Tue·Mar 5, 2019Tuesday·March 5, 2019

1. 01*

   High resolution $\gamma$-ray spectroscopy using GALILEO array

   D. Testov · J.J. Valiente-Dobón · D. Mengoni · F. Recchia · A. Goasduff · A. Boso · S. Lenzi · G. de Angelis · S. Lenzi · S. Bakes · C. Boiano · B. Cederwall and 28 other authors

   The GALILEO $\gamma$-ray spectrometer has been constructed at the Legnaro National Laboratory of INFN (LNL-INFN). It can be coupled to advanced ancillary devices which allows nuclear structure studies employing the variety of in-beam $\gamma$-ray spectroscopy methods. Such studies benefit from reactions induced by the intense stable beams delivered by the Tandem-ALPI-PIAVE accelerator complex and by the radioactive beams which will be provided by the SPES facility. In this paper we outline two experiments performed within the experimental campaign at GALILEO coupled to the EUCLIDES Si-ball and the Neutron Wall array. The first one was aimed at spectroscopic studies in A=31 mirror nuclei and the second one at measurements of lifetimes of excited states in nuclei in the vicinity of ${}^{100}$Sn.

   nucl-ex3 citations
2. 02*

   Structure of 9C through proton resonance scattering with Texas Active Target detector

   J. Hooker🇺🇸 · G.V. Rogachev🇺🇸 · E. Koshchiy🇺🇸 · S. Ahn🇺🇸 · M. Barbui🇺🇸 · V.Z. Goldberg🇺🇸 · C. Hunt🇺🇸 · H. Jayatissa🇺🇸 · E.C. Pollacco🇫🇷 · B.T. Roeder🇺🇸 · A. Saastamoinen🇺🇸 · S. Upadhyayula🇺🇸

   Background: Level structure of the most neutron deficient nucleon-bound carbon isotope, 9C, is not well known. Definitive spin-parity assignments are only available for two excited states. No positive parity states have been conclusively identified so far and the location of the sd-shell in A=9 T=3/2 isospin quadruplet is not known. Purpose: We have studied the level structure of exotic nucleus 9C at excitation energies below 6.4 MeV. Methods: Excited states in 9C were populated in 8B+p resonance elastic scattering and excitation functions were measured using active target approach. Results: Two excited states in 9C were conclusively observed, and R-matrix analysis of the excitation functions was performed to make the spin-parity assignments. The first positive parity state in A=9 T=3/2 nuclear system, the 5/2+ resonance at 4.3 MeV, has been identified. Conclusions: The new 5/2+ state at 4.3 MeV in 9C is a single-particle L=0 broad resonance and it determines the energy of the 2s shell. The 2s shell in this exotic nucleus appears well within the region dominated by the p-shell states.

   nucl-exPRC(2019)·13 citations
3. 03*

   Dynamics of clusters and fragments in heavy-ion collisions

   Akira Ono🇯🇵

   A review is given on the studies of formation of light clusters and heavier fragments in heavy-ion collisions at incident energies from several tens of MeV/nucleon to several hundred MeV/nucleon, focusing on dynamical aspects and on microscopic theoretical descriptions. Existing experimental data already clarify basic characteristics of expanding and fragmenting systems typically in central collisions, where cluster correlations cannot be ignored. Cluster correlations appear almost everywhere in excited low-density nuclear many-body systems and nuclear matter in statistical equilibrium where the properties of a cluster may be influenced by the medium. On the other hand, transport models to solve the time evolution have been developed based on the single-nucleon distribution function. Different types of transport models are reviewed putting emphasis both on theoretical features and practical performances in the description of fragmentation. A key concept to distinguish different models is how to consistently handle single-nucleon motions in the mean field, fluctuation or branching induced by two-nucleon collisions, and localization of nucleons to form fragments and clusters. Some transport codes have been extended to treat light clusters explicitly. Results indicate that cluster correlations can have strong impacts on global collision dynamics and correlations between light clusters should also be taken into account.

   ↳ nucl-thnucl-exPPNP(2019)·112 citations
4. 04*

   Multiplicity dependence of heavy-flavour correlations with charged particle and collective effects in p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$= 5.02 TeV with ALICE at LHC

   Marianna Mazzilli (for the ALICE Collaboration)🇮🇹

   Azimuthal correlation studies of heavy-flavour particles with charged particles in p--Pb collisions can give an insight into the cold nuclear matter effects \cite{Andronic:2015wma} on heavy-quark production and hadronization into heavy-flavour jets. Multiplicity-dependent measurements of angular correlations of heavy-flavour particles with charged hadrons allow us to investigate the collective behavior of the system and the initial state effects on heavy flavour hadron production. In addition, they can reveal possible modifications of the heavy-quark fragmentation and hadronization at different multiplicities. We present ALICE measurements of azimuthal correlations of prompt D-mesons with charged hadrons as a function of the multiplicity in p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02TeV. Moreover, the elliptic flow ($v_2$) of heavy-flavour hadron decay electrons in high-multiplicity p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$= 5.02 TeV, obtained using correlations with charged particles, is reported.

