Thu·Jul 23, 2020Thursday·July 23, 2020

1. 01*

   Probing neutron-hidden neutron transitions with the MURMUR experiment

   C. Stasser🇧🇪 · G. Terwagne🇧🇪 · J. Lamblin🇫🇷 · O. Méplan🇫🇷 · G. Pignol🇫🇷 · B. Coupé🇧🇪 · S. Kalcheva🇧🇪 · S. Van Dyck🇧🇪 · M. Sarrazin🇫🇷

   MURMUR is a new passing-through-walls neutron experiment designed to constrain neutron/hidden neutron transitions allowed in the context of braneworld scenarios or mirror matter models. A nuclear reactor can act as a hidden neutron source, such that neutrons travel through a hidden world or sector. Hidden neutrons can propagate out of the nuclear core and far beyond the biological shielding. However, hidden neutrons can weakly interact with usual matter, making possible for their detection in the context of low-noise measurements. In the present work, the novelty rests on a better background discrimination and the use of a mass of a material - here lead - able to enhance regeneration of hidden neutrons into visible ones to improve detection. The input of this new setup is studied using both modelizations and experiments, thanks to tests currently performed with the experiment at the BR2 research nuclear reactor (SCK$\cdot$CEN, Mol, Belgium). A new limit on the neutron swapping probability p has been derived thanks to the measurements taken during the BR2 Cycle 02/2019A: $p<4.0\times 10^{-10}$ at 95% CL. This constraint is better than the bound from the previous passing-through-wall neutron experiment made at ILL in 2015, despite BR2 is less efficient to generate hidden neutrons by a factor 7.4, thus raising the interest of such experiment using regenerating materials.

   nucl-exhep-exhep-phphysics.ins-detEPJC(2021)·19 citations
2. 02*

   Front-end control system and precise threshold configuration of the v-Angra experiment

   Mariana L Migliorini · Antonio Fernandes Jr · Joao C Anjos · Pietro Chimenti🇧🇷 · Igor A Costa · Luis F G Gonzalez · Germano P Guedes🇧🇷 · Ernesto Kemp🇧🇷 · Herman P Lima Jr · Guilherme S P Lopes · Amaro S Lopes Jr · Rafael A Nobrega and 4 other authors

   The v-Angra experiment aims to estimate the flux of antineutrino particles coming out from the Angra II nuclear reactor. Such flux is proportional to the thermal power released in the fission process and therefore can be used to infer the quantity of fuel that has been burned during a certain period. To do so, the v-Angra Collaboration has developed an antineutrino detector and a complete acquisition system to readout and store the signals generated by its sensors. The entire detection system has been installed inside a container laboratory placed beside the dome of the nuclear reactor, in a restricted zone of the Angra II site. The system is supposed to work standalone for a few years in order to collect enough data so that the experiment can be validated. The detector's readout electronics and its environmental conditions are crucial parts of the experiment and they should work autonomously and be controlled and monitored remotely. Additionally, threshold configuration is a central issue of the experiment since antineutrino particles produce low energy signals in the detector, being necessary to carefully adjust it for all the detector channels in order to make the system capable of detecting signals as low as those generated by single photons. To this end, an embedded system was developed and integrated to the detection apparatus installed in the container at the Angra II site and is now operational and accessible to the v-Angra Collaboration. This article aims at describing the proposed embedded system and presenting the results obtained during its commissioning phase.

   ↳ physics.ins-detnucl-exJINST(2020)·2 citations
3. 03*

   $\Omega$-dibaryon production with hadron interaction potential from the lattice QCD in relativistic heavy-ion collisions

