Tue·Feb 16, 2021Tuesday·February 16, 2021

1. 01*

   Neutron background measurement for rare event search experiments in the YangYang Underground Laboratory

   Young Soo Yoon🇰🇷 · Jungho Kim🇰🇷 · Hyeonseo Park🇰🇷

   Several experiments have been conducted in the YangYang Underground Laboratory in the Republic of Korea such as the search for dark matter and the search for neutrinoless double-beta decay, which require an extremely low background event rate due to the detector system and the environment. In underground experiments, neutrons have been identified as one of the background sources. The neutron flux in the experimental site needs to be determined to design a proper shielding system and for precise background estimation. We measured the neutron spectrum with a Bonner sphere spectrometer, with Helium-3 (${}^3$He) proportional counters. The neutron flux at the underground laboratory was so low that the radioactive decays from the radioisotopes contained in the detector created a significant background interference to the neutron measurement. Using Monte Carlo simulations, the intrinsic $\alpha$ background distribution due to the radioactive isotopes in the detector materials, was estimated. The neutron count rate of each Bonner sphere was measured from the pulse height spectrum of the ${}^3$He proportional counter, after subtracting the $\alpha$ particle background. The neutron flux and the energy spectrum were determined using the unfolding technique. The total neutron flux measured was (4.46 $\pm$ 0.66) $\times$ $10^{-5}$ $\mathrm{c}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$, and the thermal and fast neutron flux (in the range 1 to 10 MeV) were (1.44 $\pm$ 0.15) $\times$ 10${}^{-5}$ $\mathrm{c}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$ and (0.71 $\pm$ 0.10) $\times$ 10${}^{-5}$ $\mathrm{c}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$, respectively.

   nucl-exAstropart.Phys.(2021)·17 citations
2. 02*

   Measurement of deeply virtual Compton scattering off Helium-4 with CLAS at Jefferson Lab

   R. Dupré🇫🇷 · M. Hattawy🇺🇸 · N.A. Baltzell🇺🇸 · S. Bültmann🇺🇸 · R. De Vita🇮🇹 · A. El Alaoui🇨🇱 · L. El Fassi🇺🇸 · H. Egiyan🇺🇸 · F.X. Girod🇺🇸 · M. Guidal🇫🇷 · K. Hafidi🇺🇸 · D. Jenkins🇺🇸 and 129 other authors

   We report on the measurement of the beam spin asymmetry in the deeply virtual Compton scattering off ${}^4$He using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab using a 6 GeV longitudinally polarized electron beam incident on a pressurized ${}^4$He gaseous target. We detail the method used to ensure the exclusivity of the measured reactions, in particular the upgrade of CLAS with a radial time projection chamber to detect the low-energy recoiling ${}^4$He nuclei and an inner calorimeter to extend the photon detection acceptance at forward angles. Our results confirm the theoretically predicted enhancement of the coherent ($e^4$He$\to e^{\prime }$${}^4$He${}^{\prime }{\gamma }^{\prime }$) beam spin asymmetries compared to those observed on the free proton, while the incoherent ($e^4$He$\to e^{\prime }$p${}^{\prime }{\gamma }^{\prime }$X${}^{\prime }$) asymmetries exhibit a 30$\%$ suppression. From the coherent data, we were able to extract, in a model-independent way, the real and imaginary parts of the only ${}^4$He Compton form factor, ${\mathcal{H}}_{\mathcal{A}}$, leading the way toward 3D imaging of the partonic structure of nuclei.

   nucl-exPRC(2021)·20 citations
3. 03*

   ${}^{210}$Pb measurements at the André E. Lalonde AMS Laboratory for the radioassay of materials used in rare event search detectors

   Carlos Vivo-Vilches🇨🇦 · Benjamin Weiser🇨🇦 · Xiaolei Zhao🇨🇦 · Barbara B.A. Francisco🇺🇸 · Razvan Gornea🇨🇦 · William E. Kieser🇨🇦

   Naturally occurring radionuclide ${}^{210}$Pb ($T_{1/2}$=22.2 y) is an important source of background in rare event searches, such as neutrinoless double-$\beta$ decay and dark matter direct detection experiments. When a sample mass of hundreds of grams is available, $\gamma$-counting measurements can be performed. However, there are other cases where only grams of sample can be used. For these cases, better sensitivities are required. In this paper, in collaboration with the Astroparticle Physics group at Carleton University, the capabilities of the A.E. Lalonde AMS Laboratory at the University of Ottawa for ${}^{210}$Pb measurements are discussed. PbF${}_2$ and PbO targets were used, selecting in the low energy sector, respectively, (PbF${}_3$)${}^{-}$ or (PbO${}_2$)${}^{-}$ ions. For fluoride targets, the blank ${}^{210}$Pb/${}^{206}$Pb ratio was in the 10${}^{-14}$ to 10${}^{-13}$ range, but current output was lower and less stable. For oxide targets, current output showed better stability, despite a significant difference in current output for commercial PbO and processed samples, and background studies suggested a background not much higher than that of the fluoride targets. Both target materials showed, therefore, good performance for ${}^{210}$Pb AMS assay. Measurements of Kapton films, an ultra-thin polymer material, where masses available are typically just several grams, were performed. 90% C.L. upper limits for the ${}^{210}$Pb specific activity in the range of 0.74-2.8 Bq/kg were established for several Kapton HN films.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.B(2022)·4 citations
4. 04*

