Fri·May 20, 2016Friday·May 20, 2016

1. 01*

   Measurement of neutron capture on ${}^{136}$Xe

   Joshua B. Albert🇺🇸 · Sean J. Daugherty🇺🇸 · Tessa N. Johnson🇺🇸 · Thomasina O'Conner🇺🇸 · Lisa J. Kaufman🇺🇸 · Aaron Couture🇺🇸 · John L. Ullmann🇺🇸 · Milan Krtička🇨🇿

   ${}^{136}$Xe is a 0{\nu}{\beta}{\beta} decay candidate isotope, and is used in multiple experiments searching for this hypothetical decay mode. These experiments require precise information about neutron capture for their background characterization and minimization. Thermal and resonant neutron capture on ${}^{136}$Xe have been measured at the Detector for Advanced Neutron Capture Experiments (DANCE) at the Los Alamos Neutron Science Center. A neutron beam ranging from thermal energy to greater than 100 keV was incident on a gas cell filled with isotopically pure ${}^{136}$Xe. The relative neutron capture cross sections for neutrons at thermal energies and the first resonance at 2.154 keV have been measured. Additionally, the {\gamma} cascades for these captures have been measured, and cascade models have been developed which may be used by 0{\nu}{\beta}{\beta} experiments using ${}^{136}$Xe.

   nucl-exphysics.ins-detPRC(2016)·11 citations
2. 02*

   New neutron-deficient isotopes from ${}^{78}$Kr fragmentation

   B. Blank🇫🇷 · T. Goigoux🇫🇷 · P. Ascher🇫🇷 · M. Gerbaux🇫🇷 · J. Giovinazzo🇫🇷 · S. Grevy🇫🇷 · T. Kurtukian Nieto🇫🇷 · C. Magron🇫🇷 · J. Agramunt🇪🇸 · A. Algora🇪🇸 · V. Guadilla🇪🇸 · A. Montaner-Piza🇪🇸 and 40 other authors

   In an experiment with the BigRIPS separator at the RIKEN Nishina Center, the fragmentation of a ${}^{78}$Kr beam allowed the observation of new neutron-deficient isotopes at the proton drip-line. Clean identification spectra could be produced and ${}^{63}$Se, ${}^{67}$Kr, and ${}^{68}$Kr were identified for the first time. In addition, ${}^{59}$Ge was also observed. Three of these isotopes, ${}^{59}$Ge, ${}^{63}$Se, and ${}^{67}$Kr, are potential candidates for ground-state two-proton radioactivity. In addition, the isotopes ${}^{58}$Ge, ${}^{62}$Se, and ${}^{66}$Kr were also sought but without success. The present experiment also allowed the determination of production cross sections for some of the most exotic isotopes. These measurements confirm the trend already observed that the empirical parameterization of fragmentation cross sections, EPAX, significantly overestimates experimental cross sections in this mass region.

   nucl-exPRC(2016)·30 citations
3. 03*

   Double electron capture searches in ${}^{74}$Se

   B. Lehnert🇩🇪 · T. Wester🇩🇪 · D. Degering🇩🇪 · D. Sommer🇩🇪 · L. Wagner🇩🇪 · K. Zuber🇩🇪

   A search for various double electron capture modes of ${}^{74}$Se has been performed using an ultralow background Ge-detector in the Felsenkeller laboratory, Germany. Especially for the potentially resonant transition into the 1204.2 keV excited state of ${}^{74}$Ge a lower half-life limit of $0.70\cdot 10^{19}$ yr (90% credibility) has been obtained. Serious concerns are raised about the validity of obtained ${}^{74}$Se limits in some recent publications.

   nucl-exJ.Phys.G(2016)·9 citations
4. 04*

   Experimental observation of $\beta$-delayed neutrons from ${}^9$Li as a way to study short-pulse laser-driven deuteron production

   Andrea Favalli · Nevzat Guler🇺🇸 · Daniela Henzlova🇺🇸 · Katerina Falk · Stephen Croft · Donald C. Gautier · Kiril D. Ianakiev · Metodi Iliev · Sasikumar Palaniyappan · Markus Roth🇩🇪 · Juan C. Fernandez🇪🇸 · Martyn T. Swinhoe

   A short-pulse laser-driven deuteron beam is generated in the relativistic transparency regime and aimed at a beryllium converter to generate neutrons at the TRIDENT laser facility. These prompt neutrons have been used for active interrogation to detect nuclear materials, the first such demonstration of a laser-driven neutron source. During the experiments, delayed neutrons from ${}^9$Li decay was observed. It was identified by its characteristic half-life of 178.3 ms. Production is attributed to the nuclear reactions ${}^9$Be(d,2p)${}^9$Li and ${}^9$Be(n,p)${}^9$Li inside the beryllium converter itself. These reactions have energy thresholds of 18.42 and 14.26 MeV respectively, and we estimate the (d,2p) reaction to be the dominant source of ${}^9$Li production. Therefore, only the higher-energy portion of the deuteron spectrum contributes to the production of the delayed neutrons. It was observed that the delayed-neutron yield decreases with increasing distance between the converter and the deuteron source. This behavior is consistent with deuteron production with energy greater than $\sim$20 MeV within a cone with a half-angle greater than 40${}^{\circ }$. Prompt-neutron time-of-flight measurements at varying separation between the converter and the laser target indicate that the fast deuteron population above threshold is severely depleted on axis out to $\sim$20${}^{\circ }$. These measurements are consistent with emission of the fast deuterons (i.e., above 10 MeV/nucleon) in a ring-like fashion around the central axis. Such an inferred ring-like structure is qualitatively consistent with a documented signature of the breakout afterburner (BOA) laser-plasma ion acceleration mechanism. The measurement of $\beta$-delayed neutrons from ${}^9$Li decay could provide an important new diagnostic tool for the study of the features of the deuteron production mechanism in a non-intrusive way.

   ↳ physics.plasm-phnucl-exphysics.ins-det0 citations
5. 05*

   Double vector meson production in photon - hadron interactions at hadronic colliders

   V.P. Goncalves🇧🇷 · B.D. Moreira🇧🇷 · F.S. Navarra🇧🇷

   In this paper we analyse the double vector meson production in photon -- hadron ($\gamma h$) interactions at $pp/pA/AA$ collisions and present predictions for the $\rho \rho$, $J/\Psi J/\Psi$ and $\rho J/\Psi$ production considering the double scattering mechanism. We estimate the total cross sections and rapidity distributions at LHC energies and compare our results with the predictions for the double vector meson production in $\gamma \gamma$ interactions at hadronic colliders. We present predictions for the different rapidity ranges probed by the ALICE, ATLAS, CMS and LHCb Collaborations. Our results demonstrate that the $\rho \rho$ and $J/\Psi J/\Psi$ production in $PbPb$ collisions is dominated by the double scattering mechanism, while the two - photon mechanism dominates in $pp$ collisions. Moreover, our results indicate that the analysis of the $\rho J/\Psi$ production at LHC can be useful to constrain the double scattering mechanism.

   ↳ hep-phhep-exnucl-exnucl-thEPJC(2016)·26 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.