GSI Experiments Research Articles

The GosipGUI Framework for Control and Benchmarking of Readout Electronics Front-Ends

The GOSIP (Gigabit Optical Serial Interface Protocol) provides communication via optical fibres between multiple kinds of front-end electronics and the KINPEX PCIe receiver board located in the readout host PC. In recent years a stack of device driver software has been developed to utilize this hardware for several scenarios of data acquisition. On top of this driver foundation, several graphical user interfaces (GUIs) have been created. These GUIs are based on the Qt graphics libraries and are designed in a modular way: All common functionalities, like generic I/O with the front-ends, handling of configuration files, and window settings, are treated by a framework class GosipGUI. In the Qt workspace of such GosipGUI frame, specific sub classes may implement additional windows dedicated to operate different GOSIP front-end modules. These readout modules developed by GSI Experiment Electronics department are for instance FEBEX sampling ADCs, TAMEX FPGA-TDCs, or POLAND QFWs. For each kind of front-end the GUIs allow to monitor specific register contents, to set up the working configuration, and to interactively change parameters like sampling thresholds during data acquisition. The latter is extremely useful when qualifying and tuning the front-ends in the electronics lab or detector cave. Moreover, some of these GosipGUI implementations have been equipped with features for mostly automatic testing of ASICs in a prototype mass production. This has been applied for the APFEL-ASIC component of the PANDA experiment currently under construction, and for the FAIR beam diagnostic readout system POLAND.

Breit–Wigner distribution, quantum beats and GSI Anomaly

The relationship between Breit–Wigner distribution as an underlying basis for decaying unstable quantum systems and GSI experiment(anomaly) has not been addressed properly in the literatures. We show that quantum beats can be obtained using a superposition of two Breit–Wigner distributions. This modified distribution can explain the GSI time anomaly with quantum beats resulting from the existence of two energy levels of the decaying ion.

Calculation of the Coulomb barrier and the level density parameter at the fission saddle point in spallation nuclear reactions

This work studies the compound nucleus’ de-excitation during spallation nuclear reactions, with focus on the behavior of the Coulomb barrier for emission of charged particles and the level density parameter at the fission saddle point, establishing for the first time a relationship between these magnitudes and the level density. This relationship manifests itself through two differential equations explicitly dependent on the excitation energy and the level density parameter of the nucleus after the emission of light particles. These equations were implemented into the CRISP code and used to simulate proton induced spallation reactions on and 238U, respectively, comparing the results with data coming from GSI experiments as well as from other codes and obtaining satisfactory results that confirm the reliability of the new models.

The symmetry energy: Predictions and constraints

After recalling basic phenomenological features of isospin asymmetric nuclear matter, we review predictions for the interaction part of the symmetry energy obtained from different microscopic approaches. The predictions are compared to updated constraints extracted from heavy-ion (HI) reaction observables of a recent GSI experiment. The discussion is extended to the neutron skin thickness in [Formula: see text] and its relation to the density derivative of the symmetry energy. We underline the importance of giving proper consideration to the theoretical uncertainties of microscopic predictions in order to guide phenomenological analyses. In the end, we report briefly on preliminary neutron star calculations based on chiral nuclear forces and outline future plans.

Deexcitation Modes in Spallation Nuclear Reactions

Spallation nuclear reactions in the range of 0.2 to 1.2 GeV are studied using the CRISP code. A new approach for the deexcitation stage of the compound nucleus was introduced. For the calculations of the level densities, this approach is based on the Back-shifted Fermi gas model (BSFG), which takes into account pairing effects and shell corrections, whereas the calculation of the fission barriers were performed by means of the Extended Thomas-Fermi plus Strutinsky Integral (ETFSI) method, which is a high-speed approximation to the Hartree-Fock method with pairing correlations treated as in the usual BCS plus blocking approach. This procedure is more appropriate to calculate level densities for exotic nuclei. Satisfactory results were obtained and compared with experimental data obtained in the GSI experiments. As another important result, we highlight some directions for the development of a qualitatively superior version of the CRISP code with the implementation of more realistic and suitable physical models to be applied in stable and exotic nuclei that participate in the process. This new version of the code includes several substantial changes in the decay of the hot compound nucleus which allow satisfactory agreement with the experimental data and a reduction of the adjustment parameters.

