Tue·Oct 13, 2020Tuesday·October 13, 2020

1. 01*

   Surface localization of the dineutron in ${}^{11}$Li

   Y. Kubota🇯🇵 · A. Corsi🇫🇷 · G. Authelet🇫🇷 · H. Baba🇯🇵 · C. Caesar🇩🇪 · D. Calvet🇫🇷 · A. Delbart🇫🇷 · M. Dozono🇯🇵 · J. Feng🇨🇳 · F. Flavigny🇫🇷 · J.-M. Gheller🇫🇷 · J. Gibelin🇫🇷 and 55 other authors

   The formation of a dineutron in the nucleus ${}^{11}$Li is found to be localized to the surface region. The experiment measured the intrinsic momentum of the struck neutron in ${}^{11}$Li via the $(p,pn)$ knockout reaction at 246 MeV/nucleon. The correlation angle between the two neutrons is, for the first time, measured as a function of the intrinsic neutron momentum. A comparison with reaction calculations reveals the localization of the dineutron at $r\sim 3.6$ fm. The results also support the density dependence of dineutron formation as deduced from Hartree-Fock-Bogoliubov calculations for nuclear matter.

   nucl-exPRL(2020)·58 citations
2. 02*

   Assessing the impact of valence sd neutrons and protons on fusion

   Varinderjit Singh🇺🇸 · J. Vadas🇺🇸 · T.K. Steinbach · B.B. Wiggins · S. Hudan🇺🇸 · R.T. deSouza🇺🇸

   Experimental above-barrier fusion cross-sections for ${}^{17}$F + ${}^{12}$C are compared to the fusion excitation functions for ${}^{16,18}$O, ${}^{19}$F, and ${}^{20}$Ne ions on a carbon target. In comparing the different systems both the differing static size of the incident ions and changes in fusion barrier are accounted for by examining the reduced fusion cross-section. Remaining trends of the fusion cross-section above the barrier which reflect the sensitive interplay of the sd protons and neutrons are observed. The experimental data are also compared to both a widely-used analytical model of near-barrier fusion, as well as a time-dependent Hartree-Fock model. Both models fail to describe the trends observed.

   nucl-exastro-ph.SRnucl-thPRC(2021)·4 citations
3. 03*

   Experimental study of the ${}^{17}$F+ ${}^{12}$C fusion reaction and its implications for fusion of proton-halo systems

   B. W. Asher · S. Almaraz-Calderon · Vandana Tripathi🇮🇳 · K. W. Kemper🇺🇸 · L. T. Baby🇺🇸 · N. Gerken · E. Lopez-Saavedra🇪🇸 · A. B. Morelock · J. F. Perello · I. Wiedenhöver🇺🇸 · N. Keeley

   The halo nature of the low-lying $1/2$+ first excited state of the exotic weakly-bound proton drip-line nucleus ${}^{17}$F has long been hypothesized. The structure of such a halo nucleus would imply special nuclear properties including, possibly, an enhancement in its fusion cross section above the barrier. The total fusion cross section of ${}^{17}$F + ${}^{12}$C near the Coulomb barrier was studied using the newly developed "Encore" active-target detector at Florida State University. Total fusion cross sections for the stable counterpart systems ${}^{16}$O + ${}^{12}$C and ${}^{19}$F + ${}^{12}$C were also measured to enable a systematic comparison. No influence of the halo nature of the ${}^{17}$F $1/2$+ first excited state on its fusion excitation function was observed when compared with the stable counterpart systems.

   nucl-exPRC(2021)·14 citations
4. 04*

   Impact of Three-Body Forces on Elastic Nucleon-Nucleus Scattering Observables

   Matteo Vorabbi🇺🇸 · Michael Gennari🇨🇦 · Paolo Finelli🇮🇹 · Carlotta Giusti🇮🇹 · Peter Navrátil🇨🇦 · Ruprecht Machleidt🇺🇸

   In a previous series of papers we investigated the domain of applicability of chiral potentials to the construction of a microscopic optical potential (OP) for elastic nucleon-nucleus scattering. The final expression of the OP was a folding integral between the nucleon-nucleon ($NN$) $t$ matrix and the nuclear density of the target. In these calculations $NN$ and three-nucleon ($3N$) chiral interactions were used for the target density and only the $NN$ interaction for the $NN$ $t$ matrix. The purpose of this work is to achieve another step towards the calculation of a more consistent OP introducing the $3N$ force also in the dynamic part of the OP. In the present work this is approximated with a density dependent $NN$ interaction obtained after the averaging over the Fermi sphere. In practice, in our model the $3N$ force acts as a medium correction of the bare $NN$ interaction used to calculate the $NN$ $t$ matrix. Even if the $3N$ force is treated in an approximate way, this method naturally extends our previous model of the OP and allows a direct comparison of our present and previous results. We consider as case studies the elastic scattering of nucleons off ${}^{12}$C and ${}^{16}$O. We present results for the differential cross section and the spin observables for different values of the projectile energy. From the comparison with the experimental data and with the results of our previous model we assess the importance of the $3N$ interaction in the dynamic part of the OP. Our analysis indicates that the contribution of the $3N$ force in the $t$ matrix is small for the differential cross section and it is sizable for the spin observables, in particular, for the analyzing power. A chiral expansion order-by-order analysis of the scattering observables confirms the convergence of our results at the next-to-next-to-next-to-leading-order, as already established in our previous work.

