Thu·Oct 4, 2018Thursday·October 4, 2018

1. 01*

   Direct capture cross section and the $E_p$ = 71 and 105 keV resonances in the ${}^{22}$Ne($p,\gamma$)${}^{23}$Na reaction

   F. Ferraro🇮🇹 · M. P. Takács🇩🇪 · D. Piatti🇮🇹 · F. Cavanna🇮🇹 · R. Depalo🇮🇹 · M. Aliotta · D. Bemmerer🇩🇪 · A. Best🇮🇹 · A. Boeltzig🇮🇹 · C. Broggini🇮🇹 · C. G. Bruno🇬🇧 · A. Caciolli🇮🇹 and 32 other authors

   The ${}^{22}$Ne($p,\gamma$)${}^{23}$Na reaction, part of the neon-sodium cycle of hydrogen burning, may explain the observed anticorrelation between sodium and oxygen abundances in globular cluster stars. Its rate is controlled by a number of low-energy resonances and a slowly varying non-resonant component. Three new resonances at $E_p$ = 156.2, 189.5, and 259.7 keV have recently been observed and confirmed. However, significant uncertainty on the reaction rate remains due to the non-resonant process and to two suggested resonances at $E_p$ = 71 and 105 keV. Here, new ${}^{22}$Ne($p,\gamma$)${}^{23}$Na data with high statistics and low background are reported. Stringent upper limits of 6$\times$10${}^{-11}$ and 7$\times$10${}^{-11}$\,eV (90\% confidence level), respectively, are placed on the two suggested resonances. In addition, the off-resonant S-factor has been measured at unprecedented low energy, constraining the contributions from a subthreshold resonance and the direct capture process. As a result, at a temperature of 0.1 GK the error bar of the ${}^{22}$Ne($p,\gamma$)${}^{23}$Na rate is now reduced by three orders of magnitude.

   nucl-exPRL(2018)·43 citations
2. 02*

   Strongly Resonating Bosons in Hot Nuclei

   S. Zhang · A. Bonasera · M. Huang · H. Zheng · G. Zhang · Z. Kohley · L. Lu · Y.G. Ma · S.J. Yennello

   When two heavy ions near the Fermi energy collide, a warm and low-density region can form in which fragments appear. This region is mainly dominated by proton (p) and alpha particles. In such an environment, the alphas interact with each other, and especially through strong resonances, form complex systems such as 8Be and 12C. Our experiments show that in the reactions 70(64)Zn(64Ni)+70(64)Zn(64Ni) at E/A=35 MeV/nucleon levels of 8Be appear around relative energies Eij=0.092 MeV, 3.03 MeV as well as above 10 MeV and 100 MeV. For the 3 alpha systems, multi resonance processes give rise to excited levels of 12C. In particular, the Hoyle state at 7.654 MeV excitation energy shows a decay component through the ground state of 8Be and also shows components where two different alpha couples are at relative energies consistent with the ground state of 8Be at the same time. A component where the three alpha relative energies are consistent with the ground state of 8Be (i.e., E12=E13=E23=0.092 MeV) is also observed at the 7.458 MeV excitation energy, which was suggested as an Efimov state.

   nucl-exPRC(2019)·12 citations
3. 03*

   Constraints on the density dependence of the symmetry energy

   Jerzy Lukasik

   Current status and future experimental plans for constraining the symmetry energy at supra-normal densities are presented. A special emphasis is put on significance of the results obtained by the ASY-EOS Collaboration in a broader astrophysical context, including the recent interpretations of the first LIGO and Virgo GW170817 gravitational wave signal. The plans for a high energy campaign at FAIR using the NeuLAND and the KRAB detectors will be outlined.

   nucl-exNuovo Cim.C(2019)·6 citations
4. 04*

   Observation of prompt J/$\psi$ meson elliptic flow in high-multiplicity pPb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 8.16 TeV

