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P. Pawłowski,
J. Brzychczyk,
Y. Leifels,
W. Trautmann,
P. Adrich,
T. Aumann,
C. O. Bacri,
T. Barczyk,
R. Bassini,
S. Bianchin, [......],
K. Sümmerer,
M. B. Tsang,
G. Verde,
M. Veselsky,
C. Volant,
M. Wallace,
H. Weick,
J. Wiechula,
A. Wieloch,
B. Zwiegliński
[show abstract]
[hide abstract]
ABSTRACT: The performance of the LAND neutron detector is studied. Using an
event-mixing technique based on one-neutron data obtained in the S107
experiment at the GSI laboratory, we test the efficiency of various analytic
tools used to determine the multiplicity and kinematic properties of detected
neutrons. A new algorithm developed recently for recognizing neutron showers
from spectator decays in the ALADIN experiment S254 is described in detail. Its
performance is assessed in comparison with other methods. The properties of the
observed neutron events are used to estimate the detection efficiency of LAND
in this experiment.
Nuclear Instruments and Methods in Physics Research A. 03/2012; 694:47.
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R Ogul,
A S Botvina,
U Atav,
N Buyukcizmeci,
I N Mishustin,
P Adrich,
T Aumann,
C O Bacri,
T Barczyk,
R Bassini, [......],
K Suemmerer,
W Trautmann,
M B Tsang,
G Verde,
C Volant,
M Wallace,
H Weick,
J Wiechula,
A Wieloch,
B Zwieglinski
Physical Review C. 01/2012; 85(1).
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A M Rogers,
W G Lynch,
M A Famiano,
M S Wallace,
F Amorini,
D Bazin,
R J Charity,
F Delaunay,
R T de Souza,
J Elson, [......],
S Hudan,
J Lee,
S Lobostov,
S Lukyanov,
M Matoš, M Mocko,
M B Tsang,
D Shapira,
L G Sobotka,
G Verde
[show abstract]
[hide abstract]
ABSTRACT: The first direct measurement of the proton separation energy, Sp, for the proton-unbound nucleus 69Br is reported. Of interest is the exponential dependence of the 2p-capture rate on Sp which can bypass the 68Se waiting-point in the astrophysical rp process. An analysis of the observed proton decay spectrum is given in terms of the 69Se mirror nucleus and the influence of Sp is explored within the context of a single-zone X-ray burst model.
Journal of Physics Conference Series 09/2011; 312(4):042020.
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A M Rogers,
M A Famiano,
W G Lynch,
M S Wallace,
F Amorini,
D Bazin,
R J Charity,
F Delaunay,
R T de Souza,
J Elson, [......],
J Lee,
S Lobastov,
S Lukyanov,
M Matoš, M Mocko,
H Schatz,
D Shapira,
L G Sobotka,
M B Tsang,
G Verde
[show abstract]
[hide abstract]
ABSTRACT: We report on the first direct measurement of the proton separation energy for the proton-unbound nucleus (69)Br. Bypassing the (68)Se waiting point in the rp process is directly related to the 2p-capture rate through (69)Br, which depends exponentially on the proton separation energy. We find a proton separation energy for (69)Br of Sp((69)Br )= -785(-40)(+34) keV; this is less bound compared to previous predictions which have relied on uncertain theoretical calculations. The influence of the extracted proton separation energy on the rp process occurring in type I x-ray bursts is examined within the context of a one-zone burst model.
Physical Review Letters 06/2011; 106(25):252503. · 7.37 Impact Factor
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R. Ogul,
A. S. Botvina,
U. Atav,
N. Buyukcizmeci,
I. N. Mishustin,
P. Adrich,
T. Aumann,
C. O. Bacri,
T. Barczyk,
R. Bassini, [......],
K. Summerer,
W. Trautmann,
M. B. Tsang,
G. Verde,
C. Volant,
M. Wallace,
H. Weick,
J. Wiechula,
A. Wieloch,
B. Zwieglinski
[show abstract]
[hide abstract]
ABSTRACT: The N/Z dependence of projectile fragmentation at relativistic energies has
been studied with the ALADIN forward spectrometer at the GSI Schwerionen
Synchrotron (SIS). Stable and radioactive Sn and La beams with an incident
energy of 600 MeV per nucleon have been used in order to explore a wide range
of isotopic compositions. For the interpretation of the data, calculations with
the statistical multifragmentation model for a properly chosen ensemble of
excited sources were performed. The parameters of the ensemble, representing
the variety of excited spectator nuclei expected in a participant-spectator
scenario, are determined empirically by searching for an optimum reproduction
of the measured fragment-charge distributions and correlations. An overall very
good agreement is obtained. The possible modification of the liquid-drop
parameters of the fragment description in the hot freeze-out environment is
studied, and a significant reduction of the symmetry-term coefficient is found
necessary to reproduce the mean neutron-to-proton ratios /Z and the
isoscaling parameters of Z<=10 fragments. The calculations are, furthermore,
used to address open questions regarding the modification of the surface-term
coefficient at freeze-out, the N/Z dependence of the nuclear caloric curve, and
the isotopic evolution of the spectator system between its formation during the
initial cascade stage of the reaction and its subsequent breakup.
