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Lv, B. F., Petrache, C. M., Chen, Q. B., Meng, J., Astier, A., Dupon, E., . . . Andreoiu, C. (2019). Chirality of Nd-135 reexamined: Evidence for multiple chiral doublet bands. Physical Review C: Covering Nuclear Physics, 100(2), Article ID 024314.
Open this publication in new window or tab >>Chirality of Nd-135 reexamined: Evidence for multiple chiral doublet bands
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2019 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 100, no 2, article id 024314Article in journal (Refereed) Published
Abstract [en]

One new pair of positive-parity chiral doublet bands have been identified in the odd-A nucleus Nd-135 which together with the previously reported negative-parity chiral doublet bands constitute a third case of multiple chiral doublet (M chi D) bands in the A approximate to 130 mass region. The properties of the M chi D bands are well reproduced by constrained covariant density functional theory and particle rotor model calculations. The newly observed M chi D bands in Nd-135 represents an important milestone in supporting the existence of M chi D in nuclei.

Place, publisher, year, edition, pages
American Physical Society, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-257444 (URN)10.1103/PhysRevC.100.024314 (DOI)000480389500002 ()2-s2.0-85070893337 (Scopus ID)
Note

QC 20190903

Available from: 2019-09-03 Created: 2019-09-03 Last updated: 2019-09-03Bibliographically approved
Petrache, C. M., Frauendorf, S., Lv, B. F., Astier, A., Dupont, E., Guo, S., . . . Andreoiu, C. (2019). Collective rotation of an oblate nucleus at very high spin. Physical Review C: Covering Nuclear Physics, 99(4), Article ID 041301.
Open this publication in new window or tab >>Collective rotation of an oblate nucleus at very high spin
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2019 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 99, no 4, article id 041301Article in journal (Refereed) Published
Abstract [en]

A sequence of nine almost equidistant quadrupole transitions is observed in Nd-137. The sequence represents an extremely regular rotational band that extends to a spin of about 75/2 and an excitation energy of approximate to 4.5 MeV above yrast. Cranked mean-field calculations of the Nilsson-Strutinsky type suggest an oblate shape for the band. They reproduce the observed I(I +1) dependence of the rotational energy whereas predicting a pronounced decrease in the deformation, which is the hallmark of antimagnetic rotation.

Place, publisher, year, edition, pages
American Physical Society, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-249862 (URN)10.1103/PhysRevC.99.041301 (DOI)000462906600001 ()2-s2.0-85064077764 (Scopus ID)
Note

QC 20190426

Available from: 2019-04-26 Created: 2019-04-26 Last updated: 2019-04-26Bibliographically approved
Petrache, C. M., Wyss, R. A., Back, T., Cederwall, B. & Tucholski, A. (2019). Diversity of shapes and rotations in the gamma-soft Ba-130 nucleus: First observation of a t-band in the A=130 mass region. PHYSICS LETTERS B, 795, 241-247
Open this publication in new window or tab >>Diversity of shapes and rotations in the gamma-soft Ba-130 nucleus: First observation of a t-band in the A=130 mass region
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2019 (English)In: PHYSICS LETTERS B, Vol. 795, p. 241-247Article in journal (Refereed) Published
Abstract [en]

Several new bands have been identified in Ba-130, among which there is one with band-head spin 8(+). Its properties are in agreement with the Fermi-aligned nu h(11/2)(2)[523]circle times 9/2(-)[514] Nilsson configuration. This is the first observation of a two-quasiparticle t-band in the A = 130 mass region. The t-band is fed by a dipole band involving two additional h(11/2) protons. The odd-spin partners of the proton and neutron S-bands and the ground-state band at high spins are also newly identified. The observed bands are discussed using several theoretical models, total Routhians surfaces (TRS), tilted axis cranking (TAC), particle rotor model (PRM) and projected shell model (PSM), which strongly suggest the coexistence of prolate and oblate shapes polarized by rotation aligned two-proton and two-neutron configurations, as well as prolate collective rotations around axes with different orientations. With the new results, 130 Ba presents one of the best and most complete sets of collective excitations that a gamma-soft nucleus can manifest at medium and high spins, revealing a diversity of shapes and rotations for the nuclei in the A = 130 mass region.

