Wed·Apr 18, 2018Wednesday·April 18, 2018

1. 01*

   Partial-wave analyses of $\gamma p\to \eta p$ \ and $\gamma n\to \eta n$ using a multichannel framework

   B. C. Hunt🇺🇸 · D. M. Manley🇺🇸

   This paper presents results from partial-wave analyses of the photoproduction reactions $\gamma p\to \eta p$ and $\gamma n\to \eta n$. World data for the observables \DSG, $\Sigma$, $T$, $P$, $F$, and $E$ were analyzed as part of this work. The dominant amplitude in the fitting range from threshold to a c.m.\ energy of 1900 MeV was found to be $S_{11}$ in both reactions, consistent with results of other groups. At c.m.\ energies above 1600 MeV, our solution deviates from published results, with this work finding higher-order partial waves becoming significant. Data off the proton suggest that the higher-order terms contributing to the reaction include $P_{11}$, $P_{13}$, and $F_{15}$. The final results also hint that $F_{17}$ is needed to fit double-polarization observables above 1900 MeV. Data off the neutron show a contribution from $P_{13}$, as well as strong contributions from $D_{13}$ and $D_{15}$.

   nucl-exPRC(2019)·12 citations
2. 02*

   Measurement of double-polarization asymmetries in the quasi-elastic ${}^3\overrightarrow{\mathrm{He}}(\vec{\mathrm{e}},{\mathrm{e}}^{\prime }\mathrm{p})$ process

   M. Mihovilovič · G. Jin · E. Long · Y.-W. Zhang · K. Allada · B. Anderson · J. R. M. Annand · T. Averett · W. Bertozzi · W. Boeglin · P. Bradshaw · A. Camsonne and 90 other authors

   We report on a precise measurement of double-polarization asymmetries in electron-induced breakup of ${}^3\mathrm{He}$ proceeding to $\mathrm{pd}$ and $\mathrm{ppn}$ final states, performed in quasi-elastic kinematics at $Q^2=0.25(\mathrm{GeV}/c{)}^2$ for missing momenta up to $250\mathrm{MeV}/c$. These observables represent highly sensitive tools to investigate the electromagnetic and spin structure of ${}^3\mathrm{He}$ and the relative importance of two- and three-body effects involved in the breakup reaction dynamics. The measured asymmetries cannot be satisfactorily reproduced by state-of-the-art calculations of ${}^3\mathrm{He}$ unless their three-body segment is adjusted, indicating that the spin-dependent part of the nuclear interaction governing the three-body breakup process is much smaller than previously thought.

   nucl-exPLB(2019)·5 citations
3. 03*

   First observation of the electron capture of ${}^{76}$As

   A. R. Domula · K. Zuber🇩🇪

   For a variety of radionuclides which decay via ${\beta }^{-}$ and a weak ${\beta }^{+}$-channel the electron-capture (EC) is not observed yet. As the interest of exact decay characteristica increased again, not least with the need of reliable data for experiments on investigation of the neutrinoless double-beta-decay, an experiment for the investigation of the ${}^{76}$As-EC was performed. The first time observation of the EC of ${}^{76}$As by this experiment resulted in a total branching-ratio for the EC / ${\beta }^{+}$-channel of $p_{\mathrm{EC}}=0.0269\pm \left(0.0080(stat.)\pm 0.0029(sys.)\right)$ and $p_{\mathrm{EC}}=0.0263\pm \left(0.0077(stat.)\pm 0.0047(sys.)\right)$ according to two different methods. For the branching of this decay-channel into the first excited- and the ground state of \gess a limit was obtained.

   nucl-ex0 citations
4. 04*

   Experimental study of precisely selected evaporation chains in the decay of excited ${}^{25}$Mg

   A. Camaiani🇮🇹 · G. Casini🇮🇹 · L. Morelli🇫🇷 · S. Barlini🇮🇹 · S. Piantelli🇮🇹 · G. Baiocco🇮🇹 · M. Bini🇮🇹 · M. Bruno🇮🇹 · A. Buccola🇮🇹 · M. Cinausero🇮🇹 · M. Cicerchia🇮🇹 · M. D'Agostino🇮🇹 and 13 other authors

   The reaction ${}^{12}$C + ${}^{13}$C at 95 MeV bombarding energy is studied using the GARFIELD + Ring Counter apparatus located at the INFN Laboratori Nazionali di Legnaro. In this paper we want to investigate the de-excitation of ${}^{25}$Mg aiming both at a new stringent test of the statistical description of nuclear decay and a direct comparison with the decay of the system ${}^{24}$Mg formed through ${}^{12}$C+${}^{12}$C reactions previously studied. Thanks to the large acceptance of the detector and to its good fragment identification capabilities, we could apply stringent selections on fusion-evaporation events, requiring their completeness in charge. The main decay features of the evaporation residues and of the emitted light particles are overall well described by a pure statistical model; however, as for the case of the previously studied 24Mg, we observed some deviations in the branching ratios, in particular for those chains involving only the evaporation of $\alpha$ particles. From this point of view the behavior of the ${}^{24}$Mg and ${}^{25}$Mg decay cases appear to be rather similar. An attempt to obtain a full mass balance even without neutron detection is also discussed.

   nucl-exPRC(2018)·19 citations
5. 05*

   Systematic study of $\alpha$ decay of nuclei around $\mathbf{Z}=82$, $\mathbf{N}=126$ shell closure within the cluster-formation model and proximity potential 1977 formalism

   Jun-Gang Deng · Jie-Cheng Zhao · Peng-Cheng Chu🇨🇳 · Xiao-Hua Li🇨🇳

   In the present work, we systematically study the $\alpha$ decay preformation factors $P_{\alpha }$ within the cluster-formation model and $\alpha$ decay half-lives by the proximity potential 1977 formalism for nuclei around $Z=82$, $N=126$ closed shells. The calculations show that the realistic $P_{\alpha }$ is linearly dependent on the product of valance protons (holes) and valance neutrons (holes) $N_p{N}_n$. It is consistent with our previous works [X.-D. Sun \textit{et al.}, \href{https://journals.aps.org/prc/abstract/10.1103/PhysRevC.94.024338}{ Phys. Rev. C 94, 024338 (2016)}, J.-G. Deng \textit{et al.}, \href{https://journals.aps.org/prc/abstract/10.1103/PhysRevC.96.024318}{Phys. Rev. C 96, 024318 (2017)}], which $P_{\alpha }$ are model-dependent and extracted from the ratios of calculated $\alpha$ half-lives to experimental data. Combining with our previous works, we confirm that the valance proton-neutron interaction plays a key role in the $\alpha$ preformation for nuclei around $Z=82$, $N=126$ shell closures whether the $P_{\alpha }$ is model-dependent or microcosmic. In addition, our calculated $\alpha$ decay half-lives by using the proximity potential 1977 formalism taking $P_{\alpha }$ evaluated by the cluster-formation model can well reproduce the experimental data and significantly reduce the errors.

   ↳ nucl-thnucl-exPRC(2018)·65 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.