Fri·Apr 13, 2018Friday·April 13, 2018

1. 01*

   First Measurement of ${\Xi }^{-}$ Polarization in Photoproduction

   J. Bono · L. Guo. · B. Raue (CLAS Collaboration)

   Despite decades of studies of the photoproduction of hyperons, both their production mechanisms and their spectra of excited states are still largely unknown. While the parity-violating weak decay of hyperons offers a means of measuring their polarization, which could help discern their production mechanisms and identify their excitation spectra, no such study has been possible for doubly strange baryons in photoproduction, due to low production cross sections. However, by making use of the reaction $\gamma p\to K^{+}{K}^{+}{\Xi }^{-}$, we have measured, for the first time, the induced polarization, $P$, and the transferred polarization from circularly polarized real photons, characterized by $C_x$ and $C_z$, to recoiling ${\Xi }^{-}$s. The data were obtained using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab for photon energies from just over threshold (2.4 GeV) to 5.45 GeV. These first-time measurements are compared, and are shown to broadly agree, with model predictions in which cascade photoproduction proceeds through the decay of intermediate hyperon resonances that are produced via relativistic meson exchange, offering a new step forward in the understanding of the production and polarization of doubly-strange baryons.

   nucl-exPLB(2018)·8 citations
2. 02*

   System-size dependence of the viscous attenuation of anisotropic flow in p+Pb and Pb+Pb collisions at LHC energies

   Peifeng Liu (1,2)🇺🇸 · Roy A. Lacey (1,2) ((1) Chemistry Dept. Stony Brook University (2) Physics Dept., Stony Brook University, Stony Brook NY, USA)🇺🇸

   The elliptic and triangular flow coefficients (${\mathrm{v}}_{\mathrm{n}},\mathrm{n}=2,3$) measured in Pb+Pb ($\sqrt{s_{{}_{\mathrm{NN}}}}=2.76$ TeV) and p+Pb ($\sqrt{s_{{}_{\mathrm{NN}}}}=5.02$ TeV) collisions, are studied as a function of initial-state eccentricity (${\epsilon }_n$), and dimensionless size characterized by the cube root of the mid-rapidity charged hadron multiplicity density ${⟨{\mathrm{N}}_{\mathrm{ch}}⟩}^{1/3}$. The results indicate that the influence of eccentricity (${\mathrm{v}}_{\mathrm{n}}\propto {\epsilon }_n$) observed for large $⟨{\mathrm{N}}_{\mathrm{ch}}⟩$, is superseded by the effects of viscous attenuation for small $⟨{\mathrm{N}}_{\mathrm{ch}}⟩$, irrespective of the colliding species. Strikingly similar acoustic scaling patterns of exponential viscous modulation, with a damping rate proportional to ${\mathrm{n}}^2$ and inversely proportional to the dimensionless size, are observed for the eccentricity-scaled coefficients for the two sets of colliding species. The resulting scaling parameters suggest that, contrary to current predilections, the patterns of viscous attenuation, as well as the specific shear viscosity $⟨\frac{\eta }{s}(\text{T})⟩$ for the matter created in p+Pb and Pb+Pb collisions, are comparable.

   nucl-exPRC(2018)·9 citations
3. 03*

   Effects of in-medium nucleon-nucleon cross section on collective flow and nuclear stopping in heavy-ion collisions in the Fermi-energy domain

   Pengcheng Li🇨🇳 · Yongjia Wang🇨🇳 · Qingfeng Li🇨🇳 · Chenchen Guo🇨🇳 · Hongfei Zhang🇨🇳

   With the newly updated version of the ultrarelativistic quantum molecular dynamics (UrQMD) model, a systematic investigation of the effects of in-medium nucleon-nucleon ($NN$) elastic cross section on the collective flow and the stopping observables in ${}^{197}\text{Au}{+}^{197}\text{Au}$ collisions at beam energies from 40 to 150 MeV/nucleon is performed. Simulations with the medium correction factor $\mathcal{F}={\sigma }_{NN}^{\text{in-medium}}/{\sigma }_{NN}^{\text{free}}=0.2,0.3,0.5$, and the one obtained with the FU3FP1 parametrization which depends on both the density and the momentum are compared to the FOPI and INDRA experimental data. It is found that, to best fit the experimental data of the slope of the directed flow and the elliptic flow at mid-rapidity as well as the nuclear stopping, the correction factor $\mathcal{F}$=0.2 and 0.5 are required for reactions at beam energies of 40 and 150 MeV/nucleon, respectively. While calculations with the FU3FP1 parametrization can simultaneously reproduce these experimental data reasonably well. And, the observed increasing nuclear stopping with increasing beam energy in experimental data can also be reproduced by using the FU3FP1 parametrization, while the calculated stopping power in Au+Au collisions with beam energies from 40 to 150 MeV$/$nucleon almost keeps constant when take $\mathcal{F}$ equal to a fixed value.