Place, publisher, year, edition, pages
ELSEVIER, 2019
Keywords
Nuclear structure, Collective rotations, Shape coexistence, Particle rotor model, Projected shell model, Tiltid axis cranking
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-256247 (URN)10.1016/j.physletb.2019.06.040 (DOI)000477924000034 ()2-s2.0-85067816517 (Scopus ID)
Note

QC 20191022

Available from: 2019-10-22 Created: 2019-10-22 Last updated: 2019-10-22Bibliographically approved
Ralet, D., Cederwall, B. & Wieland, O. (2019). Evidence of octupole-phonons at high spin in Pb-207. Physics Letters B, 797, Article ID UNSP 134797.
Open this publication in new window or tab >>Evidence of octupole-phonons at high spin in Pb-207
2019 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 797, article id UNSP 134797Article in journal (Refereed) Published
Abstract [en]

A lifetime measurement of the 19/2(-) state in Pb-207 has been performed using the Recoil Distance Doppler-Shift (RDDS) method. The nuclei of interest were produced in multi-nucleon transfer reactions induced by a Pb-208 beam impinging on a Mo-100 enriched target. The beam-like nuclei were detected and identified in terms of their atomic mass number in the VAMOS++ spectrometer while the prompt gamma rays were detected by the AGATA tracking array. The measured large reduced transition probability B(E3, 19/2(-) -> 13/2(+)) = 40(8) W.u. is the first indication of the octupole phonon at high spin in Pb-207. An analysis in terms of a particle-octupole-vibration coupling model indicates that the measured B(E3) value in Pb-207 is compatible with the contributions from single-phonon and single particle E3 as well as E3 strength arising from the double-octupole-phonon 6(+) state, all adding coherently. A crucial aspect of the coupling model, namely the strong mixing between single-hole and the phonon-hole states, is confirmed in a realistic shell-model calculation. Crown Copyright B.V.

Place, publisher, year, edition, pages
ELSEVIER, 2019
Keywords
AGATA spectrometer, gamma-Ray tracking, VAMOS plus plus spectrometer, Plunger device, Nuclear deformation, Octupole phonon
National Category
Physical Sciences
Research subject
Physics, Atomic, Subatomic and Astrophysics
Identifiers
urn:nbn:se:kth:diva-262773 (URN)10.1016/j.physletb.2019.134797 (DOI)000488071200015 ()2-s2.0-85069864523 (Scopus ID)
Note

QC 20191022

Available from: 2019-10-22 Created: 2019-10-22 Last updated: 2019-11-26Bibliographically approved
Trombetta, D. M., Klintefjord, M., Axell, K. & Cederwall, B. (2019). Fast neutron- and γ-ray coincidence detection for nuclear security and safeguards applications. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 927, 119-124
Open this publication in new window or tab >>Fast neutron- and γ-ray coincidence detection for nuclear security and safeguards applications
2019 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 927, p. 119-124Article in journal (Refereed) Published
Abstract [en]

The use of passive and active interrogation techniques to evaluate materials concerning their content of special nuclear materials (SNM) is fundamental in fields such as nuclear safeguards and security. Detection of fast neutrons and γ rays, which are a characteristic signature of SNM, has several potential advantages compared with the commonly used systems based on thermal and epithermal neutron counters, the most important being the much shorter required coincidence times and the correspondingly reduced rate of background events due to accidental coincidences. Organic scintillators are well suited for this purpose due to their fast timing properties and composition being based on carbon and hydrogen with large elastic scattering cross-sections for fast neutrons. Organic scintillators also have suitable detection efficiency for γ rays and exhibit pulse shape properties which are favorable for distinguishing between neutrons and γ rays. This paper presents experimental results and Monte Carlo simulations for a neutron–neutron and γ-neutron coincidence detection setup for identification and characterization of SNM based on such detectors. The measurements were carried out on different samples of PuO 2 material with varying content of 240 Pu at the Joint Research Center (JRC) of the European Commission, Ispra, Italy. The results demonstrate significant advantages of fast neutron-γ coincidence detection over fast neutron–neutron coincidence counting for certain applications, e.g. for nuclear security systems, even in the presence of moderate amounts of shielding.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Fast neutron and gamma detection, Monte Carlo simulations, Non-destructive analysis (NDA), Nuclear safeguards, Nuclear security, Organic liquid scintillator detector
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-246418 (URN)10.1016/j.nima.2019.01.081 (DOI)000462142700014 ()2-s2.0-85061781911 (Scopus ID)
Note

