Tue·Jul 25, 2017Tuesday·July 25, 2017

1. 01*

   High-$j$ neutron excitations outside ${}^{136}$Xe

   R. Talwar🇺🇸 · B. P. Kay🇺🇸 · A. J. Mitchell🇬🇧 · S. Adachi🇯🇵 · J. P. Entwisle🇬🇧 · Y. Fujita🇯🇵 · G. Gey🇯🇵 · S. Noji🇺🇸 · H. J. Ong🇯🇵 · J. P. Schiffer🇺🇸 · A. Tamii🇯🇵

   The $\nu 0h_{9/2}$ and $\nu 0i_{13/2}$ strength at ${}^{137}$Xe, a single neutron outside the $N=82$ shell closure, has been determined using the ${}^{136}$Xe($\alpha$,${}^3$He)${}^{137}$Xe reaction carried out at 100 MeV. We confirm the recent observation of the second 13/2${}^{+}$ state and reassess previous data on the 9/2${}^{-}$ states, obtaining spectroscopic factors. These new data provide additional constraints on predictions of the same single-neutron excitations at ${}^{133}$Sn.

   nucl-exPRC(2017)·1 citation
2. 02*

   Comparative study of the double $K$-shell-vacancy production in single- and double-electron capture decay

   S.S. Ratkevich🇺🇦 · A.M. Gangapshev🇷🇺 · Yu.M. Gavrilyuk🇷🇺 · F.F. Karpeshin · V.V. Kazalov🇷🇺 · V.V. Kuzminov🇷🇺 · S.I. Panasenko🇺🇦 · M.B. Trzhaskovskaya · S.P. Yakimenko🇷🇺

   We carried out the comparative study of the signal from the decay of double $K$-shell vacancy production that follows after single $K$-shell electron capture of ${}^{81}$Kr and double $K$-shell electron capture of ${}^{78}$Kr. The radiative decay of a the double $1s$ vacancy state was identified by detecting the triple coincidence of two $K$ X-rays and several Auger electrons in the $ECEC$-decay, or by detecting two $K$ X-rays and (Auger electrons + ejected $K$-shell electron) in the $EC$ decay. The number of $K$-shell vacancies per the $K$-electron capture, produced as a result of the shake-off process, has been measured for the decay of ${}^{81}$Kr. The probability for this decay was found to be $P_{KK}=(5.7\pm 0.8)\times 10^{-5}$ with a systematic error of $(\Delta P_{KK}{)}_{syst}=\pm 0.4\times 10^{-5}$. For the ${}^{78}\mathrm{Kr}(2\nu 2K)$ decay, the comparative study of single- and double-capture decays allowed us to obtain the signal-to-background ratio to be 15/1. The half-life $T_{1/2}^{2\nu 2K}(g.s.\to g.s.)=[1.9_{-0.7}^{+1.3}(stat)\pm 0.3(syst)]\times 10^{22}$ y is determined from the analysis of data that have been accumulated over 782 days of live measurements in the experiment that used samples consisted of 170.6 g of ${}^{78}$Kr.

   nucl-exPRC(2017)·44 citations
3. 03*

   High-precision mass measurement of ${}^{56}$Cu and the redirection of the rp-process flow

   A.A. Valverde🇺🇸 · M. Brodeur🇺🇸 · G. Bollen🇺🇸 · M. Eibach🇺🇸 · K. Gulyuz🇺🇸 · A. Hamaker🇺🇸 · C. Izzo🇨🇦 · W.-J. Ong🇺🇸 · D. Puentes🇺🇸 · M. Redshaw🇺🇸 · R. Ringle🇺🇸 · R. Sandler🇺🇸 and 5 other authors

   We report the mass measurement of ${}^{56}$Cu, using the LEBIT 9.4T Penning trap mass spectrometer at the National Superconducting Cyclotron Laboratory at Michigan State University. The mass of ${}^{56}$Cu is critical for constraining the reaction rates of the ${}^{55}$Ni(p,$\gamma$)${}^{56}$Cu(p,$\gamma$)${}^{57}$Zn(${\beta }^{+}$)${}^{57}$Cu bypass around the ${}^{56}$Ni waiting point. Previous recommended mass excess values have disagreed by several hundred keV. Our new value, ME=$-38626.7(6.4)$ keV, is a factor of 30 more precise than the suggested value from the 2012 atomic mass evaluation [Chin. Phys. C {\bf{36}}, 1603 (2012)], and more than a factor of 12 more precise than values calculated using local mass extrapolations, while agreeing with the newest 2016 atomic mass evaluation value [Chin. Phys. C {\bf{41}}, 030003 (2017)]. The new experimental average was used to calculate the astrophysical ${}^{55}$Ni(p,$\gamma$) and ${}^{57}$Zn($\gamma$,p) reaction rates and perform reaction network calculations of the rp-process. These show that the rp-process flow redirects around the ${}^{56}$Ni waiting point through the ${}^{55}$Ni(p,$\gamma$) route, allowing it to proceed to higher masses more quickly and resulting in a reduction in ashes around this waiting point and an enhancement to higher-mass ashes.

