Fri·Sep 8, 2017Friday·September 8, 2017

1. 01*

   Measurement of longitudinal flow de-correlations in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ and 5.02 TeV with the ATLAS detector

   ATLAS Collaboration

   Measurements of longitudinal flow decorrelations are presented for charged particles in the pseudorapidity range $|\eta |<2.4$ using 7 $\mu$b${}^{-1}$ and 470 $\mu$b${}^{-1}$ of Pb+Pb collisions at $\sqrt{s_{\text{NN}}}=2.76$ and 5.02 TeV, respectively, recorded by the ATLAS detector at the LHC. It is found that the correlation between the harmonic flow coefficients $v_n$ measured in two separated $\eta$ intervals does not factorise into the product of single-particle coefficients, and this breaking of factorisation, or flow decorrelation, increases linearly with the $\eta$ separation between the intervals. The slopes for this flow decorrelation are found to be larger at 2.76 TeV than 5.02 TeV. Higher-order moments of the correlations are also measured, and the corresponding linear coefficients for the $k^{\text{th}}$-moment of the $v_n$ are found to be proportional to $k$ for $v_3$, but not for $v_2$. The decorrelation effect is separated into contributions from the magnitude of $v_n$ and the event-plane orientation changing with $\eta$. These two contributions are found to be comparable. The longitudinal flow correlations are also measured between $v_n$ of different order in $n$. The longitudinal fluctuations of $v_2$ and $v_3$ are found to be independent of each other, while the longitudinal fluctuations of $v_4$ and $v_5$ are found to be driven by the nonlinear contribution from $v_2^2$ and $v_2{v}_3$, respectively.

   nucl-exhep-exEPJC(2018)·145 citations
2. 02*

   Structure of 29F in the Rotation-aligned Coupling Scheme of the Particle-Rotor Model

   A. O. Macchiavelli🇺🇸 · P. Fallon🇺🇸 · H. L. Crawford🇺🇸 · C. M. Campbell🇺🇸 · R. M. Clark🇺🇸 · M. Cromaz🇺🇸 · M. D. Jones🇺🇸 · I. Y. Lee🇺🇸 · M. Salathe🇩🇪

   Recent results from RIKEN/RIBF on the low-lying level structure of 29F are interpreted within the Particle-Rotor Model. We show that the experimental data can be understood in the Rotation-aligned Coupling Scheme, with the 5/2+ ground state as the bandhead of a decoupled band. In this picture, the energy of the observed 1/2+1 state correlates strongly with the rotational energy of the core and provides an estimate of the 2+ energy in 28O. Our analysis suggest a moderate deformation, epsilon_2 ~ 0.17, and places the 2+ in 28O at ~ 2.4 MeV.

   nucl-exPLB(2017)·7 citations
3. 03*

   The Large Enriched Germanium Experiment for Neutrinoless Double Beta Decay (LEGEND)

   LEGEND Collaboration: N. Abgrall🇺🇸 · A. Abramov🇷🇺 · N. Abrosimov🇩🇪 · I. Abt🇩🇪 · M. Agostini🇮🇹 · M. Agartioglu🇹🇷 · A. Ajjaq🇹🇷 · S.I. Alvis🇺🇸 · F.T. Avignone III🇺🇸 · X. Bai🇺🇸 · M. Balata🇮🇹 · I. Barabanov🇷🇺 and 220 other authors

   The observation of neutrinoless double-beta decay (0$\nu \beta \beta$) would show that lepton number is violated, reveal that neutrinos are Majorana particles, and provide information on neutrino mass. A discovery-capable experiment covering the inverted ordering region, with effective Majorana neutrino masses of 15 - 50 meV, will require a tonne-scale experiment with excellent energy resolution and extremely low backgrounds, at the level of $\sim$0.1 count /(FWHM$\cdot$t$\cdot$yr) in the region of the signal. The current generation ${}^{76}$Ge experiments GERDA and the MAJORANA DEMONSTRATOR utilizing high purity Germanium detectors with an intrinsic energy resolution of 0.12%, have achieved the lowest backgrounds by over an order of magnitude in the 0$\nu \beta \beta$ signal region of all 0$\nu \beta \beta$ experiments. Building on this success, the LEGEND collaboration has been formed to pursue a tonne-scale ${}^{76}$Ge experiment. The collaboration aims to develop a phased 0$\nu \beta \beta$ experimental program with discovery potential at a half-life approaching or at $10^{28}$ years, using existing resources as appropriate to expedite physics results.

   ↳ physics.ins-dethep-exnucl-exAIP Conf.Proc.(2017)·357 citations
4. 04*

   Testing FLUKA on neutron activation of Si and Ge at nuclear research reactor using gamma spectroscopy

   Jose Bazo (1) · Jairo M. Rojas (1) · Sergio Best (1) · Ruben Bruna (2) · Eric Endress (1) · Pablo Mendoza (2) · Victor Poma (2) · Alberto M. Gago (1) ((1) Lima, Pont. U. Catolica, (2) IPEN, Lima)🇵🇪

   Samples of two characteristic semiconductor sensor materials, silicon and germanium, have been irradiated with neutrons produced at the RP-10 Nuclear Research Reactor at 4.5 MW. Their radionuclides photon spectra have been measured with high resolution gamma spectroscopy, quantifying four radioisotopes (${}^{28}$Al, ${}^{29}$Al for Si and ${}^{75}$Ge and ${}^{77}$Ge for Ge). We have compared the radionuclides production and their emission spectrum data with Monte Carlo simulation results from FLUKA. Thus we have tested FLUKA's low energy neutron library (ENDF/B-VIIR) and decay photon scoring with respect to the activation of these semiconductors. We conclude that FLUKA is capable of predicting relative photon peak amplitudes, with gamma intensities greater than 1%, of produced radionuclides with an average uncertainty of 13%. This work allows us to estimate the corresponding systematic error on neutron activation simulation studies of these sensor materials.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2018)·3 citations
5. 05*

   Independent Experimentation on the Activation of Deuterium-Loaded Materials by X-Ray Exposure

   Rob Davies

   In an attempt to replicate work performed elsewhere [1], we have searched for x-ray induced nuclear activation of deuterated materials. Our first results, reported in September 2015, showed no evidence of nuclear activation, contrary to the results reported in [1]. The primary shortcoming of our first attempt, however, was that the x-ray tube we used was capable of a maximum accelerating potential of only 160kV, less than the 200kV used on the comparison test sample from [1]. Thus, our results could not exclude processes initiated by x-rays near 200 keV in energy. A second potential shortcoming was that our x-ray tube did not have a microfocus beam, like the one used in [1]. Recently, we have irradiated additional samples with an x-ray tube matching the specifications of the tube used in [1]. By matching the test conditions with essentially identical equipment, we have overcome both of the shortcomings of our previous measurements. As before, we find no evidence of activation. The bulk of this report, pages 2 through 35, contain the results and analysis from the first round of testing. The extension to 200kV is found in the final appendix, namely Appendix A5.

   ↳ physics.ins-detnucl-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.