QC 20190319

Available from: 2019-03-19 Created: 2019-03-19 Last updated: 2019-04-24Bibliographically approved
Qiang, Y. H., Cederwall, B. & Xu, F. R. (2019). Identification of high-K rotation in Ba-130: Testing the consistency of electromagnetic observables. Physical Review C: Covering Nuclear Physics, 99(1), Article ID 014307.
Open this publication in new window or tab >>Identification of high-K rotation in Ba-130: Testing the consistency of electromagnetic observables
2019 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 99, no 1, article id 014307Article in journal (Refereed) Published
Abstract [en]

The band built on the K-pi = 8(-), T-1/2 = 9.4 ms isomer of( 130)Ba has been identified, filling the gap in the systematics of the dipole bands built on the 8(- )isomers in the N = 74 isotones from( 128)Xe to Gd-138. The use of the GALILEO array in conjunction with its ancillaries EUCLIDES and Neutron Wall, helped to firmly place the newly identified transitions on top of the long-lived isomer. The extracted g(K)and g(R) gyromagnetic factors are in agreement with the 7/2(+)[404] circle times 9/2(-)[514] two-neutron Nilsson configuration. Particle-rotor model calculations give an understanding of the limited degree of K mixing. The experimental information on the K-pi = 8(-) isomer of Ba-130 is now the most complete among the K isomers of the N = 74 isotones.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-242243 (URN)10.1103/PhysRevC.99.014307 (DOI)000455164000003 ()2-s2.0-85059834023 (Scopus ID)
Note

QC 20190129

Available from: 2019-01-29 Created: 2019-01-29 Last updated: 2019-08-06Bibliographically approved
Boso, A., Cederwall, B. & Wieland, O. (2019). Isospin dependence of electromagnetic transition strengths among an isobaric triplet. Physics Letters B, 797, Article ID UNSP 134835.
Open this publication in new window or tab >>Isospin dependence of electromagnetic transition strengths among an isobaric triplet
2019 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 797, article id UNSP 134835Article in journal (Refereed) Published
Abstract [en]

Electric quadrupole matrix elements, M-p, for the J(pi) = 2(+) -> 0(+), Delta T = 0, T = 1 transitions across the A = 46 isobaric multiplet Cr-46-V-46-Ti-46 have been measured at GSI with the FRS-LYCCA-AGATA setup. This allows direct insight into the isospin purity of the states of interest by testing the linearity of M-p with respect to T-z. Pairs of nuclei in the T = 1 triplet were studied using identical reaction mechanisms in order to control systematic errors. The M-p values were obtained with two different methodologies: (i) a relativistic Coulomb excitation experiment was performed for Cr-46 and Ti-46; (ii) a "stretched target" technique was adopted here, for the first time, for lifetime measurements in V-46 and Ti-46. A constant value of M-p across the triplet has been observed. Shell-model calculations performed within the fp shell fail to reproduce this unexpected trend, pointing towards the need of a wider valence space. This result is confirmed by the good agreement with experimental data achieved with an interaction which allows excitations from the underlying sd shell. A test of the linearity rule for all published data on complete T = 1 isospin triplets is presented.

Place, publisher, year, edition, pages
ELSEVIER, 2019
National Category
Physical Sciences
Research subject
Physics, Nuclear Engineering
Identifiers
urn:nbn:se:kth:diva-262774 (URN)10.1016/j.physletb.2019.134835 (DOI)000488071200023 ()2-s2.0-85070683080 (Scopus ID)
Note

QC 20191022

Available from: 2019-10-22 Created: 2019-10-22 Last updated: 2019-11-26Bibliographically approved
Barucca, G., Davi, F., Lancioni, G., Mengucci, P., Montalto, L., Natali, P. P., . . . Zmeskal, J. (2019). Precision resonance energy scans with the PANDA experiment at FAIR: Sensitivity study for width and line shape measurements of the X(3872). European Physical Journal A, 55(3), Article ID 42.
Open this publication in new window or tab >>Precision resonance energy scans with the PANDA experiment at FAIR: Sensitivity study for width and line shape measurements of the X(3872)
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2019 (English)In: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 55, no 3, article id 42Article in journal (Refereed) Published
Abstract [en]

.This paper summarises a comprehensive Monte Carlo simulation study for precision resonance energy scan measurements. Apart from the proof of principle for natural width and line shape measurements of very narrow resonances with PANDA, the achievable sensitivities are quantified for the concrete example of the charmonium-like X(3872) state discussed to be exotic, and for a larger parameter space of various assumed signal cross-sections, input widths and luminosity combinations. PANDA is the only experiment that will be able to perform precision resonance energy scans of such narrow states with quantum numbers of spin and parities that differ from JPC=1--.

