Thu·Mar 12, 2020Thursday·March 12, 2020

1. 01*

   Direct measurement of the ${}^7$Be $L/K$ capture ratio in Ta-based superconducting tunnel junctions

   S. Fretwell🇺🇸 · K.G. Leach🇺🇸 · C. Bray🇺🇸 · G.B. Kim🇺🇸 · J. Dilling🇨🇦 · A. Lennarz🇨🇦 · X. Mougeot🇫🇷 · F. Ponce🇺🇸 · C. Ruiz🇨🇦 · J. Stackhouse🇺🇸 · S. Friedrich🇺🇸

   We report a high-statistics measurement of the $L/K$ orbital electron capture (EC) ratio in ${}^7$Be embedded in cryogenic Ta. The thin Ta film formed part of a high-resolution superconducting tunnel junction (STJ) radiation detector that was used to identify the signals from different decay channels. The measured $L/K$ capture ratio of 0.070(7) is significantly larger than the only previous measurement of this quantity and the theoretical predictions that include in-medium effects. This value is a uniquely sensitive probe of the 1s and 2s orbital overlaps with the nucleus, and is of relevance to nuclear and atomic physics, as well as Li production in novae and other astrophysical scenarios. This is the first experiment that uses STJs for nuclear-recoil detection, opening a new experimental avenue for low-energy precision measurements with rare isotopes.

   nucl-exastro-ph.SRnucl-thPRL(2020)·37 citations
2. 02*

   Heavy-Ion Storage Rings and Their Use in Precision Experiments with Highly Charged Ions

   Markus Steck🇩🇪 · Yuri A. Litvinov🇩🇪

   Storage rings have been employed over three decades in various kinds of nuclear and atomic physics experiments with highly charged ions. Storage ring operation and precision physics experiments benefit from the availability of beam cooling which is common to nearly all facilities. The basic aspects of the storage ring components and the operation of the ring in various ion-optical modes as well as the achievable beam conditions are described. Ion storage rings offer unparalleled capabilities for high precision experiments with stable and radioactive beams. The versatile techniques and methods for beam manipulations allow for preparing beams of highest quality at any energy of interest. The rings are therefore part of the experiment . Recent experiments conducted in a wide energy range and with various experimental installations are discussed. An overview of active and planned facilities, new experimental set-ups and proposed physics experiments completes this review.

   nucl-exphysics.acc-phphysics.atom-phPPNP(2020)·72 citations
3. 03*

   Study of Silicon Photomultiplier Radiation Hardness with Proton Beam from the JULIC Cyclotron

   Tamer Tolba🇨🇳 · Dieter Grzonka🇩🇪 · Thomas Sefzick🇩🇪 · James Ritman🇩🇪

   In this work we study the performance of silicon photomultiplier (SiPM) light sensors after exposure to the JULIC cyclotron proton beam, of energy $\sim$ 39 MeV, relative to their performance before exposure. The SiPM devices used in this study show a significant change in their behavior and downward shift of their breakdown voltage by as much as $\sim$ 0.4$\pm$0.1 V. Single photon measurements appear to be no longer possible for the SiPMs under study after exposure to a dose of $\sim$ 0.2 Gy (corresponding to an integrated proton flux of $\sim$${\varphi }_p$=1.06x10${}^8$ p/cm${}^2$). No visible damage to the surface of the devices was caused by the exposure.

   ↳ physics.ins-dethep-exnucl-ex2 citations
4. 04*

   Neutron Guide Building Instruments of the Brazilian Multipurpose Reactor (RMB) Project

   Alexandre P.S. Souza🇧🇷 · Luiz P. de Oliveira🇧🇷 · Fabiano Yokaichiya🇧🇷 · Frederico A. Genezini🇧🇷 · Margareth K.K.D. Franco🇧🇷

   A growing community of scientists has been using neutrons in the most diverse areas of science. In order to meet the researchers demand in the areas of physics, chemistry, materials sciences, engineering, cultural heritage, biology and earth sciences, the Brazilian Multipurpose Reactor (RMB) will provide 3 thermal guides and 3 cold guides, with the installation of several instruments for materials characterization. In this study, we present a standard design requirement of two primordial instruments, namely Sabiá and Araponga. They are, respectively, cold and thermal neutron instruments and correspond to a Small-Angle Neutron Scattering (SANS) and High-Resolution Powder Neutron Diffractometer (HRPND) to be installed in the Neutron Guide Building (N02) of RMB. To provide adequate flux for both instruments, we propose here an initial investigation of the use of simple and split guides to transport neutron beams to two different instruments on the same guide. For this purpose, we use Monte Carlo simulations utilizing McStas software to check the efficiency of thermal neutron transport for different basic configuration and sources. By considering these results, it is possible to conclude that the split guide configuration is, in most cases, more efficient than cases that use transmitted neutron beams independently of source. We also verify that the employment of different coating indexes for concave and convex surfaces on curved guides is crucial, at least on simulated cases, to optimise neutron flux (intensity and divergence) and diminish facility installation cost.

   ↳ physics.ins-detnucl-exnucl-thquant-phJINST(2020)·5 citations
5. 05*

   Doubly Charmed Pentaquarks

   Gang Yang🇨🇳 · Jialun Ping🇨🇳 · Jorge Segovia🇪🇸

   The LHCb Collaboration, using its full data set from runs $1$ and $2$, announced in $2019$ a surprising update of the hidden-charm pentaquark states $P_c(4380{)}^{+}$ and $P_c(4450{)}^{+}$, observed in 2015. A new state, $P_c(4312{)}^{+}$, was clearly seen at lower energies; furthermore, the original $P_c(4450)$ resonance was resolved into two individual states, named the $P_c(4440{)}^{+}$ and the $P_c(4457{)}^{+}$. Motivated by the fact that these new hidden-charm pentaquark states were successfully predicted by our chiral quark model, we extend herein such study to the doubly charmed sector. The analyzed total spin and parity quantum numbers are $J^P={\frac{1}{2}}^{-}$, ${\frac{3}{2}}^{-}$ and ${\frac{5}{2}}^{-}$, in the $I=\frac{1}{2}$ and $\frac{3}{2}$ isospin channels. We find several possible narrow baryon-meson resonances (theoretical masses in parenthesis): $I{J}^P=\frac{1}{2}{\frac{1}{2}}^{-}$ ${\Sigma }_{c}D(4356)$, $\frac{1}{2}{\frac{3}{2}}^{-}$ ${\Sigma }_c^{\ast }D(4449)$, $\frac{3}{2}{\frac{1}{2}}^{-}$ ${\Sigma }_{c}D(4431)$, $\frac{3}{2}{\frac{1}{2}}^{-}$ ${\Sigma }_{c}D(4446)$, $\frac{3}{2}{\frac{3}{2}}^{-}$ ${\Sigma }_c{D}^{\ast }(4514)$ and $\frac{3}{2}{\frac{5}{2}}^{-}$ ${\Xi }_{cc}^{\ast }\rho (4461)$ whose widths are $4.8$, $8.0$, $2.6$, $2.2$, $4.0$ and $3.0\text{MeV}$, respectively. Moreover, one shallow bound-state is found, too, with quantum numbers $I{J}^P=\frac{1}{2}{\frac{3}{2}}^{-}$ ${\Xi }_{cc}^{\ast }\pi (3757)$. These doubly charmed pentaquark states are expected to be identified in future experiments.

   ↳ hep-phhep-exhep-latnucl-ex+1PRD(2020)·45 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.