Welcome

• Andrea Idini

Room: Sal A

Recent highlights from the BESIII experiment

• Karin Schönning (Uppsala universitet)

Room: Sal A The Beijing Spectrometer (BESIII) at the Beijing Electron-Positron Collider (BEPC-II) is a multi-purpose hadron physics experiment optimized in the tau-charm energy region. Its world-record samples of vector charmonia such as J/Psi, Psi(3686) and Psi(3773), as well as energy scans between 2.0 GeV and 4.95 GeV have opened new avenues in hadron spectroscopy and structure. Furthermore, recently developed experimental techniques combined with the abundant production of strange hyperon-antihyperon pairs have enabled unique tests of fundamental symmetries as well as novel probes of hyperon-nucleon and antihyperon-nucleon interactions. In this talk, I will present recent highlights from the BESIII experiment, with the ambition to reflect its broad and diverse physics potential.

Λ-Λ hyperons: journey towards the understanding of the hyperon-hyperon interactions in neutron stars

• Gandharva Appagere (Stockholms Universitet)

Room: Sal A For the P̄ANDA@HADES collaboration Hyperons, baryons incorporating at least one strange quark in the composite, are the focus of research due to several physics interests. A particularly exciting area is the investigation of interactions between hyperons, which could offer insights into the nature of hyperonization and matter in extreme conditions such as neutron star cores [1]. Hyperons, especially lambda (Λ) hyperons, are expected to appear in the core of neutron stars where the density exceeds nuclear saturation density. Their presence significantly softens the equation of state, affecting the maximum mass and radius of neutron stars leading to a discrepancy between the observation and model based predictions [2]. This study embarks on a comprehensive exploration of Λ-Λ interactions at low relative momenta. As a first step the production cross-section the Λ-Λ hyperon channel, pp → ΛΛK^+ K+, at a proton beam energy of 4.5 GeV (√s = 3.46 GeV) was measured at GSI, using the High Acceptance Di-Electron Spectrometer (HADES) [3, 4]. In this talk I will outline the analysis procedure and present a preliminary result for the production cross section as well as the Λ-Λ relative momentum distribution. [1] D. Chatterjee and I. Vidaña, “Do hyperons exist in the interior of neutron stars?,” The European Physical Journal A, vol. 52, pp. 1–18, 2016. [2] D. Lonardoni, A. Lovato, S. Gandolfi, and F. Pederiva, “Hyperon puzzle: hints from quantum monte carlo calculations,” Physical review letters, vol. 114, no. 9, p. 092301, 2015. [3] G. Agakishiev et al. Eur. Phys. J. A, vol. 41, pp. 243–277, 2009. [4] J. Adamczewski-Musch et al., “Production and electromagnetic decay of hyperons: a feasibility study with hades as a phase-0 experiment at fair,” The European Physical Journal A, vol. 57, pp. 1–21, 2021.

Wavefunctions of deformed nuclei in the collective space

• Erik Kronkvist (Lund University, LTH)
• Filip Agert (Lund University, LTH)

Room: Sal A

Hyperons in neutron stars and mergers Room: Sal A

Advancements in Hyperon Tracking with the PANDA Detector Using Geometric Deep Learning

• Nikolai in der Wiesche (Uppsala University / University of Münster)

Room: Sal A Due to their comparatively long lifetimes, hyperons decay at macroscopic distances from the primary interaction point in particle collider experiments. Because of these displaced decay vertices, the efficient and accurate reconstruction of their daughter particles has remained a long-standing challenge. In a previous work, geometric deep learning was successfully used to reconstruct simulated $\Lambda$ hyperons with part of the straw tube tracker of the PANDA experiment. Building on this work, the project presented here applies the same method to the reconstruction of $\Xi$ hyperons and aims at improving the computational and tracking performance of the software.

Chiral Lagrangians at Higher Orders

• Johan Bijnens

Room: Sal A In recent years new technologies in producing Lagrangians in Effective Field Theory at higher orders have become available. I will present the techniques used and an overview of recent results.

Radiation Detection in the environment and elsewhere - with a salty touch

• Christian Bernhardsson (Lund University, Medical Radiation Physics Malmö)

Room: Sal A

SMRs - What will the impact be on global 3H and  14C emissions?