   nucl-exPRL(2018)·32 citations
4. 04*

   Measurement of deuteron spectra and elliptic flow in Pb-Pb collisions at $\sqrt{{\mathbf{s}}_{\mathrm{NN}}}$ = 2.76 TeV at the LHC

   ALICE Collaboration

   The transverse momentum ($p_{\mathrm{T}}$) spectra and elliptic flow coefficient ($v_2$) of deuterons and anti-deuterons at mid-rapidity ($|y|<0.5$) are measured with the ALICE detector at the LHC in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV. The measurement of the $p_{\mathrm{T}}$ spectra of (anti-)deuterons is done up to 8 GeV/$c$ in 0-10% centrality class and up to GeV/$c$ in 10-20% and 20-40% centrality classes. The $v_2$ is measured in the $0.8<p_{\mathrm{T}}<5$ GeV/$c$ interval and in six different centrality intervals (0-5%, 5-10%, 10-20%, 20-30%, 30-40% and 40-50%) using the scalar product technique. Measured ${\pi }^{\pm }$, K${}^{\pm }$ and p+$\overline{\mathrm{p}}$ transverse-momentum spectra and $v_2$ are used to predict the deuteron $p_{\mathrm{T}}$ spectra and $v_2$ within the Blast-Wave model. The predictions are able to reproduce the $v_2$ coefficient in the measured $p_{\mathrm{T}}$ range and the transverse-momentum spectra for $p_{\mathrm{T}}>1.8$ GeV/$c$ within the experimental uncertainties. The measurement of the coalescence parameter $B_2$ is performed, showing a $p_{\mathrm{T}}$ dependence in contrast with the simplest coalescence model, which fails to reproduce also the measured $v_2$ coefficient. In addition, the coalescence parameter $B_2$ and the elliptic flow coefficient in the 20-40% centrality interval are compared with the AMPT model which is able, in its version without string melting, to reproduce the measured $v_2$($p_{\mathrm{T}}$) and the $B_2$($p_{\mathrm{T}}$) trend.

   nucl-exhep-exEPJC(2017)·92 citations
5. 05*

   A Comparative Study of kaon to pion ratio in Proton-Proton Collisions at different energies ---Experimental Results vs. Model Simulation

   Swarnapratim Bhattacharyya🇮🇳 · Maria Haiduc🇷🇴 · Alina Tania Neagu🇷🇴 · Elena Firu🇷🇴

   A detailed study of energy dependence of positive kaon to pion, negative kaon to pion and total kaon to pion multiplicity ratio have been carried out in pp collisions at 6.3, 17.3, 62.4, 200 and 900 GeV and also at root s =2.76 TeV and 7 TeV in the framework of UrQMD and DPMJET III model. Energy dependence of positive kaon to pion and negative kaon to pion show different behavior in case of UrQMD and DPMJET III model. The presence of the horn like structure in the variation of positive kaon to pion and negative kaon to pion ratio with energy for the experimental data is supported by the DPMJET III model. Experimentally it has been observed that as energy increases, the total kaon to pion multiplicity ratio increases systematically for pp collisions at lower energies and becomes independent of energy in LHC energy regime. Our analysis on total kaon to pion multiplicity ratio with UrQMD data is well supported by the experimental results obtained by different collaborations in different times. In case of DPMJET III data, the saturation of kaon to pion ratio at LHC region has not been observed.

