Mon·Nov 12, 2018Monday·November 12, 2018

1. 01*

   Towards a 229Th-based nuclear clock

   Lars von der Wense · Benedict Seiferle · Peter G. Thirolf🇩🇪

   An overview over the current status of the development of a nuclear clock based on the state of lowest known nuclear excitation energy in ${}^{229}$Th is presented. The text is especially written for the interested reader without any particular knowledge in this field of research. It is thus ideal as an introductory reading to get a broad overview over the various different aspects of the field, in addition it can serve as a guideline for future research. An introductory part is provided, giving a historic context and explaining the fundamental concept of clocks. Finally, potential candidates for nuclear clocks other than ${}^{229}$Th are discussed.

   nucl-exMeas.Tech.(2018)·23 citations
2. 02*

   Neutron scattering cross section of diamond nanoparticle

   Kenji Mishima🇯🇵 · Toshiya Otomoa · Kazutaka Ikeda · Hidetoshi Ohshita

   Due to their large coherent scattering cross section, diamond nanoparticles (DNPs) are considered as a promising candidate material for a new neutron reflector. For investigation of scattering cross sections of packed samples, we have developed a technique for mechanical compression of DNP powder. Application of 220 MPa allowed us to increase the bulk density from 0.40 g/cm${}^3$ to 1.1 g/cm${}^3$. The differential cross sections of uncompressed and packed samples were measured using the high-intensity total diffractometer instrument NOVA at J-PARC, covering transfer wavenumbers (q) from 0.6 to 100 nm${}^{-1}$. The q dependence for the compressed sample agreed with the theoretical expectation derived from the Born approximation applied to homogeneous spheres with inclusion of a hard-sphere model to account for the inter-particle structure, whereas the results obtained from the powder sample disagreed. This implies that the theoretical description does not well represent the mesoscopic structure of the DNP powder sample.

   ↳ physics.ins-detnucl-exEPJ Web Conf.(2019)·0 citations
3. 03*

   Towards resolving the ${}_{\Lambda }^3$H lifetime puzzle

   Avraham Gal🇮🇱 · Humberto Garcilazo🇲🇽

   Recent ${}_{\Lambda }^3$H lifetime measurements in relativistic heavy ion collision experiments have yielded values shorter by (30$\pm$8)% than the free $\Lambda$ lifetime ${\tau }_{\Lambda }$, thereby questioning the naive expectation that $\tau ({}_{\Lambda }^3\mathrm{H})\approx {\tau }_{\Lambda }$ for a weakly bound $\Lambda$ hyperon. Here we apply the closure approximation introduced by Dalitz and coworkers to evaluate the ${}_{\Lambda }^3$H lifetime, using ${}_{\Lambda }^3$H wavefunctions generated by solving three-body Faddeev equations. Our result, disregarding pion final-state interaction (FSI), is $\tau ({}_{\Lambda }^3\mathrm{H})$=(0.90$\pm$0.01)${\tau }_{\Lambda }$. In contrast to previous works, pion FSI is found attractive, reducing further $\tau ({}_{\Lambda }^3\mathrm{H})$ to $\tau ({}_{\Lambda }^3\mathrm{H})$=(0.81$\pm$0.02)${\tau }_{\Lambda }$. We also evaluate for the first time $\tau ({}_{\Lambda }^3\mathrm{n})$, finding it considerably longer than ${\tau }_{\Lambda }$, contrary to the shorter lifetime values suggested by the GSI HypHI experiment for this controversial hypernucleus.

   ↳ nucl-thhep-phnucl-exPLB(2019)·44 citations
4. 04*

   A first sketch: Construction of model defect priors inspired by dynamic time warping

   Georg Schnabel🇸🇪 · Henrik Sjöstrand🇸🇪

   Model defects are known to cause biased nuclear data evaluations if they are not taken into account in the evaluation procedure. We suggest a method to construct prior distributions for model defects for reaction models using neighboring isotopes of ${}^{56}$Fe as an example. A model defect is usually a function of energy and describes the difference between the model prediction and the truth. Of course, neither the truth nor the model defect are accessible. A Gaussian process (GP) enables to define a probability distribution on possible shapes of a model defect by referring to intuitively understandable concepts such as smoothness and the expected magnitude of the defect. Standard specifications of GPs impose a typical length-scale and amplitude valid for the whole energy range, which is often not justified, e.g., when the model covers both the resonance and statistical range. In this contribution, we show how a GP with energy-dependent length-scales and amplitudes can be constructed from available experimental data. The proposed construction is inspired by a technique called dynamic time warping used, e.g., for speech recognition. We demonstrate the feasibility of the data-driven determination of model defects by inferring a model defect of the nuclear models code TALYS for (n,p) reactions of isotopes with charge number between 20 and 30. The newly introduced GP parametrization besides its potential to improve evaluations for reactor relevant isotopes, such as ${}^{56}$Fe, may also help to better understand the performance of nuclear models in the future.

