Wed·Jul 6, 2022Wednesday·July 6, 2022

1. 01*

   Polarization observables in double neutral pion photoproduction

   CBELSA/TAPS Collaboration: T. Seifen🇩🇪 · J. Hartmann🇩🇪 · F. Afzal🇩🇪 · A.V. Anisovich🇩🇪 · R. Beck🇩🇪 · M. Becker🇩🇪 · A. Berlin🇩🇪 · M. Bichow🇩🇪 · K.-Th. Brinkmann🇩🇪 · V. Crede🇺🇸 · M. Dieterle🇨🇭 · H. Dutz🇩🇪 and 63 other authors

   Measurements of target asymmetries and double-polarization observables for the reaction $\gamma p\to p{\pi }^0{\pi }^0$ are reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility (Bonn University) using the Bonn frozen-spin butanol (C${}_4$H${}_9$OH) target, which provided transversely polarized protons. Linearly polarized photons were produced via bremsstrahlung off a diamond crystal. The data cover the photon energy range from $E_{\gamma }$=650 MeV to $E_{\gamma }$=2600 MeV and nearly the complete angular range. The results have been included in the BnGa partial wave analysis. Experimental results and the fit agree very well. Observed systematic differences in the branching ratios for decays of $N^{\ast }$ and ${\Delta }^{\ast }$ resonances are attributed to the internal structure of these excited nucleon states. Resonances which can be assigned to SU(6)$\times$O(3) two-oscillator configurations show larger branching ratios to intermediate states with non-zero intrinsic orbital angular momenta than resonances assigned to one-oscillator configurations.

   nucl-exEPJA(2025)·15 citations
2. 02*

   The Search for Electric Dipole Moments of Charged Particles in Storage Rings

   Achim Andres🇩🇪

   The matter-antimatter asymmetry cannot be explained by the Standard Model (SM) of elementary particle physics. According to A. Sakharov, additional sources of $\mathcal{C}\mathcal{P}$-Violating phenomena are needed to understand the matter-antimatter asymmetry. Electric Dipole Moments (EDMs) of subatomic elementary particles may provide additional $\mathcal{C}\mathcal{P}$ violation, since they violate $\mathcal{T}$ (and $\mathcal{P}$) symmetry. Polarized beams in storage rings offer the possibility to measure EDMs of charged particles by observing the influence of the EDM on the spin motion. The Cooler Synchrotron (COSY) at Forschungszentrum Jülich provides polarized protons and deuterons up to a momentum of 3.7 GeV/c and is therefore an ideal starting point for the JEDI - Collaboration (Jülich Electric Dipole moment Investigations) to perform the first direct measurement of the deuteron EDM. This document describes recent results of EDM activities at COSY.

   nucl-ex1 citation
3. 03*

   Quenching of Single-Particle Strength in A=15 Nuclei

   B. P. Kay🇺🇸 · T. L. Tang🇺🇸 · I. A. Tolstukhin🇺🇸 · G. B. Roderick · A. J. Mitchell🇦🇺 · Y. Ayyad🇪🇸 · S. A. Bennett🇬🇧 · J. Chen🇫🇷 · K. A. Chipps🇺🇸 · H. L. Crawford🇺🇸 · S. J. Freeman🇬🇧 · K. Garrett and 8 other authors

   Absolute cross sections for the addition of $s$- and $d$-wave neutrons to ${}^{14}$C and ${}^{14}$N have been determined simultaneously via the ($d$,$p$) reaction at 10 MeV/u. The difference between the neutron and proton separation energies, $\Delta S$, is around $-20$ MeV for the ${}^{14}$C$+$$n$ system and $+8$ MeV for ${}^{14}$N$+$$n$. The population of the $1s_{1/2}$ and $0d_{5/2}$ orbitals for both systems is reduced by a factor of approximately 0.5 compared to the independent single-particle model, or about 0.6 when compared to the shell model. This finding strongly contrasts with results deduced from intermediate-energy knockout reactions between similar nuclei on targets of ${}^9$Be and ${}^{12}$C. The simultaneous technique used removes many systematic uncertainties.

   nucl-exPRL(2022)·20 citations
4. 04*

   Precision Møller Polarimetry for PREX and CREX

   D. E. King🇺🇸 · D. C. Jones🇺🇸 · C. Gal🇺🇸 · D. Gaskell🇺🇸 · W. Henry🇺🇸 · A. D. Kaplan🇺🇸 · J. Napolitano🇺🇸 · S. Park🇺🇸 · K. D. Paschke🇺🇸 · R. Pomatsalyuk🇺🇦 · P. A. Souder🇺🇸

   The PREX-2 and CREX experiments in Hall A at Jefferson Lab are precision measurements of parity violating elastic electron scattering from complex nuclei. One requirement was that the incident electron beam polarization, typically $\approx$90\%, be known with 1\% precision. We commissioned and operated a Møller polarimeter on the beam line that exceeds this requirement, achieving a precision of 0.89\% for PREX-2, and 0.85\% for CREX. The uncertainty is purely systematic, accumulated from several different sources, but dominated by our knowledge of the target polarization. Our analysis also demonstrates the need for accurate atomic wave functions in order to correct for the Levchuk Effect. We describe the details of the polarimeter operation and analysis, as well as (for CREX) a comparison to results from a different polarimeter based on Compton scattering.

   nucl-exphysics.ins-detNucl.Instrum.Meth.A(2023)·5 citations
5. 05*

   Covariant Density Functional Theory with Localized Exchange Terms

   Qiang Zhao🇰🇷 · Zhengxue Ren🇨🇳 · Pengwei Zhao🇨🇳 · Jie Meng🇨🇳

   A new density-dependent point-coupling covariant density functional PCF-PK1 is proposed, where the exchange terms of the four-fermion terms are local and are taken into account with the Fierz transformation. The coupling constants of the PCF-PK1 functional are determined by empirical saturation properties and ab initio equation of state and proton-neutron Dirac mass splittings for nuclear matter as well as the ground-state properties of selected spherical nuclei. The success of the PCF-PK1 is illustrated with properties of the infinite nuclear matter and finite nuclei including the ground-state properties and the Gamow-Teller resonances. In particular, the PCFPK1 eliminates the spurious shell closures at Z = 58 and Z = 92, which exist commonly in many covariant density functionals without exchange terms. Moreover, the Gamow-Teller resonances are nicely reproduced without any adjustable parameters, and this demonstrates that a self-consistent description for the Gamow-Teller resonances can be achieved with the localized exchange terms in the PCF-PK1. ?

   ↳ nucl-thnucl-exPRC(2022)·26 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.