Fri·Jun 15, 2018Friday·June 15, 2018

1. 01*

   Isoscalar Giant Monopole, Dipole, and Quadrupole Resonances in ${}^{90,92}$Zr and ${}^{92}$Mo

   Y. K. Gupta🇺🇸 · K. B. Howard🇺🇸 · U. Garg🇺🇸 · J. T. Matta🇺🇸 · M. Senyigit🇺🇸 · M. Itoh🇯🇵 · S. Ando🇳🇱 · T. Aoki · A. Uchiyama🇯🇵 · S. Adachi🇯🇵 · M. Fujiwara🇯🇵 · C. Iwamoto🇯🇵 and 10 other authors

   The isoscalar giant monopole, dipole, and quadrupole strength distributions have been deduced in ${}^{90,92}$Zr, and ${}^{92}$Mo from "background-free" spectra of inelastic $\alpha$-particle scattering at a beam energy of 385 MeV at extremely forward angles, including 0${}^{\circ }$. These strength distributions were extracted by a multipole-decomposition analysis based on the expected angular distributions of the respective multipoles. All these strength distributions for the three nuclei practically coincide with each other, affirming that giant resonances, being collective phenomena, are not influenced by nuclear shell structure near $A\sim$90, contrary to the claim in a recent measurement.

   nucl-exnucl-thPRC(2018)·30 citations
2. 02*

   The ORNL Analysis Technique for Extracting $\beta$-Delayed Multi-Neutron Branching Ratios with BRIKEN

   B.C. Rasco🇺🇸 · N.T. Brewer🇺🇸 · R. Yokoyama🇯🇵 · R. Grzywacz🇺🇸 · K.P. Rykaczewski🇺🇸 · A. Tolosa-Delgado · J. Agramunt🇪🇸 · J.L. Tain🇪🇸 · A. Algora🇪🇸 · O. Hall · C. Griffin · T. Davinson🇬🇧 and 6 other authors

   Many choices are available in order to evaluate large radioactive decay networks. %multi-particle decay data. There are many parameters that influence the calculated $\beta$-decay delayed single and multi-neutron emission branching fractions. We describe assumptions about the decay model, background, and other parameters and their influence on $\beta$-decay delayed multi-neutron emission analysis. An analysis technique, the ORNL BRIKEN analysis procedure, for determining $\beta$-delayed multi-neutron branching ratios in $\beta$-neutron precursors produced by means of heavy-ion fragmentation is presented. The technique is based on estimating the initial activities of zero, one, and two neutrons occurring in coincidence with an ion-implant and $\beta$ trigger. The technique allows one to extract $\beta$-delayed multi-neutron decay branching ratios measured with the hybrid \textsuperscript{3}He BRIKEN neutron counter. As an example, two analyses of the $\beta$-neutron emitter \textsuperscript{77}Cu based on different {\it a priori} assumptions are presented along with comparisons to literature values.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2018)·9 citations
3. 03*

   Charge-dependent Flow Induced by Magnetic and Electric Fields in Heavy Ion Collisions

   Umut Gürsoy🇳🇱 · Dmitri Kharzeev🇺🇸 · Eric Marcus🇳🇱 · Krishna Rajagopal🇺🇸 · Chun Shen🇺🇸

   We investigate the charge-dependent flow induced by magnetic and electric fields in heavy ion collisions. We simulate the evolution of the expanding cooling droplet of strongly coupled plasma hydrodynamically, using the iEBE-VISHNU framework, and add the magnetic and electric fields as well as the electric currents they generate in a perturbative fashion. We confirm the previously reported effect of the electromagnetically induced currents, that is a charge-odd directed flow $\Delta v_1$ that is odd in rapidity, noting that it is induced by magnetic fields (à la Faraday and Lorentz) and by electric fields (the Coulomb field from the charged spectators). In addition, we find a charge-odd $\Delta v_3$ that is also odd in rapidity and that has a similar physical origin. We furthermore show that the electric field produced by the net charge density of the plasma drives rapidity-even charge-dependent contributions to the radial flow $⟨p_T⟩$ and the elliptic flow $\Delta v_2$. Although their magnitudes are comparable to the charge-odd $\Delta v_1$ and $\Delta v_3$, they have a different physical origin, namely the Coulomb forces within the plasma.

   ↳ hep-phhep-thnucl-exnucl-thPRC(2018)·127 citations
4. 04*

   A Cryogenic Supersonic Jet Target for Electron Scattering Experiments at MAGIX@MESA and MAMI

   Silke Grieser🇩🇪 · Daniel Bonaventura🇩🇪 · Philipp Brand🇩🇪 · Catharina Hargens🇩🇪 · Benjamin Hetz🇩🇪 · Lukas Leßmann🇩🇪 · Christina Westphälinger🇩🇪 · Alfons Khoukaz🇩🇪

   High-performance cluster-jet targets are ideally suited and applied since years in hadron and laser plasma physics. Therefore, the forthcoming MAGIX experiment at the future energy recovering electron accelerator MESA will use a cluster-jet target to perform high precision measurements on electron scattering experiments, i.e., determination of the proton radius. For this purpose, a cluster-jet target was designed, built up and set successfully into operation at the University of Münster considering the requirements of the experimental setup of MAGIX. The details on these requirements, calculations to their realization, e.g., on the nozzle geometry and stagnation conditions of the target gas, their technical implementation and the features of the target which make the target a powerful state-of-the-art target, are highlighted in this publication. Furthermore, the measured and analysed jet beam characteristics from this target using a Mach Zehnder interferometer are presented and discussed. These are of highest interest for the final design of the complete experimental setup of MAGIX. Moreover, first measurements from commissioning beam times performed with the target installed at the already running MAinzer MIkrotron will be presented.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2018)·26 citations
5. 05*