06/2010;
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T. Pietrzak,
P. Adrich,
T. Aumann,
C. O. Bacri,
T. Barczyk,
R. Bassini,
S. Bianchin,
C. Boiano,
A. S. Botvina,
A. Boudard, [......],
K. Summerer,
W. Trautmann,
M. B. Tsang,
G. Verde,
C. Volant,
M. Wallace,
H. Weick,
J. Wiechula,
A. Wieloch,
B. Zwieglinski
[show abstract]
[hide abstract]
ABSTRACT: A phase transition signature associated with cumulants of the largest fragment size distribution has been identified in statistical multifragmentation models and examined in analysis of the ALADIN S254 data on fragmentation of neutron-poor and neutron-rich projectiles. Characteristics of the transition point indicated by this signature are weakly dependent on the A/Z ratio of the fragmenting spectator source. In particular, chemical freeze-out temperatures are estimated within the range 5.9 to 6.5 MeV. The experimental results are well reproduced by the SMM model. Comment: 7 pages, 3 figures, Proceedings of the International Workshop on Multifragmentation and Related Topics (IWM2009), Catania, Italy, November 2009.
03/2010;
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S. Lukyanov, M. Mocko,
L. Andronenko,
M. Andronenko,
D. Bazin,
M. A. Famiano,
A. Gade,
S. P. Lobastov,
W. G. Lynch,
A. M. Rogers,
O. B. Tarasov,
M. B. Tsang,
G. Verde,
M. S. Wallace,
R. G. T. Zegers
[show abstract]
[hide abstract]
ABSTRACT: The fragment production cross sections of secondary neutron-rich beams of 68Ni, 69Cu, and 72Zn isotopes at energies of about 95A MeV have been measured. We compare the measured cross sections to EPAX, an empirical parametrization of fragmentation cross sections. A reasonable agreement of the experimental data and EPAX predictions suggests that an EPAX parametrization used for stable beams seems to be valid for unstable neutron-rich ion beams. EPAX tends to overestimate the yields of neutron-rich isotopes. This problem is amplified when neutron-rich radioactive beams are employed, leading to overly optimistic estimates of the production of neutron-rich isotopes.
Phys. Rev. C. 07/2009; 80(1).
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the ALADiN2000 Collaboration,
W. Trautmann,
P. Adrich,
T. Aumann,
C. O. Bacri,
T. Barczyk,
R. Bassini,
S. Bianchin,
C. Boiano,
A. S. Botvina, [......],
H. Simon,
K. Suemmerer,
M. B. Tsang,
G. Verde,
C. Volant,
M. Wallace,
H. Weick,
J. Wiechula,
A. Wieloch,
B. Zwieglinski
[show abstract]
[hide abstract]
ABSTRACT: Isotopic effects in projectile fragmentation at relativistic energies have been studied with the ALADIN forward spectrometer at SIS. Stable and radioactive Sn and La beams with an incident energy of 600 MeV per nucleon have been used in order to explore a wide range of isotopic compositions. Chemical freeze-out temperatures are found to be nearly invariant with respect to the A/Z ratio of the produced spectator sources, consistent with predictions for expanded systems. Consequences for the proposed interpretation of chemical breakup temperatures as representing the limiting temperatures predicted by microscopic models are discussed. Comment: 7 pages, 4 figures, contribution to proceedings of International School of Nuclear Physics, 30th Course, Heavy-Ion Collisions from the Coulomb Barrier to the Quark-Gluon Plasma, Erice-Sicily: 16 - 24 September 2008
07/2009;
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D Bazin,
R J Charity,
R T de Souza,
M A Famiano,
A Gade,
V Henzl,
D Henzlova,
S Hudan,
J Lee,
S Lukyanov,
W G Lynch,
S McDaniel, M Mocko,
A Obertelli,
A M Rogers,
L G Sobotka,
J R Terry,
J A Tostevin,
M B Tsang,
M S Wallace
[show abstract]
[hide abstract]
ABSTRACT: We report the first detailed study of the relative importance of the stripping and diffraction mechanisms involved in nucleon knockout reactions, by the use of a coincidence measurement of the residue and fast proton following one-proton knockout reactions. The measurements used the S800 spectrograph in combination with the HiRA detector array at the NSCL. Results for the reactions 9Be(9C,8B+X)Y and 9Be(8B,7Be+X)Y are presented and compared with theoretical predictions for the two reaction mechanisms calculated using the eikonal model. The data show a clear distinction between the stripping and diffraction mechanisms and the measured relative proportions are very well reproduced by the reaction theory. This agreement adds support to the results of knockout reaction analyses and their applications to the spectroscopy of rare isotopes.
