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Publications (10 of 73) Show all publications
Singh, B., Erni, W., Krusche, B., Steinacher, M., Walford, N., Liu, H., . . . Semenov-Tian-Shansky, K. M. (2017). Feasibility study for the measurement of pi N transition distribution amplitudes at (P)over-barANDA in (P)over-barp -> J/psi pi(0). Physical Review D: covering particles, fields, gravitation, and cosmology, 95(3), Article ID 032003.
Open this publication in new window or tab >>Feasibility study for the measurement of pi N transition distribution amplitudes at (P)over-barANDA in (P)over-barp -> J/psi pi(0)
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2017 (English)In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 95, no 3, article id 032003Article in journal (Refereed) Published
Abstract [en]

The exclusive charmonium production process in (P) over barp annihilation with an associated pi 0 meson (p) over barp -> J/psi pi(0) is studied in the framework of QCD collinear factorization. The feasibility of measuring this reaction through the J/psi -> e(+) e(-) decay channel with the AntiProton ANnihilation at DArmstadt ((P) over bar ANDA) experiment is investigated. Simulations on signal reconstruction efficiency as well as the background rejection from various sources including the (P) over barp -> pi(+)pi(-)pi(0) and (p) over barp -> J/psi pi(0)pi(0) reactions are performed with PANDAROOT, the simulation and analysis software framework of the (P) over bar ANDA experiment. It is shown that the measurement can be done at (P) over bar ANDA with significant constraining power under the assumption of an integrated luminosity attainable in four to five months of data taking at the maximum design luminosity.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-204693 (URN)10.1103/PhysRevD.95.032003 (DOI)000393744600003 ()2-s2.0-85021668121 (Scopus ID)
Funder
EU, FP7, Seventh Framework Programme, HP3 GA283286Swedish Research Council
Note

QC 20170602

Available from: 2017-06-02 Created: 2017-06-02 Last updated: 2017-11-29Bibliographically approved
Ralet, D., Bäck, T., Cederwall, B., Doncel, M., Ghazi Moradi, F., Zielinska, M. & et al., . (2017). Lifetime measurement of neutron-rich even-even molybdenum isotopes. Physical Review C: Covering Nuclear Physics, 95(3), Article ID 034320.
Open this publication in new window or tab >>Lifetime measurement of neutron-rich even-even molybdenum isotopes
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2017 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 95, no 3, article id 034320Article in journal (Refereed) Published
Abstract [en]

Background: In the neutron-rich A approximate to 100 mass region, rapid shape changes as a function of nucleon number as well as coexistence of prolate, oblate, and triaxial shapes are predicted by various theoretical models. Lifetime measurements of excited levels in the molybdenum isotopes allow the determination of transitional quadrupole moments, which in turn provides structural information regarding the predicted shape change. Purpose: The present paper reports on the experimental setup, the method that allowed one to measure the lifetimes of excited states in even-even molybdenum isotopes from mass A = 100 up to mass A = 108, and the results that were obtained. Method: The isotopes of interest were populated by secondary knock-out reaction of neutron-rich nuclei separated and identified by the GSI fragment separator at relativistic beam energies and detected by the sensitive PreSPEC-AGATA experimental setup. The latter included the Lund-York-Cologne calorimeter for identification, tracking, and velocity measurement of ejectiles, and AGATA, an array of position sensitive segmented HPGe detectors, used to determine the interaction positions of the gamma ray enabling a precise Doppler correction. The lifetimes were determined with a relativistic version of the Doppler-shift-attenuation method using the systematic shift of the energy after Doppler correction of a gamma-ray transition with a known energy. This relativistic Doppler-shift-attenuation method allowed the determination of mean lifetimes from 2 to 250 ps. Results: Even-even molybdenum isotopes from mass A = 100 to A = 108 were studied. The decays of the low-lying states in the ground-state band were observed. In particular, two mean lifetimes were measured for the first time: tau = 29.7(-9.1)(+11.3) ps for the 4(+) state of Mo-108 and tau = 3.2(-0.7)(+ 0.7) ps for the 6(+) state of Mo-102. Conclusions: The reduced transition strengths B(E2), calculated from lifetimes measured in this experiment, compared to beyond-mean-field calculations, indicate a gradual shape transition in the chain of molybdenum isotopes when going from A = 100 to A = 108 with a maximum reached at N = 64. The transition probabilities decrease for Mo-108 which may be related to its well-pronounced triaxial shape indicated by the calculations.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-207464 (URN)10.1103/PhysRevC.95.034320 (DOI)000399143200002 ()2-s2.0-85016484924 (Scopus ID)
Note

