11 research outputs found
Collectivity at the prolate-oblate transition : The 2<sup>+</sup> lifetime of <sup>190</sup>W
No full textThe neutron-rich rare isotope 190W is discussed as a candidate for a prolate-oblate transitional nucleus with maximum γ-softness. The collectivity of this isotope is assessed for the first time by the measurement of the reduced E2 transition probability of its first 2+ state to the ground state. The experiment employed the FAst TIming Array (FATIMA), comprised of 36 LaBr3(Ce) scintillators, which was part of the DESPEC setup at GSI, Darmstadt. The 41+ and 21+ states of 190W were populated subsequently to the decay of its 127(12) μs isomeric Jπ=10− state. The mean lifetime of the 21+ state was determined to be τ=274(28) ps, which corresponds to a B(E2;21+→01+) value of 95(10) W.u. The results motivated a revision of previous calculations within an energy-density functional-based interacting boson model-2 approach, yielding E2 transition properties and spectroscopic quadrupole moments for tungsten isotopes. From comparison to theory, the new data suggest that 190W is at the transition from prolate to oblate structure along the W isotopic chain, which had previously been discussed as a nuclear shape-phase transition.</p
Λ-Λ hyperons: the road to estimate the production cross-section in protonproton collisions [Elektronisk resurs]
No full textIn this study, we analyse the - hyperon channel in proton-proton scattering, , with a proton beam energy of GeV using the High Acceptance Di-Electron Spectrometer (HADES) at GSI.The purpose of the study presented here is to measure the production cross-section for the - channel. %at the above beam Kinetic energy. The following measurement will be the first at this energy scale (CoM: GeV).We develop a multi-stage analysis strategy to first determine the acceptance-reconstruction efficiency for the - channel from simulations produced according to phase space.The analysis of data is perforned for three different event selections: inclusive (), semi-exclusive () and the fully exclusive.For each selection, the data is represented by a two-dimensional histogram, where the axes correspond to the invariant mass of the respective candidate. %The same strategy was employed on the experimental data to build a - 2D correlation matrix. The \sloppy{- signal} is determined using a Statistical sideband analysis (SSB) and a Linear least squares (LLS) fit.The inclusive selection provides the most significant - signal.Cross-section values corresponding to the two analyses are calculated as weighted average of the result of the three selections.The production cross-section for - in collisions at GeV is measured \sloppy{to be nb} (one standard deviation uncertainity).</p
Arrhythmic genotypes in dilated cardiomyopathy and risk of advanced heart failure
No full textPublisher Copyright: © The Author(s) 2025. Published by Oxford University Press on behalf of the European Society of Cardiology.Peer reviewe
Competing single-particle and collective states in the low-energy structure of I
No full textTo understand the low-energy structure of the neutron deficient iodine isotopes, lifetimes for the low-lying 9/2+ and 11/2+ positive-parity states in 113I have been measured as τ = 28(4) ps and τ = 3.7(7) ps, respectively. The lifetime for the 11/2− state, which feeds the 9/2+ and 11/2+ states, was remeasured with improved accuracy as τ = 216(7) ps. The reduced transition probability, B(E2) = 32(5) W.u., for the 9/2+ → 5/2+ transition agrees with that calculated within the shell model using a Hamiltonian based on the charge-dependent Bonn nucleon-nucleon interaction. In contrast, the much larger transition probability, B(E2) = 209(39) W.u., measured for the 11/2+ → 7/2+ transition has been interpreted, with the aid of configuration-constrained total Routhian surface calculations, as resulting from a slightly γ -soft rotor with an associated quadrupole deformation of β2 ≈ 0.18. Remarkably similar reduced E1 transition probabilities of 5.5(5) × 10−4 and 4.9(5) × 10−4 W.u. were deduced for the 11/2− → 9/2+ and 11/2− → 11/2+ transitions, respectively, which feed apparently dissimilar but competing structures
First identification of excited states in <sup>78</sup>Zr and implications for isospin nonconserving forces in nuclei
No full textAt a fundamental level, the interactions between protons and protons, protons and neutrons, and neutrons and neutrons are not identical. Such isospin nonconserving interactions emerge when comparing the excitation energy of analog states in =1 triplet nuclei. Here, we extend such an analysis to the =78, =1 triplet system—the heaviest system for which such complete data exists—and find strong disagreement with contemporary theory. This was achieved by pioneering the technique of recoil-− tagging to identify excited states in 78Zr . We also established a 78Zr half-life of 25+17 −8 ms and extended the =1 band in 78Y to =(10+)
Anomalous <sub>4/2</sub> ratio in the yrast band of <sup>167</sup>Os
No full textSeveral instances of anomalously low values of the (2;4+ 1→2+ 1) (2;2+ 1→0+ gs) ratio (4/2)<1 have previously been observed in several nuclei among the highly neutron deficient W-Os-Pt isotopes with even numbers of neutrons and protons. The relatively large number of cases suggests a striking new phenomenon that currently has no theoretical explanation. A clue to its origin might be achieved by comparing the 4/2 ratios in even-even nuclei with the corresponding ratios of transition rates in neighboring odd-mass nuclei. However, until now only one case ( 169 Os ) has been observed with an unusually low corresponding 4/2 ratio, approximately 1 below 1. Electromagnetic transition rates between excited states in the extremely neutron deficient nuclide 167 Os were measured using 15 single-crystal germanium detectors from the jurogam 3 array coupled to the RITU gas-filled separator. The excited states of interest were populated via the 92 Mo ( 78 Kr ,2pn) fusion-evaporation reaction and studied by selecting the rare reaction channel via recoil--decay tagging. The lifetimes of low-lying states were measured using the recoil distance Doppler shift method with the APPA plunger device. From the measured lifetimes in the rotational-like band structure assigned to the 13/2 yrast intruder configuration, the (2;17/2+→13/2+) and (2;21/2+→17/2+) values were deduced, resulting in the ratio (2;21/2+→17/2+) (2;17/2+→13/2+) =0.49(10). The results were compared with previous measurements in the Os isotopic chain and theoretical mean-field calculations, implying that the odd neutron valence particle has limited, if any, influence on the 4/2 values for this particular single-particle configuration