Physical Review Letters 07/2009; 102(23):232501. · 7.37 Impact Factor
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C Sfienti,
P Adrich,
T Aumann,
C O Bacri,
T Barczyk,
R Bassini,
S Bianchin,
C Boiano,
A S Botvina,
A Boudard, [......],
K Sümmerer,
W Trautmann,
M B Tsang,
G Verde,
C Volant,
M Wallace,
H Weick,
J Wiechula,
A Wieloch,
B Zwiegliński
[show abstract]
[hide abstract]
ABSTRACT: The A/Z dependence of projectile fragmentation at relativistic energies has been studied with the ALADIN forward spectrometer at SIS. A stable beam of (124)Sn and radioactive beams of (124)La and (107)Sn at 600 MeV per nucleon have been used in order to explore a wide range of isotopic compositions. Chemical freeze-out temperatures are found to be nearly invariant with respect to the A/Z of the produced spectator sources, consistent with predictions for expanded systems. Small Coulomb effects (DeltaT approximately 0.6 MeV) appear for residue production near the onset of multifragmentation.
Physical Review Letters 05/2009; 102(15):152701. · 7.37 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The collisions in four different reaction systems using $^{40,48}$Ca and $^{58,64}$Ni isotope beams and a Be target have been simulated using the Heavy Ion Phase Space Exploration and the Antisymmetrized Molecular Dynamics models. The present study mainly focuses on the model predictions for the excitation energies of the hot fragments and the cross sections of the final fragments produced in these reactions. The effects of various factors influencing the final fragment cross sections, such as the choice of the statistical decay code and its parameters have been explored. The predicted fragment cross sections are compared to the projectile fragmentation cross sections measured with the A1900 mass separator. At $E/A=140$ MeV, reaction dynamics can significantly modify the detection efficiencies for the fragments and make them different from the efficiencies applied to the measured data reported in the previous work. The effects of efficiency corrections on the validation of event generator codes are discussed in the context of the two models.