Influence of thenpinteraction on theβdecay of94Pd

We present results from stopped beam rare isotope spectroscopic investigations at the GSI (RISING) experiment based on the detection of gamma-ray transitions following the beta decay of Pd-94. A comparison between the measured low-lying level scheme of Rh-94 and the prediction from shell-model calculations reveals the important roles of the g(7/2) and g(9/2) orbitals in explaining the structural features. The low values of the Gamow-Teller strengths B(GT) can be attributed to the influence of the neutron-proton interaction, which gives rise to an increased seniority mixing for the nuclear states, thereby leading to a fragmentation of the strength to several daughter levels. These results provide further strong indications that Pd-94 resides in the middle of a structural transition region in the Pd isotopes as the N = Z line is approached.

16+Spin-Gap Isomer inCd96

A β-decaying high-spin isomer in (96)Cd, with a half-life T(1/2)=0.29(-0.10)(+0.11) s, has been established in a stopped beam rare isotope spectroscopic investigations at GSI (RISING) experiment. The nuclei were produced using the fragmentation of a primary beam of (124)Xe on a (9)Be target. From the half-life and the observed γ decays in the daughter nucleus, (96)Ag, we conclude that the β-decaying state is the long predicted 16(+) "spin-gap" isomer. Shell-model calculations, using the Gross-Frenkel interaction and the πν(p(1/2),g(9/2)) model space, show that the isoscalar component of the neutron-proton interaction is essential to explain the origin of the isomer. Core excitations across the N=Z=50 gaps and the Gamow-Teller strength, B(GT) distributions have been studied via large-scale shell-model calculations using the πν(g,d,s) model space to compare with the experimental B(GT) value obtained from the half-life of the isomer.

Observation of a new high-spin isomer inPd94

A second gamma-decaying high-spin isomeric state, with a half-life of 197(22) ns, has been identified in the N = Z + 2 nuclide Pd-94 as part of a stopped-beam Rare Isotope Spectroscopic INvestigation at GSI (RISING) experiment. Weisskopf estimates were used to establish a tentative spin/parity of 19(-), corresponding to the maximum possible spin of a negative parity state in the restricted (p(1/2), g(9/2)) model space of empirical shell model calculations. The reproduction of the E3 decay properties of the isomer required an extension of the model space to include the f (5/2) and p(3/2) orbitals using the CD-Bonn potential. This is the first time that such an extension has been required for a high-spin isomer in the vicinity of Sn-100 and reveals the importance of such orbits for understanding the decay properties of high-spin isomers in this region. However, despite the need for the extended model space for the E3 decay, the dominant configuration for the 19(-) state remains (p p(1/2)(-1)g(9/2)(-3))(11)circle times(nu g(9/2)(-2))(8). The half-life of the known, 14(+), isomer was remeasured and yielded a value of 499(13) ns.

Comment on “Time Modulation of theK-Shell Electron Capture Decay Rates of H-like Heavy Ions at GSI Experiments”

A Comment on the Letter by A.N. Ivanov and P. Kienle, Physical Review Letters volume 103, Issue 6, 062502 (2009). The authors of the Letter offer a Reply to experimental data at GSI, the rates of the number of daughter ions, produced by the nuclear K shell electron capture decays of the H-like heavy ions with one electron in the K shell, such as {sup 140}Pr{sup 58+}, {sup 142}Pm{sup 60+}, and {sup 122}I{sup 52+}, are modulated in time with periods T{sub EC} of the order of a few seconds, obeying an A scaling T{sub EX}=A/20 s, where A is the mass number of the mother nuclei, and with amplitudes a{sub d {sup EC}}{approx}0.21. We show that these data can be explained in terms of the interference of two massive neutrino mass eigenstates. The appearance of the interference term is due to overlap of massive neutrino mass eigenstate energies and of the wave functions of the daughter ions in two-body decay channels, caused by the energy and momentum uncertainties introduced by time differential detection of the daughter ions in GSI experiments.

