Fri·Apr 22, 2016Friday·April 22, 2016

1. 01*

   Accuracy of the geometric-mean method for determining spatial resolutions of tracking detectors in the presence of multiple Coulomb scattering

   Aiwu Zhang🇺🇸 · Marcus Hohlmann🇺🇸

   The geometric-mean method is often used to estimate the spatial resolution of a position-sensitive detector probed by tracks. It calculates the resolution solely from measured track data without using a detailed tracking simulation and without considering multiple Coulomb scattering effects. Two separate linear track fits are performed on the same data, one excluding and the other including the hit from the probed detector. The geometric mean of the widths of the corresponding exclusive and inclusive residual distributions for the probed detector is then taken as a measure of the intrinsic spatial resolution of the probed detector: $\sigma =\sqrt{{\sigma }_{ex}\cdot {\sigma }_{in}}$. The validity of this method is examined for a range of resolutions with a stand-alone Geant4 Monte Carlo simulation that specifically takes multiple Coulomb scattering in the tracking detector materials into account. Using simulated as well as actual tracking data from a representative beam test scenario, we find that the geometric-mean method gives systematically inaccurate spatial resolution results. Good resolutions are estimated as poor and vice versa. The more the resolutions of reference detectors and probed detector differ, the larger the systematic bias. An attempt to correct this inaccuracy by statistically subtracting multiple-scattering effects from geometric-mean results leads to resolutions that are typically too optimistic by 10-50\%. This supports an earlier critique of this method based on simulation studies that did not take multiple scattering into account.

   ↳ physics.data-anhep-exnucl-exJINST(2016)·3 citations
2. 02*

   A Database for Storing the Results of Material Radiopurity Measurements

   J.C. Loach🇨🇳 · J. Cooley🇺🇸 · G.A. Cox🇩🇪 · Z. Li🇨🇳 · K.D. Nguyen🇺🇸 · A.W.P. Poon🇺🇸

   Searches for rare nuclear processes, such as neutrinoless double beta-decay and the interactions of WIMP dark matter, are motivating experiments with ever-decreasing levels of radioactive backgrounds. These background reductions are achieved using various techniques, but amongst the most important is minimizing radioactive contamination in the materials from which the experiment is constructed. To this end there have been decades of advances in material sourcing, manufacture and certification, during which researchers have accumulated many thousands of measurements of material radiopurity. Some of these assays are described in publications, others are in databases, but many are still communicated informally. Until this work, there has been no standard format for encoding assay results and no effective, central location for storing them. The aim of this work is to address these long-standing problems by creating a concise and flexible material assay data format and powerful software application to manipulate it. A public installation of this software, available at http://www.radiopurity.org, is the largest database of assay results ever compiled and is intended as a long-term repository for the community's data.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2016)·30 citations
3. 03*

   Determining astrophysical three-body radiative capture reaction rates from inclusive Coulomb break-up measurements

   J. Casal🇪🇸 · M. Rodríguez-Gallardo🇪🇸 · J. M. Arias🇪🇸 · J. Gómez-Camacho

   A relationship between the Coulomb inclusive break-up probability and the radiative capture reaction rate for weakly-bound three-body systems is established. This direct link provides a robust procedure to estimate the reaction rate for nuclei of astrophysical interest by measuring inclusive break-up processes at different energies and angles. This might be an advantageous alternative to the determination of reaction rates from the measurement of $B(E1)$ distributions through exclusive Coulomb break-up experiments. In addition, it provides a reference to assess the validity of different theoretical approaches that have been used to calculate reaction rates. The procedure is applied to ${}^{11}$Li (${}^9$Li+n+n) and ${}^6$He (${}^4$He+n+n) three-body systems for which some data exist.

   ↳ nucl-thnucl-exPRC(2016)·6 citations
4. 04*

   Octupole correlations in low-lying states of 150Nd and 150Sm and their impact on neutrinoless double-beta decay

   J. M. Yao🇺🇸 · J. Engel🇺🇸

   We present a generator-coordinate calculation, based on a relativistic energy-density functional, of the low-lying spectra in the isotopes ${}^{150}$Nd and ${}^{150}$Sm and of the nuclear matrix element that governs the neutrinoless double-beta decay of the first isotope to the second. We carefully examine the impact of octupole correlations on both nuclear structure and the double-beta decay matrix element. Octupole correlations turn out to reduce quadrupole collectivity in both nuclei. Shape fluctuations, however, dilute the effects of octupole deformation on the double-beta decay matrix element, so that the overall octupole-induced quenching is only about 7\%.

   ↳ nucl-thnucl-exPRC(2016)·41 citations
5. 05*

   Deformation effects in the alpha accompanied cold ternary fission of even-even ${}^{244-260}$Cf isotopes

   K P Santhosh🇮🇳 · Sreejith Krishnan

   Within the Unified ternary fission model (UTFM), the alpha accompanied ternary fission of even-even ${}^{244-260}$Cf isotopes has been studied by taking the interacting barrier as the sum of Coulomb and proximity potential. For the alpha accompanied ternary fission of 244^Cf isotope, the highest yield is obtained for the fragment combination 108^Ru+4^He+132^Te, which contain near doubly magic nuclei 132^Te (N=80, Z=52). In the case of 246^Cf and 248^Cf isotopes, the highest yield is obtained for the fragment combinations with near doubly magic nuclei 134^Te (N=82, Z=52) as the heavier fragment. The highest yield obtained for 250^Cf, 252^Cf, 254^Cf, 256^Cf, 258^Cf and 260^Cf isotopes is for the fragment combination with doubly magic nuclei 132^Sn (N=82, Z=50) as the heavier fragment. We have included the effect of deformation and orientation of fragments and this has revealed that in addition to closed shell effect, ground state deformation also plays an important role in the calculation of relative yield of favorable fragment combinations. The computed isotopic yields for alpha accompanied ternary fission of 252^Cf isotope are found to be in agreement with the experimental data. The emission probability and kinetic energy of long range alpha particle is calculated for the various isotopes of Cf and are found to be in good agreement with the experimental data.

   ↳ nucl-thnucl-exEPJA(2016)·10 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.