Mon·Apr 8, 2019Monday·April 8, 2019

1. 01*

   $\omega N$ scattering length from $\omega$ photoproduction on the proton near the threshold

   T. Ishikawa · H. Fujimura · H. Fukasawa · R. Hashimoto · Q. He · Y. Honda · A. Hosaka · T. Iwata · S. Kaida · A. Kawano · S. Kuwasaki · K. Maeda and 26 other authors

   Photoproduction of the $\omega$ meson on the proton has been experimentally studied near the threshold. The total cross sections are determined at incident energies ranging from 1.09 to 1.15 GeV. The 1/2 and 3/2 spin-averaged scattering length $a_{\omega p}$ and effective range $r_{\omega p}$ between the $\omega$ meson and proton are estimated from the shape of the total cross section as a function of the incident photon energy: $a_{\omega p}=\left(-0.97_{-0.16_{\mathrm{stat}}}^{+0.16_{\mathrm{stat}}}{}_{-0.00_{\mathrm{syst}}}^{+0.03_{\mathrm{syst}}}\right)+i\left(0.07_{-0.14_{\mathrm{stat}}}^{+0.15_{\mathrm{stat}}}{}_{-0.09_{\mathrm{syst}}}^{+0.17_{\mathrm{syst}}}\right)$ fm and $r_{\omega p}=\left(+2.78_{-0.54_{\mathrm{stat}}}^{+0.68_{\mathrm{stat}}}{}_{-0.13_{\mathrm{syst}}}^{+0.11_{\mathrm{syst}}}\right)+i\left(-0.01_{-0.50_{\mathrm{stat}}}^{+0.46_{\mathrm{stat}}}{}_{-0.00_{\mathrm{syst}}}^{+0.07_{\mathrm{syst}}}\right)$ fm, resulting in a repulsive force. The real and imaginary parts for $a_{\omega p}$ and $r_{\omega p}$ are determined separately for the first time. A small $P$-wave contribution does not affect the obtained values.

   nucl-exPRC(2020)·19 citations
2. 02*

   Restricted spin-range correction in the Oslo Method: The example of nuclear level density and $\gamma$-ray strength function from ${}^{239}\mathrm{Pu}(\mathrm{d},\mathrm{p}\gamma {)}^{240}\mathrm{Pu}$

   F. Zeiser🇳🇴 · G.M. Tveten🇳🇴 · G. Potel🇺🇸 · A.C. Larsen🇳🇴 · M. Guttormsen🇳🇴 · T.A. Laplace🇺🇸 · S. Siem🇳🇴 · D. L. Bleuel🇺🇸 · B.L. Goldblum🇺🇸 · L.A. Bernstein🇺🇸 · F.L. Bello Garrote🇳🇴 · L. Crespo Campo🇳🇴 and 10 other authors

   The Oslo Method has been applied to particle-$\gamma$ coincidences following the ${}^{239}\mathrm{Pu}$(d,p) reaction to obtain the nuclear level density (NLD) and $\gamma$-ray strength function ($\gamma$SF) of ${}^{240}\mathrm{Pu}$. The experiment was conducted with a 12 MeV deuteron beam at the Oslo Cyclotron Laboratory. The low spin transfer of this reaction leads to a spin-parity mismatch between populated and intrinsic levels. This is a challenge for the Oslo Method as it can have a significant impact on the extracted NLD and $\gamma$SF. We have developed an iterative approach to ensure consistent results even for cases with a large spin-parity mismatch, in which we couple Green's Function Transfer calculations of the spin-parity dependent population cross-section to the nuclear decay code RAINIER. The resulting $\gamma$SF shows a pronounced enhancement between 2-4 MeV that is consistent with the location of the low-energy orbital $M1$ scissors mode.

   nucl-exphysics.data-anPRC(2019)·16 citations
3. 03*

   Nuclear physics at the energy frontier: recent heavy ion results from the perspective of the Electron Ion Collider

   Astrid Morreale🇫🇷

   Quarks and gluons are the fundamental constituents of nucleons. Their interactions rather than their mass, is responsible for $99\%$ of the mass of all visible matter in the universe. Measuring the fundamental properties of matter has had a large impact on our understanding of the nucleon structure and it has given us decades of research and technological innovation. Despite the large number of discoveries made, many fundamental questions remain open and in need of a new and more precise generation of measurements. The future Electron Ion Collider (EIC) will be a machine dedicated to hadron structure research. It will study the content of protons and neutrons in a largely unexplored regime in which gluons are expected to dominate and eventually saturate. While the EIC will be the machine of choice to quantify this regime, recent surprising results from the heavy ion community begin to exhibit similar signatures as those expected from a regime dominated by gluons. Many of the heavy ion results that will be discussed in this document highlight the kinematic limitations of hadron-hadron and hadron-nucleus collisions. The reliability of using as a reference proton-proton (pp) and proton-Nucleus(pA) collisions to quantify and disentangle vacuum and Cold Nuclear Matter (CNM) effects from a Quark Gluon Plasma (QGP) may be under question. An selection of relevant pp and pA results which highlight the need of an EIC will be presented