   Hadronic resonance production and interaction in p-Pb collisions at LHC energies in EPOS3

   A. G. Knospe🇺🇸 · C. Markert🇺🇸 · K. Werner🇫🇷 · J. Steinheimer🇩🇪 · M. Bleicher🇩🇪

   Using the EPOS3 model with UrQMD to describe the hadronic phase, we study the production of short-lived hadronic resonances and the modification of their yields and $p_T$ spectra in p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. High-multiplicity p-Pb collisions exhibit similar behavior to mid-peripheral Pb-Pb collisions at LHC energies, and we find indications of a short-lived hadronic phase in p-Pb collisions that can modify resonance yields and $p_T$ spectra through scattering processes. The evolution of resonance production is investigated as a function of the system size, which is related to the lifetime of the hadronic phase, in order to study the onset of collective effects in p-Pb collisions. We also study hadron production separately in the core and corona parts of these collisions, and explore how this division affects the total particle yields as the system size increases.

   ↳ nucl-thnucl-exPRC(2021)·27 citations
5. 05*

   Thermodynamics of partonic matter in relativistic heavy-ion collisions from a multiphase transport model

   Han-Sheng Wang🇨🇳 · Guo-Liang Ma🇨🇳 · Zi-Wei Lin🇺🇸 · Wei-jie Fu🇨🇳

   Using the string melting version of a multiphase transport model, we focus on the evolution of thermodynamic properties of the central cell of parton matter produced in Au$+$Au collisions ranging from 200 GeV down to 2.7 GeV. The temperature and chemical potentials have been calculated based on both Boltzmann and quantum statistics in order to locate their evolution trajectories in the QCD phase diagram. We demonstrate that the trajectories can depend on many physical factors, especially the finite nuclear thickness at lower energies. However, from the evolution of pressure anisotropy, only partial thermalization can be achieved when the partonic systems reach the predicted QCD phase boundary. It provides some helpful insights to studying the QCD phase structure through relativistic heavy-ion collisions.

   ↳ nucl-thhep-phnucl-exPRC(2022)·15 citations
6. 06*

   Suppression of the nuclear rainbow in the inelastic nucleus-nucleus scattering

   Nguyen Hoang Phuc🇻🇳 · Dao T. Khoa🇻🇳 · Nguyen Tri Toan Phuc🇻🇳 · Do Cong Cuong🇻🇳

   The nuclear rainbow observed in the elastic $\alpha$-nucleus and light heavy-ion scattering is proven to be due to the refraction of the scattering wave by a deep, attractive real optical potential. The nuclear rainbow pattern, established as a broad oscillation of the Airy minima in the elastic cross section, originates from an interference of the refracted far-side scattering amplitudes. It is natural to expect a similar rainbow pattern also in the inelastic scattering of a nucleus-nucleus system that exhibits a pronounced rainbow pattern in the elastic channel. Although some feature of the nuclear rainbow in the inelastic nucleus-nucleus scattering was observed in experiment, the measured inelastic cross sections exhibit much weaker rainbow pattern, where the Airy oscillation is suppressed and smeared out. To investigate this effect, a novel method of the near-far decomposition of the inelastic scattering amplitude is proposed to explicitly reveal the coupled partial-wave contributions to the inelastic cross section. Using the new decomposition method, our coupled channel analysis of the elastic and inelastic ${}^{12}$C+${}^{12}$C and ${}^{16}$O+${}^{12}$C scattering at the refractive energies shows unambiguously that the suppression of the nuclear rainbow pattern in the inelastic scattering cross section is caused by a destructive interference of the partial waves of different multipoles. However, the inelastic scattering remains strongly refractive in these cases, where the far-side scattering is dominant at medium and large angles like that observed in the elastic scattering.

   ↳ nucl-thnucl-exEPJA(2021)·4 citations
7. 07*

   A new mass model for nuclear astrophysics: crossing 200 keV accuracy

   M. Shelley🇬🇧 · A. Pastore🇬🇧

   By using a machine learning algorithms, we present an improved nuclear mass table with a root mean square deviation of less than $200$k̇eV. The model is equipped with statistical error bars in order to compare with available experimental data. We use the resulting model to predict the composition of the outer crust of a neutron star. By means of simple Monte Carlo methods, we propagate the statistical uncertainties of the mass model to the equation of state of the system.

   ↳ nucl-thnucl-exUniverse(2021)·25 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.