Tue·May 23, 2017Tuesday·May 23, 2017

1. 01*

   Survival Mediated Heavy Element Capture Cross Sections

   Walter Loveland · Larry Yao🇺🇸

   Formally, the cross section for producing a heavy evaporation residue, {\sigma}EVR, in a fusion reaction can be written as. \begin{equation} \sigma_{\rm EVR}(E)=\frac{\pi h^2}{2\mu E}\sum\limits_{\ell=0}^\infty (2\ell+1)T(E,\ell)P_{\rm CN}(E,\ell)W_{\rm sur}(E,\ell), \end{equation} where E is the center of mass energy, and T is the probability of the colliding nuclei to overcome the potential barrier in the entrance channel and reach the contact point. PCN is the probability that the projectile-target system will evolve from the contact point to the compound nucleus. Wsur is the probability that the compound nucleus will decay to produce an evaporation residue rather than fissioning. However, one must remember that the Wsur term effectively sets the allowed values of the spin, which in turn, restricts the values of the capture and fusion cross sections. We point out the implications of this fact for capture cross sections for heavy element formation reactions.

   nucl-exEPJ Web Conf.(2017)·2 citations
2. 02*

   Measurement of cross section of the residues from the ${}^{11}$B-induced reaction on ${}^{89}$Y and ${}^{93}$Nb: Production of ${}^{97}$Ru and ${}^{101m}$Rh

   Deepak Kumar · Moumita Maiti

   The heavy-ion induced reactions on intermediate mass targets are complex in nature, even at the low energies. To understand those nuclear reaction phenomena in detail, more experimental studies are required in a wide range of energy. Heavy-ion reactions were investigated by measuring production cross sections of the residues produced in the ${}^{11}$B-induced reactions on ${}^{89}$Y and ${}^{93}$Nb at low energies, near and above the barrier, and to check the effectiveness of the different nuclear models to explain them. Further, aim is also to optimize the production parameters of neutron deficient medically relevant ${}^{97}$Ru and ${}^{101m}$Rh radioisotopes produced in those reactions, respectively. The ${}^{11}$B-beam was allowed to impinge on ${}^{89}$Y and ${}^{93}$Nb foils supported by an aluminum catcher foil, arranged in a stack, in 27.5-58.7 and 30.6-62.3 MeV energy range, respectively. The $\gamma$-spectrometry was carried out after EOB to measure the activity of the radionuclides produced in each foil and cross sections were calculated. Measured cross-sectional data were analyzed in terms of compound and precompound model calculations. The measured cross sections of the residues showed good agreement with the model calculations based on the Hauser-Feshbach formulation and exciton model. A substantial preequilibrium contribution was noticed in the 3$n$ reaction channel in both the reactions. Theoretical estimations confirmed that major production yields are mostly contributed by the compound reaction process. Preequilibrium emissions contributed at the high energy tail of the 3$n$ channel for both the reactions. Moreover, an indirect signature of a direct reaction influence was also observed in the ${}^{90m}$Y production.

   nucl-exPRC(2017)·26 citations
3. 03*

   Nuclear resonant scattering experiment with fast time response: new scheme for observation of ${}^{229\mathrm{m}}$Th radiative decay

   A.Yoshimi🇯🇵 · H.Hara🇯🇵 · T. Hiraki🇯🇵 · Y.Kasamatsu · S.Kitao · Y.Kobayashi · K.Konashi · R.Masuda🇯🇵 · T.Masuda🇯🇵 · Y.Miyamoto🇯🇵 · K.Okai · S.Okubo and 15 other authors

   Nuclear resonant excitation of the 29.19-keV level in ${}^{229}$Th with high-brilliance synchrotron- radiation and detection of its decay signal, are proposed with the aim of populating the extremely low-energy isomeric state of ${}^{229}$Th.The proposed experiment, known as nuclear resonant scattering (NRS), has the merit of being free from uncertainties about the isomer level energy. However, it requires higher time resolution and shorter tail in the response function of the detector than that of conventional NRS experiments because of the short lifetime of the 29.19-keV state. We have fabricated an X-ray detector system which has a time resolution of 56 ps and a shorter tail function than the previously reported one. We have demonstrated an NRS experiment with the 26.27-keV nuclear level of ${}^{201}$Hg for feasibility assessment of the ${}^{229}$Th experiment. The NRS signal is clearly distinct from the prompt electronic scattering signal by the implemented detector system. The half-life of the 26.27-keV state of ${}^{201}$Hg is determined as 629 $\pm$ 18 ps which is better precision by a factor three than that reported to date.

   nucl-exphysics.atom-phPhys. Rev. C 97, 024607 (2018)·0 citations
4. 04*

   First measurement of the polarization observable $E$ and helicity-dependent cross sections in single ${\pi }^0$ photoproduction from quasi-free nucleons

   M. Dieterle · L. Witthauer · F. Cividini · S. Abt · P. Achenbach · P. Adlarson · F. Afzal · Z. Ahmed · C.S. Akondi · J.R.M. Annand · H.J. Arends · M. Bashkanov and 75 other authors