QC 20170519

Available from: 2017-05-19 Created: 2017-05-19 Last updated: 2017-11-29Bibliographically approved
Ertoprak, A., Cederwall, B., Jakobsson, U., Nyako, B. M., Nyberg, J., Davies, P., . . . Xiao, Z. G. (2017). LIFETIME MEASUREMENTS WITH THE DOPPLER SHIFT ATTENUATION METHOD USING A THICK HOMOGENEOUS PRODUCTION TARGET - VERIFICATION OF THE METHOD. Paper presented at Zakopane Conference on Nuclear Physics - Extremes of the Nuclear Landscape, AUG 28-SEP 04, 2016, Zakopane, POLAND. Acta Physica Polonica B, 48(3), 325-329
Open this publication in new window or tab >>LIFETIME MEASUREMENTS WITH THE DOPPLER SHIFT ATTENUATION METHOD USING A THICK HOMOGENEOUS PRODUCTION TARGET - VERIFICATION OF THE METHOD
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2017 (English)In: Acta Physica Polonica B, ISSN 0587-4254, E-ISSN 1509-5770, Vol. 48, no 3, p. 325-329Article in journal (Refereed) Published
Abstract [en]

Doppler Shift Attenuation Method (DSAM) analysis of excited-state lifetimes normally employs thin production targets mounted on a thick stopper foil ("backing") serving to slow down and stop the recoiling nuclei of interest in a well-defined manner. Use of a thick, homogeneous production target leads to a more complex analysis as it results in a substantial decrease in the energy of the incident projectile which traverses the target with an associated change in the production cross section of the residues as a function of penetration depth. Here, a DSAM lifetime analysis using a thick homogeneous target has been verified using the Doppler broadened lineshapes of gamma rays following the decay of highly excited states in the semi-magic (N = 50) nucleus Ru-94. Lifetimes of excited states in the Ru-94 nucleus have been obtained using a modified version of the LINESHAPE package from the Doppler broadened lineshapes resulting from the emission of the gamma rays, while the residual nuclei were slowing down in the thick (6 mg/cm(2)) metallic Ni-58 target. The results have been validated by comparison with a previous measurement using a different (RDDS) technique.

Place, publisher, year, edition, pages
Jagiellonian University Press, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-206296 (URN)10.5506/APhysPolB.48.325 (DOI)000398717500013 ()2-s2.0-85017146840 (Scopus ID)
Conference
Zakopane Conference on Nuclear Physics - Extremes of the Nuclear Landscape, AUG 28-SEP 04, 2016, Zakopane, POLAND
Note

QC 20170508

Available from: 2017-05-08 Created: 2017-05-08 Last updated: 2017-11-09Bibliographically approved
Saygi, B., Joss, D. T., Page, R. D., Grahn, T., Simpson, J., O'Donnell, D., . . . Uusitalo, J. (2017). Reduced transition probabilities along the yrast line in W-166. Physical Review C: Covering Nuclear Physics, 96(2), Article ID 021301.
Open this publication in new window or tab >>Reduced transition probabilities along the yrast line in W-166
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2017 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 96, no 2, article id 021301Article in journal (Refereed) Published
Abstract [en]

Lifetimes of excited states in the yrast band of the neutron-deficient nuclide W-166 have been measured utilizing the DPUNS plunger device at the target position of the JUROGAM II gamma-ray spectrometer in conjunction with the RITU gas-filled separator and the GREAT focal-plane spectrometer. Excited states in W-166 were populated in the Mo-92(Kr-78, 4p) reaction at a bombarding energy of 380 MeV. The measurements reveal a low value for the ratio of reduced transitions probabilities for the lowest-lying transitions B(E2; 4(+)-> 2(+)) / B(E2; 2(+)-> 0(+)) = 0.33(5), compared with the expected ratio for an axially deformed rotor (B-4/2 = 1.43).

Place, publisher, year, edition, pages
American Physical Society, 2017
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-212331 (URN)10.1103/PhysRevC.96.021301 (DOI)000406755100001 ()2-s2.0-85028710771 (Scopus ID)
Note

QC 20170821

Available from: 2017-08-21 Created: 2017-08-21 Last updated: 2017-11-29Bibliographically approved
Doncel, M., Bäck, T., Qi, C., Cullen, D. M., Hodge, D., Cederwall, B., . . . Uusitalo, J. (2017). Spin-dependent evolution of collectivity in Te 112. Physical Review C: Covering Nuclear Physics, 96(5), Article ID 051304.
Open this publication in new window or tab >>Spin-dependent evolution of collectivity in Te 112
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2017 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 96, no 5, article id 051304Article in journal (Refereed) Published
Abstract [en]

The evolution of collectivity with spin along the yrast line in the neutron-deficient nucleus Te112 has been studied by measuring the reduced transition probability of excited states in the yrast band. In particular, the lifetimes of the 4+ and 6+ excited states have been determined by using the recoil distance Doppler-shift method. The results are discussed using both large-scale shell-model and total Routhian surface calculations.

