Wed·Jan 29, 2020Wednesday·January 29, 2020

1. 01*

   A New Neutron Lifetime Experiment with Cold Neutron Beam Decay in Superfluid Helium-4

   Wanchun Wei🇺🇸

   The puzzle remains in the large discrepancy between neutron lifetime measured by the two distinct experimental approaches -- counts of beta decays in a neutron beam and storage of ultracold neutrons in a potential trap, namely, the beam method versus the bottle method. In this paper, we propose a new experiment to measure the neutron lifetime in a cold neutron beam with a sensitivity goal of 0.1% or sub-1 second. The neutron beta decays will be counted in a superfluid helium-4 scintillation detector at 0.5 K, and the neutron flux will be simultaneously monitored by the helium-3 captures in the same volume. The cold neutron beam must be of wavelength $\lambda >16.5$ A to eliminate scattering with superfluid helium. A new precise measurement of neutron lifetime with the beam method of unique inherent systematic effects will greatly advance in resolving the puzzle.

   nucl-exphysics.ins-detJ.Phys.G(2020)·4 citations
2. 02*

   In-beam gamma-ray and electron spectroscopy of ${}^{249,251}$Md

   R. Briselet🇫🇷 · Ch. Theisen🇫🇷 · B. Sulignano🇫🇷 · M. Airiau🇫🇷 · K. Auranen🇫🇮 · D. M. Cox🇫🇮 · F. Déchery🇫🇷 · A. Drouart🇫🇷 · Z. Favier🇫🇷 · B. Gall🇫🇷 · T. Goigoux🇫🇷 · T. Grahn🇫🇮 and 31 other authors

   The odd-$Z$ ${}^{251}$Md nucleus was studied using combined $\gamma$-ray and conversion-electron in-beam spectroscopy. Besides the previously observed rotational band based on the $[521]1/2^{-}$ configuration, another rotational structure has been identified using $\gamma$-$\gamma$ coincidences. The use of electron spectroscopy allowed the rotational bands to be observed over a larger rotational frequency range. Using the transition intensities that depend on the gyromagnetic factor, a $[514]7/2^{-}$ single-particle configuration has been inferred for this band, i.e., the ground-state band. A physical background that dominates the electron spectrum with an intensity of $\simeq$ 60% was well reproduced by simulating a set of unresolved excited bands. Moreover, a detailed analysis of the intensity profile as a function of the angular momentum provided a method for deriving the orbital gyromagnetic factor, namely $g_K=0.69_{-0.16}^{+0.19}$ for the ground-state band. The odd-$Z$ ${}^{249}$Md was studied using $\gamma$-ray in-beam spectroscopy. Evidence for octupole correlations resulting from the mixing of the $\Delta l=\Delta j=3$ $[521]3/2^{-}$ and $[633]7/2^{+}$ Nilsson orbitals were found in both ${}^{249,251}$Md. A surprising similarity of the ${}^{251}$Md ground-state band transition energies with those of the excited band of ${}^{255}$Lr has been discussed in terms of identical bands. Skyrme-Hartree-Fock-Bogoliubov calculations were performed to investigate the origin of the similarities between these bands.

   nucl-exnucl-thPRC(2020)·10 citations
3. 03*

   Studies of Strange and Non-Strange Beauty Productions in PbPb Collisions with the CMS Detector

   Zhaozhong Shi🇺🇸

   Beauty quarks are considered as one of the best probes of the strongly interacting medium created in relativistic heavy-ion collisions because they are predominantly produced via initial hard scatterings. Our measurements of B mesons productions provide information on the diffusion of beauty quarks and the flavor dependence of in-medium energy loss. In these studies, clarifying the hadronization mechanism is crucial for understanding the transport properties of beauty quarks. We propose to show our experimental results on three sets of particles: nonprompt $J/\psi$ and $D^0$, $B_s^0$ and $B^{+}$, and prompt $D_s^{+}$ and $D^0$. Our measurements of $B_s^0$ production can shed light on the mechanisms of beauty recombination in the medium. In addition, the measurements of mesons productions containing both strange and beauty quarks can provide more information about strangeness enhancement in the quark-gluon plasma. The ratio of $B_s^0$ over $B^{+}$ nuclear modification factors at a nucleon-nucleon center-of-mass energy of 5.02 TeV, using fully reconstructed B mesons with the CMS detector, are presented. We will also show the nonprompt $J/\psi$ and $D^0$ from the partial B mesons decay chains as well as our precise measurement the prompt $D_s^{+}$ to $D^0$ ratio in pp and PbPb collisions.

   nucl-exhep-exNPA(2021)·0 citations
4. 04*

   Shape isomers in Pt, Hg and Pb isotopes with N $\le$ 126

   Krzysztof Pomorski🇵🇱 · Bozena Nerlo-Pomorska🇵🇱 · Artur Dobrowolski🇵🇱 · Johann Bartel🇫🇷 · Costel M. Petrache🇫🇷

   Deformation-energy surfaces of 54 even-even isotopes of Pt, Hg and Pb nuclei with neutron numbers up to 126 are investigated within a macroscopic-microscopic model based on the Lublin-Strasbourg-Drop macroscopic energy and shell plus pairing-energy corrections obtained from a Yukawa-folded mean-field potential at the desired deformation. A new, rapidly converging Fourier shape parametrization is used to describe nuclear shapes. The stability of shape isomeric states with respect to non-axial and higher-order deformations is investigated.

   ↳ nucl-thnucl-exEPJA(2020)·6 citations
5. 05*

   Flow in collisions of light nuclei

   Wojciech Broniowski🇵🇱 · Piotr Bożek🇵🇱 · Maciej Rybczyński🇵🇱 · Enrique Ruiz Arriola🇪🇸

   In this talk we discuss several interesting aspects of collective flow in small systems in reference to planned future experiments. First, we bring in the novel possibility of exploring elliptic flow with heavy nuclei collisions on polarized deuteron targets, accessible in AFTER@LHC program after Long Shutdown 3. Then we pass to the Glauber model predictions for the presently considered ${}^{16}\mathrm{O}-{}^{16}\mathrm{O}$ program and RHIC and the LHC. Finally, we turn to our previous proposal concerning specific flow signatures of intrinsic correlations (such as the supposed $\alpha$ clusterization) in the structure of light nuclei in collisions with heavy nuclei. In particular, ${}^{12}\mathrm{C}$--heavy nucleus ultrarelativistic reactions would provide insight into the ground-state ${}^{12}\mathrm{C}$ structure, complementary to the traditional nuclear structure features.

   ↳ nucl-thnucl-exNPA(2021)·6 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.