   The double-polarization observable $E$ and the helicity-dependent cross sections ${\sigma }_{1/2}$ and ${\sigma }_{3/2}$ have been measured for the first time for single ${\pi }^0$ photoproduction from protons and neutrons bound in the deuteron at the electron accelerator facility MAMI in Mainz, Germany. The experiment used a circularly polarized photon beam and a longitudinally polarized deuterated butanol target. The reaction products, recoil nucleons and decay photons from the ${\pi }^0$ meson were detected with the Crystal Ball and TAPS electromagnetic calorimeters. Effects from nuclear Fermi motion were removed by a kinematic reconstruction of the ${\pi }^{0}N$ final state. A comparison to data measured with a free proton target showed that the absolute scale of the cross sections is significantly modified by nuclear final-state interaction (FSI) effects. However, there is no significant effect on the asymmetry $E$ since the ${\sigma }_{1/2}$ and ${\sigma }_{3/2}$ components appear to be influenced in a similar way. Thus, the best approximation of the two helicity-dependent cross sections for the free neutron is obtained by combining the asymmetry $E$ measured with quasi-free neutrons and the unpolarized cross section corrected for FSI effects under the assumption that the FSI effects are similar for neutrons and protons.

   nucl-exPLB(2017)·29 citations
5. 05*

   New directions with transfer reactions

   Kate L. Jones (for the VANDLE, GODDESS, HAGRiD, and CLARION-BareBall Collaborations)

   Over the last two decades transfer reactions have seen a resurgence following developments in methods to use them with exotic beams. An important step in this evolution was the ability to perform the (d,p) reaction on fission fragment beams using the inverse kinematics technique, built on the experience with light beams. There has been renewed interest in using (${}^9$Be, ${}^8$Be) and (${}^{13}$C, ${}^{12}$C) reactions to selectively populate single-particle like states that can be studied via their subsequent decay. These reactions have been successfully utilized in the ${}^{132}$Sn region. Additionally, our collaboration has recently performed experiments with GODDESS, a combination of the full ORRUBA detector and Gammasphere arrays. Another new direction is measuring neutrons from (d,n) reactions, performed in inverse kinematics, with the VANDLE array of plastic scintillators. Presented below is an overview of these new techniques and some of the early data from recent experiments.

   nucl-ex0 citations
6. 06*

   Time-dependent mean-field investigations of the quasifission process

   A.S. Umar🇺🇸 · C. Simenel🇦🇺 · S. Ayik🇺🇸

   We demonstrate that the microscopic Time-dependent Hartree-Fock (TDHF) theory provides an important approach to shed light on the nuclear dynamics leading to the formation of superheavy elements. In particular, we discuss studying quasifission dynamics and calculating ingredients for compound nucleus formation probability calculations. We also discuss possible extensions to TDHF to address the distribution of observables.

   ↳ nucl-thnucl-exEPJ Web Conf.(2017)·0 citations
7. 07*

   Precision analysis of electron energy spectrum and angular distribution of neutron beta decay with polarized neutron and electron

   A. N. Ivanov🇦🇹 · R. Höllwieser🇦🇹 · N. I. Troitskaya🇦🇹 · M. Wellenzohn🇦🇹 · Ya. A. Berdnikov🇷🇺

   We give a precision analysis of the correlation coefficients of the electron-energy spectrum and angular distribution of the beta decay and radiative beta decay of the neutron with polarized neutron and electron to order 10^(-3). The calculation of correlation coefficients is carried out within the Standard model with contributions of order 10^(-3), caused by the weak magnetism and proton recoil, taken to next-to-leading order in the large proton mass expansion, and with radiative corrections of order "alpha/pi ~ 10^(-3", calculated to leading order in the large proton mass expansion. The obtained results can be used for the planning of experiments on the search for contributions of order 10^(-4) of interactions beyond the Standard model.

   ↳ hep-phastro-ph.COhep-exnucl-exPRC(2017)·23 citations
8. 08*

   Multi-cluster dynamics in ${}_{\Lambda }^{13}\mathrm{C}$ and analogy to clustering in ${}^{12}\mathrm{C}$

