Fri·Feb 13, 2015Friday·February 13, 2015

1. 01*

   Assessment of molecular effects on neutrino mass measurements from tritium beta decay

   L.I. Bodine🇺🇸 · D.S. Parno🇺🇸 · R.G.H. Robertson🇺🇸

   The beta decay of molecular tritium currently provides the highest sensitivity in laboratory-based neutrino mass measurements. The upcoming Karlsruhe Tritium Neutrino (KATRIN) experiment will improve the sensitivity to 0.2 eV, making a percent-level quantitative understanding of molecular effects essential. The modern theoretical calculations available for neutrino-mass experiments agree with spectroscopic data. Moreover, when neutrino-mass experiments performed in the 1980s with gaseous tritium are re-evaluated using these modern calculations, the extracted neutrino mass-squared values are consistent with zero instead of being significantly negative. On the other hand, the calculated molecular final-state branching ratios are in tension with dissociation experiments performed in the 1950s. We re-examine the theory of the final-state spectrum of molecular tritium decay and its effect on the determination of the neutrino mass, with an emphasis on the role of the vibrational- and rotational-state distribution in the ground electronic state. General features can be reproduced quantitatively from considerations of kinematics and zero-point motion. We summarize the status of validation efforts and suggest means for resolving the apparent discrepancy in dissociation rates.

   nucl-exhep-phnucl-thPRC(2015)·76 citations
2. 02*

   Ab-initio calculation of the photonuclear cross section of ${}^{10}$B

   M.K.G. Kruse🇺🇸 · W.E. Ormand🇺🇸 · C.W. Johnson🇺🇸

   We present for the first-time the photonuclear cross section of ${}^{10}$B calculated within the ab-initio No Core Shell Model framework. Realistic two-nucleon (NN) chiral forces up to next-to-next-to-next-order (N3LO), which have been softened by the similarity renormalization group method (SRG) to $\lambda =2.02$ fm${}^{-1}$, were utilized. The electric-dipole response function is calculated using the Lanczos method. The effects of the continuum were accounted for by including neutron escape widths derived from R-matrix theory. The calculated cross section agrees well with experimental data in terms of structure as well as in absolute peak height, ${\sigma }_{\max }=4.85\mathrm{mb}$ at photon energy $\omega =23.61\mathrm{MeV}$, and integrated cross section $85.36\mathrm{MeV}\cdot \mathrm{mb}$. We test the Brink hypothesis by calculating the electric-dipole response for the first five positive-parity states in ${}^{10}$B and verify that dipole excitations built upon the ground- and excited states have similar characteristics.

   ↳ nucl-thnucl-ex1 citation
3. 03*

   Low-energy antiproton physics and the FLAIR facility

   Eberhard Widmann🇦🇹

   FLAIR, the Facility for Low-energy Antiproton and Ion Research has been proposed in 2004 as an extension of the planned FAIR facility at Darmstadt, Germany. FLAIR was not included into the Modularized Start Version of FAIR, but the recent installation of the CRYRING storage ring at GSI Darmstadt has opened new perspectives for physics with low-energy antiprotons at FAIR.

   ↳ physics.ins-detnucl-exphysics.acc-phPhys.Scripta T(2015)·7 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.