   nucl-exAdv.High Energy Phys.(2018)·8 citations
6. 06*

   Recent experimental results in sub- and near-barrier heavy ion fusion reactions

   Giovanna Montagnoli · Alberto M. Stefanini🇮🇹

   Recent advances obtained in the field of near and sub-barrier heavy-ion fusion reactions are reviewed. Emphasis is given to the results obtained in the last decade, and focus will be mainly on the experimental work performed concerning the influence of transfer channels on fusion cross sections and the hindrance phenomenon far below the barrier. Indeed, early data of sub-barrier fusion taught us that cross sections may strongly depend on the low-energy collective modes of the colliding nuclei, and, possibly, on couplings to transfer channels. The coupled-channels (CC) model has been quite successful in the interpretation of the experimental evidences. Fusion barrier distributions often yield the fingerprint of the relevant coupled channels. Recent results obtained by using radioactive beams are reported. At deep sub-barrier energies, the slope of the excitation function in a semi-logarithmic plot keeps increasing in many cases and standard CC calculations over-predict the cross sections. This was named a hindrance phenomenon, and its physical origin is still a matter of debate. Recent theoretical developments suggest that this effect, at least partially, may be a consequence of the Pauli exclusion principle. The hindrance may have far-reaching consequences in astrophysics where fusion of light systems determines stellar evolution during the carbon and oxygen burning stages, and yields important information for exotic reactions that take place in the inner crust of accreting neutron stars.

   nucl-exEPJA(2017)·102 citations
7. 07*

   Emergence of low-energy monopole strength in the neutron-rich calcium isotopes

   J. Piekarewicz🇺🇸

   The isoscalar monopole response of neutron-rich nuclei is sensitive to both the incompressibility coefficient of symmetric nuclear matter and the density dependence of the symmetry energy. The main goal of this paper is to explore the emergence, evolution, and origin of low energy monopole strength along the even-even calcium isotopes: from 40Ca to 60Ca. The distribution of isoscalar monopole strength is computed in a relativistic random phase approximation (RPA) using three effective interactions that have been calibrated to the properties of finite nuclei and neutron stars. A non-spectral approach is adopted that allows for an exact treatment of the continuum without any reliance on discretization. For the stable calcium isotopes, no evidence of low-energy monopole strength is observed, even as the 1f7/2 neutron orbital is being filled and the neutron-skin thickness progressively grows. Further, in contrast to experimental findings, a mild softening of the monopole response with increasing mass number is predicted. Beyond 48Ca, a significant amount of low-energy monopole strength emerges as soon as the weak-binding neutron orbitals (2p and 1f5/2) become populated. The emergence and evolution of low-energy strength is identified with transitions from these weakly-bound states into the continuum. Moreover, given that models with a soft symmetry energy tend to reach the neutron-drip line earlier than their stiffer counterparts, we identify an inverse correlation between the neutron-skin thickness and the inverse energy weighted sum.

   ↳ nucl-thnucl-exPRC(2017)·7 citations
8. 08*

   Holographic estimate of the meson cloud contribution to nucleon axial form factor

   G. Ramalho🇧🇷

   We use light-front Holography to estimate the valence quark and the meson cloud contributions to the nucleon axial form factor. The free couplings of the holographic model are determined by the empirical data and by the information extracted from lattice QCD. The holographic model provides a good description of the empirical data when we consider a meson cloud mixture of about 30\% in the physical nucleon state. The estimate of the valence quark contribution to the nucleon axial form factor compares well with the lattice QCD data for small pion masses. Our estimate of the meson cloud contribution to the nucleon axial form factor has a slower falloff with the square momentum transfer compared to typical estimates from quark models with meson cloud dressing.

   ↳ hep-phhep-exhep-latnucl-ex+1PRD(2018)·12 citations
9. 09*

   Investigating different $\Lambda$ and $\bar{\Lambda }$ polarizations in relativistic heavy-ion collisions

   Zhang-Zhu Han🇨🇳 · Jun Xu🇨🇳

   Based on the chiral kinetic equations of motion, spin polarizations of various quarks, due to the magnetic field induced by spectator protons as well as the quark-antiquark vector interaction, are studied within a partonic transport approach. Although the magnetic field in QGP enhances the splitting of the spin polarizations of partons compared to the results under the magnetic field in vacuum, the spin polarizations of $s$ and $\bar{s}$ quarks are also sensitive to the quark-antiquark vector interaction, challenging that the different $\Lambda$ and $\bar{\Lambda }$ spin polarization is a good measure of the magnetic field in relativistic heavy-ion collisions. It is also found that there is no way to obtain the large splitting of the spin polarization between $\Lambda$ and $\bar{\Lambda }$ at $\sqrt{s_{NN}}=7.7$ GeV with partonic dynamics.