• Simon Brandt (Lund University)

Room: Sal A

Radiocarbon in Swedish coastal waters

• Kristina Stenström (Lunds universitet)

Room: Sal A

Non-linear time-dependent modelling of heterogeneous nuclear reactors

• Fredrik Öhrlund (Lund University)

Room: Sal A

Theoretical study on physiochemical properties and dispersion of radioactive particles/aerosols and their effect on minimum detectable dose in exposed humans for European Spallation Source releases

• Belikse Ramljak (Lund University)

Room: Sal A The European Spallation Source (ESS) is a neutron facility under construction near Lund, Sweden. The facility will produce neutrons via proton-induced spallation reactions for various scientific applications. Under normal operation, many radionuclides will be produced and contained inside the tungsten target. However, in the scenario of the loss of coolant, it is predicted that these radionuclides can be spread into the ambient environment in the form of aerosol particles, potentially causing internal contamination in exposed workers and members of the public. There is little research into the possible detectability of members of the public contaminated with spallation source products in terms of minimum detectable dose (MDD) and how this quantity varies depending on the measurement conditions. This study aims to examine the variability in MDD caused by the variability in particle physiochemical properties for selected dosimetrically important radionuclides such as 148Gd (pure alpha emitter with a half-life of 84±4 y), 187W, 172Hf, 182Ta and 125I (gamma emitters, with half-lives of 23.7 h, 1.87 y, 114.4 d, and 59.49 d, respectively). Using an in-house Lagrangian dispersion model, we estimated parameters describing particle size distributions and spatial dispersions in a radius of 10 km from the ESS. The corresponding committed effective dose was calculated using gamma-ray spectra simulated with Nucleonica and ICRP's tabulations for occupational intakes of radionuclides. Variations in MDD at various distances from the ESS and over time after the accident were calculated using the Monte Carlo method. This project is part of ongoing efforts to design a methodology for internal contamination assessment from ESS radionuclides.

Developments of neutron-gamma emission tomography for radioactive waste characterization

• Rafael Escudeiro (KTH Royal Institute of Technology)

Room: Sal A The capability to detect and accurately localize special nuclear materials (SNM) or other actinide materials is crucial for various nuclear security and safeguards applications including the management of radioactive waste. The Neutron-Gamma Emission Tomography (NGET) technique enables rapid detection and precise location of fissile materials by correlating the energy and the time of the emitted gamma rays and neutrons emitted from the same fission event using statistical or machine learning approaches. The technique has been developed in a system employing fast organic liquid scintillators (EJ309) detectors featuring fast-timing and neutron-gamma discrimination capabilities and applied to a novel imaging radiation portal monitor system for nuclear security applications and for radioactive waste characterization. NGET detectors of different sizes have been integrated into an automated scanning system for enhanced non-destructive assay of radioactive legacy waste at the Studsvik nuclear decommissioning site. In this system, the NGET imaging modality is combined with additional gamma-ray transmission and high-resolution gamma-ray emission tomography enabling a comprehensive non-destructive characterization station for the Swedish legacy radioactive waste drum inventory. The NGET setup integrated into this advanced radwaste characterization (ARC) station is composed of sixteen cylindrical detectors, eight detectors with 12.7 cm diameter by 12.7 cm height, and eight detectors with 7.62 cm diameter by 7.62 cm height. A characteristic feature of the NGET technique is that it allows imaging with a spatial resolution up to an order of magnitude better than the dimensions of the detector cells. In this work, 252Cf source measurements were performed and compared with Monte Carlo simulations using the GEANT4 code, illustrating the influence of the detector dimensions on the imaging performance.

Teaching advanced courses in a sustainable manner – example from the GRE@T-PIONEeR project

• Christophe Demaziere (Chalmers University of Technology)

Room: Sal A

Modelling fission particle evaporation using TALYS

• Ali Al-Adili (Uppsala University)

Room: Sal A

Local Bayesian mixture of different occupations for nuclear mass predictions

• Melvin Storbacka (KTH Royal Institute of Technology)

Room: Sal A Theoretically modelling ground-state properties across the nuclear chart remains an elusive task. While modern theoretical frameworks can predict nuclear masses with root mean square deviation below 600 keV in comparison to experimental data, recent Bayesian model averaging approaches present statistical frameworks to significantly decrease the rms. These Bayesian approaches also provide information about the relative performance of different models in predicting nuclear masses. In this talk, we discuss local Bayesian Dirichlet mixture of different occupations for shell-model mass predictions. We find that introducing new occupations to the mixture generally decreases the rms, and briefly discuss the connection between occupations and theoretical nuclear charge radii.

