Tue·Jun 20, 2023Tuesday·June 20, 2023

1. 01*

   Mass Measurement of ${}^{27}$P to Constrain Type-I X-ray Burst Models and Validate the IMME for the A=27, T=$\frac{3}{2}$ Isospin Quartet

   I. T. Yandow🇺🇸 · A. Abdullah-Smoot · G. Bollen🇺🇸 · A. Hamaker🇺🇸 · C. R. Nicoloff🇺🇸 · D. Puentes🇺🇸 · M. Redshaw🇺🇸 · K. Gulyuz🇺🇸 · Z. Meisel🇺🇸 · W.-J. Ong🇺🇸 · R. Ringle🇺🇸 · R. Sandler🇺🇸 and 3 other authors

   Light curves are the primary observable of type-I x-ray bursts. Computational x-ray burst models must match simulations to observed light curves. Most of the error in simulated curves comes from uncertainties in $rp$ process reaction rates, which can be reduced via precision mass measurements of neutron-deficient isotopes in the $rp$ process path. We perform a precise Penning trap mass measurement of ${}^{27}$P utilizing the ToF-ICR technique. We use this measurement to calculate $rp$ process reaction rates and input these rates into an x-ray burst model to reduce simulated light curve uncertainty. We also use the mass measurement of ${}^{27}$P to validate the Isobaric Multiplet Mass Equation (IMME) for the A=27 T=$\frac{3}{2}$ isospin quartet which ${}^{27}$P belongs to. The mass excess of ${}^{27}$P was measured to be -670.7(6) keV, a fourteen-fold precision increase over the mass reported in the 2020 Atomic Mass Evaluation (AME2020). X-ray burst light curves were produced with the MESA (Modules for Experiments in Stellar Astrophysics) code using the new mass and associated reaction rates. Changes in the mass of ${}^{27}$P seem to have minimal effect on light curves, even in burster systems tailored to maximize impact. The mass of ${}^{27}$P does not play a significant role in x-ray burst light curves. It is important to understand that more advanced models do not just provide more precise results, but often qualitatively different ones. This result brings us a step closer to extracting stellar parameters from individual x-ray burst observations. The IMME has been validated for the $A=27,T=3/2$ quartet. The normal quadratic form of the IMME using the latest data yields a reduced ${\chi }^2$ of 2.9. The cubic term required to generate an exact fit to the latest data matches theoretical attempts to predict this term.

   nucl-exastro-ph.HEPRC(2023)·7 citations
2. 02*

   Advancements of $\gamma$-ray spectroscopy of isotopically identified fission fragments with AGATA and VAMOS++

   A. Lemasson🇫🇷 · J. Dudouet🇫🇷 · M. Rejmund🇫🇷 · J. Ljungvall🇫🇷 · A. Görgen🇳🇴 · W. Korten🇫🇷

   $\gamma$-ray spectroscopy of fission fragments is a powerful method for studies of nuclear structure properties. Recent results on the spectroscopy of fission fragments, using the combination of the AGATA $\gamma$-ray tracking array and the VAMOS++ large acceptance magnetic spectrometer at GANIL, are reported. A comparison of the performance of the large germanium detector arrays EXOGAM and AGATA illustrates the advances in $\gamma$-ray spectroscopy of fission fragments. Selected results are highlighted for prompt $\gamma$-ray spectroscopy studies, measurements of short lifetimes of excited states with the Recoil Distance Doppler-Shift method, using both AGATA and VAMOS++ and prompt-delayed $\gamma$-ray spectroscopy studies using AGATA, VAMOS++ and EXOGAM.

   nucl-exEPJA(2023)·6 citations
3. 03*

   Transverse Single-Spin Asymmetries of Midrapidity ${\pi }^0$ and $\eta$ Mesons in $\sqrt{s_{NN}}=200$ GeV $p^{\uparrow }+$Au and $p^{\uparrow }+$Al Collisions from PHENIX