   S. Zhang🇨🇳 · Y. G. Ma🇨🇳

   Recently the HAL QCD Collaboration reported the $\Omega -\Omega$ and $N-\Omega$ interaction potentials by the lattice QCD simulations. Based on these results, $N\Omega$ (${}^5{S}_2$) and $\Omega \Omega$ (${}^1{S}_0$) bound states were predicted with the binding energy about a few MeV. In addition, $N-\Omega$ HBT correlation function was also measured by the STAR Collaboration as well as the ALICE Collaboration. These results provide dynamical information whether or not $\Omega$-dibaryons exist in the interaction aspects. Another necessary point for the detection of $\Omega$-dibaryons is the experimental environment where the bound state could be produced and survived in the system. In this context, there are at least two necessary conditions to constrain the production probability of $\Omega$-dibaryons, i.e. the one is the necessary short-range attractive interaction to form the bound state and the another is the experimental environment such as heavy-ion collision provides abundant enough strangeness and multiplicity of nucleons. In this Letter the $\Omega -\Omega$ and $\Omega -$nucleon interaction potentials by the lattice QCD simulations were employed to obtain $\Omega \Omega$ (${}^1{S}_0$) and $N\Omega$ (${}^5{S}_2$) wave functions, and then the productions of $\Omega$-dibaryons were estimated by using of a dynamical coalescence mechanism for the relativistic heavy-ion collisions at $\sqrt{s_{NN}}=$ 200 GeV and 2.76 TeV.

   ↳ hep-phnucl-exnucl-thPLB(2020)·19 citations
4. 04*

   Nucleus giant resonances from an improved isospin-dependent Boltzmann-Uehling-Uhlenbeck transport approach

   Jun Xu🇨🇳 · Wen-Tao Qin

   We have studied the isoscalar giant quadruple resonance (ISGQR) and the isovector giant dipole resonance (IVGDR) in ${}^{208}$Pb based on an improved isospin-dependent Boltzmann-Uehling-Uhlenbeck transport approach using an improved isospin- and momentum-dependent interaction. With the isoscalar nucleon effective mass and the nucleon-nucleon cross section which reproduces respectively the excitation energy and the width of the ISGQR strength function, the slope parameter of the symmetry energy and the neutron-proton effective mass splitting are constrained respectively within $36<L<62$ MeV and $0.08\delta <(m_{n0}^{\ast }-m_{p0}^{\ast })/m<0.42\delta$, by comparing the resulting centroid energy of the IVGDR and the electric dipole polarizability with the experimental data. It is found that nucleon-nucleon collisions have considerable effects on the resulting electric dipole polarizability, which needs to be measured more accurately in order to pin down isovector nuclear interactions.

   ↳ nucl-thnucl-exPRC(2020)·22 citations
5. 05*

   Neutron lifetime measurement with pulsed cold neutrons

   K. Hirota · G. Ichikawa · S. Ieki · T. Ino · Y. Iwashita · M. Kitaguchi · R. Kitahara · J. Koga · K. Mishima · T. Mogi · K. Morikawa · A. Morishita and 17 other authors

   The neutron lifetime has been measured by comparing the decay rate with the reaction rate of ${}^3$He nuclei of a pulsed neutron beam from the spallation neutron source at the Japan Proton Accelerator Research Complex (J-PARC). The decay rate and the reaction rate were determined by simultaneously detecting electrons from the neutron decay and protons from the ${}^3$He(n,p)${}^3$H reaction using a gas chamber of which working gas contains diluted ${}^3$He. The measured neutron lifetime was $898\pm 10{}_{\mathrm{stat}}{}_{-18}^{+15}{}_{\mathrm{sys}}$s.

   ↳ hep-exnucl-exPTEP(2020)·33 citations
6. 06*

   Evidence for the general dominance of proton shells in low-energy fission

   K. Mahata🇮🇳 · C. Schmitt🇫🇷 · Shilpi Gupta🇮🇳 · A. Shrivastava🇮🇳 · G. Scamps🇧🇪 · K.-H. Schmidt🇩🇪

   A regular pattern, revealing the leading role of the light-fragment nuclear charge, is found to emerge from a consistent analysis of the experimental information collected recently on low-energy asymmetric fission of neutron-deficient nuclei around lead. The observation is corroborated by a theoretical investigation within a microscopic framework, suggesting the importance of proton configurations driven by quadrupole-octupole correlations. This is in contrast to the earlier theoretical interpretations in terms of dominant neutron shells. The survey of a wider area of the nuclear chart by a semi-empirical approach points to the lack of understanding of the competition between the different underlying macroscopic and microscopic forces in a quantitative manner. Combined with previously identified stabilizing forces, the present finding shows a striking connection between the "old" (actinide) and "new" (pre-actinide) islands of asymmetric fission which could steer the strive for an unified theory of fission.

   ↳ nucl-thnucl-exPLB(2022)·60 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.