Tue·Dec 13, 2016Tuesday·December 13, 2016

1. 01*

   Problems to be clarified by means of redioactive ion beams provided by the ACCULINNA-2 separator

   G.M. Ter-Akopian🇷🇺 · A.A. Bezbakh · V. Chudoba🇨🇿 · A.S. Fomichev🇷🇺 · M.S. Golovkov · A.V. Gorshkov🇺🇸 · L.V. Grigorenko🇷🇺 · G. Kaminski · A.G. Knyazev · S.A. Krupko🇷🇺 · M. Mentel · E.Yu. Nikolskii and 8 other authors

   Fragment separator ACCULINNA-2 has been built in the Flerov Laboratory of Nuclear reactions (JINR, Dubna). It is timely now to choose meaningful and challenging objectives for experiments dedicated to the study of light drip-line nuclei. Considerable interest makes the search for the minor $2p$-decay branch of the first excited state of ${}^{17}$Ne. The knowledge on the ${\Gamma }_{2p}/{\Gamma }_{\gamma }$ width ratio for this excited state is of considerable interest because the reverse process of simultaneous two-proton radiative capture could be a bypass for the ${}^{15}$O "waiting point" occurring in the rp-process of nucleosynthesis. Accumulation of high-statistics data for the ${}^{10}$He excitation spectrum populated in the ${}^2$H(${}^8$He,$p$)${}^9$He and ${}^3$H(${}^8$He,$p$)${}^{10}$He reactions, as well as the study of cross-check reactions made with the ${}^{11}$Li and ${}^{14}$Be beams, will make an effective way to clarify the succession of ${}^{10}$He excited states. A hot topic beyond the neutron drip line makes the observation of results capable to elucidate the low-energy resonance states anticipated for the $4n$ decay of ${}^7$H. The RIB beams provided by ACCULINNA-2 will allow one to perform experiments where luminosity coming to a level of more than $2\times 10^{26}$ cm${}^{-2}$ s${}^{-1}$ will be achievable in experiments aimed study of the ${}^2$H(${}^8$He,${}^3$He)${}^7$H and ${}^2$H(${}^{11}$Li,${}^6$Li)${}^7$H reactions.

   nucl-ex0 citations
2. 02*

   Chaos and regularity in the doubly magic nucleus 208Pb

   B. Dietz · A. Heusler · K. H. Maier · A. Richter🇩🇪 · B. A. Brown🇺🇸

   High resolution experiments have recently lead to a complete identification (energy, spin, and parity) of 151 nuclear levels up to an excitation Energy of Ex= 6.20 MeV in 208Pb. We present a thorough study of the fluctuation properties in the energy spectra of the unprecedented set of nuclear bound states. In a first approach we grouped states with the same spin and parity into 14 subspectra, analyzed standard statistical measures for short- and long-range correlations and then computed their ensemble average. Their comparison with a random matrix ensemble which interpolates between Poisson statistics expected for regular systems and the Gaussian Orthogonal Ensemble (GOE) predicted for chaotic systems shows that the data are well described by the GOE. In a second approach, following an idea of Rosenzweig and Porter we considered the complete spectrum composed of the independent subspectra. We analyzed their fluctuation properties using the method of Bayesian inference involving a quantitative measure, called the chaoticity parameter f, which also interpolates between Poisson (f=0) and GOE statistics (f=1). It turns out to be f~0.9. This is so far the closest agreement with GOE observed in spectra of bound states in a nucleus. The same analysis has also been performed with spectra computed on the basis of shell model calculations with different interactions (SDI, KB, M3Y). While the simple SDI exhibits features typical for nuclear many-body systems with regular dynamics, the other, more realistic interactions yield chaoticity parameters f close to the experimental values.

   ↳ nucl-thnlin.CDnucl-exPRL(2017)·26 citations
3. 03*

   Temperature dependence of the plastic scintillator detector for DAMPE

   Zhao-Min Wang🇨🇳 · Yu-Hong Yu🇨🇳 · Zhi-Yu Sun🇨🇳 · Ke Yue🇨🇳 · Duo Yan🇨🇳 · Yong-Jie Zhang🇨🇳 · Yong Zhou🇨🇳 · Fang Fang🇨🇳 · Wen-Xue Huang🇨🇳 · Jun-Ling Chen🇨🇳

   The Plastic Scintillator Detector (PSD) is one of the main sub-detectors in the DArk Matter Particle Explorer (DAMPE) project. It will be operated over a large temperature range from -$10$ to $30^{\circ }$C, so the temperature effect of the whole detection system should be studied in detail. The temperature dependence of the PSD system is mainly contributed by the three parts: the plastic scintillator bar, the photomultiplier tube (PMT), and the Front End Electronics (FEE). These three parts have been studied in detail and the contribution of each part has been obtained and discussed. The temperature coefficient of the PMT is $-0.320(\pm 0.033)\%{/}^{\circ }$C, and the coefficient of the plastic scintillator bar is $-0.036(\pm 0.038)\%{/}^{\circ }$C. This result means that after subtracting the FEE pedestal, the variation of the signal amplitude of the PMT-scintillator system due to temperature mainly comes from the PMT, and the plastic scintillator bar is not sensitive to temperature over the operating range. Since the temperature effect cannot be ignored, the temperature dependence of the whole PSD has been also studied and a correction has been made to minimize this effect. The correction result shows that the effect of temperature on the signal amplitude of the PSD system can be suppressed.

   ↳ physics.ins-detnucl-exCPC(2017)·1 citation

* 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.