Tue·Jul 28, 2015Tuesday·July 28, 2015

1. 01*

   Shapes of the ${}^{192,190}$Pb ground states from beta decay studies using the total absorption technique

   M. E. Estevez Aguado · A. Algora · J. Agramunt · B. Rubio · J. L. Tain · D. Jordan · L. M. Fraile · W. Gelletly · A. Frank · M. Csatlos · Zs. Dombradi · A. Krasznahorkay and 16 other authors

   The beta decay of ${}^{192,190}$Pb has been studied using the total absorption technique at the ISOLDE(CERN) facility. The beta-decay strength deduced from the measurements, combined with QRPA theoretical calculations, allow us to infer that the ground states of the ${}^{192,190}$Pb isotopes are spherical. These results represent the first application of the shape determination method using the total absorption technique for heavy nuclei and in a region where there is considerable interest in nuclear shapes and shape effects.

   nucl-exPRC(2015)·21 citations
2. 02*

   Measurement of interaction between antiprotons

   STAR Collaboration

   One of the primary goals of nuclear physics is to understand the force between nucleons, which is a necessary step for understanding the structure of nuclei and how nuclei interact with each other. Rutherford discovered the atomic nucleus in 1911, and the large body of knowledge about the nuclear force since acquired was derived from studies made on nucleons or nuclei. Although antinuclei up to antihelium-4 have been discovered and their masses measured, we have no direct knowledge of the nuclear force between antinucleons. Here, we study antiproton pair correlations among data taken by the STAR experiment at the Relativistic Heavy Ion Collider and show that the force between two antiprotons is attractive. In addition, we report two key parameters that characterize the corresponding strong interaction: namely, the scattering length (f0) and effective range (d0). As direct information on the interaction between two antiprotons, one of the simplest systems of antinucleons, our result provides a fundamental ingredient for understanding the structure of more complex antinuclei and their properties.

   nucl-exhep-exnucl-thNature(2015)·132 citations
3. 03*

   Suppression of baryon diffusion and transport in a baryon rich strongly coupled quark-gluon plasma

   Romulo Rougemont (Sao Paulo U.)🇧🇷 · Jorge Noronha (Sao Paulo U. & Columbia U.)🇧🇷 · Jacquelyn Noronha-Hostler (Columbia U.)🇺🇸

   Five dimensional black hole solutions that describe the QCD crossover transition seen in $(2+1)$-flavor lattice QCD calculations at zero and nonzero baryon densities are used to obtain predictions for the baryon susceptibility, baryon conductivity, baryon diffusion constant, and thermal conductivity of the strongly coupled quark-gluon plasma in the range of temperatures $130\text{MeV}\le T\le 300\text{MeV}$ and baryon chemical potentials $0\le {\mu }_B\le 400\text{MeV}$. Diffusive transport is predicted to be suppressed in this region of the QCD phase diagram, which is consistent with the existence of a critical end point at larger baryon densities. We also calculate the fourth-order baryon susceptibility at zero baryon chemical potential and find quantitative agreement with recent lattice results. The baryon transport coefficients computed in this paper can be readily implemented in state-of-the-art hydrodynamic codes used to investigate the dense QGP currently produced at RHIC's low energy beam scan.

   ↳ hep-phhep-thnucl-exnucl-thPRL(2015)·96 citations
4. 04*

   Halo effective field theory constrains the solar Beryllium-7 + proton -> Boron-8 + photon rate

   Xilin Zhang🇺🇸 · Kenneth M. Nollett🇺🇸 · D. R. Phillips🇺🇸

   We report an improved low-energy extrapolation of the cross section for the process Beryllium-7+proton -> Boron-8+photon, which determines the Boron-8 neutrino flux from the Sun. Our extrapolant is derived from Halo Effective Field Theory (EFT) at next-to-leading order. We apply Bayesian methods to determine the EFT parameters and the low-energy S-factor, using measured cross sections and scattering lengths as inputs. Asymptotic normalization coefficients of Boron-8 are tightly constrained by existing radiative capture data, and contributions to the cross section beyond external direct capture are detected in the data at E < 0.5 MeV. Most importantly, the S-factor at zero energy is constrained to be S(0)= 21.3 + - 0.7 eV b, which is an uncertainty smaller by a factor of two than previously recommended. That recommendation was based on the full range for S(0) obtained among a discrete set of models judged to be reasonable. In contrast, Halo EFT subsumes all models into a controlled low-energy approximant, where they are characterized by nine parameters at next-to-leading order. These are fit to data, and marginalized over via Monte Carlo integration to produce the improved prediction for S(E).

   ↳ nucl-thastro-ph.SRnucl-exPLB(2015)·64 citations
5. 05*

   Large scale evaluation of beta-decay rates of r-process nuclei with the inclusion of first-forbidden transitions

   T. Marketin🇭🇷 · L. Huther🇩🇪 · G. Martínez-Pinedo🇩🇪

   R-process nucleosynthesis models rely, by necessity, on nuclear structure models for input. Particularly important are beta-decay half-lives of neutron rich nuclei. At present only a single systematic calculation exists that provides values for all relevant nuclei making it difficult to test the sensitivity of nucleosynthesis models to this input. Additionally, even though there are indications that their contribution may be significant, the impact of first-forbidden transitions on decay rates has not been systematically studied within a consistent model. We use a fully self-consistent covariant density functional theory (CDFT) framework to provide a table of $\beta$-decay half-lives and $\beta$-delayed neutron emission probabilities, including first-forbidden transitions. We observe a significant contribution of the first-forbidden transitions to the total decay rate in nuclei far from the valley of stability. The experimental half-lives are in general well reproduced, both for even-even, odd-A and odd-odd nuclei, in particular for short-lived nuclei.

   ↳ nucl-thastro-ph.HEnucl-exPRC(2016)·280 citations
6. 06*

   Ultracold neutron production and up-scattering in superfluid helium between 1.1 K and 2.4 K

   K. K. H. Leung🇫🇷 · S. Ivanov🇫🇷 · F. M. Piegsa🇨🇭 · M. Simson · O. Zimmer🇫🇷

   Ultracold neutrons (UCNs) were produced in a 4 liter volume of superfluid helium using the PF1B cold neutron beam facility at the Institut Laue-Langevin and then extracted to a detector at room temperature. With a converter temperature of 1.08 K the number of accumulated UCNs was counted to be $91,700\pm 300$. From this, we derive a volumetric UCN production rate of $(6.9\pm 1.7)\mathrm{c}{\mathrm{m}}^{-3}{\mathrm{s}}^{-1}$, which includes a correction for losses in the converter during UCN extraction caused by a short storage time, but not accounting for UCN transport and detection efficiencies. The up-scattering rate of UCNs due to excitations in the superfluid was studied by scanning the temperature between 1.2-2.4 K. Using the temperature-dependent UCN production rate calculated from inelastic neutron scattering data in the analysis, the only UCN up-scattering process found to be present was from two-phonon scattering. Our analysis rules out contributions from the other scattering processes to $\lesssim 10\%$ of their predicted levels.

   ↳ physics.ins-detnucl-exPRC(2016)·30 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.