Comment on “Time Modulation of theK-Shell Electron Capture Decay Rates of H-like Heavy Ions at GSI Experiments”

According to GSI experiment Phys.Lett.B 664, 162 (2008), the rate of the daughter ion production by the K-shell electron capture (with neutrino emission) in H-like ions 142Pm, 140Pr and 152I is modulated with a period of 6 to 7 seconds. In PRL 103, 062502, 2009 by Ivanov and Kienle (also by Lipkin}) there is a claim that neutrino oscillations may explain this result. In arXiv:0811.2302 by Lambiase et al a different explanation is suggested which is based on the rotation of electron and nuclear spins. The aim of this Comment is to show why these explanations are not satisfactory and to discuss other possibilities.

On “GSI Oscillations” as Interference of Two Closely Spaced Ground Mass Eigenstates of H-Like Mother Ions

We analyse the hypothesis that the “GSI oscillations” of the K-shell electron capture decay (EC) rates of the H-like heavy ions are caused by quantum beats from a coherent state of two closely spaced ground mass-eigenstates and of decaying H-like heavy ions. We apply this mechanism to the calculation of the -decay rates of the H-like heavy ions and discuss the dynamics of the production of the H-like heavy ions with two closely spaced ground mass-eigenstates at GSI experiments. We show that such a mechanism cannot describe simultaneously the experimental data on both the EC-decay and -decay rates of the H-like heavy ions, measured at GSI.

Time Modulation of theK-Shell Electron Capture Decay Rates of H-like Heavy Ions at GSI Experiments

According to experimental data at GSI, the rates of the number of daughter ions, produced by the nuclear K shell electron capture decays of the H-like heavy ions with one electron in the K shell, such as ;{140}Pr;{58+}, ;{142}Pm;{60+}, and ;{122}I;{52+}, are modulated in time with periods T_{EC} of the order of a few seconds, obeying an A scaling T_{EC} = A/20 s, where A is the mass number of the mother nuclei, and with amplitudes a_{d};{EC} approximately 0.21. We show that these data can be explained in terms of the interference of two massive neutrino mass eigenstates. The appearance of the interference term is due to overlap of massive neutrino mass eigenstate energies and of the wave functions of the daughter ions in two-body decay channels, caused by the energy and momentum uncertainties introduced by time differential detection of the daughter ions in GSI experiments.

Disentangling neutrino oscillations

The theory underlying neutrino oscillations has been described at length in the literature. The neutrino state produced by a weak decay is usually portrayed as a linear superposition of mass eigenstates with, variously, equal energies or equal momenta. We point out that such a description is incorrect, that in fact, the neutrino is entangled with the other particle or particles emerging from the decay. We offer an analysis of oscillation phenomena involving neutrinos (applying equally well to neutral mesons) that takes entanglement into account. Thereby we present a theoretically sound proof of the universal validity of the oscillation formulæ ordinarily used. In so doing, we show that the departures from exponential decay reported by the GSI experiment cannot be attributed to neutrino mixing. Furthermore, we demonstrate that the ‘Mössbauer’ neutrino oscillation experiment proposed by Raghavan, while technically challenging, is correctly and unambiguously describable by means of the usual oscillation formalæ.

Could the GSI decay rate oscillations be observed in a standard electron capture decay experiment?