05/2008;
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J. Lukasik,
P. Adrich,
T. Aumann,
C. O. Bacri,
T. Barczyk,
R. Bassini,
S. Bianchin,
C. Boiano,
A. S. Botvina,
A. Boudard, [......],
K. Summerer,
W. Trautmann,
M. B. Tsang,
G. Verde,
C. Volant,
M. Wallace,
H. Weick,
J. Wiechula,
A. Wieloch,
B. Zwieglinski
[show abstract]
[hide abstract]
ABSTRACT: The discriminant-analysis method has been applied to optimize the exotic-beam charge recognition in a projectile fragmentation experiment. The experiment was carried out at the GSI using the fragment separator (FRS) to produce and select the relativistic secondary beams, and the ALADIN setup to measure their fragmentation products following collisions with Sn target nuclei. The beams of neutron poor isotopes around 124La and 107Sn were selected to study the isospin dependence of the limiting temperature of heavy nuclei by comparing with results for stable 124Sn projectiles. A dedicated detector to measure the projectile charge upstream of the reaction target was not used, and alternative methods had to be developed. The presented method, based on the multivariate discriminant analysis, allowed to increase the efficacy of charge recognition up to about 90%, which was about 20% more than achieved with the simple scalar methods. Comment: 6 pages, 7 eps figures, elsart, submitted to Nucl. Instr. and Meth. A
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 03/2008; · 1.21 Impact Factor
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W. Trautmann,
P. Adrich,
T. Aumann,
C. O. Bacri,
T. Barczyk,
R. Bassini,
S. Bianchin,
C. Boiano,
A. S. Botvina,
A. Boudard, [......],
H. Simon,
K. Suemmerer,
M. B. Tsang,
G. Verde,
C. Volant,
M. Wallace,
H. Weick,
J. Wiechula,
A. Wieloch,
B. Zwieglinski
[show abstract]
[hide abstract]
ABSTRACT: The N/Z dependence of projectile fragmentation at relativistic energies has been studied in a recent experiment at the GSI laboratory with the ALADiN forward spectrometer coupled to the LAND neutron detector. Besides a primary beam of 124Sn, also secondary beams of 124La and 107Sn delivered by the FRS fragment separator have been used in order to extend the range of isotopic compositions of the produced spectator sources. With the achieved mass resolution of \Delta A/A \approx 1.5%, lighter isotopes with atomic numbers Z \le 10 are individually resolved. The presently ongoing analyses of the measured isotope yields focus on isoscaling and its relation to the properties of hot fragments at freeze-out and on the derivation of chemical freeze-out temperatures which are found to be independent of the isotopic composition of the studied systems. The latter result is at variance with the predictions for limiting temperatures as obtained with finite-temperature Hartree-Fock calculations.
12/2007;
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M. B. Tsang,
W. G. Lynch,
W. A. Friedman, M. Mocko,
Z. Y. Sun,
N. Aoi,
J. M. Cook,
F. Delaunay,
M. A. Famiano,
H. Hui, [......],
H. Iwasaki,
T. Motobayashi,
M. Niikura,
T. Onishi,
A. M. Rogers,
H. Sakurai,
H. Suzuki,
E. Takeshita,
S. Takeuchi,
M. S. Wallace
[show abstract]
[hide abstract]
ABSTRACT: An exponential dependence of the fragmentation cross section on the average binding energy is observed and reproduced with a statistical model. The observed functional dependence is robust and allows the extraction of binding energies from measured cross sections. From the systematics of Cu isotope cross sections, the binding energies of 76,77,78,79Cu have been extracted. They are 636.94±0.4,647.1±0.4,651.6±0.4, and 657.8±0.5 MeV, respectively. Specifically, the uncertainty of the binding energy of 75Cu is reduced from 980 keV, as listed in the 2003 mass table of Audi, Wapstra, and Thibault to 400 keV. The predicted cross sections of two near drip-line nuclei, 39Na and 40Mg from the fragmentation of 48Ca are discussed.
Phys. Rev. C. 10/2007; 76(4).
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[show abstract]
[hide abstract]
ABSTRACT: A remarkably simple dependence of fragmentation cross-section on average binding energy has been established in experimental data. This dependence was empirically parametrised leading to a very useful formula for extrapolation. We find that the canonical thermodynamic model, which has been used in the past for successful computations of many observables resulting from multifragmentation, reproduces the salient fetures of fragmentation cross-sections of very neutron rich nuclei very well. This helps towards a theoretical understanding of the observed data.
08/2007;
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M. Mocko,
M. B. Tsang,
Z. Y. Sun,
L. Andronenko,
M. Andronenko,
F. Delaunay,
M. Famiano,
W. A. Friedman,
V. Henzl,
D. Henzlova,
H. Hui,
X. D. Liu,
S. Lukyanov,
W. G. Lynch,
A M Rogers,
M S Wallace
[show abstract]
[hide abstract]
ABSTRACT: Using the measured fragmentation cross sections produced from the 48Ca and 64Ni beams at 140 MeV per nucleon on 9Be and 181Ta targets, we find that the cross sections of unmeasured neutron rich nuclei can be extrapolated using a systematic trend involving the average binding energy. The extrapolated cross-sections will be very useful in planning experiments with neutron rich isotopes produced from projectile fragmentation. The proposed method is general and could be applied to other fragmentation systems including those used in other radioactive ion beam facilities.