Lifetime measurement of the yrast 2 state in Te
No full textInternational audienceThe electromagnetic transition probabilities of the yrast states in the midshell Te isotopes, two protons above the closed shell at Sn, are of great importance for the understanding of nuclear collectivity in these isotopes and the role played by the neutron-proton interactions and cross-shell excitations. However, the large uncertainty of the experimental data for the midshell nucleus Te and the missing data for Te make it difficult to pin down the general trend of the evolution of transition probabilities as a function of the neutron number. In this work, the lifetime of the yrast state in Te was measured, with the aim of reducing the uncertainty of the previous measurement. The result is ps. In addition, the lifetime of the state was measured to be ps. The experimental transition rates are extracted from the measured lifetimes and compared with systematic large-scale shell-model calculations. The trend of the values in the midshell area is in good agreement with the calculations and the calculated ratio provide evidence for Te as a near perfect harmonic vibrator
Lifetime measurements in the even-even Cd isotopes
No full textInternational audienceBackground: The heaviest Tz=0 doubly-magic nucleus, Sn100, and the neighboring nuclei offer unique opportunities to investigate the properties of nuclear interaction. For instance, the structure of light-Sn nuclei has been shown to be affected by the delicate balance between nuclear-interaction components, such as pairing and quadrupole correlations. From Cd to Te, many common features and phenomena have been observed experimentally along the isotopic chains, leading to theoretical studies devoted to a more general and comprehensive study of the region. In this context, having only two proton holes in the Z=50 shell, the Cd isotopes are expected to present properties similar to those found in the Sn isotopic chain.Purpose: The aim of this work was to measure lifetimes of excited states in neutron-deficient nuclei in the vicinity of Sn100.Methods: The neutron-deficient nuclei in the N≈Z≈50 region were populated using a multinucleon transfer reaction with a Cd106 beam and a Mo92 target. The beamlike products were identified by the VAMOS++ spectrometer, while the γ rays were detected using the AGATA array. Lifetimes of excited states were determined using the recoil distance Doppler-shift method, employing the Cologne differential plunger.Results: Lifetimes of low-lying states were measured in the even-mass Cd102–108 isotopes. In particular, multiple states with excitation energy up to ≈3 MeV, belonging to various bands, were populated in Cd106 via inelastic scattering. The transition strengths corresponding to the measured lifetimes were compared with those resulting from state-of-the-art beyond-mean-field calculations using the symmetry-conserving configuration-mixing approach.Conclusions: Despite the similarities in the electromagnetic properties of the low-lying states, there is a fundamental structural difference between the ground-state bands in the Z=48 and Z=50 isotopes. The comparison between experimental and theoretical results revealed a rotational character of the Cd nuclei, which have prolate-deformed ground states with β2≈0.2. At this deformation Z=48 becomes a closed-shell configuration, which is favored with respect to the spherical one
Lifetime Measurements of Excited States in 172Pt and the Variation of Quadrupole Transition Strength with Angular Momentum
No full textLifetimes of the first excited
2
+
and
4
+
states in the extremely neutron-deficient nuclide
172
Pt
have been measured for the first time using the recoil-distance Doppler shift and recoil-decay tagging techniques. An unusually low value of the ratio
B
(
E
2
:
4
+
1
→
2
+
1
)
/
B
(
E
2
:
2
+
1
→
0
+
gs
)
=
0.55
(
19
)
was found, similar to a handful of other such anomalous cases observed in the entire Segré chart. The observation adds to a cluster of a few extremely neutron-deficient nuclides of the heavy transition metals with neutron numbers
N
≈
90
–
94
featuring the effect. No theoretical model calculations reported to date have been able to explain the anomalously low
B
(
E
2
:
4
+
1
→
2
+
1
)
/
B
(
E
2
:
2
+
1
→
0
+
gs
)
ratios observed in these cases. Such low values cannot, e.g., be explained within the framework of the geometrical collective model or by algebraic approaches within the interacting boson model framework. It is proposed that the group of
B
(
E
2
:
4
+
1
→
2
+
1
)
/
B
(
E
2
:
2
+
1
→
0
+
gs
) ratios in the extremely neutron-deficient even-even W, Os, and Pt nuclei around neutron numbers
N
≈
90
–
94
reveal a quantum phase transition from a seniority-conserving structure to a collective regime as a function of neutron number. Although a system governed by seniority symmetry is the only theoretical framework for which such an effect may naturally occur, the phenomenon is highly unexpected for these nuclei that are not situated near closed shells.peerReviewe
Hyperon signatures in the PANDA experiment at FAIR
No full textWe present a detailed simulation study of the signatures from the sequential decays of the triple-strange pbar p -> Ω+Ω- -> K+ΛbarK- Λ -> K+pbarπ+K-pπ- process in the PANDA central tracking system with focus on hit patterns and precise time measurement. We present a systematic approach for studying physics channels at the detector level and develop input criteria for tracking algorithms and trigger lines. Finally, we study the beam momentum dependence on the reconstruction efficiency for the PANDA detector