   ↳ nucl-thnucl-exPRC(2018)·37 citations
4. 04*

   Determination of the nuclear incompressibility from the rapidity-dependent elliptic flow in heavy-ion collisions at beam energies 0.4\emph{A} - 1.0\emph{A} GeV

   Yongjia Wang🇨🇳 · Chenchen Guo🇨🇳 · Qingfeng Li🇨🇳 · Arnaud Le Fevre🇩🇪 · Yvonne Leifels🇩🇪 · Wolfgang Trautmann🇩🇪

   Heavy-ion-collision measurements in combination with transport model simulations serve as important tools for extracting the nuclear incompressibility. However, uncertainties in transport models (or model dependence) partly affect the reliability of the extracted result. In the present work, by using the recently measured data of rapidity-dependent flows, we constrain the incompressibility of nuclear matter and analyse the impact of model uncertainties on the obtained value. The method is based on the newly updated version of the ultrarelativistic quantum molecular dynamics (UrQMD) model in which the Skyrme potential energy-density functional is introduced. Three different Skyrme interactions which give different incompressibilities varying from $K_0$=201 to 271 MeV are adopted. The incompressibility is deduced from the comparison of the UrQMD model simulations and the FOPI data for rapidity-dependent elliptic flow in Au+Au collisions at beam energies 0.4\emph{A} - 1.0\emph{A} GeV. The elliptic flow $v_2$ as a function of rapidity $y_0$ can be well described by a quadratic fit $v_2=v_{20}+v_{22}\cdot y_0^2$. It is found that the quantity $v_{2n}$ defined by $v_{2n}=|v_{20}|+|v_{22}|$ is quite sensitive to the incompressibility $K_0$ and the in-medium nucleon-nucleon cross section, but not sensitive to the slope parameter $L$ of the nuclear symmetry energy. With the FU3FP4 parametrization of the in-medium nucleon-nucleon cross section, an averaged $K_0=220\pm 40$~MeV is extracted from the $v_{2n}$ of free protons and deuterons. However, remaining systematic uncertainties, partly related to the choice of in-medium nucleon-nucleon cross sections, are of the same magnitude ($\pm 40$~MeV). Overall, the rapidity dependent elliptic flow supports a soft symmetric-matter equation-of-state.

   ↳ nucl-thnucl-exPLB(2018)·68 citations
5. 05*

   The effect of Lorentz-like force on collective flows of K${}^{+}$ in Au+Au collisions at 1.5 GeV/nucleon}{The effect of Lorentz-like force on collective flows of $K^{+}$ in Au+Au collisions at 1.5 GeV/nucleon

   Yushan Du🇨🇳 · Yongjia Wang🇨🇳 · Qingfeng Li🇨🇳 · Ling Liu🇨🇳

   Producing kaon mesons in heavy-ion collisions at beam energies below their threshold energy is an important way to investigate the properties of dense nuclear matter. In this study, based on the newly updated version of the ultrarelativistic quantum molecular dynamics model, we introduce the kaon-nucleon (KN) potential, including both the scalar and vector (also dubbed Lorentz-like) aspects. We revisit the influence of the KN potential on the collective flow of K${}^{+}$ mesons produced in Au+Au collisions at $E_{lab}$ = 1.5 GeV/nucleon and find that the contribution of the newly included Lorentz-like force is very important, particulary for describing the directed flow of K${}^{+}$. Finally, the corresponding KaoS data of both directed and elliptic flows can be simultaneously reproduced well.

   ↳ nucl-thnucl-exSCPMA(2018)·16 citations
6. 06*

   Collective flows of pions in Au+Au collisions at energies 1.0 and 1.5 GeV/nucleon

   Yangyang Liu🇨🇳 · Yongjia Wang🇨🇳 · Qingfeng Li · Ling Liu🇨🇳

   Based on the newly updated version of the ultrarelativistic quantum molecular dynamics (UrQMD) model, the pion potentials obtained from the in-medium dispersion relation of the $\Delta$-hole model and from the modified phenomenological approach are further introduced. Both the rapidity $y_0$ and transverse-velocity $u_{t0}$ dependence of directed $v_1$ and elliptic $v_2$ flows of ${\pi }^{+}$ and ${\pi }^{-}$ charged mesons produced from Au+Au collisions at two beam energies of 1.0 GeV/nucleon and 1.5 GeV/nucleon and within a large centrality region of $0<b_0<0.55$ are scanned. Calculations with pion potentials as well as without considering the pion potential are compared to the newly experimental data released by the FOPI collaboration at GSI. It is found that the directed flow is more sensitive to the pion potential than the elliptic one, and the attractive pion potential from the phen.B mode of the phenomenological approach is too strong to describe the flow data and can be safely ruled out. The relatively weak pion potential from the $\Delta$-hole model can supply a good description for the FOPI data of both flows as functions of both centrality and rapidity. A two-peak/valley structure occurs in the transverse-velocity dependent directed flow but the elliptic flow drops monotonously with increasing $u_{t0}$. Finally, both $v_1$ and $v_2$ flows with large $u_{t0}$ from semi-central heavy ion collisions can be taken as sensitive probes for the pion potential.

