Tue·Nov 10, 2020Tuesday·November 10, 2020

1. 01*

   High-Precision Branching Ratio Measurement and Spin Assignment Implications for ${}^{62}$Ga Superallowed $\beta$ Decay

   A.D. MacLean🇨🇦 · A.T. Laffoley🇨🇦 · C.E. Svensson🇨🇦 · G.C. Ball🇨🇦 · J.R. Leslie🇨🇦 · C. Andreoiu🇨🇦 · A. Babu🇨🇦 · S.S. Bhattacharjee🇨🇦 · H. Bidaman🇨🇦 · V. Bildstein🇨🇦 · C. Burbadge🇨🇦 · M. Bowry🇨🇦 and 39 other authors

   A high-precision branching ratio measurement for the superallowed Fermi ${\beta }^{+}$ emitter ${}^{62}$Ga was performed with the Gamma-Ray Infrastructure for Fundamental Investigations of Nuclei (GRIFFIN) spectrometer at the Isotope Separator and Accelerator (ISAC) radioactive ion beam facility at TRIUMF. The high efficiency of the GRIFFIN spectrometer allowed 63 $\gamma$-ray transitions, with intensities down to $\approx$1 part per million (ppm) per ${}^{62}$Ga ${\beta }^{+}$ decay, to be placed in the level scheme of the daughter nucleus ${}^{62}$Zn, establishing the superallowed $\beta$ branching ratio for ${}^{62}$Ga decay to be 99.8577${}_{-0.0029}^{+0.0023}\%$, a factor of 4 more precise than the previous world average. For several cascades, $\gamma -\gamma$ angular correlation measurements were performed to assign spins and/or determine the mixing ratios of transitions. In particular, the spin of the 2.342 MeV excited state in the daughter nucleus ${}^{62}$Zn was definitively assigned as $J=0$. This assignment resolves a discrepancy between previous measurements and has important implications for the isospin symmetry breaking correction, ${\delta }_{C1}$, in ${}^{62}$Ga superallowed Fermi $\beta$ decay.

   nucl-exPRC(2020)·9 citations
2. 02*

   Excitation Function of ${}^{12}$C(p,po) for Ep=16 $÷$ 19.5 MeV measured by MSS with resolution ~10 keV

   A.Gafarov

   The elastic scattering ${}^{12}$C(p,po) Excitation Function (EF) was measured in the energy range Ep =16 - 19.5 MeV with resolution about 10 keV by means of innovative approach - MSS - the Method of Spectra Superposition at the 14-angle Magnetic Spectrograph (Apelsin) at beam with an energy spread of about 200 keV from U-150 cyclotron of INP Ulugbek (Tashkent) of Science Academy of Uzbekistan [1-8]. The obtained EF has a reach structure of anomalies in precise agreement with thresholds and levels data [2,9-12]. Measurements were done on the 12C self-supporting target with thickness 13 mg/cm2 and an area of 1 cm2 in the center of Apelsin. The 20-step Energy Moderator controlled the proton energy, providing a 3.5 MeV wide Ep interval with no readjustment of cyclotron and all the ionic-optics on the 41-meter-long beam-pipe. Energy resolution of Apelsin for protons is better than 5 keV along all focal plane, where particle-product were detected by specially designed coordinate-sensitive gas mixture MWPC with two particle counters in coincidence. The acquisition system was based on IBM PC online with a fast CAMAC branch (custom designed at St-Petersburg PNPI) with fast TDC modules and other fast electronics providing immediate selection and accumulations of events from MWPCs. The NMR-monitor system stabilized spectrographs magnetic field to 3ppm [1,9]. The EF of 12C (p,po) scattering has many resonances that precisely correspond to g.s. and levels of well-known product-nuclei. But 80 percent of anomalies did not have any explanation. A new concept is proposed to explain all unrecognized anomalies. Two expressions Writing I and Writing II proposed to explain the unknown peaks which corresponds to population of A13 phase volume states. The results of the proposed explanation look very promising (Fig. 13). Concept of the Combinative Isobaric Resonances (CIRs) proposed

   nucl-ex1 citation
3. 03*

   Properties of 187Ta revealed through isomeric decay

   P.M. Walker🇬🇧 · Y. Hirayama · G.J. Lane🇦🇺 · H. Watanabe🇯🇵 · G.D. Dracoulis · M. Ahmed🇪🇬 · M. Brunet · T. Hashimoto🇯🇵 · S. Ishizawa · F.G. Kondev🇺🇸 · Yu.A. Litvinov🇩🇪 · H. Miyatake🇯🇵 and 11 other authors

   Mass-separated 187Ta in a high-spin isomeric state has been produced for the first time by multi-nucleon transfer reactions, employing an argon gas stopping cell and laser ionisation. Internal gamma rays revealed a 7.3 s isomer at 1778 keV, which decays through a rotational band with perturbations associated with the approach to a prolate-oblate shape transition. Model calculations show less influence from triaxiality compared to heavier elements in the same mass region. The isomer decay reduced E2 hindrance factor of 27 supports the interpretation that axial symmetry is approximately conserved.