   ↳ nucl-thhep-exnucl-exPLB(2018)·33 citations
10. 10*

    $\psi (2S)$ versus $J/\psi$ suppression in proton-nucleus collisions from factorization violating soft color exchanges

    Yan-Qing Ma🇨🇳 · Raju Venugopalan🇺🇸 · Kazuhiro Watanabe🇺🇸 · Hong-Fei Zhang🇨🇳

    We argue that the large suppression of the $\psi (2S)$ inclusive cross-section relative to the $J/\psi$ inclusive cross-section in proton-nucleus (p+A) collisions can be attributed to factorization breaking effects in the formation of quarkonium. These factorization breaking effects arise from soft color exchanges between charm-anticharm pairs undergoing hadronization and comoving partons that are long-lived on time scales of quarkonium formation. We compute the short distance pair production of heavy quarks in the Color Glass Condensate (CGC) effective field theory and employ an improved Color Evaporation model (ICEM) to describe their hadronization into quarkonium at large distances. The combined CGC+ICEM model provides a quantitative description of $J/\psi$ and $\psi (2S)$ data in proton-proton (p+p) collisions from both RHIC and the LHC. Factorization breaking effects in hadronization, due to additional parton comovers in the nucleus, are introduced heuristically by imposing a cutoff $\Lambda$, representing the momentum kick from soft color exchanges, in the ICEM model. Such soft exchanges have no perceptible effect on $J/\psi$ suppression in p+A collisions. In contrast, the interplay of the physics of these soft exchanges at large distances, with the physics of semi-hard rescattering at short distances, causes a significant additional suppression of $\psi (2S)$ yields relative to that of the $J/\psi$. A good fit of all RHIC and LHC $J/\psi$ and $\psi (2S)$ data, for transverse momenta $P_{\perp }\le 5$ GeV in p+p and p+A collisions, is obtained for $\Lambda \sim 10$ MeV.

    ↳ hep-phhep-exnucl-exnucl-thPRC(2018)·58 citations
11. 11*

    Effects of hadronic mean-field potentials on Hanbury-Brown-Twiss correlations in relativistic heavy-ion collisions

    Chun-Jian Zhang🇨🇳 · Jun Xu🇨🇳

    With the parameters fitted by the particle multiplicity, the energy density at chemical freeze-out, and the charged particle elliptic flow, we have studied the effects of the hadronic mean-field potentials on the Hanbury-Brown and Twiss (HBT) correlation in relativistic heavy-ion collisions based on a multiphase transport model. The hadronic mean-field potentials are found to delay the emission time of the system and lead to large HBT radii extracted from the correlation function. Effects on the energy dependence of $R_o^2-R_s^2$ and $R_o/R_s$ as well as the eccentricity of the emission source are discussed. The HBT correlations can also be useful in understanding the mean-field potentials of protons, kaons, and antiprotons as well as baryon-antibaryon annihilations.

    ↳ nucl-thhep-exnucl-exPRC(2017)·9 citations
12. 12*

    Correlations within the Non-Equilibrium Green's Function Method

    M. H. Mahzoon (Michigan State U)🇺🇸 · P. Danielewicz (Michigan State U)🇺🇸 · A. Rios (U Surrey)🇬🇧

    Non-equilibrium Green's Function (NGF) method is a powerful tool for studying the evolution of quantum many-body systems. Different types of correlations can be systematically incorporated within the formalism. The time evolution of the single-particle Green's functions is described in terms of the Kadanoff-Baym equations. The current work initially focuses on introducing the correlations within infinite nuclear matter in one dimension and then in a finite system in the NGF approach. Starting from the harmonic oscillator Hamiltonian, by switching on adiabatically the mean-field and correlations simultaneously, a correlated state with ground-state characteristics is arrived at within the NGF method. Furthermore the use of cooling to for improving the adiabatic switching is explored.

    ↳ nucl-thnucl-exphysics.comp-phAIP Conf.Proc.(2017)·1 citation
13. 13*

    Resonances in positron scattering on a supercritical nucleus and spontaneous production of $e^{+}{e}^{-}$ pairs

    S.I. Godunov🇷🇺 · B. Machet🇫🇷 · M.I. Vysotsky🇷🇺

    We re-examine the physics of supercritical nuclei, specially focusing on the scattering phase ${\delta }_{\varkappa }$ and its dependence on the energy $\epsilon$ of the diving electronic level, for which we give both exact and approximate formulas. The Coulomb potential $Z\alpha /r$ is rounded to the constant $Z\alpha /R$ for $r<R$. We confirm the resonant behavior of ${\delta }_{\varkappa }$ that we investigate in details. In addition to solving the Dirac equation for an electron, we solve it for a positron, in the field of the same nucleus. This clarifies the interpretation of the resonances. Our results are compared with claims made in previous works.

    ↳ hep-phnucl-exnucl-thEPJC(2017)·24 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.