06/2007;
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M. Mocko,
M. B. Tsang,
Z. Y. Sun,
N. Aoi,
J Cook,
F. Delaunay,
M A Famiano,
H. Hui,
N Imai,
H Iwasaki, [......],
T. Motobayashi,
M. Niikura,
T Onishi,
A M Rogers,
H Sakurai,
A. Stolz,
H Suzuki,
E Takeshita,
S Takeuchi,
M S Wallace
[show abstract]
[hide abstract]
ABSTRACT: We measured fragmentation cross sections produced using the primary beam of $^{86}$Kr at 64 MeV/nucleon on $^9$Be and $^{181}$Ta targets. The cross sections were obtained by integrating the momentum distributions of isotopes with 25<Z<36 measured using the RIPS fragment separator at RIKEN. The cross-section ratios obtained with the $^{181}$Ta and $^{9}$Be targets depend on the fragment masses, contrary to the simple geometrical models. We compared the extracted cross sections to EPAX; an empirical parameterization of fragmentation cross sections. Predictions from current EPAX parameterization severely overestimate the production cross sections of very neutron-rich isotopes. Attempts to obtain another set of EPAX parameters specific to the reaction studied here, to extrapolate the neutron-rich nuclei more accurately have not been very successful, suggesting that accurate predictions of production cross sections of nuclei far from the valley of stability require information of nuclear properties which are not present in EPAX.
06/2007;
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C. Sfienti,
M. De Napoli,
P. Adrich,
T. Aumann,
C.O. Bacri,
T. Barczyk,
R. Bassini,
S. Bianchin,
C. Boiano,
A.S. Botvina, [......],
C. Schwarz,
H. Simon,
K. Sümmerer,
W. Trautmann,
C. Volant,
M. Wallace,
H. Weick,
J. Wiechula,
A. Wieloch,
B. Zwieglinski
[show abstract]
[hide abstract]
ABSTRACT: A systematic study of isotopic effects in the break-up of projectile spectators at relativistic energies has been performed with the ALADiN spectrometer at the GSI laboratory. Searching for signals of criticality in the fragment production we have applied the model-independent universal fluctuations theory already proposed to track criticality signals in multifragmentation to our data. The fluctuation of the largest fragment charge and of the asymmetry of the two and three largest fragments and their bimodal distribution have also been analysed.
Nuclear Physics A. 05/2007; 787:627.
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R J Charity,
S A Komarov,
L G Sobotka,
J Clifford,
D Bazin,
A Gade,
Jenny Lee,
S M Lukyanov,
W G Lynch, M Mocko,
S P Lobastov,
A M Rogers,
A Sanetullaev,
M B Tsang,
M S Wallace,
S Hudan,
C Metelko,
M A Famiano,
A H Wuosmaa,
M J Goethem
[show abstract]
[hide abstract]
ABSTRACT: The breakup of E/A=50 MeV Be-12 fragments following inelastic scattering off of hydrogen and carbon target nuclei has been studied. The breakup channels alpha+He-8, He-6+He-6, t+Li-9, and p+Li-11 were observed. Two doublets at excitation energies of 12.8 and 15.5 MeV were found for the alpha+He-8 channel. A low-energy shoulder in the excitation-energy spectra at 10.2 MeV indicates one or more additional states. This work could not confirm the presence of He-6-He-6 rotational structure reported by Freer [Phys. Rev. C 63, 034301 (2001)], although possible peaks at excitation energies of 13.5 and 14.5 MeV were found for He-6+He-6 decay. Significant structure is observed in the excitation-energy spectrum for p+Li-11 at 25-30 MeV which maybe associated with T=3 analog states.
Physical Review C. 01/2007; 76.
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M. Mocko,
M. B. Tsang,
L. Andronenko,
M. Andronenko,
F. Delaunay,
M. Famiano,
T. Ginter,
V. Henzl,
D. Henzlová,
H. Hua,
S. Lukyanov,
W. G. Lynch,
A. M. Rogers,
M. Steiner,
A. Stolz,
O. Tarasov,
M.-J. van Goethem,
G. Verde,
W. S. Wallace,
A. Zalessov
[show abstract]
[hide abstract]
ABSTRACT: We have measured fragment cross-sections of projectile fragmentation reactions using primary beams of 40Ca, 48Ca, 58Ni, and 64Ni at 140 MeV/nucleon on 9Be and 181Ta targets. The cross-sections were obtained by integrating the momentum distributions of isotopes with Z⩾5 measured in the A1900 fragment separator. We compare the extracted cross-sections to the predictions of the empirical parametrization of fragmentation cross-sections (EPAX).
Phys. Rev. C. 11/2006; 74(5).