   ↳ nucl-thnucl-exPRC(2021)·19 citations
5. 05*

   Topological studies of light-flavor hadron production in pp, p-Pb, and Pb-Pb collisions with ALICE at the LHC

   Sushanta Tripathy (for the ALICE Collaboration)🇲🇽

   Recent results for high multiplicity pp and p-Pb collisions have revealed that they exhibit heavy-ion-like behaviors. To understand the origin(s) of these unexpected phenomena, event shape observables such as transverse spherocity ($S_0^{p_{\mathrm{T}}=1}$) and the relative transverse activity classifier ($R_{\mathrm{T}}$) can be exploited as a powerful tools to disentangle soft (non-perturbative) and hard (perturbative) particle production. Here, the production of light-flavor hadrons is shown for various $S_0^{p_{\mathrm{T}}=1}$ classes in pp collisions at $\sqrt{s}$ = 13 $\text{TeV}$ measured with the ALICE detector at the LHC are presented. The evolution of average transverse momentum ($⟨p_{\mathrm{T}}⟩$) with charged-particle multiplicity, and identified particle ratios as a function of $p_{\mathrm{T}}$ for different $S_0^{p_{\mathrm{T}}=1}$ are also presented. In addition, the system size dependence of charged-particle production in pp, p-Pb, and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV is presented. The evolution of $⟨p_{\mathrm{T}}⟩$ in different topological regions as a function of $R_{\mathrm{T}}$ are presented. Finally, using the same approach, we present a search for jet quenching behavior in small collision systems.

   ↳ hep-exnucl-exJ.Phys.Conf.Ser.(2020)·3 citations
6. 06*

   Reaction rate weighted multilayer nuclear reaction network

   H. L. Liu🇨🇳 · D. D. Han · P. Ji🇨🇳 · Y. G. Ma🇨🇳

   Nuclear reaction rate ($\lambda$) is a significant factor in the process of nucleosynthesis. A multi-layer directed-weighted nuclear reaction network in which the reaction rate as the weight, and neutron, proton, ${}^4$He and the remainder nuclei as the criterion for different reaction-layers is for the first time built based on all thermonuclear reactions in the JINA REACLIB database. Our results show that with the increase of the stellar temperature ($T_9$), the distribution of nuclear reaction rates on the $R$-layer network demonstrates a transition from unimodal to bimodal distributions. Nuclei on the $R$-layer in the region of $\lambda =[1,2.5\times 10^1]$ have a more complicated out-going degree distribution than the one in the region of $\lambda =[10^{11},10^{13}]$, and the number of involved nuclei at $T_9=1$ is very different from the one at $T_9=3$. The redundant nuclei in the region of $\lambda =[1,2.5\times 10^1]$ at $T_9=3$ prefer $(\gamma ,p)$ and $(\gamma ,\alpha )$ reactions to the ones at $T_9=1$, which produce nuclei around the $\beta$ stable line. This work offers a novel way to the big-data analysis on nuclear reaction network at stellar temperatures.

   ↳ nucl-thnucl-exChin.Phys.Lett.(2020)·5 citations
7. 07*

   Azimuthal anisotropy and multiplicities of hard photons and free nucleons in intermediate-energy heavy-ion collisions

   S. S. Wang🇨🇳 · Y. G. Ma🇨🇳 · X. G. Cao🇨🇳 · D. Q. Fang🇨🇳 · C. W. Ma🇨🇳

   Anisotropic flow can offer significant information of evolution dynamics in heavy-ion collisions. A systematic study of the directed flow $v_1$ and elliptic flow $v_2$ of hard photons and free nucleons is performed for ${}^{40}$Ca+${}^{40}$Ca collisions in a framework of isospin dependent quantum molecular dynamics (IQMD) model. The study firstly reveals that thermal photons emitted in intermediate-energy heavy-ion collisions have the behaviors of directed and elliptic flows. The interesting phenomena of incident energy dependence of $v_1$ and $v_2$ for thermal photons in central collisions also confirmed that it can be regarded as a good probe of evolution dynamics. Moreover, the multiplicities of hard photons and free nucleons and their correlation are also investigated. We find that direct photon emission is positively related to free nucleons emission, however, there exists an anti-correlation for thermal photons with free nucleons.

   ↳ nucl-thnucl-exEPJA(2020)·4 citations
8. 08*

   Parallel data readout for background rejection in CANDLES experiment

   Bui Tuan Khai🇯🇵

   CANDLES experiment in Kamioka Underground Observatory aims to obtain the neutrino-less double beta decay ($0\nu \beta \beta$) from ${}^{48}$Ca. This measurement is a big challenge due to the extremely rare decay rate of ${}^{48}$Ca. Thus, in order to obtain 0\nu\beta\beta, it is needed to reduce background as much as possible. Series of alpha and beta decays originated from radioactive impurities can remain as background in the energy region of $0\nu \beta \beta$. Because they are sequential decays, we can remove them by tagging preceding and following events. This tagging method requires minimized dead-time of DAQ system. A new DAQ system was introduced in CANDLES with new FADC (Flash Analog-to-Digital Converter) modules using 8 event buffers and SpaceWire-to-GigabitEthernet network for data readout. To reduce the dead-time, we developed our DAQ system with 4 parallel reading processes. As a result, the read-time is reduced by 4 times: 40msec down to 10msec, which is in equivalent to a half of previous DAQ's read-time. With reduced read-time accompanied by multiple event buffers, the new DAQ system is realized with efficiency is very close to 100$\%$ (no event lost at 20cps, which is CANDLES trigger rate, after 63 hours of data taking). With improved performance, it is expected to achieve higher background suppression for CANDLES experiment.

   ↳ physics.ins-dethep-exnucl-ex0 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.