Fri·Jul 21, 2017Friday·July 21, 2017

1. 01*

   The Processing of Enriched Germanium for the MAJORANA DEMONSTRATOR and R&D for a Possible Future Ton-Scale Ge-76 Double-Beta Decay Experiment

   N. Abgrall🇺🇸 · I.J. Arnquist🇺🇸 · F.T. Avignone III🇺🇸 · A.S. Barabash🇷🇺 · F.E. Bertrand🇺🇸 · A.W. Bradley🇺🇸 · V. Brudanin🇷🇺 · M. Busch🇺🇸 · M. Buuck🇺🇸 · J. Caja🇺🇸 · M. Caja🇺🇸 · T.S. Caldwell🇺🇸 and 58 other authors

   The MAJORANA DEMONSTRATOR is an array of point-contact Ge detectors fabricated from Ge isotopically enriched to 88% in Ge-76 to search for neutrinoless double beta decay. The processing of Ge for germanium detectors is a well-known technology. However, because of the high cost of Ge enriched in Ge-76, special procedures were required to maximize the yield of detector mass and to minimize exposure to cosmic rays. These procedures include careful accounting for the material; shielding it to reduce cosmogenic generation of radioactive isotopes; and development of special reprocessing techniques for contaminated solid germanium, shavings, grindings, acid etchant and cutting fluids from detector fabrication. Processing procedures were developed that resulted in a total yield in detector mass of 70%. However, none of the acid-etch solution and only 50% of the cutting fluids from detector fabrication were reprocessed. Had they been processed, the projections for the recovery yield would be between 80 -- 85%. Maximizing yield is critical to justify a possible future ton-scale experiment. A process for recovery of germanium from the acid-etch solution was developed with yield of about 90%. All material was shielded or stored underground whenever possible to minimize the formation of Ge-68 by cosmic rays, which contributes background in the double-beta decay region of interest and cannot be removed by zone refinement and crystal growth. Formation of Ge-68 was reduced by a significant factor over that in natural abundance detectors not protected from cosmic rays.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2018)·37 citations
2. 02*

   Supernova Signatures of Neutrino Mass Ordering

   Kate Scholberg🇺🇸

   A suite of detectors around the world is poised to measure the flavor-energy-time evolution of the ten-second burst of neutrinos from a core-collapse supernova occurring in the Milky Way or nearby. Next-generation detectors to be built in the next decade will have enhanced flavor sensitivity and statistics. Not only will the observation of this burst allow us to peer inside the dense matter of the extreme event and learn about the collapse processes and the birth of the remnant, but the neutrinos will bring information about neutrino properties themselves. This review surveys some of the physical signatures that the currently-unknown neutrino mass pattern will imprint on the observed neutrino events at Earth, emphasizing the most robust and least model-dependent signatures of mass ordering.

   ↳ hep-exastro-ph.HEhep-phnucl-exJ.Phys.G(2018)·81 citations
3. 03*

   Effect of Finite Binding on the Apparent Spin-Orbit Splitting in Nuclei

   B. P. Kay🇺🇸 · C. R. Hoffman · A. O. Macchiavelli🇺🇸

   The apparent splitting between orbitals that are spin-orbit partners can be substantially influenced by the effects of finite binding. In particular, such effects can account for the observed decrease in separation of the neutron $1p_{3/2}$ and $1p_{1/2}$ orbitals between the ${}^{41}$Ca and ${}^{35}$Si isotopes. This behavior has been the subject of recent experimental and theoretical works and cited as evidence for a proton "bubble" in ${}^{34}$Si causing an explicit weakening of the spin-orbit interaction. The results reported here suggest that the change in the separation between the $1p_{3/2}$ and $1p_{1/2}$ partners occurs dominantly because of the behavior of the energies of these $1p$ neutron states near zero binding.

   ↳ nucl-thnucl-exPRL(2017)·19 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.