Wed·Mar 7, 2018Wednesday·March 7, 2018

1. 01*

   First Measurement of the Ti$(e,e^{\prime })\mathrm{X}$ Cross Section at Jefferson Lab

   H. Dai🇺🇸 · M. Murphy🇺🇸 · V. Pandey🇺🇸 · D. Abrams🇺🇸 · D. Nguyen🇺🇸 · B. Aljawrneh🇺🇸 · S. Alsalmi🇺🇸 · A. M. Ankowski🇺🇸 · J. Bane🇺🇸 · S. Barcus🇺🇸 · O. Benhar🇮🇹 · V. Bellini🇮🇹 and 45 other authors

   To probe CP violation in the leptonic sector using GeV energy neutrino beams in current and future experiments using argon detectors, precise models of the complex underlying neutrino and antineutrino interactions are needed. The E12-14-012 experiment at Jefferson Lab Hall A was designed to perform a combined analysis of inclusive and exclusive electron scatterings on both argon ($N=22$) and titanium ($Z=22$) nuclei using GeV energy electron beams. The measurement on titanium nucleus provides essential information to understand the neutrino scattering on argon, large contribution to which comes from scattering off neutrons. Here we report the first experimental study of electron-titanium scattering as double differential cross section at beam energy $E=2.222$ GeV and electron scattering angle $\theta =15.541$ deg, measured over a broad range of energy transfer, spanning the kinematical regions in which quasielastic scattering and delta production are the dominant reaction mechanisms. The data provide valuable new information needed to develop accurate theoretical models of the electromagnetic and weak cross sections of these complex nuclei in the kinematic regime of interest to neutrino experiments.

   nucl-exhep-exnucl-thPRC(2018)·44 citations
2. 02*

   Halo structure of ${}^8$B determined from intermediate energy proton elastic scattering in inverse kinematics

   G.A. Korolev🇷🇺 · A.V. Dobrovolsky🇷🇺 · A.G. Inglessi🇷🇺 · G.D. Alkhazov🇷🇺 · P. Egelhof🇩🇪 · A. Estrade🇩🇪 · I. Dillmann🇩🇪 · F. Farinon🇩🇪 · H. Geissel🇩🇪 · S. Ilieva🇩🇪 · Y. Ke🇩🇪 · A.V. Khanzadeev🇷🇺 and 15 other authors

   The absolute differential cross section for small-angle proton elastic scattering on the proton-rich ${}^8$B nucleus has been measured in inverse kinematics for the first time. The experiment was performed using a secondary radioactive beam with an energy of 0.7 GeV/u at GSI, Darmstadt. The active target, namely hydrogen-filled time projection ionization chamber IKAR, was used to measure the energy, angle and vertex point of the recoil protons. The scattering angle of the projectiles was simultaneously determined by the tracking detectors. The measured differential cross section is analyzed on the basis of the Glauber multiple scattering theory using phenomenological nuclear-density distributions with two free parameters. The radial density distribution deduced for ${}^8$B exhibits a halo structure with the root-mean-square (rms) matter radius $R_{\mathrm{m}}=2.58(6)$ fm and the rms halo radius $R_{\mathrm{h}}=4.24(25)$ fm. The results on ${}^8$B are compared to those on the mirror nucleus ${}^8$Li investigated earlier by the same method. A comparison is also made with previous experimental results and theoretical predictions for both nuclei.

   nucl-exnucl-thPLB(2018)·43 citations
3. 03*

   Beam energy dependence of squeeze-out effect on the directed and elliptic flow in Au+Au collisions at high baryon density region

   Chao Zhang🇨🇳 · Jiamin Chen🇨🇳 · Xiaofeng Luo🇨🇳 · Feng Liu🇨🇳 · Yasushi Nara🇯🇵

   We present a detailed analysis of the beam energy dependence of the mechanisms for the generation of directed and elliptic flows in Au+Au collisions focusing on the role of hadronic rescattering and spectator shadowing within a microscopic transport model JAM with different equation of state. A systematic study of the beam energy dependence is performed for Au+Au collisions at $\sqrt{s_{NN}}=2.3-62.4$ GeV. The transition of the dynamical origin of the directed flow is observed. We find that the initial Glauber type nucleon-nucleon collisions generate negative $v_1$ for nucleons at midrapidity due to the presence of spectator matter, and this negative nucleon $v_1$ is turned to be positive by the meson-baryon interactions at the beam energy region of $\sqrt{s_{NN}}<30$ GeV. In contrast, above 30 GeV there is no spectator shadowing at midrapidity, and initial nucleon-nucleon collisions do not generate directed flow, but subsequent rescatterings among produced particles generate negative $v_1$ for nucleons. It is demonstrated that negative pion-directed flows are mostly generated by the interaction with the spectator matter. It is also shown that the squeeze-out effect is largely suppressed in the case of softening, which leads to the enhancement of elliptic flow around $\sqrt{s_{NN}}=5-7$ GeV. The elliptic flow at midrapidity above 10 GeV is not influenced by the squeeze-out due to spectator matter, while its effect is seen at the forward rapidity range of $y/y_{c.m.}>0.5$, which decreases as beam energy increases.

   nucl-exhep-exhep-phnucl-thPRC(2018)·32 citations
4. 04*

   Hot fusion reactions with deformed nuclei for synthesis of superheavy nuclei: an extension of the fusion-by-diffusion model

   K. Hagino

   The fusion-by-diffusion model proposed by Swiatecki {\it et al.} [Phys. Rev. C71, 014602 (2005)] has provided a simple and convenient tool to estimate evaporation residue cross sections for superheavy nuclei. I extend this model by taking into account deformation of the target nucleus, and discuss the role of orientation of deformed target in hot fusion reactions at energies around the Coulomb barrier. To this end, I introduce an injection point for the diffusion process over an inner barrier which depends on the orientation angle. I apply this model to the ${}^{48}$Ca+${}^{248}$Cm reaction and show that the maximum of evaporation residue cross section appears at an energy slightly above the height of the capture barrier for the side collision, for which the effective inner barrier is considerably lower than that for the tip collision, thus enhancing the diffusion probability. I also discuss the energy dependence of the injection point, and show that a large part of the energy dependence found in the previous analyses can be attributed to the deformation effect of a target nucleus.

