BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Evolution of the neutron 1d spin-orbit splitting in $^{35}$S and $^{39}$Ca DTSTART;VALUE=DATE-TIME:20231129T085500Z DTEND;VALUE=DATE-TIME:20231129T091000Z DTSTAMP;VALUE=DATE-TIME:20260811T114242Z UID:indico-contribution-470-3373@indico.tlabs.ac.za DESCRIPTION:Speakers: Sandile Jongile (iThemba LABS)\nNuclei along N=20 pr ovide an excellent region to investigate the change in nuclear structure a nd interactions. From their evolution from the doubly magic nucleus $^{40} $Ca through to the Z=16 and Z=14 nuclei $^{36}$S and $^{34}$Si\, respectiv ely\, to $^{32}$Mg with a deformed $2p-2h$ intruder ground state [1]. The mechanism responsible for the change in shell structure is not well unders tood and is suspected to be a subtle combination of the different componen ts of the nuclear force namely the central\, spin-orbit (SO)\, and tensor parts. A significant reduction of the neutron $d_{5/2}$ and $d_{3/2}$ spi n-orbit splitting between $^{40}$Ca and $^{36}$S\, as protons are removed from the $d_{3/2}$ orbital\, would be indicative of the proton-neutron ten sor force. By comparing the neutron $d_{5/2}$ hole strength between these nuclei\, the strength of the tensor force is probed in an unprecedented ma nner. The centroids of the hole states in $^{35}$S have been inferred from a $^{36}$S(p\,d)$^{35}$S experiment performed at iThemba LABS. A $^{36} $S(p\,d)$^{35}$S reaction is a useful tool to probe the neutron spin-orbit splitting in $^{36}$S\, provided a reliable $^{36}$S target is available. This was achieved by specifically developing a new target system at iThem ba LABS which allows for a cost-effective $^{36}$S target without heavy co ntaminants. This novel target encapsulates sulfur between two Mylar foils and has been shown to be an effective way to produce targets with a signif icant amount of material (0.5-1 mg/cm$^2$). Using this moving $^{36}$S tar get with 66 MeV incident protons states in $^{35}$S were measured with the K600 magnetic spectrometer at iThemba LABS. States up to 20 MeV were obse rved\\\, identifying the neutron single-particle strength below and above the Fermi surface using the detection of the deuterons at the focal plane of the K600 spectrometer with an energy resolution of approximately 30 keV [2]. The results from the $^{36}$S(p\,d)$^{35}$S experiment were compared to the $^{40}$Ca(p\,d)$^{39}$Ca study by Matoba *et al.* [3]. The results show an increase of the neutron $1d_{5/2}$ - $1d_{3/2}$ SO splitting bet ween $^{35}$S and $^{39}$Ca by 0.411 MeV. This is contrary to the univers al trend of SO splitting with increasing mass number which would predict a decrease of ~0.450 MeV. This deviation is highly indicative of the effect of tensor forces. At present\, the tensor force is not implemented in the vast majority of the available mean field and relativistic mean field cal culations\, whereby the amplitude of the SO splitting is solely attributed to the spin-orbit force. This study provides an unambiguous result indica ting the role of the tensor force. It is shown that the strength of the te nsor force is\, however\, lower than predicted by the shell model and ab-i nitio theory.\n[1] O. Sorlin and M.-G. Porquet\, Prog in Particle and Nucl ear \n Physics 61\,602 (2008)\, ISSN 0146-6410 \n[2] R. Neveling\, H. Fuji ta\,*et. al* NIM in Physics Research Section A: Accelerators\, Spectromete rs\, Detectors\, and Associated Equipment 654\, 29 (2011)\, ISSN 0168-9002 \n[3] M. Matoba\, *et. al* Phys. Rev. C 48\, 95 (1993).\nThis work is sup ported by the National Research Foundation of South\nAfrica grant 118846.\ n\nhttps://indico.tlabs.ac.za/event/119/contributions/3373/ LOCATION: URL:https://indico.tlabs.ac.za/event/119/contributions/3373/ END:VEVENT BEGIN:VEVENT SUMMARY:Nuclear structure via Coulomb excitation DTSTART;VALUE=DATE-TIME:20231129T083000Z DTEND;VALUE=DATE-TIME:20231129T085500Z DTSTAMP;VALUE=DATE-TIME:20260811T114242Z UID:indico-contribution-470-3348@indico.tlabs.ac.za DESCRIPTION:Speakers: Akaa Daniel Ayangeakaa (University of North Carolina at Chapel Hill)\nCoulomb excitation is a well-established and powerful ex perimental technique for probing the structure and dynamics of nuclei in a model-independent way. The technique is especially sensitive to the quadr upole shape degrees of freedom as it selectively excites low-lying collect ive states with cross sections that directly measure the E2 matrix element s involved in the excitation. In particular\, the technique allows the det ermination of transitional and diagonal E2 matrix elements between low-lyi ng states\, the most direct and unambiguous measure of the collective shap e parameters. In addition\, the technique provides unique and model-indepe ndent information on the relative signs of the diagonal E2 matrix elements \, thus allowing a link between reduced transition probabilities and spect roscopic quadrupole moments and the β\,γ shape parameters of the Bohr H amiltonian. In this presentation\, I will explain the principles and appli cations of Coulomb excitation as a tool for exploring quadrupole collectiv ity in nuclei. I will also briefly review the theoretical framework of Cou lomb excitation\, describe experimental setups and methods\, and present r ecent studies that illustrate its contribution to our understanding of sha pe dynamics in neutron-rich nuclei.\n\nhttps://indico.tlabs.ac.za/event/11 9/contributions/3348/ LOCATION: URL:https://indico.tlabs.ac.za/event/119/contributions/3348/ END:VEVENT BEGIN:VEVENT SUMMARY:Nuclear structure studies relevant for new physics searches with x enon detectors DTSTART;VALUE=DATE-TIME:20231129T080500Z DTEND;VALUE=DATE-TIME:20231129T083000Z DTSTAMP;VALUE=DATE-TIME:20260811T114242Z UID:indico-contribution-470-3352@indico.tlabs.ac.za DESCRIPTION:Speakers: Smarajit Triambak (University of Western Cape)\nXeno n detector experiments have provided some of the most sensitive searches o f physics beyond the standard model (BSM). These campaigns have placed emp hasis on observing dark matter interactions and/or neutrinoless double bet a decays (0ν2β). Several next-generation experiments aim to build on thi s work and probe for BSM physics with significantly improved sensitivity. In relation to the above\, this talk will present results from recent two- nucleon transfer studies in the A = 136 region. The measurements are used to robustly test predictions made with Hamiltonians that are also used to evaluate the nuclear matrix element for 136Xe 0ν2β. Further implications concerning the detection of solar neutrinos and fermionic dark matter can didates in large xenon-based detectors will also be briefly presented.\n\n https://indico.tlabs.ac.za/event/119/contributions/3352/ LOCATION: URL:https://indico.tlabs.ac.za/event/119/contributions/3352/ END:VEVENT END:VCALENDAR