The beta-decay properties of N=Z nuclei: Role of neutron-proton pairing and the shell model interpretation

• Priyanka Choudhary (KTH Royal Institute of Technology)

Room: Sal A We have done a systematic beta-decay study of the even-even nuclei A=58,62,66, and 70 into N=Z odd-odd nuclei using the large-scale shell model. It was reported that the enhancement in GT transition strength in 70Br compared to the beta-decay of lighter 62Ge might be an indication of increased neutron-proton pairing correlation. To explore the np correlation in nuclei, we have employed an interaction involving only pairing matrix elements and observed that the GT strength does not necessarily increase with increasing np pairing. We have further compared those results with realistic calculations in the fp and f5/2pg9/2 model space and examined the contribution from different orbitals in the GT strengths. We have also modified the single-particle energies and the T=0 monopole pairing matrix elements of the interaction in order to understand the impact on B(GT).

Modeling of fission-fragment charge and istotopic distributions

• Peter Möller (Lund University)

Room: Sal A

Formation of heavy elements in drift plus diffusion dynamics

• Martin Albertsson (Lund university / Lawrence Berkeley National Laboratory)

Room: Sal A Within the Langevin framework, we investigate the dynamics of the fusion process for production of transfermium elements in reactions with 208Pb target. After the reacting nuclei have made contact, the early dynamical stage is dominated by the dissipation of the initial radial kinetic energy, while the subsequent shape evolution is diffusive. The probability for surmounting the inner barrier and forming a compound system is obtained by simulating the evolution as a Metropolis random walk in a five-dimensional potential-energy landscape.

Inclusive cross-section of deformed 24Mg from the Generator Coordinate Method

• Jennifer Boström (Lund University)

Room: Sal A

NuPeCC Matters

• Dirk Rudolph (Lund University)

Room: Sal A

Exploring nuclear structures with QFS reactions at R3B

• Valerii Panin (GSI, Darmstadt)

Room: Sal A

Characterising a Super Heavy element RECoil detector (SHREC)

• Marwan Mohamed (Lund University)

Room: Sal A A new focal plane detector system for the Berkeley Gas-filled Separator (BGS) was designed, constructed, and tested offline with various α-decay and conversion-electron sources. The detector for SuperHeavy RECoils (SHREC) aims to identify separated recoiling heavy and superheavy nuclei using their implantation signal as well as their correlated radioactive decay paths. Following a characterisation of SHREC with radioactive sources in Lund and Berkeley, the in-beam commissioning was done with the fusion-evaporation reaction 208Pb(48Ca,xn)256-xNo, x=1,2, at two beam energies. The read-out electronics converted the preamplifier signals of SHREC’s 540 detector channels into typically 30-µs long digitised traces. My master thesis aims to optimise SHREC energy resolution with a trace analysis code using the known decay chain of 254No and to verify the present Geant4 version of SHREC. As a second step partially known and possibly new short-lived isomeric states in 254No and 255No will be investigated by searching for electron signals tagging isomeric decay between the implantation and α-decay signals of 254,255No, respectively.

Isomeric yield ratio measurements in the alpha-particle induced fission of Thorium at 32 MeV

• Simone Cannarozzo (Uppsala University)

Room: Sal A The mechanism generating fission fragments’ large angular momenta is still a heavily discussed question in nuclear physics. Since they are not directly measurable, experimentally accessible observables are used to derive the angular momenta using nuclear model codes. One of these observables is the yield ratio between spin isomers produced in a fission reaction. For this reason, twenty-one FF’s isomeric yield ratios were measured for Th(a,f) at 32 MeV, through the phase-imaging ion-cyclotron-resonance (PI-ICR) technique using the JYFLTRAP double Penning trap at the IGISOL-4 facility in Jyväskylä university. This reaction was chosen in order to compare the newly measured IYR with results from earlier 238U(p,f) campaigns and data in the literature involving the thermal n-induced fission of to investigate, e.g., the impact of the initial spin of the compound system on the IYR. Through PI-ICR, isomers are separated with a high mass resolving power, allowing e.g. to resolve the Sn-129 isomeric pair, with a mass difference corresponding to 35 keV. The separated ions are then projected onto a position sensitive detector (MCP). The images produced are then analyzed to calculate the number of ions measured for each state, using angular projection and clustering methods. The measured IYRs are then corrected to account for the MCP efficiency and the decay and feeding effects from eventual precursors in the beam, as the time from extraction to measurement can be comparable to their half-lives. The analysis and results of the measurement campaign will be presented.