   nucl-exUniverse(2019)·1 citation
4. 04*

   New results on spectra and fluctuations from NA61/SHINE

   Katarzyna Grebieszkow (for the NA61/SHINE Collaboration)🇵🇱

   The NA61/SHINE experiment aims to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. For this purpose we perform a two-dimensional scan of the ($T-{\mu }_B$) phase diagram by varying the energy ($5.1<\sqrt{s_{NN}}<16.8/17.3$ GeV) and the system size (p+p, p+Pb, Be+Be, Ar+Sc, Xe+La, Pb+Pb) of the collisions. In this article the NA61/SHINE results on particle spectra as well as fluctuations and correlations in p+p, Be+Be, Ar+Sc, and Pb+Pb collisions are presented. In particular, the latest results on charged kaons spectra, charged pions ratios (electromagnetic effects), proton intermittency, and anisotropic flow are discussed. Finally, the motivation, NA61/SHINE plans, and the first measurements of open charm production in heavy ion collisions at the Super Proton Synchrotron energies are shown.

   nucl-exPoS(2019)·14 citations
5. 05*

   Comparison of heavy-ion transport simulations: Collision integral with pions and $\Delta$ resonances in a box

   Akira Ono🇯🇵 · Jun Xu🇨🇳 · Maria Colonna🇮🇹 · Pawel Danielewicz🇺🇸 · Che Ming Ko🇺🇸 · Manyee Betty Tsang🇺🇸 · Yong-Jia Wang🇨🇳 · Hermann Wolter🇩🇪 · Ying-Xun Zhang🇨🇳 · Lie-Wen Chen🇨🇳 · Dan Cozma🇷🇴 · Hannah Elfner🇩🇪 and 12 other authors

   We compare ten transport codes for a system confined in a box, aiming at improved handling of the production of $\Delta$ resonances and pions, which is indispensable for constraining high-density symmetry energy from observables such as the ${\pi }^{-}/{\pi }^{+}$ yield ratio in heavy-ion collisions. The system in a box is initialized with nucleons at saturation density and at 60 MeV temperature. The reactions $NN\leftrightarrow N\Delta$ and $\Delta \leftrightarrow N\pi$ are implemented, but the Pauli blocking and the mean-field potential are deactivated in the present comparison. Results are compared to those from the two reference cases of a chemically equilibrated ideal gas mixture and of the rate equation. In the results of the numbers of $\Delta$ and $\pi$, deviations from the reference values are observed in many codes, and they depend significantly on the size of the time step. These deviations are tied to different ways in ordering the sequence of collisions and decays, that take place in the same time step. Better agreements are seen in the reaction rates and the number ratios among the isospin species of $\Delta$ and $\pi$. These are, however, affected by the correlations, which are absent in the Boltzmann equation, but are induced by the way particle scatterings are treated in transport calculations. The uncertainty in the transport-code predictions of the ${\pi }^{-}/{\pi }^{+}$ ratio for the system initialized at n/p = 1.5, after letting the existing $\Delta$ resonances decay, is found to be within a few percent, which is sufficiently small so that it does not strongly impact constraining the high-density symmetry energy from heavy-ion collisions. Most of the sources of uncertainties have been understood, and individual codes may be further improved. This investigation will be extended in the future to heavy-ion collisions to ensure the problems identified here remain under control.

   ↳ nucl-thnucl-exPRC(2019)·111 citations
6. 06*

   Density-constraint Time-dependent Hartree-Fock-Bogoliubov method

   G. Scamps🇧🇪 · Y. Hashimoto🇯🇵

   Background: The Density-constraint Time-dependent Hartree-Fock method is currently the tool of choice to predict fusion cross-sections. However, it does not include pairing correlations, which have been found recently to play an important role. Purpose: To describe the fusion cross-section with a method that includes the superfluidity and to understand the impact of pairing on both the fusion barrier and cross-section. Method: The density-constraint method is tested first on the following reactions without pairing, ${}^{16}$O+${}^{16}$O and ${}^{40}$Ca+${}^{40}$Ca. A new method is developed, the Density-constraint Time-dependent Hartree-Fock-Bogoliubov method. Using the Gogny-TDHFB code, it is applied to the reactions ${}^{20}$O+${}^{20}$O and ${}^{44}$Ca+${}^{44}$Ca. Results: The Gogny approach for systems without pairing reproduces the experimental data well. The DC-TDHFB method is coherent with the TDHFB fusion threshold. The effect of the phase-lock mechanism is shown for those reactions. Conclusions: The DC-TDHFB method is a useful new tool to determine the fusion potential between superfluid systems and to deduce their fusion cross-sections.