Place, publisher, year, edition, pages
Springer, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-249877 (URN)10.1140/epja/i2019-12718-2 (DOI)000462672600001 ()2-s2.0-85063462704 (Scopus ID)
Note

QC 20190503

Available from: 2019-05-03 Created: 2019-05-03 Last updated: 2019-05-03Bibliographically approved
B Singh, ., Bäck, T., Cederwall, B., Zmeskal, J. & et al., . (2019). Technical design report for the (P)over-barANDA Barrel DIRC detector. JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS (4)
Open this publication in new window or tab >>Technical design report for the (P)over-barANDA Barrel DIRC detector
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2019 (English)In: JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS, no 4Article in journal (Refereed) Published
Abstract [en]

The (P) over bar ANDA (anti-Proton ANnihiliation at DArmstadt) experiment will be one of the four flagship experiments at the new international accelerator complex FAIR (Facility for Antiproton and Ion Research) in Darmstadt, Germany. (P) over bar ANDA will address fundamental questions of hadron physics and quantum chromodynamics using high-intensity cooled antiproton beams with momenta between 1.5 and 15 GeV/c and a design luminosity of up to 2 x 10(32) cm(-2) S-1. Excellent particle identification (PID) is crucial to the success of the (P) over bar ANDA physics program. Hadronic PID in the barrel region of the target spectrometer will be performed by a fast and compact Cherenkov counter using the detection of internally reflected Cherenkov light (DIRC) technology. It is designed to cover the polar angle range from 22 degrees to 140 degrees and will provide at least 3 standard deviations (s.d.) pi/K separation up to 3.5 GeV/c, matching the expected upper limit of the final state kaon momentum distribution from simulation. This documents describes the technical design and the expected performance of the (P) over bar ANDA Barrel DIRC detector. The design is based on the successful BaBar DIRC with several key improvements. The performance and system cost were optimized in detailed detector simulations and validated with full system prototypes using particle beams at GSI and CERN. The final design meets or exceeds the PID goal of clean pi/K separation with at least 3 s.d. over the entire phase space of charged kaons in the Barrel DIRC.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2019
Keywords
particle identification; ring imaging Cherenkov detector; DIRC counter; PANDA experiment; hadron physics
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-247986 (URN)10.1088/1361-6471/aade3d (DOI)000460153900001 ()
Note

QC 20190401

Available from: 2019-04-01 Created: 2019-04-01 Last updated: 2019-04-01Bibliographically approved
Petrache, C. M., Lv, B. F., Astier, A., Dupont, E., Wang, Y. K., Zhang, S. Q., . . . Andreoiu, C. (2018). Evidence of chiral bands in even-even nuclei. Physical Review C: Covering Nuclear Physics, 97(4), Article ID 041304.
Open this publication in new window or tab >>Evidence of chiral bands in even-even nuclei
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2018 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 97, no 4, article id 041304Article in journal (Refereed) Published
Abstract [en]

Evidence for chiral doublet bands has been observed for the first time in the even-even nucleus Nd136. One chiral band was firmly established. Four other candidates for chiral bands were also identified, which can contribute to the realization of the multiple pairs of chiral doublet bands (MχD) phenomenon. The observed bands are investigated by the constrained and tilted axis cranking covariant density functional theory (TAC-CDFT). Possible configurations have been explored. The experimental energy spectra, angular momenta, and B(M1)/B(E2) values for the assigned configurations are globally reproduced by TAC-CDFT. Calculated results support the chiral interpretation of the observed bands, which correspond to shapes with maximum triaxiality induced by different multiquasiparticle configurations in Nd136.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-229638 (URN)10.1103/PhysRevC.97.041304 (DOI)000431992700001 ()2-s2.0-85046626065 (Scopus ID)
Funder
Swedish Research Council, 621-2014-5558EU, FP7, Seventh Framework Programme, 262010 (ENSAR)
Note

QC 20180605

Available from: 2018-06-05 Created: 2018-06-05 Last updated: 2018-06-05Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-1771-2656

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