Imaging the Nuclear Structure in Ultra-Relativistic Nuclear Collisions

• You Zhou (Niels Bohr Institute)

Room: Sal A

Anomalous B4/2 ratio in the osmium isotopic chain

• Irene Zanon (KTH - Royal Institute of Technology)

Room: Sal A Spectroscopic properties of exotic nuclei are powerful tools to obtain a better insight on the evolution of nuclear structure far from the stability. Mid-shell nuclei are expected to exhibit collective behaviour which is typically reflected in the observation of low excitation energies of the first excited states and high transition probabilities. Moreover, the collectivity is expected to increase with the spin, causing both the $R_{4/2}=E_X(4^+)/E_X(2^+)$ to be higher than 2 and the $B_{4/2} = B(E2;4^+\to 2^+)/B(E2;2^+\to 0^+)$ to be higher than the unit. However, an increasing number of mid-shell nuclei had been found to present a $B_{4/2}<1$. This has already been observed in two neutron-deficient regions, one located close to the $Z=50$ shell closure and one in the rare-earth region, as in the case of Os and W isotopes. In particular, the osmium isotopic chain presents cases both in even-even nuclei, such as $^{168,170}$Os, and one in an even-odd nucleus, $^{169}$Os, where the $B_{4/2}$ ratio has been redefined as $B(E2; 21/2^+ \to 17/2^+) / B(E2; 17/2^+ \to 13/2^+)$. According to theory, this anomaly could only be explained by a change from collective to seniority-like regimes or by phenomena such as shape coexistence. However, none of these explanations can justify the anomalous $B_{4/2}$ ratio in Os isotopes. In this context, lifetime measurements of the excited states of these nuclei can provide a meaningful insight on the structure of the low-lying bands. An experiment aimed at measuring lifetimes in the neutron-deficient rare-earth region was performed at the Accelerator Laboratory of Jyv\"askyl\"a (Finland), using the Jurogam3 array coupled to the RITU spectrometer and the plunger device. The lifetimes were extracted using the Recoil Distance Doppler Shift method. From the measured lifetimes, it was possible to extract the reduced transition probabilities of the low-lying states and the $B_{4/2}$ ratio. The experimental results were then compared to potential energy surface calculations in order to shed light on the influence of the unpaired neutron. In this contribution, a summary of the performed experiment, the new results and the comparison with theory are presented.

Lifetime measurements in odd-mass tellurium

• Ebba Ahlgren Cederlöf (KTH/Uppsala university)

Room: Sal A Reduced transition probabilities B(E2) in even-mass tellurium nuclei, accessible experimentally through lifetime measurements, have long been of particular interest in order to study the effect on collectivity when adding two extra protons outside the closed Z=50 shell of Sn. Historically, the main focus has been on the extreme neutron deficient area, close to the neutron shell closure at N=50. However, recently more eyes have turned towards the midshell region, where the number of valence particles is maximal. New measurements of lifetimes in midshell nuclei Te-116 and Te-118 have given more information on the structure of the ground state band and further helped the understanding of the evolution of collectivity over the isotopic chain. Thus far these lifetime measurements have almost exclusively been restricted to even-mass Te. In the odd-mass Te isotopes, the yrast 23/2-, 19/2- and 15/2- states have been interpreted as due to the coupling of a h11/2 neutron to the 6+, 4+ and 2+ states in the neighboring even-mass isotopes. Thus, odd-mass nuclei may also contain useful information on the structure of the ground state band and the role of the unpaired neutron. In this work, lifetime measurements of low lying states in the neutron h11/2 band of midshell region odd-mass Te have been measured for the first time, using the Recoil Distance Doppler Shift technique and Differential Decay Curve Method in coincidence mode. Preliminary results of the ongoing analysis will be presented.

Closing Remarks

• Andrea Idini

Room: Sal A