   ↳ nucl-thnucl-exPRC(2018)·20 citations
7. 07*

   Nuclear chiral doublet bands data tables

   Binwu Xiong · Yuanyuan Wang

   Since the prediction of nuclear chirality in 1997, tremendous progresses both theoretically and experimentally have been achieved. Experimentally, 59 chiral doublet bands in 47 chiral nuclei (including 8 nuclei with multiple chiral doublets) have been reported in $A\sim 80,100,130$,~and~190 mass regions. The spins, parities, energies, ratios of the magnetic dipole transition strengths to the electric quadrupole transition strengths, and related references for these nuclei are compiled and listed in Table 1. For these nuclei with the magnetic dipole transition strengths and the electric quadrupole transition strengths measured, the corresponding results are given in Table 2. A brief discussion is provided after the presentation of energy $E$, energy difference $\Delta E$, energy staggering parameter $S(I)$, rotational frequency $\omega$, kinematic moment of inertia ${\mathcal{J}}^{(1)}$, dynamic moment of inertia ${\mathcal{J}}^{(2)}$, and ratio of the magnetic dipole transition strength to the electric quadrupole transition strength $B(M1)/B(E2)$ versus spin $I$ in each mass region.

   ↳ nucl-thnucl-exAtom.Data Nucl.Data Tabl.(2019)·98 citations
8. 08*

   Giant Dipole Resonance Parameters of Ground-State Photoabsorption: Experimental Values with Uncertainties

   V. A. Plujko🇺🇦 · O. M. Gorbachenko · R. Capote🇦🇹 · P. Dimitriou🇦🇹

   Updated values and corresponding uncertainties of Isovector Giant Dipole Resonance (GDR) parameters which are obtained by the least-squares fitting of theoretical photoabsorption cross sections to experimental data are presented. The theoretical photoabsorption cross sections are taken as a sum of the components corresponding to the excitation of the GDR and quasideuteron photodisintegration. The current compilation is an extension and improvement of the earlier compilations of Lorentzian parameters for ground-state photoneutron and photoabsorption cross sections and covers experimental data made available up to June 2017.

   ↳ nucl-thnucl-exAtom.Data Nucl.Data Tabl.(2018)·59 citations
9. 09*

   Large proton cumulants from the superposition of ordinary multiplicity distributions

   Adam Bzdak🇵🇱 · Volker Koch🇺🇸 · Dmytro Oliinychenko🇺🇸 · Jan Steinheimer🇩🇪

   We construct a multiplicity distribution characterized by large factorial cumulants (integrated correlation functions) from a simple combination of two ordinary multiplicity distributions characterized by small factorial cumulants. We find that such a model, which could be interpreted as representing two event classes, reproduces the preliminary data for the proton cumulants measured by the STAR collaboration at $7.7$ GeV very well. This model then predicts very large values for the fifth and sixth order factorial cumulants, which can be tested in experiment.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2018)·32 citations
10. 10*

    Branching ratios for deexcitation processes of daughter nuclei following invisible dinucleon decays in ${}^{16}$O

    K. Hagino🇯🇵 · M. Nirkko🇬🇧

    Various theories beyond the standard model of particle physics predict the existence of baryon number violating processes resulting in nucleon decay. When occurring within an atomic nucleus, such a decay will be followed by secondary decays of the daughter nucleus unless its ground state is directly populated. In this paper, we estimate branching ratios for processes associated with dinucleon decays of the ${}^{16}$O nucleus. To this end, we use a simple shell model for the ground state of ${}^{16}$O. For decays from the 1$s_{1/2}$ configuration, which result in highly excited states in the daughter nucleus, we employ a statistical model with the Hauser-Feshbach theory. Our analysis indicates that the branching ratio for gamma-ray emission in the energy range between 5 and 9 MeV, which is relevant to low-threshold water Cherenkov experiments such as SNO+, is 4.53%, 35.7%, and 20.2% for the $nn$, $pp$, and $pn$ decays in ${}^{16}$O, respectively. In particular, emission of 6.09 MeV and 7.01 MeV gamma-rays from ${}^{14}$C, and 6.45 MeV and 7.03 MeV gamma-rays from ${}^{14}$N, have branching ratios as large as 10.9%, 20.1%, 7.73% and 8.90%, respectively.

    ↳ nucl-thhep-exhep-phnucl-exJ.Phys.G(2018)·4 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.