   nucl-exPRL(2020)·16 citations
4. 04*

   Model independent reconstruction of impact parameter distributions for intermediate energy heavy ion collisions

   INDRA Collaboration : J. D. Frankland (1)🇫🇷 · D. Gruyer (2)🇫🇷 · E. Bonnet (3)🇫🇷 · B. Borderie (4)🇫🇷 · R. Bougault (2)🇫🇷 · A. Chbihi (1)🇫🇷 · J. E. Ducret (1)🇫🇷 · D. Durand (2)🇫🇷 · Q. Fable (2)🇫🇷 · M. Henri (1)🇫🇷 · J. Lemarié (1)🇫🇷 · N. Le Neindre (2)🇫🇷 and 8 other authors

   We present a model-independent method to reconstruct the impact parameter distributions of experimental data for intermediate energy heavy ion collisions, adapted from a recently proposed approach for ultra-relativistic heavy ion collisions. The method takes into account the fluctuations which are inherent to the relationship between any experimental observable and the impact parameter in this energy range. We apply the method to the very large dataset on heavy ion collisions in the energy range 20-100 MeV/nucleon obtained with the INDRA multidetector since 1993, for two observables which are the most commonly used for the estimation of impact parameters in this energy range. The mean impact parameters deduced with this new method for "central" collisions selected using typical observable cuts are shown to be significantly larger than those found when fluctuations are neglected, and as expected the difference increases as bombarding energy decreases. In addition, we will show that this new approach may provide previously inaccessible experimental constraints for transport models, such as an estimation of the extrapolated mean value of experimental observables for b = 0 collisions. The ability to give more realistic, model-independent, estimations of the impact parameters associated to different experimental datasets should improve the pertinence of comparisons with transport model calculations which are essential to better constrain the equation of state of nuclear matter.

   nucl-exPRC(2021)·27 citations
5. 05*

   Possible Magnetic Rotational Bands in 84^Rb

   Shuifa Shen · Jiejie Shen · Guangbing Han🇨🇳 · Shuxian Wen🇨🇳 · Yupeng Yan🇹🇭 · Haibing Jiang · Zhixiong He🇨🇳 · Yaodong Song · Weiwei Gao · Jieqing Lan

   High-spin states in 84Rb are studied by using the 70Zn(18O, p3n)84Rb reaction at a beam energy of 75 MeV. Three high-lying negative-parity bands are established, whose level spacings are very regular, i.e., there is no signature splitting. The dipole character of the transitions of these three bands is assigned by the gamma-gamma directional correlations of oriented states (DCO) intensity ratios and the multipolarity M1 is suggested by analogy with multiparticle excitations in neighboring nuclei. Strong M1 and weak or no E2 transitions are observed. All these characteristic features show they are magnetic rotational bands.

   nucl-exhep-exPhys.Open(2021)·0 citations
6. 06*

   A hydrodynamic study of hyperon spin polarization in relativistic heavy ion collisions

   Baochi Fu🇨🇳 · Kai Xu🇨🇳 · Xu-Guang Huang🇨🇳 · Huichao Song🇨🇳

   We perform a systematic study of the spin polarization of hyperons in heavy-ion collisions using the MUSIC hydrodynamic model with A Multi-Phase Transport (AMPT) pre-equilibrium dynamics. Our model calculations nicely describe the measured collision-energy, centrality, rapidity, and $p_T$ dependence of $\Lambda$ polarization. We also study and predict the global spin polarization of ${\Xi }^{-}$ and ${\Omega }^{-}$ as a function of collision energy, which provides a baseline for the studies of the magnetic moment, spin, and mass dependence of the spin polarization. For the local spin polarization, we calculate the radial and azimuthal components of the transverse $\Lambda$ polarization and find specific modulating behavior which could reflect the circular vortical structure. However, our model fails to describe the azimuthal-angle dependence of the longitudinal and transverse $\Lambda$ polarization, which indicates that the hydrodynamic framework with the spin Cooper-Frye formula under the assumption of thermal equilibrium of spin degree of freedom needs to be improved.

   ↳ nucl-thhep-phnucl-exPRC(2021)·118 citations
7. 07*

   Nuclear Potential of Final State Nucleons and Nucleons Plus Pions in Lepton Nucleus Scattering