   ↳ nucl-thnucl-exphysics.data-anEPJ Web Conf.(2019)·6 citations
5. 05*

   Silicon Photomultipliers in Particle and Nuclear Physics

   Frank Simon🇩🇪

   Following first large-scale applications in highly granular calorimeters and in neutrino detectors, Silicon Photomultipliers have seen a wide adoption in accelerator-based particle and nuclear physics experiments. Today, they are used for a wide range of different particle detector types, ranging from calorimeters and trackers to particle identification and veto detectors, large volume detectors for neutrino physics and timing systems. This article reviews the current state and expected evolution of these applications, highlighting strengths and limitation of SiPMs and the corresponding design choices in the respective contexts. General trends and adopted technical solutions in the applications are discussed.

   ↳ physics.ins-dethep-exnucl-exNucl.Instrum.Meth.A(2019)·61 citations
6. 06*

   Simulation of neutron production in hadron-nucleus and nucleus-nucleus interactions in Geant4

   A. Galoyan🇷🇺 · A. Ribon🇨🇭 · V. Uzhinsky🇷🇺

   Studying experimental data obtained at ITEP [1] on neutron production in interactions of protons with various nuclei in the energy range from 747 MeV up to 8.1 GeV, we have found that slow neutron spectra have scaling and asymptotic properties [2]. The spectra weakly depend on the collision energy at momenta of projectile protons larger than 5 - 6 GeV/c. These properties are taken into account in the Geant4 Fritiof (FTF) model. The improved FTF model describes as well as the Geant4 Bertini model the experimental data on neutron production by 1.2 GeV and 1.6 GeV protons on targets (Fe, Pb) [3] and by 3.0 GeV protons on various targets (Al, Fe, Pb) [4]. For neutron production in antiproton-nucleus interactions, it was demonstrated that the FTF results are in a satisfactory agreement with experimental data of the LEAR collaboration [5]. The FTF model gives promising results for neutron production in nucleus - nucleus interactions at projectile energy 1 - 2 GeV per nucleon [6]. The observed properties allow one to predict neutron yields in the nucleus-nucleus interactions at high and very high energies. Predictions for the NICA/MPD experiment at JINR are presented.

   ↳ hep-phhep-exnucl-exEPJ Web Conf.(2019)·0 citations
7. 07*

   Elliptic flow fluctuations in central collisions of spherical and deformed nuclei

   Giuliano Giacalone🇫🇷

   Elliptic flow ($v_2$) fluctuations in central heavy-ion collisions are direct probes of the fluctuating geometry of the quark-gluon plasma, and, as such, are strongly sensitive to any deviation from spherical symmetry in the shape of the colliding nuclei. We investigate the consequences of nuclear deformation for $v_2$ fluctuations, and we assess whether current models of medium geometry are able to predict and capture such effects. Assuming linear hydrodynamic response between $v_2$ and the eccentricity of the medium, ${\epsilon }_2$, we perform accurate comparisons between model calculations of ${\epsilon }_2$ fluctuations and STAR data on cumulants of elliptic flow, in central Au+Au and U+U collisions. From these comparisons, we evince that the most distinct signatures of nuclear deformation appear in the non-Gaussianities of $v_2$ fluctuation, and we show, in particular, that the non-Gaussian $v_2$ fluctuations currently observed in central Au+Au collisions are incompatible with model calculations that implement a quadrupole coefficient of order 12\% in the ${}^{197}$Au nuclei. Finally, we make robust predictions for the behavior of higher-order cumulants of $v_2$ in collisions of non-spherical nuclei.

   ↳ nucl-thhep-phnucl-exPRC(2019)·36 citations
8. 08*

   From the liquid drop model to lattice QCD

   V. Somà🇫🇷

   The present article aims to give a concise account of the main developments in nuclear structure theory, from its origin in the 1930s to date, taking the modelling of inter-nucleon interactions as guideline.

   ↳ nucl-thnucl-exEur.Phys.J.Plus(2018)·13 citations
9. 09*

   nEDM experiment at PSI: data-taking strategy and sensitivity of the dataset

   C. Abel · N. J. Ayres · G. Ban · G. Bison · K. Bodek · V. Bondar · E. Chanel · P.-J. Chiu · M. Daum · S. Emmenegger · L. Ferraris-Bouchez · P. Flaux and 31 other authors

   We report on the strategy used to optimize the sensitivity of our search for a neutron electric dipole moment at the Paul Scherrer Institute. Measurements were made upon ultracold neutrons stored within a single chamber at the heart of our apparatus. A mercury cohabiting magnetometer together with an array of cesium magnetometers were used to monitor the magnetic field, which was controlled and shaped by a series of precision field coils. In addition to details of the setup itself, we describe the chosen path to realize an appropriate balance between achieving the highest statistical sensitivity alongside the necessary control on systematic effects. The resulting irreducible sensitivity is better than 1*10-26 ecm. This contribution summarizes in a single coherent picture the results of the most recent publications of the collaboration.

   ↳ physics.ins-detnucl-exEPJ Web Conf.(2019)·20 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.