Wed·Feb 15, 2023Wednesday·February 15, 2023

1. 01*

   Creation of super-high-flux photo-neutrons and gamma-rays > 8 MeV using a petawatt laser to irradiate high-Z solid targets

   E. Liang🇨🇳 · W. Lo · B. Cage · E. Fang · S. Arora · K. Q. Zheng · H .Quvedo · S. A. Bruce · M. Spinks · E. Medina · A. Helal · T. Ditmire

   We report the creation of super-high-flux gamma-rays with energy >8 MeV and photo-neutrons via the (g,n) reaction near giant dipole resonance energies (8 - 20 MeV), using the ~130 J Texas Petawatt laser to irradiate high-Z (Au, Pt, Re, W) targets of mm - cm thickness, at laser intensities up to ~5x1021W/cm2. We detected up to ~ several x 1012 gamma-rays > 8 MeV (~3% of incident laser energy) and ~ 1010 photo-neutrons per shot. Due to the short pulse and narrow gamma-ray cone (~17o half-width) around laser forward, the peak emergent gamma-ray flux >8 MeV reached ~1027 gammas/cm2/sec, and the peak emergent neutron flux reached ~1020 neutrons/cm2/sec. Such intense gamma-ray and neutron fluxes are among the highest achieved for short-pulse laser experiments. They will facilitate the study of nuclear reactions requiring super-high-flux of gamma-rays or neutrons, such as the creation of r-process elements. These results may also have far-reaching applications for nuclear energy, such as the transmutation of nuclear waste, isotope production and inertial fusion.

   ↳ physics.app-phnucl-ex0 citations
2. 02*

   Directed and elliptic flows of protons and deuterons in HADES Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=2.4$ GeV

   Huan Du🇨🇳 · Gao-Feng Wei🇨🇳 · Gao-Chan Yong🇨🇳

   Within a transport model coupled with a microscopic coalescence model, the directed and elliptic flows of protons and deuterons as well as their scalling properties are studied in the centrality of 20-30% Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=2.4$ GeV. It is found that the flows as well as their scaling properties simulated with the isospin- and momentum-dependent nuclear mean field with an incompressibility $K_0=230$ MeV fit fairly the HADES data, while those simulated with the commonly used momentum-independent nuclear mean field with an incompressibility $K_0=380$ MeV can only fit partially the HADES data. Moreover, by checking the rapidity distributions of both protons and deuterons in the centrality of 0-10% Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=2.4$ GeV, we find that the rapidity distributions of deuterons are underestimated while those of protons are overestimated by the simulations with the momentum-independent nuclear mean field. In contrast, the rapidity distributions of both protons and deuterons simulated with the isospin- and momentum-dependent nuclear mean field are in good agreement with the HADES data. Our findings imply that the momentum dependence of nuclear mean field is an unavoidable feature for a fundamental understanding of nuclear matter properties and for the successful interpretation of the HADES data.

   ↳ nucl-thnucl-exPLB(2023)·13 citations
3. 03*

   ${}^{113}$Cd $\beta$-decay spectrum and $g_{\mathrm{A}}$ quenching using spectral moments

   Joel Kostensalo🇫🇮 · Eligio Lisi🇮🇹 · Antonio Marrone🇮🇹 · Jouni Suhonen🇫🇮

   We present an alternative analysis of the ${}^{113}$Cd $\beta$-decay electron energy spectrum in terms of spectral moments ${\mu }_n$, corresponding to the averaged values of $n^{\mathrm{th}}$ powers of the $\beta$ particle energy. The zeroth moment ${\mu }_0$ is related to the decay rate, while higher moments ${\mu }_n$ are related to the spectrum shape. The here advocated spectral-moment method (SMM) allows for a complementary understanding of previous results, obtained using the so-called spectrum-shape method (SSM) and its revised version, in terms of two free parameters: $r=g_{\mathrm{A}}/g_{\mathrm{V}}$ (the ratio of axial-vector to vector couplings) and $s$ (the small vector-like relativistic nuclear matrix element, $s$-NME). We present numerical results for three different nuclear models with the conserved vector current hypothesis (CVC) assumption of $g_{\mathrm{V}}=1$. We show that most of the spectral information can be captured by the first few moments which are simple quadratic forms (conic sections) in the $(r,s)$ plane: an ellipse for $n=0$ and hyperbolae for $n\ge 1$, all being nearly degenerate as a result of cancellations among nuclear matrix elements. The intersections of these curves, as obtained by equating theoretical and experimental values of ${\mu }_n$, identify the favored values of $(r,s)$ at a glance, without performing detailed fits. In particular, we find that values around $r\sim 1$ and $s\sim 1.6$ are consistently favored in each nuclear model, confirming the evidence for $g_{\mathrm{A}}$ quenching in ${}^{113}$Cd, and shedding light on the role of the $s$-NME. We briefly discuss future applications of the SMM to other forbidden $\beta$-decay spectra sensitive to $g_{\mathrm{A}}$.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2023)·18 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.