   Arie Bodek🇺🇸 · Tejin Cai🇺🇸

   Within the impulse approximation, the modeling of the energy of final state leptons in electron and neutrino quasielastic and pion production processes on nuclear targets in the region of the $\Delta$ resonance depends on several parameters. These parameters include the removal energy of the initial state nucleon from the nucleus ${ϵ}^{P,N}$, the potentials of electrons, nucleons and pions in the Coulomb field of the nucleus $|V_{eff}|$, and the kinetic energy dependent nuclear potential for final state nucleons ($U_{opt}^{QE}$) and "nucleon plus pion" final states in the region of the $\Delta$ resonance which we refer to as $U_{opt}^{\Delta }$. We extract these parameters from electron scattering data. Previous studies have shown that real part of the optical potential for a nucleon bound in ${}_6^{12}C$ at zero kinetic energy $U_{opt}^{P,N}(T=0)\approx$ 44 MeV is larger than that for the $\Delta$(1232) resonance $U_{opt}^{\Delta }(T=0)\approx$ 30 MeV. We find the reverse at higher kinetic energies. For example at T=100 MeV we find a nucleon potential $U_{opt}^{P,N}(T=100MeV)$=20$\pm$5 MeV and $U_{opt}^{\Delta }(T=100MeV)$= 30$\pm$5 MeV. The two results are consistent for two reasons. First, theoretically the kinetic energy dependence of the $\Delta$ potential is flatter than that of the nucleon. Secondly, in our analysis the extracted $U_{opt}^{\Delta }$ values are the nuclear potential for {\it"nucleon plus pion"} final states in the region of the $\Delta$ resonances and therefore includes contributions from both resonance and non resonance pion production processes. For Monte Carlo generators that only include the effects of Fermi motion and nuclear potentials, the relevant parameter is the effective nuclear potential for the "nucleon plus pion" final state.

   ↳ nucl-thhep-exhep-phnucl-exPoS(2021)·0 citations
8. 08*

   Influence of modified light-flavor hadron spectra on particle yields in the statistical hadronization model

   A. Andronic🇩🇪 · P. Braun-Munzinger🇩🇪 · D. Gündüz🇩🇪 · Y. Kirchhoff🇩🇪 · M. K. Köhler🇩🇪 · J. Stachel🇩🇪 · M. Winn🇫🇷

   Hadron production in relativistic nuclear collisions is well described in the framework of the Statistical Hadronization Model (SHM). We investigate the influence on SHM predictions of hadron mass spectra for light-flavor baryons and mesons modified by the addition of about 500 new states as predicted by lattice QCD and a relativistic quark model. The deterioration of the resulting thermodynamic fit quality obtained for PbPb collision data at sqrt(s_nn) = 2.76 TeV suggests that the additional states are not suited to be naively used since also interactions among the states as well as non-resonant contributions need to be considered in the SHM approach. Incorporating these effects via the pion nucleon interaction determined from measured phase shifts leads again to excellent reproduction of the experimental data. This is a strong indication that at least the additional nucleon excited states cannot be understood and used as independent resonances.

   ↳ nucl-thhep-lathep-phnucl-exNPA(2021)·20 citations
9. 09*

   Novel Rosenbluth Extraction Framework for Compton Form Factors from Deeply Virtual Exclusive Experiments

   Brandon Kriesten · Simonetta Liuti

   We use a generalization of the Rosenbluth separation method for a model independent simultaneous extraction of the Compton Form Factors $\mathcal{H}$ and $\mathcal{E}$, from virtual Compton scattering data on an unpolarized target. A precise evaluation of $\mathcal{H}$ and $\mathcal{E}$, enabled by the proposed method, is the first step towards pinning down the the distribution of angular momentum inside the proton.

   ↳ hep-phnucl-exnucl-thPLB(2022)·24 citations
10. 10*

    A first estimate of $\eta /s$ in Au+Au reactions at E${}_{\mathrm{lab}}=1.23$ $A$GeV

    Tom Reichert🇩🇪 · Gabriele Inghirami🇩🇪 · Marcus Bleicher🇩🇪

    The HADES experiment at GSI has recently provided data on the flow coefficients $v_1,...,v_4$ for protons in Au+Au reactions at $E_{\mathrm{lab}}=1.23$~$A$GeV (or $\sqrt{s_{\mathrm{NN}}}=2.4$ GeV). This data allows to estimate the shear viscosity over entropy ratio, $\eta /s$ at low energies via a coarse graining analysis of the UrQMD transport simulations of the flow harmonics in comparison to the experimental data. By this we can provide for the first time an estimate of $\eta /s\approx 0.65\pm 0.15$ (or $(8\pm 2)(4\pi {)}^{-1}$) at such low energies.

    ↳ nucl-thnucl-exPLB(2021)·19 citations
11. 11*

    Discerning nuclear pairing properties from magnetic dipole excitation

    Tomohiro Oishi🇭🇷 · Goran Kruzic · Nils Paar🇭🇷

    Pairing correlation of Cooper pair is a fundamental property of multi-fermion interacting systems. For nucleons, two modes of the Cooper-pair coupling may exist, namely of $S_{12}=0$ with $L_{12}=0$ (spin-singlet s-wave) and $S_{12}=1$ with $L_{12}=1$ (spin-triplet p-wave). In nuclear physics, it has been an open question whether the spin-singlet or spin-triplet coupling is dominant, as well as how to measure their role. We investigate a relation between the magnetic-dipole (M1) excitation of nuclei and the pairing modes within the framework of relativistic nuclear energy-density functional (RNEDF). The pairing correlations are taken into account by the relativistic Hartree-Bogoliubov (RHB) model in the ground state, and the relativistic quasi-particle random-phase approximation (RQRPA) is employed to describe M1 transitions. We have shown that M1 excitation properties display a sensitivity on the pairing model involved in the calculations. The systematic evaluation of M1 transitions together with the accurate experimental data enables us to discern the pairing properties in finite nuclei.

    ↳ nucl-thcond-mat.supr-connucl-exEPJA(2021)·7 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.