   ↳ nucl-thnucl-exPRC(2018)·40 citations
5. 05*

   Nearly isentropic flow at sizeable $\eta /s$

   Aleksi Kurkela🇨🇭 · Urs Achim Wiedemann🇨🇭 · Bin Wu🇨🇭

   Non-linearities in the harmonic spectra of hadron-nucleus and nucleus-nucleus collisions provide evidence for the dynamical response to azimuthal spatial eccentricities. Here, we demonstrate within the framework of transport theory that even the mildest interaction correction to a picture of free-streaming particle distributions, namely the inclusion of one perturbatively weak interaction ("one-hit dynamics"), will generically give rise to all observed linear and non-linear structures. We further argue that transport theory naturally accounts within the range of its validity for realistic signal sizes of the linear and non-linear response coefficients observed in azimuthal momentum anisotropies with a large mean free path of the order of the system size in peripheral ($\sim 50\%$ centrality) PbPb or central pPb collisions. The shear viscosity to entropy density ratio $\eta /s$ of such a transport theory is approximately an order of magnitude larger than that of an almost perfect fluid. The phenomenological success of transport simulations thus challenges the perfect fluid paradigm of ultra-relativistic nucleus-nucleus and hadron-nucleus collisions.

   ↳ hep-phhep-exnucl-exnucl-thPLB(2018)·67 citations
6. 06*

   $\alpha$ decay properties of ${}^{296}$Og within the two-potential approach

   Jun-Gang Deng · Jie-Cheng Zhao · Jiu-Long Chen🇨🇳 · Xi-Jun Wu · Xiao-Hua Li🇨🇳

   The present work is a continuations of our previous paper [J.-G. Deng, et al., Chin. Phys. C, {\bf41}: 124109 (2017)]. In present work, the $\alpha$ decay half-life of unknown nucleus ${}^{296}$Og is predicted within the two-potential approach and the hindrance factors of all 20 even-even nuclei in the same region with ${}^{296}$Og, i.e. proton number $82<Z<126$ and neutron number $152<N<184$, from ${}^{250}$Cm to ${}^{294}$Og are extracted. The prediction is 1.09 ms within a factor of 5.12. In addition, based on the latest experimental data, a new set of parameters of $\alpha$ decay hindrance factors for the even-even nuclei in this region considering the shell effect and proton-neutron interaction are obtained.

   ↳ nucl-thnucl-exCPC(2018)·19 citations
7. 07*

   Nuclear quantum shape-phase transitions in odd-mass systems

   S. Quan · Z. P. Li · D. Vretenar🇭🇷 · J. Meng

   Microscopic signatures of nuclear ground-state shape phase transitions in odd-mass Eu isotopes are explored starting from excitation spectra and collective wave functions obtained by diagonalization of a core-quasiparticle coupling Hamiltonian based on energy density functionals. As functions of the physical control parameter -- the number of nucleons -- theoretical low-energy spectra, two-neutron separation energies, charge isotope shifts, spectroscopic quadrupole moments, and $E2$ reduced transition matrix elements accurately reproduce available data, and exhibit more pronounced discontinuities at neutron number $N=90$, compared to the adjacent even-even Sm and Gd isotopes. The enhancement of the first-order quantum phase transition in odd-mass systems can be attributed to a shape polarization effect of the unpaired proton which, at the critical neutron number, starts predominantly coupling to Gd core nuclei that are characterized by larger quadrupole deformation and weaker proton pairing correlations compared to the corresponding Sm isotopes.

   ↳ nucl-thnucl-exPRC(2018)·30 citations
8. 08*

   RHIP, a Radio-controlled High-Voltage Insulated Picoammeter and its usage in studying ion backflow in MPGD-based photon detectors

   M. Bari🇮🇹 · B. Gobbo🇮🇹 · S. Dalla Torre🇮🇹 · M. Gregori🇮🇹 · S. Levorato🇮🇹 · G. Menon🇮🇹 · F. Tessarotto🇮🇹

   A picoammeter system has been developed and engineering. It consists in a current-voltage converter, based on an operational amplifier with very low input current, a high precision ADC, a radio controlled data acquisition unit and the computer-based control, visualization and storage. The precision is of the order of a tenth of picoampers and it can measure currents between electrodes at potentials up to 8 kV. The system is battery powered and a number of strategies have been implemented to limit the power consumption. The system is designed for multichannel applications, up to 256 parallel channels. The overall implementation is cost-effective to make the availability of multichannel setups easily affordable. The design, implementation and performance of the picoammeter system are described in detail as well as a an application: the measurement of ion backflow in MPGD-based photon detectors.

   ↳ physics.ins-dethep-exnucl-exPoS(2019)·3 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.