The electron-capture decay of 180Re has been investigated to search for oscillations in the decay probability as reported from a recent measurement at GSI, Darmstadt. The production period was kept short compared to the reported oscillation period. No such oscillation was observed, indicating that the reported oscillations would not have been observable in a conventional experiment with radioactive atoms in a solid environment but must have to do with the unique conditions in the GSI experiment where hydrogen-like ions are moving independently in a storage ring and decaying directly by a true two-body decay to a long-lived (ground-)state. Our finding could restrict possible theoretical interpretations of the oscillations.

GSI experiments on synthesis and nuclear structure investigations of the heaviest nuclei

Isotopes of elements up to Z = 113 have been synthesized using medium heavy projectiles and target nuclei around doubly magic 208Pb. Synthesis of still heavier elements in reactions of 48Ca projectiles with actinide target nuclei has been reported. To obtain more information about production mechanism of transfermium isotopes nuclear reaction studies including investigations of massive transfer were resumed at SHIP, GSI. Nuclear structure investigations at SHIP have been concentrated so far mainly on systematic investigations of low lying Nilsson levels in odd-mass nuclei. Recently this field has been extended to decay studies of isomeric states in nobelium nuclei at E* > 1 MeV.

The cos2φ asymmetry of Drell–Yan and J/ψ production in unpolarized pp̄ scattering

We investigate the cos2φ azimuthal asymmetry in Drell–Yan and J/ψ production from unpolarized pp̄ scattering at GSI-HESR energies. The contribution to this asymmetry arising from the leading-twist Boer–Mulders function \(h_1^{\perp}\)(x,k T 2), which describes a correlation between the transverse momentum and the transverse spin of quarks in an unpolarized hadron, is explicitly evaluated, and predictions for the GSI-HESR kinematic regime are presented. We show that the cos2φ asymmetry is quite sizable both on the J/ψ peak and in the Drell–Yan continuum region. Therefore these processes may offer experimentally viable access to the Boer–Mulders function in the early unpolarized stage of GSI experiments.

GSI EXPERIMENTS ON SYNTHESIS AND NUCLEAR STRUCTURE INVESTIGATIONS OF HEAVIEST NUCLEI

The method of 'cold' fusion reactions has been applied successfully to synthesize isotopes of elements up to Z =113. However, the cross sections were found to decrease nearly exponential with increasing atomic number. The production of isotopes up to Z =118 using 48 Ca - projectiles and actinide targets was claimed from experiments performed at the Dubna Gasfilled Separator (DGFRS). Attempts to confirm the results from one of the used reactions (48 Ca + 238 U ) have been performed at other laboratories. The results of the different experiments are compared. In order to increase our knowledge on the structure of heaviest nuclei an experimental program on α - γ - decay spectroscopy of transfermium isotopes was started at SHIP, GSI. Results on trends in single particle levels in odd mass einsteinium isotopes as well as on the identification of a (possible) K -isomer in 252 No will be presented.

Origin of Fragments in Multifragmentation Reactions

Using the quantum molecular dynamics approach we have started to analyze the results of the recent INDRA experiments at GSI experiments. For the first time we could identify a midrapidity source in which fragments are formed from a almost identical fraction of projectile and target nucleons. In smaller systems we have not found this source. Nevertheless the fragment spectra at small and large angles are completely determined by the dynamics. We discuss how fragments are formed in the different regions of phase space and what they tell us about the reaction mechanism.

GSI experiments in the region of heaviest elements

In the course of the SHIP experiments aimed to synthesize new elements with atomic numbers , improved decay data on elements Z = (103-109) were also obtained. The presentation of recent results is the subject of this paper.

Chiral symmetry breaking in QED with an external field varying in 3D space and time

We study quantum electrodynamics in an external field of gaussian configuration varying in all four dimensions and find that for certain ranges of the widths there is a non-zero value for 〈 ΨΨ〉 ext . This indication of chiral symmetry breaking in QED via a varying external field configuration which is quite similar to those in the GSI experiments, provides further evidence that the peaks seen in those experiments may be explained by a “new” phase of QED.