   Dillon Fitzgerald🇺🇸

   Understanding the spin structure of the proton is of large interest to the nuclear physics community and it is one of the main goals of the spin physics program at the Relativistic Heavy Ion Collider (RHIC). Measurements from data taken by the PHENIX detector with transverse ($p^{\uparrow }+p$, $p^{\uparrow }$ + Al, $p^{\uparrow }$ + Au) proton polarization play an important role in this, in particular, due to the leading order access to gluons in polarized protons. Transverse single-spin asymmetries (TSSAs) provide insight into initial and final state spin-momentum and spin-spin parton-hadron correlations. In addition to possible final state contributions, ${\pi }^0$ and $\eta$ TSSAs access both quark and gluon correlations in the polarized proton. Furthermore, the $p^{\uparrow }+A$ data from RHIC provides an opportunity to study the effect of TSSAs in the presence of additional nuclear matter. Midrapidity ${\pi }^0$ and $\eta$ mesons are measured at PHENIX by detecting the 2$\gamma$ decay with the electromagnetic calorimeter (EMCal) in the central arm spectrometer, which has fine granularity for the resolution of separate decay photons. New results for TSSAs of midrapidity ${\pi }^0$ and $\eta$ mesons in $\sqrt{s_{NN}}=200$ GeV $p^{\uparrow }$ + Au and $p^{\uparrow }$ + Al collisions from the 2015 running year will be presented, and compared with the recent $\sqrt{s}=200$ GeV $p^{\uparrow }+p$ results.

   ↳ hep-exnucl-ex0 citations
4. 04*

   Quark mass difference effects in hadronic Fermi matrix elements from first principles

   Chien-Yeah Seng🇺🇸 · Vincenzo Cirigliano🇺🇸 · Xu Feng🇨🇳 · Mikhail Gorchtein🇩🇪 · Luchang Jin🇺🇸 · Gerald A. Miller🇺🇸

   It was recently estimated that the strong isospin-symmetry breaking (ISB) corrections to the Fermi matrix element in free neutron decay could be of the order $10^{-4}$, one order of magnitude larger than the na\"ıve estimate based on the Behrends-Sirlin-Ademollo-Gatto theorem. To investigate this claim, we derive a general expression of the leading ISB correction to hadronic Fermi matrix elements, which takes the form of a four-point correlation function in lattice gauge theory and is straightforward to compute from first principles. Our formalism paves the way for the first determination of such correction in the neutron sector with fully-controlled theory uncertainties.

   ↳ hep-phhep-exhep-latnucl-ex+1PLB(2023)·7 citations
5. 05*

   Helicity of Quarks and Gluons at Small Bjorken $x$

   Yossathorn Tawabutr🇺🇸

   The proton spin puzzle is a longstanding problem in high-energy nuclear physics: how the proton spin distributes among the spin and orbital angular momenta of the quarks and gluons inside. Two of the unresolved pieces of the puzzle are the contributions to quark and gluon spins from the region of small Bjorken $x$. This dissertation fills the gap by constructing the evolution of these quantities into the small-$x$ region using a modified dipole formalism. The dominant contributions to the evolution equations resum powers of ${\alpha }_s{\ln }^2(1/x)$, where ${\alpha }_s$ is the strong coupling constant. In general, these evolution equations do not close. However, once the large-$N_c$ or large-$N_c\&N_f$ limit is taken, they turn into a system of linear integral equations that can be solved iteratively. At large $N_c$, the evolution equations are shown to be consistent with the gluon sector of the polarized DGLAP evolution in the small-$x$ limit. We numerically solve the equations in the large-$N_c$ and large-$N_c\&N_f$ limits and obtain the exponential growth in $\ln (1/x)$ for $N_f\le 5$, with the intercept decreasing with $N_f$. For the large-$N_c$ limit, we have ${\alpha }_h=3.66$, which agrees up to the uncertainty with the earlier work by Bartels, Ermolaev and Ryskin. Furthermore, at $N_f=6$, the asymptotic form attains an oscillation in $\ln (1/x)$ on top of the exponential growth, with the period spanning several units of rapidity. Finally, parts of the single-logarithmic corrections to the small-$x$ helicity evolution is also derived, resumming powers of ${\alpha }_s\ln (1/x)$. There, the effects of the unpolarized small-$x$ evolution and the running coupling are also included for consistency. The complete single-logarithmic corrections can be derived based on the framework established here. Altogether, these equations will provide the most precise small-$x$ helicity evolution to date.

   ↳ hep-phhep-exnucl-exnucl-th4 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.