Mon·Oct 20, 2014Monday·October 20, 2014

1. 01*

   Constraining the 6.05 MeV 0${}^{+}$ and 6.13 MeV 3${}^{-}$ cascade transitions in the ${}^{12}$C($\alpha$,$\gamma$)${}^{16}$O reaction using the Asymptotic Normalization Coefficients

   M. L. Avila · G. V. Rogachev🇺🇸 · E. Koshchiy · L. T. Baby🇺🇸 · J. Belarge · K. W. Kemper🇺🇸 · A. N. Kuchera🇺🇸 · A. M. Mukhamedzhanov🇺🇸 · D. Santiago-Gonzalez · E. Uberseder🇺🇸

   Background. The ${}^{12}$C$(\alpha ,\gamma {)}^{16}$O reaction plays a fundamental role in astrophysics and needs to be known with accuracy better than 10%. Cascade $\gamma$ transitions through the excited states of ${}^{16}$O are contributing to the uncertainty. Purpose. To constrain the contribution of the 0${}^{+}$ (6.05 MeV) and 3${}^{-}$ (6.13 MeV) cascade transitions. Method. The $\alpha$ Asymptotic Normalization Coefficient for these states were measured using the $\alpha$-transfer reaction ${}^{12}$C${(}^6$Li,$d{)}^{16}$O at sub-Coulomb energies. Results. The 0${}^{+}$ and 3${}^{-}$ cascade transitions contribution was found to be 1.96$\pm$0.3 keV b and 0.12$\pm$0.04 keV b for destructive interference of the direct and resonance capture and 4.36$\pm$0.45 keV b and 1.44$\pm$0.12 keV b for constructive interference respectively. Conclusions. The combined contribution of the 0${}^{+}$ and 3${}^{-}$ cascade transitions to the reaction at 300 keV does not exceed 4%. Significant uncertainties have been dramatically reduced.

   nucl-exPRL(2015)·61 citations
2. 02*

   Dispersive analysis of the pion transition form factor

   Martin Hoferichter🇨🇭 · Bastian Kubis🇩🇪 · Stefan Leupold🇸🇪 · Franz Niecknig🇩🇪 · Sebastian P. Schneider🇩🇪

   We analyze the pion transition form factor using dispersion theory. We calculate the singly-virtual form factor in the time-like region based on data for the $e^{+}{e}^{-}\to 3\pi$ cross section, generalizing previous studies on $\omega ,\varphi \to 3\pi$ decays and $\gamma \pi \to \pi \pi$ scattering, and verify our result by comparing to $e^{+}{e}^{-}\to {\pi }^0\gamma$ data. We perform the analytic continuation to the space-like region, predicting the poorly-constrained space-like transition form factor below 1 GeV, and extract the slope of the form factor at vanishing momentum transfer $a_{\pi }=(30.7\pm 0.6)\times 10^{-3}$. We derive the dispersive formalism necessary for the extension of these results to the doubly-virtual case, as required for the pion-pole contribution to hadronic light-by-light scattering in the anomalous magnetic moment of the muon.

   ↳ hep-phhep-exnucl-exnucl-thEPJC(2014)·178 citations
3. 03*

   High-resolution, vacuum-ultraviolet absorption spectrum of boron trifluoride

   Patrick P. Hughes · Amy Beasten · Jacob C. McComb · Michael A. Coplan · Alan K. Thompson🇺🇸 · Robert E. Vest · Matthew K. Sprague · Karl K. Irikura · Charles W. Clark🇺🇸

   In the course of investigations of thermal neutron detection based on mixtures of ${}^{10}$BF${}_3$ with other gases, knowledge was required of the photoabsorption cross sections of ${}^{10}$BF${}_3$ for wavelengths between 135 and 205 nm. Large discrepancies in the values reported in existing literature led to the absolute measurements reported in this communication. The measurements were made at the SURF III synchrotron radiation facility at the National Institute of Standards and Technology. The measured absorption cross sections vary from 10${}^{-20}$ cm${}^2$ at 135 nm to less than 10${}^{-21}$ cm${}^2$ in the region from 165 to 205 nm. Three previously unreported absorption features with resolvable structure were found in the regions 135 to 145 nm, 150 to 165 nm and 190 to 205 nm. Quantum mechanical calculations, using the TD-B3LYP/aug-cc-pVDZ variant of time-dependent density functional theory implemented in Gaussian 09, suggest that the observed absorption features arise from symmetry-changing adiabatic transitions.

   ↳ physics.atom-phnucl-exphysics.chem-phphysics.ins-det+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.