   ↳ hep-exnucl-exMDPI Proc.(2019)·0 citations
5. 05*

   A new spectroscopic probe to search for magic numbers at high-excitation energies

   Cebo Ngwetsheni · Nico Orce🇿🇦

   Empirical drops in ground-state nuclear polarizabilities indicate deviations from the effect of giant dipole resonances and may reveal the presence of shell effects in semi-magic nuclei with neutron magic numbers $N=50$, 82 and 126. Similar drops of polarizability in the quasi-continuum of nuclei with, or close to, magic numbers $N=28$, 50 and 82, could reflect the continuing influence of shell closures up to the nucleon separation energy. These findings open a new avenue to investigating magic numbers at high-excitation energies and strongly support recent large-scale shell-model calculations in the quasi-continuum region, which describe the origin of the low-energy enhancement of the photon strength function as induced paramagnetism. The nuclear-structure dependence of the photon-strength function asserts the generalized Brink-Axel hypothesis as more universal than originally expected.

   ↳ nucl-thnucl-ex0 citations
6. 06*

   57Fe enrichment in mice for \b{eta}-thalassaemia studies via Mossbauer spectroscopy of blood samples

   G. Charitou · Ch. Tsertos (Dept. of Physics, Univ. of Cyprus) · Y. Parpottas (Frederick University, Cyprus)🇨🇾 · M. Kleanthous · C. Lederer🇬🇧 · M. Phylactides (Dept. of Molecular Genetics Thalassaemia, Cyprus Institute of Neurology and Genetics, Cyprus)

   In this work, wild-type and heterozygous \b{eta}-thalassaemic mice were enriched with 57Fe through gastrointestinal absorption to characterize in more details the iron complexes appeared in the measured Mossbauer spectra. The 57Fe enrichment method was validated and Mossbauer spectra were obtained at 80K from blood samples from wild-type and \b{eta}-thalassaemic mice at 1, 3, 6, and 9 months of age. As expected, the haemoglobin levels of the thalassaemic mice were lower than from normal mice indicating anaemia. Furthermore, significant amounts of ferritin-like iron were observed in the thalassaemic mice samples, which decreased with mouse age, reflecting the pattern of reticulocyte count reduction reported in the literature.

   ↳ physics.bio-phnucl-exphysics.med-ph0 citations
7. 07*

   Ionization-density-dependent Scintillation Pulse Shape and Mechanism of Luminescence Quenching in LaBr3:Ce

   Jirong Cang🇨🇳 · XinChao Fang🇨🇳 · Zhi Zeng🇨🇳 · Ming Zeng🇨🇳 · Yinong Liu🇨🇳 · Zhigang Sun🇨🇳 · Ziyun Chen🇨🇳

   Pulse-shape discrimination (PSD) is usually achieved using the different fast and slow decay components of inorganic scintillators, such as BaF2, CsI:Tl, etc. However, LaBr3:Ce is considered to not possess different components at room temperature, but has been proved to have the capability of discriminating {\gamma} and {\alpha} events using fast digitizers. In this paper, ionization-density-dependent transport and rate equations are used to quantitatively model the competing processes in a particle track. With one parameter set, the model reproduces the nonproportionality response of electrons or {\alpha} particles, and explains the measured {\alpha} and {\gamma} pulse-shape difference well. In particular, the nonlinear quenching of excited dopant ions, Ce3+, is confirmed herein to mainly contribute observable ionization {\alpha} and {\gamma} pulse-shape differences. Further study of the luminescence quenching can also help to better understand the fundamental physics of nonlinear quenching and thus improve the crystal engineering. Moreover, based on the mechanism of dopant quenching, the ionization-density-dependent pulse-shape differences in other fast single-decay-component inorganic scintillators, such as lutetium yttrium oxyorthosilicate, Lu2(1-x)Y2xSiO5:Ce (LYSO) and CeBr3, are also predicted and verified with experiments.

   ↳ physics.ins-dethep-exnucl-exPhys.Rev.Applied(2020)·8 citations
8. 08*

   Deep learning based pulse shape discrimination for germanium detectors

   P. Holl🇩🇪 · L. Hauertmann🇩🇪 · B. Majorovits🇩🇪 · O. Schulz🇩🇪 · M. Schuster🇩🇪 · A.J. Zsigmond🇩🇪

   Experiments searching for rare processes like neutrinoless double beta decay heavily rely on the identification of background events to reduce their background level and increase their sensitivity. We present a novel machine learning based method to recognize one of the most abundant classes of background events in these experiments. By combining a neural network for feature extraction with a smaller classification network, our method can be trained with only a small number of labeled events. To validate our method, we use signals from a broad-energy germanium detector irradiated with a ${}^{228}$Th gamma source. We find that it matches the performance of state-of-the-art algorithms commonly used for this detector type. However, it requires less tuning and calibration and shows potential to identify certain types of background events missed by other methods.

   ↳ physics.ins-detcs.LGnucl-exEPJC(2019)·34 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.