Place, publisher, year, edition, pages
American Physical Society, 2017
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-227137 (URN)10.1103/PhysRevC.96.051304 (DOI)2-s2.0-85036617472 (Scopus ID)
Note

QC 20180518

Available from: 2018-05-18 Created: 2018-05-18 Last updated: 2018-05-18Bibliographically approved
Davies, P. J., Grawe, H., Moschner, K., Blazhev, A., Wadsworth, R., Boutachkov, P., . . . Zhu, Y. (2017). The role of core excitations in the structure and decay of the 16(+) spin-gap isomer in Cd-96. Physics Letters B, 767, 474-479
Open this publication in new window or tab >>The role of core excitations in the structure and decay of the 16(+) spin-gap isomer in Cd-96
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2017 (English)In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 767, p. 474-479Article in journal (Refereed) Published
Abstract [en]

The first evidence for beta-delayed proton emission from the 16(+) spin gap isomer in Cd-96 is presented. The data were obtained from the Rare Isotope Beam Factory, at the RIKEN Nishina Center, using the BigRIPS spectrometer and the EURICA decay station. beta p branching ratios for the ground state and 16(+) isomer have been extracted along with more precise lifetimes for these states and the lifetime for the ground state decay of Cd-95. Large scale shell model (LSSM) calculations have been performed and WKB estimates made for l = 0, 2, 4 proton emission from three resonance-like states in Ag-96, that are populated by the beta decay of the isomer, and the results compared to the new data. The calculations suggest that l = 2 proton emission from the resonance states, which reside similar to 5 MeV above the proton separation energy, dominates the proton decay. The results highlight the importance of core-excited wavefunction components for the 16(+) state.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
beta-decay, beta p-decay, gamma-ray spectroscopy, Half-life, Shell-model, WKB
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-205432 (URN)10.1016/j.physletb.2017.02.013 (DOI)000397861700072 ()2-s2.0-85014733974 (Scopus ID)
Note

QC 20170522

Available from: 2017-05-22 Created: 2017-05-22 Last updated: 2017-06-30Bibliographically approved
Li, H., Cederwall, B., Doncel, M., Bäck, T., Jakobsson, U., Xiao, Z. G. & et al., . (2016). Lifetime measurements in Re-166: Collective versus magnetic rotation. PHYSICAL REVIEW C, 93(3), Article ID 034309.
Open this publication in new window or tab >>Lifetime measurements in Re-166: Collective versus magnetic rotation
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2016 (English)In: PHYSICAL REVIEW C, ISSN 2469-9985, Vol. 93, no 3, article id 034309Article in journal (Refereed) Published
Abstract [en]

Lifetimes of excited states in the neutron-deficient odd-odd nucleus Re-166 have been measured for the first time using the recoil distance Doppler-shift method. The measured lifetime for the (8(-)) state; tau = 480 (80) ps, enabled an assessment of the multipolarities of the gamma rays depopulating this state. Information on electromagnetic transition strengths were deduced for the gamma-ray transitions from the (9(-)), (10(-)), and (11(-)) states, and in the case of the (10(-)) and (11(-)) states limits on the B (M1) and B(E2) strengths were estimated. The results are compared with total Routhian surface predictions and semiclassical calculations. Tilted-axis cranking calculations based on a relativistic mean-field approach (TAC-RMF) have also been performed in order to test the possibility of magnetic rotation in the 166Re nucleus. While the TAC-RMF calculations predict a quadrupole-deformed nuclear shape with similar beta(2) deformation as obtained by using the TRS model, it was found that the experimental electromagnetic transition rates are in better agreement with a collective -rotational description.

Place, publisher, year, edition, pages
American Physical Society, 2016
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-184527 (URN)10.1103/PhysRevC.93.034309 (DOI)000371740600004 ()2-s2.0-84960540453 (Scopus ID)
Funder
Swedish Research Council, 621-2010-3694
Note

QC 20160406

Available from: 2016-04-06 Created: 2016-04-01 Last updated: 2017-06-01Bibliographically approved
Singh, B. P., Bäck, T., Cederwall, B., Semenov-Tian-Shansky, T. & et al., . (2015). Experimental access to Transition Distribution Amplitudes with the PANDA experiment at FAIR. European Physical Journal A, 51(8), Article ID 107.
Open this publication in new window or tab >>Experimental access to Transition Distribution Amplitudes with the PANDA experiment at FAIR
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2015 (English)In: European Physical Journal A, ISSN 1434-6001, E-ISSN 1434-601X, Vol. 51, no 8, article id 107Article in journal (Refereed) Published
Abstract [en]

Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new information on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion (pi N) TDAs from (p) over barp -> e(+)e(-)pi(0) reaction with the future PANDA detector at the FAIR facility. At high center-of-mass energy and high invariant mass squared of the lepton pair q(2), the amplitude of the signal channel (p) over barp -> e(+)e(-)pi(0) admits a QCD factorized description in terms of pi N TDAs and nucleon Distribution Amplitudes (DAs) in the forward aid backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring (p) over barp -> e(+)e(-)pi(0) with the PANDA detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. (p) over barp -> pi(+)pi(-)pi(0) were performed for the center-of-mass energy squared s = 5 GeV2 and s = 10 GeV2, in the kinematic regions 3.0 < q(2) < 4.3 GeV2 and 5 < q(2) < 9 GeV2, respectively, with a neutral pion scattered in the forward or backward cone vertical bar cos theta(pi 0)vertical bar > 0.5 in the proton-antiproton center-of-mass frame. Results of the simulation show that the particle identification capabilities of the PANDA detector will allow to achieve a background rejection factor of 5 . 10(7) (1 . 10(7)) at low (high) q(2) for s = 5 GeV2, and of 1 . 10(8) (6 . 10(6)) at low (high) q(2) for s = 10 GeV2, while keeping the signal reconstruction efficiency at around 40%. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to 2 of integrated luminosity. The cross sections obtained from the simulations are used to show that a test of QCD collinear factorization can be done at the lowest order by measuring scaling laws and angular distributions. The future measurement of the signal channel cross section with PANDA will provide a new test of the perturbative QCD description of a novel class of hard exclusive reactions and will open the possibility of experimentally accessing pi N TDAs.

National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-173920 (URN)10.1140/epja/i2015-15107-y (DOI)000360439700001 ()2-s2.0-84940490717 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20150923

Available from: 2015-09-23 Created: 2015-09-23 Last updated: 2017-12-01Bibliographically approved
Li, H., Doncel, M., Patial, M., Cederwall, B., Bäck, T., Jakobsson, U., . . . Xiao, Z. G. (2015). First identification of rotational band structures in Re-166(75)91. Physical Review C. Nuclear Physics, 92(1), Article ID 014310.
Open this publication in new window or tab >>First identification of rotational band structures in Re-166(75)91
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2015 (English)In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 92, no 1, article id 014310Article in journal (Refereed) Published
Abstract [en]

Excited states in the odd-odd, highly neutron-deficient nucleus Re-166 have been investigated via the Mo-92(Kr-78, 3p1n)Re-166 reaction. Prompt gamma rays were detected by the JUROGAM II. gamma-ray spectrometer, and the recoiling fusion-evaporation products were separated by the recoil ion transport unit (RITU) gas-filled recoil separator and implanted into the Gamma Recoil Electron Alpha Tagging spectrometer located at the RITU focal plane. The tagging and coincidence techniques were applied to identify the gamma-ray transitions in Re-166, revealing two collective, strongly coupled rotational structures, for the first time. The more strongly populated band structure is assigned to the pi h(11/2)[514]9/2(-) circle times vi(13/2)[660]1/2(+) Nilsson configuration, while the weaker structure is assigned to be built on a two-quasiparticle state of mixed pi h(11/2)[514]9/2(-) circle times v[h(9/2)f(7/2)]3/2(-) character. The configuration assignments are based on the electromagnetic characteristics and rotational properties, in comparison with predictions from total Routhian surface and particle-rotor model calculations.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-171888 (URN)10.1103/PhysRevC.92.014310 (DOI)000358021600002 ()
Funder
Swedish Research Council, 621-2010-3694
Available from: 2015-08-14 Created: 2015-08-10 Last updated: 2017-12-04Bibliographically approved
Doncel, M., Bäck, T., Cullen, D. M., Hodge, D., Qi, C., Cederwall, B., . . . Uusitalo, J. (2015). Lifetime measurement of the first excited 2(+) state in Te-112. Physical Review C. Nuclear Physics, 91(6), Article ID 061304.
Open this publication in new window or tab >>Lifetime measurement of the first excited 2(+) state in Te-112
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2015 (English)In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 91, no 6, article id 061304Article in journal (Refereed) Published
Abstract [en]

The lifetime of the 2(+) --> 0(g.s.)(+) transition in the neutron-deficicient nucleus Te-112 has been measured for the first time using the DPUNS plunger and the recoil distance Doppler shift technique. The deduced value for the reduced transition probability is B(E2 :0(g.s.)(+) --> 2(+)) = 0.46 +/- 0.04 e(2)b(2), indicating that there is no unexpected enhancement of the B(E2 :0(g.s.)(+) --> 2(+)) values in Te isotopes below the midshell. The result is compared to and discussed in the framework of large-scale shell-model calculations.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-170961 (URN)10.1103/PhysRevC.91.061304 (DOI)000356659000001 ()
Note

QC 20150713

Available from: 2015-07-13 Created: 2015-07-13 Last updated: 2017-12-04Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-1996-0805

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