   Y. Funaki🇯🇵 · M. Isaka🇯🇵 · E. Hiyama🇯🇵 · T. Yamada🇯🇵 · K. Ikeda

   We investigate structure of ${}_{\Lambda }^{13}\mathrm{C}$ and discuss the difference and similarity between the structures of ${}^{12}\mathrm{C}$ and ${}_{\Lambda }^{13}\mathrm{C}$ by answering the questions if the linear-chain and gaslike cluster states, which are proposed to appear in ${}^{12}\mathrm{C}$, survives, or new structure states appear or not. We introduce a microscopic cluster model called, Hyper-Tohsaki-Horiuchi-Schuck-Röpke (H-THSR) wave function, which is an extended version of the THSR wave function so as to describe $\Lambda$ hypernuclei. We obtained two bound states and two resonance (quasi-bound) states for $J^{\pi }=0^{+}$ in ${}_{\Lambda }^{13}\mathrm{C}$, corresponding to the four $0^{+}$ states in ${}^{12}\mathrm{C}$. However, the inversion of level ordering between the spectra of ${}^{12}\mathrm{C}$ and ${}_{\Lambda }^{13}\mathrm{C}$, i.e. that the $0_3^{+}$ and $0_4^{+}$ states in ${}_{\Lambda }^{13}\mathrm{C}$ correspond to the $0_4^{+}$ and $0_3^{+}$ states in ${}^{12}\mathrm{C}$, respectively, is shown to occur. The additional $\Lambda$ particle reduces sizes of the $0_2^{+}$ and $0_3^{+}$ states in ${}_{\Lambda }^{13}\mathrm{C}$ very much, but the shrinkage of the $0_4^{+}$ state is only a half of the other states. In conclusion, the Hoyle state becomes quite a compact object with ${}_{\Lambda }^9\mathrm{Be}+\alpha$ configuration in ${}_{\Lambda }^{13}\mathrm{C}$ and is no more gaslike state composed of the $3\alpha$ clusters. Instead, the $0_4^{+}$ state in ${}_{\Lambda }^{13}\mathrm{C}$, coming from the ${}^{12}\mathrm{C}(0_3^{+})$ state, appears as a gaslike state composed of $\alpha +\alpha {+}_{\Lambda }^5\mathrm{He}$ configuration, i.e. the Hoyle analog state. A linear-chain state in a $\Lambda$ hypernucleus is for the first time predicted to exist as the $0_3^{+}$ state in ${}_{\Lambda }^{13}\mathrm{C}$ with more shrunk arrangement of the $3\alpha$ clusters along $z$-axis than the $3\alpha$ linear-chain configuration realized in the ${}^{12}\mathrm{C}(0_4^{+})$ state.

   ↳ nucl-thnucl-exPLB(2017)·22 citations
9. 09*

   An Empirical Scaling formula for fragments production in projectile fragmentation reactions

   Yi-Dan Song · Chun-Wang Ma🇨🇳 · Xue-Ying Liu · Hui-Ling Wei🇨🇳

   A scaling phenomenon in the cross section for fragments has been found in the projectile fragmentation reaction, and an empirical scaling formula is proposed by considering the dependence of cross section on the size and asymmetry of the reaction system and the fragment itself. Furthermore, the empirical scaling formula is used to predict the production of fragment in the ${}^{68}$Ni/${}^{69}$Cu/${}^{72}$Zn + ${}^9$Be reactions around 90$A$ MeV. Compared to the results calculated by the statistical abrasion ablation model and the {\sc epax3} parameterizations, the empirical scaling formula can better reproduce the measured fragments. The empirical scaling formula can be used to predict the yield for fragment in projectile fragmentation reaction.

   ↳ nucl-thnucl-ex1 citation
10. 10*

    Toward a complete theory for predicting inclusive deuteron breakup away from stability

    G. Potel · G. Perdikakis · B. V. Carlson · M. C. Atkinson · P. Capel · W. H. Dickhoff · J. E. Escher · M. S. Hussein · J. Lei · W. Li · A. O. Macchiavelli · A. M. Moro and 3 other authors

    We present an account of the current status of the theoretical treatment of inclusive $(d,p)$ reactions in the breakup-fusion formalism, pointing to some applications and making the connection with current experimental capabilities. Three independent implementations of the reaction formalism have been recently developed, making use of different numerical strategies. The codes also originally relied on two different but equivalent representations, namely the prior (Udagawa-Tamura, UT) and the post (Ichimura-Austern-Vincent, IAV) representations. The different implementations have been benchmarked, and then applied to the Ca isotopic chain. The neutron-Ca propagator is described in the Dispersive Optical Model (DOM) framework, and the interplay between elastic breakup (EB) and non-elastic breakup (NEB) is studied for three Ca isotopes at two different bombarding energies. The accuracy of the description of different reaction observables is assessed by comparing with experimental data of $(d,p)$ on ${}^{40,48}$Ca. We discuss the predictions of the model for the extreme case of an isotope (${}^{60}$Ca) currently unavailable experimentally, though possibly available in future facilities (nominally within production reach at FRIB). We explore the use of $(d,p)$ reactions as surrogates for $(n,\gamma )$ processes, by using the formalism to describe the compound nucleus formation in a $(d,p\gamma )$ reaction as a function of excitation energy, spin, and parity. The subsequent decay is then computed within a Hauser-Feshbach formalism. Comparisons between the $(d,p\gamma )$ and $(n,\gamma )$ induced gamma decay spectra are discussed to inform efforts to infer neutron captures from $(d,p\gamma )$ reactions. Finally, we identify areas of opportunity for future developments, and discuss a possible path toward a predictive reaction theory.

    ↳ nucl-thnucl-exEPJA(2017)·80 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.