Fri·Apr 12, 2019Friday·April 12, 2019

1. 01*

   Final results for the neutron $\beta$-asymmetry parameter $A_0$ from the UCNA experiment

   B. Plaster🇺🇸 · E. Adamek🇺🇸 · B. Allgeier🇺🇸 · J. Anaya🇺🇸 · H.O. Back🇺🇸 · Y. Bagdasarova🇺🇸 · D.B. Berguno🇺🇸 · M. Blatnik🇺🇸 · J.G. Boissevain🇺🇸 · T.J. Bowles🇺🇸 · L.J. Broussard🇺🇸 · M. A.-P. Brown🇺🇸 and 82 other authors

   The UCNA experiment was designed to measure the neutron $\beta$-asymmetry parameter $A_0$ using polarized ultracold neutrons (UCN). UCN produced via downscattering in solid deuterium were polarized via transport through a 7 T magnetic field, and then directed to a 1 T solenoidal electron spectrometer, where the decay electrons were detected in electron detector packages located on the two ends of the spectrometer. A value for $A_0$ was then extracted from the asymmetry in the numbers of counts in the two detector packages. We summarize all of the results from the UCNA experiment, obtained during run periods in 2007, 2008--2009, 2010, and 2011--2013, which ultimately culminated in a 0.67\% precision result for $A_0$.

   nucl-exphysics.ins-detEPJ Web Conf.(2019)·6 citations
2. 02*

   Projectile fragment emission in the fragmentation of 56Fe on Al, C and CH2 targets

   Luo-Huan Wang🇨🇳 · Liang-Di Huo🇨🇳 · Jia-Huan Zhu🇨🇳 · Hui-Ling Li🇨🇳 · Jun-Sheng Li🇨🇳 · S. Kodaira🇯🇵 · N. Yasuda🇯🇵 · Dong-Hai Zhang🇨🇳

   The emission angle distribution of projectile fragments (PFs) and the temperature of PFs emission source for fragmentation of ${}^{56}$Fe on polyethylene, carbon and aluminum targets at the highest energy of 496 A MeV are investigated using CR-39 plastic nuclear track detector. It is found that the averaged emission angle of PFs increases with the decrease of PF charge for the same target, and no obvious dependence of angular distribution on the mass of target nucleus is found for the same PF. The cumulated squared transverse momentum distribution of PF can be well represented by a single Rayleigh distribution, the temperature of PFs emission source is extracted from the distribution, which is about 1.0-8.0 MeV and do not depend on the mass of target for PF with charge of 9<=Z<=25.

   nucl-exNucl.Sci.Tech.(2019)·8 citations
3. 03*

   A New Approach to Determine Radiative Capture Reaction Rates at Astrophysical Energies

   I. Friščić🇭🇷 · T. W. Donnelly🇺🇸 · R. G. Milner🇺🇸

   Radiative capture reactions play a crucial role in stellar nucleosynthesis but have proved challenging to determine experimentally. In particular, the large uncertainty ($\sim$100%) in the measured rate of the ${}^{12}$C$(\alpha ,\gamma {)}^{16}$O reaction is the largest source of uncertainty in any stellar evolution model. With development of new high current energy-recovery linear accelerators (ERLs) and high density gas targets, measurement of the ${}^{16}$O$(e,e^{\prime }\alpha {)}^{12}$C reaction close to threshold using detailed balance opens up a new approach to determine the ${}^{12}$C$(\alpha ,\gamma {)}^{16}$O reaction rate with significantly increased precision ($<$20%). We present the formalism to relate photo- and electro-disintegration reactions and consider the design of an optimal experiment to deliver increased precision. Once the new ERLs come online, an experiment to validate the new approach we propose should be carried out. This new approach has broad applicability to radiative capture reactions in astrophysics.

   nucl-exastro-ph.SRnucl-thJ.Phys.Conf.Ser.(2020)·18 citations
4. 04*

   Barium Chemosensors with Dry-Phase Fluorescence for Neutrinoless Double Beta Decay

   P. Thapa🇺🇸 · I. Arnquist🇺🇸 · N. Byrnes🇺🇸 · A. A. Denisenko🇺🇸 · F. W. Foss Jr.🇺🇸 · B. J. P. Jones🇺🇸 · A. D. McDonald🇺🇸 · D. R. Nygren🇺🇸 · K. Woodruff🇺🇸

   The nature of the neutrino is one of the major open questions in experimental nuclear and particle physics. The most sensitive known method to establish the Majorana nature of the neutrino is detection of the ultra-rare process of neutrinoless double beta decay. However, identification of one or a handful of decay events within a large mass of candidate isotope, without obfuscation by backgrounds is a formidable experimental challenge. One hypothetical method for achieving ultra-low-background neutrinoless double beta decay sensitivity is the detection of single ${}^{136}$Ba ions produced in the decay of ${}^{136}$Xe (`barium tagging'). To implement such a method, a single-ion-sensitive barium detector must be developed and demonstrated in bulk liquid or dry gaseous xenon. This paper reports on the development of two families of dry-phase barium chemosensor molecules for use in high pressure xenon gas detectors, synthesized specifically for this purpose. One particularly promising candidate, an anthracene substituted aza-18-crown-6 ether, is shown to respond in the dry phase with almost no intrinsic background from the unchelated state, and to be amenable to barium sensing through fluorescence microscopy. This interdisciplinary advance, paired with earlier work demonstrating sensitivity to single barium ions in solution, opens a new path toward single ion detection in high pressure xenon gas.

   ↳ physics.ins-detnucl-exSci.Rep.(2019)·29 citations
5. 05*

   ChAKRA : The high resolution charged particle detector array at VECC

   Samir Kundu · T. K. Rana · C. Bhattacharya · K. Banerjee · R. Pandey · Santu Manna J. K. Meena · A. K. Saha · J. K. Sahoo · P. Dhara A. Dey D. Gupta T. K. Ghosh Pratap Roy · G. Mukherjee · R Mandal Saha · S. Roy and 3 other authors

   A large 4$\pi$ array of charged particle detectors has been developed at Variable Energy Cyclotron Centre to facilitate high resolution charged particle reaction and spectroscopy studies by detecting event-by-event the charged reaction products emitted in heavy ion reactions at energy $\sim$ 10-60 MeV/A. The forward part ($\theta \sim \pm$ $7^0$ - $\pm 45^0$) of the array consists of 24 highly granular, high resolution charged particle telescopes, each of which is made by three layers [single sided silicon strip($\Delta$E) + double sided silicon strip (E/$\Delta$E) + CsI(Tl)(E)]of detectors. The backward part of the array consists of 112 CsI(Tl) detectors which are capable of detecting primarily the light charged particles (Z $\le$ 2) emitted in the angular range of $\theta \sim \pm$ $45^0$ - $\pm 175^0$. The extreme forward part of the array ($\theta \sim \pm$ $3^0$ - $\pm 7^0$) is made up of 32 slow-fast plastic phoswich detectors that are capable of detecting light (Z $\le$2) and heavy charged particles (3 $\le$ Z $\lesssim$ 20) as well as handling high count rates. The design, construction and characterization of the array has been described.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2019)·15 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.