   Final results on ${}^{\text{82}}$Se double beta decay to the ground state of ${}^{\text{82}}$Kr from the NEMO-3 experiment

   NEMO-3 Collaboration: R. Arnold🇫🇷 · C. Augier🇫🇷 · A.S. Barabash🇷🇺 · A. Basharina-Freshville🇬🇧 · S. Blondel🇫🇷 · S. Blot🇬🇧 · M. Bongrand🇫🇷 · D. Boursette🇫🇷 · V. Brudanin🇷🇺 · J. Busto🇫🇷 · A.J. Caffrey🇺🇸 · S. Calvez🇫🇷 and 86 other authors

   Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay ($2\nu \beta \beta$) half-life of ${}^{82}$Se as $T_{1/2}^{2\nu }=\left[9.39\pm 0.17\left(\text{mbox}stat\right)\pm 0.58\left(\text{mbox}syst\right)\right]\times 10^{19}$ y under the single-state dominance hypothesis for this nuclear transition. The corresponding nuclear matrix element is $\left|M^{2\nu }\right|=0.0498\pm 0.0016$. In addition, a search for neutrinoless double beta decay ($0\nu \beta \beta$) using 0.93 kg of ${}^{82}$Se observed for a total of 5.25 y has been conducted and no evidence for a signal has been found. The resulting half-life limit of $T_{1/2}^{0\nu }>2.5\times 10^{23}\text{mbox}y(90\%\text{mbox}C.L.)$ for the light neutrino exchange mechanism leads to a constraint on the effective Majorana neutrino mass of $⟨m_{\nu }⟩<\left(1.2-3.0\right)\text{mbox}eV$, where the range reflects $0\nu \beta \beta$ nuclear matrix element values from different calculations. Furthermore, constraints on lepton number violating parameters for other $0\nu \beta \beta$ mechanisms, such as right-handed currents, majoron emission and R-parity violating supersymmetry modes have been set.

   ↳ hep-exnucl-exEPJC(2018)·81 citations
6. 06*

   Low-energy quadrupole states in neutron-rich tin nuclei

   E. Yüksel🇹🇷 · G. Colò🇮🇹 · E. Khan🇫🇷 · Y. F. Niu🇷🇴

   We present a study on the isoscalar quadrupole strength in tin nuclei, focusing mainly on the low-energy region. The calculations are performed using the Skyrme type energy density functionals within the fully self-consistent quasiparticle random phase approximation, allowing for a good description of the experimental data for the first 2${}^{+}$ state and the isoscalar giant quadrupole resonance. It is found that the first $2^{+}$ state and the low-energy quadrupole states between 3 and 6 MeV display an opposite behavior with increasing neutron number. While the strength of the first $2^{+}$ state decreases, some excited states start to accumulate between 3 and 6 MeV, and increase their strength with increasing neutron number. This low-energy region between 3 and 6 MeV is quite sensitive to the changes in the shell structure with increasing neutron number. In particular, between ${}^{116}$Sn and ${}^{132}$Sn, the filling of the neutron orbitals with large values of $j$, has an important impact on the low-energy region. Our analysis shows that the low-energy states have a non-collective character, except the first 2${}^{+}$ state. In addition, the states in the low-energy region above 5 MeV display an interesting pattern: with the increase of the neutron number, their strength increases and their nature changes, namely they switch from proton excitations to neutron-dominated one. We conclude that the low-energy quadrupole states between 3 and 6 MeV can provide information about the shell evolution in open-shell nuclei.

   ↳ nucl-thnucl-exPRC(2018)·14 citations
7. 07*

   Probing the in-Medium QCD Force by Open Heavy-Flavor Observables

   Shuai Y.F. Liu🇺🇸 · Min He🇨🇳 · Ralf Rapp🇺🇸

   The determination of the color force in a quark-gluon plasma (QGP) is a key objective in the investigation of strong-interaction matter. Open and hidden heavy-flavor observables in heavy-ion collisions (HICs) are believed to provide insights into this problem by comparing calculations of heavy-quark (HQ) and quarkonium transport with pertinent experimental data. In this work, we utilize the $T$-matrix formalism to compute charm-quark transport coefficients for various input potentials previously extracted from simultaneous fits to lattice-QCD data for HQ free energies, quarkonium correlators and the QGP equation of state. We investigate the impact of off-shell effects (spectral functions) in the QGP medium on the HQ transport, and compare to earlier results using the free or internal HQ energies as potential proxies. We then employ the transport coefficients in relativistic Langevin simulations for HICs to test the sensitivity of heavy-flavor observables to the HQ interactions in the QGP. We find that a strongly-coupled $T$-matrix solution generates a HQ elliptic flow comparable to the results from the internal energy at low momentum, driven by a long-range remnant of the confining force, while falling off stronger with increasing 3-momentum. The weakly coupled $T$-matrix solution, whose underlying potential is close to the free energy, leads to an elliptic flow well below the experimentally observed range.

   ↳ nucl-thhep-phnucl-exPRC(2019)·42 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.