   CMS Collaboration

   A measurement of the elliptic flow ($v_2$) of prompt J/$\psi$ mesons in high-multiplicity pPb collisions is reported using data collected by the CMS experiment at a nucleon-nucleon center-of-mass energy $\sqrt{s_{\mathrm{NN}}}=$ 8.16 TeV. Prompt J/$\psi$ mesons decaying into two muons are reconstructed in the rapidity region in the nucleon-nucleon center-of-mass frame ($y_{\mathrm{cm}}$), corresponding to either $-$2.86 $<y_{\mathrm{cm}}<$ $-$1.86 or 0.94 $<y_{\mathrm{cm}}<$ 1.94. The average $v_2$ result from the two rapidity ranges is reported over the transverse momentum (p${}_{\mathrm{T}}$) range from 0.2 to 10 GeV. Positive $v_2$ values are observed for the prompt J/$\psi$ meson, as extracted from long-range two-particle correlations with charged hadrons, for 2 $<p_{\mathrm{T}}<$ 8 GeV. The prompt J/$\psi$ results are compared with previous CMS measurements of elliptic flow for open charm mesons (D${}^0$) and strange hadrons. From these measurements, constraints can be obtained on the collective dynamics of charm quarks produced in high-multiplicity events arising from small systems.

   ↳ hep-exnucl-exPLB(2019)·81 citations
5. 05*

   The role of hidden-charm pentaquark resonance $P_c^{+}(4450)$ in $J/\psi$ photoproduction on nuclei near threshold

   E. Ya. Paryev🇷🇺 · Yu. T. Kiselev🇷🇺

   We study the $J/\psi$ photoproduction from nuclei at near-threshold incident photon energies of 5--11 GeV within the nuclear spectral function approach by considering incoherent direct ($\gamma N\to J/\psi N$) and two-step ($\gamma p\to P_c^{+}(4450)$, $P_c^{+}(4450)\to J/\psi p$) photon--nucleon charmonium creation processes. We calculate the absolute and relative excitation functions within the different scenarios for in-medium modification of the directly photoproduced $J/\psi$ mesons. We show that the overall subthreshold $J/\psi$ production in $\gamma A$ reactions reveals some sensitivity to adopted in-medium modification scenarios for $J/\psi$ mesons only if branching ratio $Br[P_c^{+}(4450)\to J/\psi p]$ $\sim$ 1% and less. Our studies also demonstrate that the presence of the $P_c^{+}(4450)$ resonance in $J/\psi$ photoproduction produces above threshold additional enhancements in the behavior of the total $J/\psi$ creation cross section on nuclei, which could be also studied in the future JLab experiments at the upgraded up to 12 GeV CEBAF facility to provide further evidence for its existence.

   ↳ nucl-thnucl-exNPA(2018)·21 citations
6. 06*

   VME Readout at and Below the Conversion Time Limit

   M. Munch🇩🇰 · J. H. Jensen🇩🇰 · B. Löher🇩🇪 · H. Törnqvist🇩🇪 · H. T. Johansson🇸🇪

   The achievable acquisition rates of modern triggered nuclear physics experiments are heavily dependent on the readout software, in addition to the limits given by the utilized hardware. This paper presents an asynchronous readout scheme that significantly improves the livetime of an otherwise synchronous triggered VME-based data acquisition system. A detailed performance analysis of this and other readout schemes, in terms of the basic data transfer operations, is described. The performance of the newly developed scheme as well as synchronous schemes on two systems has been measured. The measurements show excellent agreement with the detailed description. For the second system, which previously used a synchronous readout, the deadtime ratio is at a 20 kHz trigger request frequency reduced by 30 % compared to the nearest contender, allowing 10 % more events to be recorded in the same time. The interaction between the network and readout tasks for single-core processors is also investigated. A livetime ratio loss of a few percent can be observed, depending on the size of the data chunks given to the operating system kernel for network transfer. With appropriately chosen chunk size, the effect can be mitigated.

   ↳ physics.ins-detnucl-exIEEE Trans.Nucl.Sci.(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.