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439 records · Page 25

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DOE OSTI2022

νi 13/2 structures in 155 Sm and 159 Gd: Supporting evidence of a Z = 60 deformed subshell gap

Maximal ground-state deformation should occur when both proton and neutron Fermi surfaces are located at midshell. However, subshell gaps that stabilize large deformation can exist at proton or neutron values other than midshell. One such gap may occur at Z = 60 in the rare-earth region, as the energy of the first 2 + states in even-even nuclei are often lowest in an isotonic chain for neodymium (Z = 60) rather than the midshell isotopes of dysprosium (Z = 66). Further evidence of this deformed gap has now been observed by investigating the signature splitting systematics of the νi 13/2 bands found in the odd-N, rare-earth nuclei. Furthermore, these were aided by the present observation of the νi 13/2 band in 159 Gd and the confirmation of the same structure in 155 Sm via the transfer of a neutron from a 160 Gd beam to a 154 Sm target.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2025

Shining a Light on the Nucleus: Photonuclear Measurements from Correlations to Charmonium

The atomic nucleus is comprised of a collection of nucleons (protons and neutrons), which are bound together by the nucleon-nucleon (NN) interaction that originates from Quantum Chromodynamics (QCD). While most nucleons experience the force from the rest of the nu- cleus as a single net “mean-field” interaction that binds them relatively weakly, a small but impactful fraction are in configurations called “Short-Range Correlations” (SRCs), in which they pair with another nucleon at very short distance to experience strong interactions, sig- nificant binding, and high momentum. Hard, high-energy scattering reactions in which an SRC pair is broken apart, knocking both nucleons out of the nucleus, provide the ability to probe the details of these SRC configurations in the nucleus. Previous measurements have had limited statistics and kinematic reach, and the theoretical tools available were in- sufficient to draw quantitative conclusions regarding the ground-state properties of SRCs. The studies described in this thesis represent the first global analysis of SRC breakup mea- surements in order to present a unified picture of SRCs within light- to medium-size nuclei. This includes the use of a novel theoretical framework, the Generalized Contact Formalism, which connects scattering cross-section measurements and the ground-state properties of the SRC pair, to quantitatively interpret a variety of electron-scattering measurements. This is brought to culmination by a report on the first measurement of SRC pairs via the use of hard meson photoproduction reactions, which, despite differing significantly from the me- chanics of electron-scattering, is well-described under a common framework, pointing to a consistent and universal picture of SRCs across reaction channels. I also report on the first measurement of J/¿ photoproduction in the near- and below-threshold kinematic region, giving the first insights to the gluonic structure of bound nucleons in the large-x “valence” region and providing constraints on a gluonic “EMC effect”. In addition to these studies, I provide details on the search for Primakoff production of axion-like particles using the pho- toproduction data taken for this experiment, and I conclude by describing studies of nucleon spin structure measurements that will be performed at the forthcoming U.S. Electron-Ion Collider.

Pybus, Jackson↗

DOE OSTI2021

Long-lived isomeric states and quasiparticle band structures in neutron-rich 162,164 Gd nuclei from β decay

Neutron-rich nuclei 162,164 Eu were produced by bombarding a proton beam on a 238 U target at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory and mass separating the 162,164 Eu products. New level schemes and new γ-ray transitions of the daughters 162,164 Gd were identified from β-decay spectroscopy studies. Additionally, half-lives of the 162,164 Eu were remeasured to clarify the previous ambiguous results. Two quasiparticle band structures were built and compared with neighboring nuclei. The β and γ bands were extended in 162 Gd and a γ band was extended in 164 Gd. Half-lives of the isomeric states at (6 - ) 1449 keV in 162 Gd and (4 - ) 1096 keV in 164 Gd were measured to be 99(3) μs and 0.56(3) μs, respectively. Projected shell model calculations were performed and found to be in good agreement with all of the experimental data.

150 ≤ A ≤ 189↗

DOE OSTI2026

Proton isovector helicity PDF at NNLO and the twist-3 moment $\tilde{d}$ 2 from lattice QCD at physical quark masses

We present a lattice quantum chromodynamics calculation of the 𝑥-dependent isovector quark helicity parton distribution function (PDF) of the proton in the large momentum effective theory (LaMET) framework. Through operator product expansion (OPE) we also extract the $\tilde{d}$ 2 moment of the twist-3 PDF 𝑔 𝑇 ⁡(𝑥) for the first time in the $\overline{MS}$ scheme, which is proportional to the average color Lorentz force experienced by the quark in the proton. This calculation is performed on a lattice of spacing 𝑎 =0.076 fm at physical quark masses. The quasi-PDF matrix elements are measured in proton states boosted to momenta 𝑃 𝑧 ={0,0.25,1.02,1.53} GeV. We first extract the lowest few helicity PDF moments from the renormalization-group (RG) invariant ratios of the matrix elements with OPE. Combined with the matrix elements relevant for 𝑔 𝑇 ⁡(𝑥), we obtain $\tilde{d}$$^{u-d}_2$⁡(2 GeV) =0.0024⁢(46) at next-to-leading order in $\overline{MS}$. Then, the helicity quasi-PDF matrix elements are renormalized in the hybrid scheme with linear renormalon resummation and Fourier transformed to the 𝑥-space after an asymptotic extrapolation. The quasi-PDF is perturbatively matched to the $\overline{MS}$ PDF with RG and threshold resummations at next-to-leading power and next-to-next-to-leading logarithmic accuracies. After resummations, we determine the PDF in the region 𝑥 ∈[0.25,0.75]. The end-point regions are then parametrized, combined with the LaMET prediction at moderate 𝑥, and fitted to the short-distance matrix elements in coordinate space.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2025

