Mon·Aug 10, 2015Monday·August 10, 2015

1. 01*

   Photoproduction of {\omega} Mesons off the Proton

   A. Wilson🇩🇪 · V. Crede🇺🇸 · A. V. Anisovich🇩🇪 · J. C. S. Bacelar🇳🇱 · B. Bantes🇩🇪 · O. Bartholomy🇩🇪 · D. Bayadilov🇩🇪 · R. Beck🇩🇪 · Y. A. Beloglazov🇷🇺 · K. T. Brinkmann🇩🇪 · R. Castelijns🇳🇱 · H. Dutz🇩🇪 and 53 other authors

   The differential cross sections and unpolarized spin-density matrix elements for the reaction $\gamma p\to p\omega$ were measured using the CBELSA/TAPS experiment for initial photon energies ranging from the reaction threshold to 2.5 GeV. These observables were measured from the radiative decay of the $\omega$ meson, $\omega \to {\pi }^0\gamma$. The cross sections cover the full angular range and show the full extent of the $t$-channel forward rise. The overall shape of the angular distributions in the differential cross sections and unpolarized spin-density matrix elements are in fair agreement with previous data. In addition, for the first time, a beam of linearly-polarized tagged photons in the energy range from 1150 MeV to 1650 MeV was used to extract polarized spin-density matrix elements. These data were included in the Bonn-Gatchina partial wave analysis (PWA). The dominant contribution to $\omega$ photoproduction near threshold was found to be the $3/2^{+}$ partial wave, which is primarily due to the sub-threshold $N(1720)3/2^{+}$ resonance. At higher energies, pomeron-exchange was found to dominate whereas $\pi$-exchange remained small. These $t$-channel contributions as well as further contributions from nucleon resonances were necessary to describe the entire dataset: the $1/2^{-}$, $3/2^{-}$, and $5/2^{+}$ partial waves were also found to contribute significantly.

   nucl-exhep-exPLB(2015)·34 citations
2. 02*

   New Photodisintegration Model of GEANT4 for the $d\gamma \to np$ Reaction with a Dibaryon Effective Field Theory

   Jae Won Shin🇰🇷 · Chang Ho Hyun🇰🇷

   We develop a new hadronic model for GEANT4 that is specialized for the disintegration of the deuteron by photons, $d\gamma \to np$. For the description of two-nucleon interactions, we employ a pionless effective field theory with dibaryon fields (dEFT). We apply the new model of GEANT4 (G4dEFT) to the calculations of the total and the differential cross sections in $d\gamma \to np$ and compare the results with empirical data. As an application of the new model, we calculate the neutron yield from the $\gamma +{\mathrm{CD}}_2$ process. G4dEFT predicts peaks for the neutron yield, but the existing model of GEANT4 does not show such behavior.

   nucl-exnucl-thJ.Korean Phys.Soc.(2016)·1 citation
3. 03*

   Shell evolution approaching the N=20 island of inversion: structure of 26Na

   G.L. Wilson · W.N. Catford · N.A. Orr · C.Aa. Diget · A. Matta · G. Hackman · S.J. Williams · I.C. Celik · N.L. Achouri · H. Al Falou · R. Ashley · R.A.E. Austin and 28 other authors

   The levels in 26Na with single particle character have been observed for the first time using the d(25Na,p gamma) reaction at 5 MeV/nucleon. The measured excitation energies and the deduced spectroscopic factors are in good overall agreement with (0+1) hbar-omega shell model calculations performed in a complete spsdfp basis and incorporating a reduction in the N=20 gap. Notably, the 1p3/2 neutron configuration was found to play an enhanced role in the structure of the low-lying negative parity states in 26Na, compared to the isotone 28Al. Thus, the lowering of the 1p3/2 orbital relative to the 0f7/2 occurring in the neighbouring Z=10 and 12 nuclei -- 25,27Ne and 27,29Mg -- is seen also to occur at Z=11 and further strengthens the constraints on the modelling of the transition into the island of inversion.

   nucl-exPLB(2016)·15 citations
4. 04*

   Double-beta decay investigation with highly pure enriched ${}^{82}$Se for the LUCIFER experiment

   J.W. Beeman🇺🇸 · F. Bellini🇮🇹 · P. Benetti🇮🇹 · L. Cardani🇮🇹 · N. Casali🇮🇹 · D. Chiesa🇮🇹 · M. Clemenza🇮🇹 · I. Dafinei🇮🇹 · S. Di Domizio🇮🇹 · F. Ferroni🇮🇹 · L. Gironi🇮🇹 · A. Giuliani🇫🇷 and 17 other authors

   The LUCIFER project aims at deploying the first array of enriched scintillating bolometers for the investigation of neutrinoless double-beta decay of ${}^{82}$Se. The matrix which embeds the source is an array of ZnSe crystals, where enriched ${}^{82}$Se is used as decay isotope. The radiopurity of the initial components employed for manufacturing crystals, that can be operated as bolometers, is crucial for achieving a null background level in the region of interest for double-beta decay investigations. In this work, we evaluated the radioactive content in 2.5 kg of 96.3\% enriched ${}^{82}$Se metal, measured with a high-purity germanium detector at the Gran Sasso deep underground laboratory. The limits on internal contaminations of primordial decay chain elements of ${}^{232}$Th, ${}^{238}$U and ${}^{235}$U are respectively: $<$61 $\mu$Bq/kg, $<$110 $\mu$Bq/kg and $<$74 $\mu$Bq/kg at 90\% C.L.. The extremely low-background conditions in which the measurement was carried out and the high radiopurity of the ${}^{82}$Se allowed us to establish the most stringent lower limits on the half-lives of double-beta decay of ${}^{82}$Se to 0${}_1^{+}$, 2${}_2^{+}$ and 2${}_1^{+}$ excited states of ${}^{82}$Kr of 3.4$\cdot$10${}^{22}$ y, 1.3$\cdot$10${}^{22}$ y and 1.0$\cdot$10${}^{22}$ y, respectively, with a 90\% C.L..

   ↳ physics.ins-dethep-exnucl-exEPJC(2015)·52 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.