   ↳ nucl-thnucl-exPRC(2019)·16 citations
7. 07*

   Transition form factors: ${\gamma }^{\ast }+p\to \Delta (1232)$, $\Delta (1600)$

   Ya Lu🇨🇳 · Chen Chen🇧🇷 · Zhu-Fang Cui🇨🇳 · Craig D. Roberts🇺🇸 · Sebastian M. Schmidt🇩🇪 · Jorge Segovia🇪🇸 · Hong-Shi Zong🇨🇳

   Electroproduction form factors describing the ${\gamma }^{\ast }p\to {\Delta }^{+}(1232),{\Delta }^{+}(1600)$ transitions are computed using a fully-dynamical diquark-quark approximation to the Poincaré-covariant three-body bound-state problem in relativistic quantum field theory. In this approach, the $\Delta (1600)$ is an analogue of the Roper resonance in the nucleon sector, appearing as the simplest radial excitation of the $\Delta (1232)$. Precise measurements of the ${\gamma }^{\ast }p\to {\Delta }^{+}(1232)$ transition already exist on $0\le Q^2\lesssim 8$GeV${}^2$ and the calculated results compare favourably with the data outside the meson-cloud domain. The predictions for the ${\gamma }^{\ast }p\to {\Delta }^{+}(1600)$ magnetic dipole and electric quadrupole transition form factors are consistent with the empirical values at the real photon point, and extend to $Q^2\approx 6m_p^2$, enabling a meaningful direct comparison with experiment once analysis of existing data is completed. In both cases, the electric quadrupole form factor is particularly sensitive to deformation of the $\Delta$-baryons. Interestingly, whilst the ${\gamma }^{\ast }p\to {\Delta }^{+}(1232)$ transition form factors are larger in magnitude than those for ${\gamma }^{\ast }p\to {\Delta }^{+}(1600)$ in some neighbourhood of the real photon point, this ordering is reversed on $Q^2\gtrsim 2m_p^2$, suggesting that the ${\gamma }^{\ast }p\to {\Delta }^{+}(1600)$ transition is more localised in configuration space.

   ↳ nucl-thhep-lathep-phnucl-exPRD(2019)·51 citations
8. 08*

   The Innovative Design of the PANDA Barrel DIRC

   G. Schepers🇩🇪 · A. Ali🇩🇪 · A. Belias🇩🇪 · R. Dzhygadlo🇩🇪 · A. Gerhardt🇩🇪 · M. Krebs🇩🇪 · D. Lehmann🇩🇪 · K. Peters🇩🇪 · C. Schwarz🇩🇪 · J. Schwiening🇩🇪 · M. Traxler🇩🇪 · L. Schmitt🇺🇸 and 20 other authors

   The Barrel DIRC of the PANDA experiment at FAIR will cleanly separate pions from kaons for the physics program of PANDA. Innovative solutions for key components of the detector sitting in the strong magnetic field of the compact PANDA target spectrometer as well as two reconstruction methods were developed in an extensive prototype program. The technical design and present results from the test beam campaigns at the CERN PS in 2017 and 2018 are discussed.

   ↳ physics.ins-detnucl-exNuovo Cim.C(2019)·0 citations
9. 09*

   Temperature dependence of the probability of "small heating" and total losses of ucns on the surface of fomblin oils of different molecular mass

   S.M. Cherniavsky🇷🇺 · E.V. Lychagin🇷🇺 · A.Yu. Muzychka🇷🇺 · G.V. Nekhaev🇷🇺 · V.V. Nesvizhevsky🇫🇷 · S. Reynaud🇫🇷 · A.V. Strelkov🇷🇺 · K. Turlybekuly🇷🇺

   We measured the temperature dependence of the probability of small heating and total losses of UCNs on the PFPE Fomblin Y surface with various molecular masses Mw=2800, 3300, 6500 amu in the temperature range of 100-300 K. The probability of small heating sharply decreases with increasing Mw and decreasing temperature. The probability of total loss weakly decreases with decreasing temperature and takes the minimum value at Mw=3300 amu. As this oil provides a homogeneous surface with minimal probabilities of small heating and total losses of UCNs, it is the preferred candidate for experiments on measuring the neutron lifetime.

   ↳ physics.ins-detnucl-exEPJC(2019)·2 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.