refereegranskat)abstract
    • A complete kinematics study of the B-10(He-3,p alpha alpha alpha) and B-11(He-3,d alpha alpha alpha) reactions has been performed to study the multi-particle break-up of C-12 resonances above the triple-alpha threshold. Four-particle coincidence detection gives us complete information on the direction and energy of the individual alpha particles from the decay of C-12, allowing us to extract new information on the structure of C-12 which we shall present in this contribution. We have observed gamma de-excitation of the T=1 15.11 MeV resonance using charged particle detectors, and have constructed Dalitz plots of the individual resonances in C-12 using the complete kinematics information of the alpha particles which come from their break-up.
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2.
  • Fynbo, H. O. U., et al. (författare)
  • The β-decay approach for studying 12C
  • 2008
  • Ingår i: Journal of Physics: Conference Series. - 17426588. ; 111:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The β-decays of the mirror nuclei 12B and 12N both populate states in 12C and they are therefore a precious source of information about this nucleus. Due to the selection rules of β-decay only 0+, 1+ and 2+ states are populated. This allows a very clean study of unbound states just above the 3α-threshold with those spin and parities. This probe has been applied in two experiments using two complementary experimental techniques: in the first the three α-particles emitted after β-decay are measured in coincidence in separate detectors using the ISOL method, while in the second method 12B and 12N are implanted in a detector and the summed energy of the three α-particles is measured directly. Preliminary results from the two approaches are presented. © 2008 IOP Publishing Ltd.
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3.
  • Hyldegaard, S., et al. (författare)
  • Precise branching ratios to unbound 12C states from 12N and 12B [beta]-decays
  • 2009
  • Ingår i: Physics Letters B. - 0370-2693. ; 678:5, s. 459-464
  • Tidskriftsartikel (refereegranskat)abstract
    • Two complementary experimental techniques have been used to extract precise branching ratios to unbound states in 12C from 12N and 12B [beta]-decays. In the first the three [alpha]-particles emitted after [beta]-decay are measured in coincidence in separate detectors, while in the second method 12N and 12B are implanted in a detector and the summed energy of the three [alpha]-particles is measured directly. For the narrow states at 7.654 MeV (0+) and 12.71 MeV (1+) the resulting branching ratios are both smaller than previous measurements by a factor of [similar, equals]2. The experimental results are compared to no-core shell model calculations with realistic interactions from chiral perturbation theory, and inclusion of three-nucleon forces is found to give improved agreement.
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4.
  • Hyldegaard, S., et al. (författare)
  • STUDIES OF C-12 USING beta-DECAYS
  • 2008
  • Ingår i: INTERNATIONAL JOURNAL OF MODERN PHYSICS E-NUCLEAR PHYSICS. - 0218-3013. ; 17:10, s. 2182-2187
  • Konferensbidrag (refereegranskat)abstract
    • The nuclear structure of states in C-12 have been a subject of interest for both theory and experiment since the early days of nuclear physics. Many open questions remain, especially concerning the existence and properties of 0(+) and 2(+) states in the triple alpha continuum. A series of experiments have been performed using beta-decay of N-12 and B-12 to probe these states. The latest experiment was performed at KVI using an implantation method, measuring the sum energy of the three alpha-particles directly. Preliminary results from this experiment will be presented.
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5.
  • Kirsebom, O. S., et al. (författare)
  • Observation of gamma-delayed 3 alpha breakup of the 15.11 and 12.71 MeV states in C-12
  • 2009
  • Ingår i: Physics Letters B. - 0370-2693. ; 680:1, s. 44-49
  • Tidskriftsartikel (refereegranskat)abstract
    • The reactions B-10(He-3, p alpha alpha alpha) at 4.9 MeV and B-11(He-3, d alpha alpha alpha) at 8.5 MeV have been used to investigate the gamma decay of states in C-12. By measuring the four-body final state in complete kinematics we are able to detect gamma transitions indirectly. We find gamma transitions from the 15.11 MeV state in C-12 to the 12.71, 11.83, 10.3 and 7.65 MeV states followed by their breakup into three alpha particles. The relative gamma-ray branching ratios obtained are (1.2 +/- 0.3), (0.32 +/- 0.12), (1.4 +/- 0.2) and (4.4 +/- 0.8)%, respectively, with the remaining (92.7 +/- 1.0)% of the gamma decays going to the bound states. We obtain Gamma(alpha)/Gamma = (2.8 +/- 1.2)% for the isospinforbidden alpha decay of the 15.11 MeV state. From the 12.71 MeV state we find gamma transitions to the 10.3 and 7.65 MeV states. The relative gamma-ray branching ratios are (0.9(-0.5)(+0.6)) and (2.6(-1.2)(+1.6))%, respectively, with the remaining (96.6(-1.3)(+1.7))% of the gamma decays going to the bound states. Finally. we discuss the relation between the beta decay of N-12 and B-12 to states in C-12 and the gamma decay of the 15.11 MeV analog in C-12 to the same states. (C) 2009 Elsevier B.V. All rights reserved.
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6.
  • Madurga, M., et al. (författare)
  • Evidence of a new state in Be-11 observed in the Li-11 beta-decay
  • 2009
  • Ingår i: Physics Letters B. - 0370-2693. ; 677:5, s. 255-259
  • Tidskriftsartikel (refereegranskat)abstract
    • Coincidences between charged particles emitted in the beta-decay of Li-11 were observed using highly segmented detectors. The breakup channels involving three particles were Studied in full kinematics allowing for the reconstruction of the excitation energy of the Be-11 states participating in the decay. In particular, the contribution of a previously unobserved state at 16.3 MeV in Be-11 has been identified selecting the alpha + He-7 -> alpha + He-6 + n channel. The angular correlations between the alpha particle and the center of mass of the He-6 + n system favors spin and parity assignment of 3/2(-) for this state as well as for the previously known state at 18 MeV. (C) 2009 Elsevier B.V. All rights reserved.
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7.
  • Madurga, M., et al. (författare)
  • Kinematic identification of the t branch in the decay of 11Li
  • 2009
  • Ingår i: The European Physical Journal A - Hadrons and Nuclei. - 1434-6001. ; 42:3, s. 415-419
  • Tidskriftsartikel (refereegranskat)abstract
    • The -delayed 8 Li + t branch of the 11Li decay was identified via kinematical analysis of the charged particles observed in coincidence. The back-to-back events observed in a narrow angular acceptance were compared to a Monte Carlo simulation. The 8 Li + t sum energy spectrum was fitted assuming that the decay occurs through an intermediate state in 11Be . The resulting energy centroid and full-width half maximum for the intermediate state are 18.35(30)MeV and 1.5(4)MeV, respectively. The -delayed 8 Li + t branching ratio obtained from the coincidence spectrum, BR t = 0.93(8)×10-4 , is in agreement with previous measurements but more precise.
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