Tue·Aug 11, 2015Tuesday·August 11, 2015

1. 01*

   ${}^{24}$Mg($p$, $\alpha$)${}^{21}$Na reaction study for spectroscopy of ${}^{21}$Na

   S.M. Cha · K.Y. Chae🇰🇷 · A. Kim🇺🇸 · E.J. Lee🇰🇷 · S. Ahn🇺🇸 · D.W. Bardayan🇺🇸 · K.A. Chipps🇺🇸 · J.A. Cizewski🇺🇸 · M.E. Howard🇺🇸 · B. Manning🇺🇸 · P.D. O'Malley🇺🇸 · A. Ratkiewicz🇺🇸 and 7 other authors

   The ${}^{24}$Mg($p$, $\alpha$)${}^{21}$Na reaction was measured at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory in order to better constrain spins and parities of energy levels in ${}^{21}$Na for the astrophysically important ${}^{17}$F($\alpha ,p$)${}^{20}$Ne reaction rate calculation. 31 MeV proton beams from the 25-MV tandem accelerator and enriched ${}^{24}$Mg solid targets were used. Recoiling ${}^4$He particles from the ${}^{24}$Mg($p$, $\alpha$)${}^{21}$Na reaction were detected by a highly segmented silicon detector array which measured the yields of ${}^4$He particles over a range of angles simultaneously. A new level at 6661 $\pm$ 5 keV was observed in the present work. The extracted angular distributions for the first four levels of ${}^{21}$Na and Distorted Wave Born Approximation (DWBA) calculations were compared to verify and extract angular momentum transfer.

   nucl-exJ.Korean Phys.Soc.(2015)·1 citation
2. 02*

   Stochastic modeling and survival analysis of marginally trapped neutrons for a magnetic trapping neutron lifetime experiment

   K.J. Coakley · M.S. Dewey🇺🇸 · M. G. Huber · P. R. Huffman🇺🇸 · C. R. Huffer · D. E. Marley · H.P. Mumm🇺🇸 · C. M. O'Shaughnessy · K. W. Schelhammer · A. K. Thompson🇺🇸 · A.T. Yue🇺🇸

   In a variety of neutron lifetime experiments, in addition to $\beta -$decay, neutrons can be lost by other mechanisms including wall losses. Failure to account for these other loss mechanisms produces systematic measurement error and associated systematic uncertainties in neutron lifetime measurements. In this work, we develop a physical model for neutron wall losses and construct a competing risks survival analysis model to account for losses due to the joint effect of $\beta -$decay losses, wall losses of marginally trapped neutrons, and an additional absorption mechanism. We determine the survival probability function associated with the wall loss mechanism by a Monte Carlo method. Based on a fit of the competing risks model to a subset of the NIST experimental data, we determine the mean lifetime of trapped neutrons to be approximately 700 s -- considerably less than the current best estimate of (880.1 $\pm$ 1.1) s promulgated by the Particle Data Group [1]. Currently, experimental studies are underway to determine if this discrepancy can be explained by neutron capture by ${}^3$He impurities in the trapping volume. Analysis of the full NIST data will be presented in a later publication.

   nucl-exphysics.ins-detNucl.Instrum.Meth.A(2016)·3 citations
3. 03*

   On $m_T$ dependence of femtoscopy scales for meson and baryon pairs

   Yu. M. Sinyukov🇺🇦 · V. M. Shapoval🇺🇦 · V. Yu. Naboka🇺🇦

   The $m_T$-dependencies of the femto-scales, the so-called interferometry and source radii, are investigated within the hydrokinetic model for different types of particle pairs - pion-pion, kaon-kaon, proton-proton and proton-lambda, - produced in Pb+Pb and $p+p$ collisions at the LHC. In particular, such property of the femto-scales momentum behavior as $m_T$-scaling is studied for the systems with (w) and without (w/o) intensive transverse flow, and also w and w/o re-scattering at the final afterburner stage of the matter evolution. The detail spatiotemporal description obtained within hydrokinetic model is compared with the simple analytical results for the spectra and longitudinal interferometry radii depending on the effective temperature on the hypersurface of maximal emission, proper time of such emission, and intensity of transverse flow. The derivation of the corresponding analytical formulas and discussion about a possibility for their utilization by the experimentalists for the simple femtoscopy data analysis is the main aim of this theoretical investigation.

   ↳ hep-phhep-exnucl-exnucl-thNPA(2016)·34 citations
4. 04*

   Monitoring method for neutron flux for a spallation target in an accelerator driven sub-critical system

   Qiang Zhao🇨🇳 · Zhiyong He · Lei Yang🇺🇸 · Xueying Zhang · Wenjuan Cui · Zhiqiang Chen🇨🇳 · Hushan Xu🇨🇳

   In this paper, we study a monitoring method for neutron flux for the spallation target used in an accelerator driven sub-critical (ADS) system, where a spallation target located vertically at the centre of a sub-critical core is bombarded vertically by high-energy protons from an accelerator. First, by considering the characteristics in the spatial variation of neutron flux from the spallation target, we propose a multi-point measurement technique, i.e. the spallation neutron flux should be measured at multiple vertical locations. To explain why the flux should be measured at multiple locations, we have studied neutron production from a tungsten target bombarded by a 250 MeV-proton beam with Geant4-based Monte Carlo simulations. The simulation results indicate that the neutron flux at the central location is up to three orders of magnitude higher than the flux at lower locations. Secondly, we have developed an effective technique in order to measure the spallation neutron flux with a fission chamber (FC), by establishing the relation between the fission rate measured by FC and the spallation neutron flux. Since this relation is linear for a FC, a constant calibration factor is used to derive the neutron flux from the measured fission rate. This calibration factor can be extracted from the energy spectra of spallation neutrons. Finally, we have evaluated the proposed calibration method for a FC in the environment of an ADS system. The results indicate that the proposed method functions very well.

   ↳ physics.ins-detnucl-exCPC(2016)·2 citations
5. 05*

   Test of the notch technique for determining the radial sensitivity of the optical model potential

   Lei Yang · Cheng-Jian Lin🇺🇸 · Hui-ming Jia · Xin-Xing Xu🇩🇪 · Nan-Ru Ma · Li-Jie Sun · Feng Yang · Huan-Qiao Zhang🇨🇳 · Zu-Hua Li · Dong-Xi Wang

   Detailed investigations on the notch technique are performed on the ideal data generated by the optical model potential parameters extracted from the 16O+208Pb system at the laboratory energy of 129.5 MeV, to study the sensitivities of this technique on the model parameters as well as the experimental data. It is found that, for the perturbation parameters, a sufficient large reduced fraction and an appropriate small perturbation width are necessary to determine the accurate radial sensitivity; while for the potential parameters, almost no dependence was observed. For the experimental measurements, the number of data points has little influence for the heavy target system, and the relative inner information of the nuclear potential can be derived when the measurement extended to a lower cross section.

   ↳ nucl-thnucl-exCPC(2016)·4 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.