H-cluster Intermediates and Catalytic Properties of Clostridium pasteurianum [FeFe]-Hydrogenase III

[FeFe]-Hydrogenases are structurally diverse enzymes that catalyze reversible H2 activation at a catalytic cofactor or H-cluster. The H-cluster is a [4Fe-4S] cubane linked by a cysteine thiolate to a diiron subsite containing unique CO, CN-, and dithiomethylamine ligands. The established H-cluster resting state of [4Fe-4S]2+-[FeII-FeI], or Hox, functions in H2 binding and oxidation, or by proton-coupled reduction initiates H2 evolution. In contrast, in Clostridium pasteurianum [FeFe]-hydrogenase III (CpIII) the resting state of the H-cluster is fully oxidized, [4Fe-4S]2+-[FeII-FeII], or Hox+1. To begin to understand if Hox+1 has a role in the mechanism of CpIII, we determined the spectroscopic and redox properties of CpIII H-cluster states under catalytic conditions. CpIII poised in Hox+1 and either equilibrated under 1 atm of H2 or reduced with sodium dithionite, resulted in a mixture of reduced states including Hox (Em8 = -407 mV), Htrans-like [4Fe-4S]+-[FeII-FeII] (Em8 = -418 mV), Hred [4Fe-4S]+-[FeII-FeI], and HredH+ [4Fe-4S]2+-[FeI-FeI] (Em8 = -455-480 mV). Under H2 the population of the Htrans-like state was >20-fold higher than Hox, implicating a role in CpIII catalysis. Unlike other enzymes, there was no spectral evidence of fully reduced states, such as HsredH+ ([4Fe-4S]+-[FeI-FeI]) or Hhyd ([4Fe-4S]+-[FeII-FeII]-H-). Thus, while the H-cluster states of CpIII encompass most of the catalytic intermediates, it is either unable to form HsredH+ and Hhyd, or these states are highly destabilized in CpIII. Thus, these results demonstrate that catalytic intermediates of reduced CpIII differ from the typical intermediates of other catalytic [FeFe]-hydrogenases and may explain the catalytic preference for H2 production.

08 HYDROGEN↗

DOE OSTI2024

Observation of New Charmonium or Charmoniumlike States in B + → D * ± D ∓ K + Decays

A study of resonant structures in B + → D * + D − K + and B + → D * − D + K + decays is performed, using proton-proton collision data at center-of-mass energies of s = 7 , 8, and 13 TeV recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb − 1 . A simultaneous amplitude fit is performed to the two channels with contributions from resonances decaying to D * − D + and D * + D − states linked by C parity. This procedure allows the C parities of resonances in the D * ± D ∓ mass spectra to be determined. Four charmonium or charmoniumlike states are observed decaying into D * ± D ∓ : η c ( 3945 ) , h c ( 4000 ) , χ c 1 ( 4010 ) , and h c ( 4300 ) , with quantum numbers J P C equal to 0 − + , 1 + − , 1 + + , and 1 + − , respectively. At least three of these states have not been observed previously. In addition, the existence of the T c ¯ s ¯ 0 * ( 2870 ) 0 and T c ¯ s ¯ 1 * ( 2900 ) 0 resonances in the D − K + mass spectrum, already observed in the B + → D + D − K + decay, is confirmed in a different production channel. © 2024 CERN, for the LHCb Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2026

Realizing the scientific program with polarized ion beams at the future BNL Electron Ion Collider

Polarized ion beams at the Electron Ion Collider (EIC) are essential to address some of the most important open questions at the twenty-first century frontiers of understanding of the fundamental structure of matter. Here, in this work, we summarize the science case and identify polarized 2 H, 3 He, 6 Li, and 7 Li ion beams as critical technology that will enable experiments which address the most important science. Furthermore, we discuss the required ion polarimetry and spin manipulation at the EIC. The current EIC accelerator design is presented. We identify a significant research and development effort across national and international laboratories and universities that is required over about a decade to realize the polarized ion beams and estimate (based on previous experience) that it will require about 20 full-time equivalent (FTE) over 10 years (or a total of about 200 FTE-years) of personnel, including graduate students, postdoctoral researchers, technicians, and engineers. Attracting, educating, and training a new generation of physicists in experimental spin techniques will be essential for the successful realization. Artificial intelligence and machine learning are seen as having significant potential for both acceleration of research and development and amplification of discovery in the optimal realization of this unique quantum technology on a cutting-edge collider. The research and development effort is synergistic with research in atomic physics and fusion energy science.

43 PARTICLE ACCELERATORS↗