Thu·Nov 1, 2018Thursday·November 1, 2018

1. 01*

   Solar Neutrino Physics with Borexino

   Andrea Pocar

   We present the most recent solar neutrino results from the Borexino experiment at the Gran Sasso underground laboratory. In particular, refined measurements of all neutrinos produced in the {\it pp} fusion chain have been made. It is the first time that the same detector measures the entire range of solar neutrinos at once. These new data weakly favor a high-metallicity Sun. Prospects for measuring CNO solar neutrinos are also discussed.

   nucl-exphysics.ins-detSciPost Phys.Proc.(2019)·3 citations
2. 02*

   Updated determination of $N^{\ast }$ resonance parameters using a unitary, multichannel formalism

   B C Hunt🇺🇸 · D M Manley🇺🇸

   Results are presented for an updated multichannel energy-dependent partial-wave analysis of $\pi N$ scattering. Our earlier work incorporated single-energy amplitudes for $\pi N\to \pi N$, $\gamma N\to \pi N$, $\pi N\to \pi \pi N$, $\pi N\to \eta N$, and $\pi N\to K\Lambda$. The present work incorporates new single-energy solutions for $\gamma p\to \eta p$ up to a c.m.\ energy of 1990~MeV, $\gamma p\to K^{+}\Lambda$ up to a c.m.\ energy of 2230~MeV, and $\gamma n\to \eta n$ up to a c.m.\ energy of 1885~MeV, as well as updated single-energy solutions for $\pi N\to \eta N$, $\pi N\to K\Lambda$, and $\gamma N\to \pi N$. In this paper, we present and discuss the resonance parameters obtained from a combined fit of all these single-energy amplitudes. Our determined energy-dependent amplitudes provide an excellent description of the corresponding measured observables.

   nucl-exPRC(2019)·47 citations
3. 03*

   Isotopic trends of quasifission and fusion-fission in the reactions ${}^{48}$Ca+${}^{239,244}$Pu

   Lu Guo🇨🇳 · Caiwan Shen🇨🇳 · Chong Yu · Zhenji Wu🇨🇳

   Background: Quasifission and fusion-fission are primary mechanisms to prevent the production of superheavy elements. The recent experimental measurements reveal that the fusion-evaporation cross section in the $3n$ reaction channel of ${}^{48}$Ca+${}^{239}$Pu is 50 times lower than using ${}^{244}$Pu as target nucleus. However, the precise mechanisms of this remarkable isotopic dependence are not well understood. Purpose: To understand the experimental observation of the rapid decrease of stability of superheavy nuclei as the neutron number decreases, the theoretical studies of quasifission and fusion-fission in connection with experimental production for $Z$=114 flerovium isotopes are required to investigate the possible differences in reaction mechanisms induced by these two targets. Methods: We propose an approach called TDHF+HIVAP to take into account both the evolution of dinuclear system and the deexcitation of compound nucleus, which combines the microscopic time-dependent Hartree-Fock (TDHF) method for the fusion and quasifission dynamics with the statistical evaporation model HIVAP for fusion-fission dynamics. Results: ......The quantum shell effect displays a crucial role in both the quasifission and the fusion-fission processes. The quasifission is considerably reduced and the survival probability is enhanced around one order of magnitude in the reaction using ${}^{244}$Pu target as compared to the ${}^{239}$Pu case. Conclusions: The studies by using TDHF+HIVAP method well account for the experimental observations and the present method clearly shows its applicability in the reaction mechanisms of quasifission and fusion-fission dynamics. The experimental and theoretical results encourage the use of neutron-rich targets for the production of new superheavy elements.

   ↳ nucl-thnucl-exPRC(2018)·45 citations
4. 04*

   Directional fast neutron detection using a time projection chamber and plastic scintillation detectors

   Yidong Fu · Yang Tian · Yulan Li🇨🇳 · Jian Yang · Jin Li

   A new method for directional fast neutron detection is proposed based on a neutron time projection chamber (TPC) and position-sensitive plastic scintillation detectors. The detection system can efficiently locate the approximate location of a hot spot with 4{\pi} field-of-view using only the neutron TPC. Then, the system generates a high-resolution image of the hot spot using selected coincidence events in the TPC and the scintillation detectors. A prototype was built and tested using a Cf-252 source. An efficiency of 7.1x10-3 was achieved for fast searching. The angular resolution was 7.8{\deg} (full width at half maximum, FWHM) for high-resolution imaging using the simple back projection method.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2020)·6 citations
5. 05*

   High $p_t$ squeezed-out n/p ratio as a probe of $K_{\mathrm{sym}}$ of the symmetry energy

   Ya-Fei Guo🇨🇳 · Gao-Chan Yong🇨🇳

   By involving the constraints of the slope of nuclear symmetry energy $L$ into the question of determination of the high-density symmetry energy, one needs to probe the curvature of nuclear symmetry energy $K_{\mathrm{sym}}$. Based on the Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, effects of the curvature of nuclear symmetry energy on the squeezed-out nucleons are demonstrated in the semi-central Au+Au reaction at 400 and 600 MeV/nucleon. It is shown that the squeezed-out isospin-dependent nucleon emissions at high transverse momenta are sensitive to the curvature of nuclear symmetry energy. The curvature of nuclear symmetry energy at saturation density thus can be determined by the high momentum squeezed-out isospin-dependent nucleon emissions experiments from the semi-central Au+Au reaction at 400 or 600 MeV/nucleon.

   ↳ nucl-thnucl-exPRC(2019)·14 citations
6. 06*

   Development of a 3-D Position Sensitive Neutron Detector Based on Organic Scintillators with Double Side SiPM Readout

   Yang Tian · Yidong Fu · Yulan Li🇨🇳 · Yuanjing Li🇨🇳

   A 3-D position sensitive neutron detector is being developed based on a plastic scintillator array. A double side SiPM readout is used to determine the depth of interaction (DOI) in each scintillator unit. In the preliminary test, the DOI in a 254 x 6 x 6 mm3 SP101 plastic scintillator is measured at different positions using a collimated Co-60 source. The SiPM (KETEK PM6660) signals are recorded by a 2.5 GS/s digital oscilloscope. The DOI results are calculated using both the amplitude and the temporal information. Position resolutions (FWHM) of 2.5 cm and 6.6 cm are realized, respectively. A detector based on a 2-D array is capable of recording the 3-D position information of the incident neutron. The 3-D detector is to be used together with a neutron time projection chamber as a directional fast neutron detector. According to the simulation results, the angular resolution (8 degree FWHM) is much better than that of a typical neutron scatter camera.

   ↳ physics.ins-detnucl-ex1 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.