Fri·Mar 3, 2017Friday·March 3, 2017

1. 01*

   Background free search for neutrinoless double beta decay with GERDA Phase II

   M. Agostini🇮🇹 · M. Allardt🇩🇪 · A. M. Bakalyarov🇷🇺 · M. Balata🇮🇹 · I. Barabanov🇷🇺 · L. Baudis🇨🇭 · C. Bauer🇩🇪 · E. Bellotti🇮🇹 · S. Belogurov🇷🇺 · S. T. Belyaev🇷🇺 · G. Benato🇨🇭 · A. Bettini🇮🇹 and 104 other authors

   The Standard Model of particle physics cannot explain the dominance of matter over anti-matter in our Universe. In many model extensions this is a very natural consequence of neutrinos being their own anti-particles (Majorana particles) which implies that a lepton number violating radioactive decay named neutrinoless double beta ($0\nu \beta \beta$) decay should exist. The detection of this extremely rare hypothetical process requires utmost suppression of any kind of backgrounds. The GERDA collaboration searches for $0\nu \beta \beta$ decay of ${}^{76}$Ge (${}^{76}\mathrm{Ge}\to {}^{76}\mathrm{Se}+2{\mathrm{e}}^{-}$) by operating bare detectors made from germanium with enriched ${}^{76}$Ge fraction in liquid argon. Here, we report on first data of GERDA Phase II. A background level of $\approx 10^{-3}$ cts/(keV$\cdot$kg$\cdot$yr) has been achieved which is the world-best if weighted by the narrow energy-signal region of germanium detectors. Combining Phase I and II data we find no signal and deduce a new lower limit for the half-life of $5.3\cdot 10^{25}$ yr at 90 % C.L. Our sensitivity of $4.0\cdot 10^{25}$ yr is competitive with the one of experiments with significantly larger isotope mass. GERDA is the first $0\nu \beta \beta$ experiment that will be background-free up to its design exposure. This progress relies on a novel active veto system, the superior germanium detector energy resolution and the improved background recognition of our new detectors. The unique discovery potential of an essentially background-free search for $0\nu \beta \beta$ decay motivates a larger germanium experiment with higher sensitivity.

   nucl-exhep-exphysics.ins-detNature(2017)·311 citations
2. 02*

   Missing-mass spectroscopy with the ${}^6$Li(${\pi }^{-},K^{+}$)X reaction to search for ${}_{\Lambda }^6$H

   R. Honda🇯🇵 · M. Agnello🇮🇹 · J. K. Ahn🇰🇷 · S. Ajimura🇯🇵 · Y. Akazawa🇯🇵 · N. Amano🇯🇵 · K. Aoki🇯🇵 · H. C. Bhang🇰🇷 · N. Chiga🇯🇵 · M. Endo🇯🇵 · P. Evtoukhovitch🇷🇺 · A. Feliciello🇮🇹 and 54 other authors

   We searched for the bound state of the neutron-rich $\Lambda$-hypernucleus ${}_{\Lambda }^6$H, using the ${}^6$Li(${\pi }^{-},K^{+}$)X double charge-exchange reaction at a ${\pi }^{-}$ beam momentum of 1.2 GeV/c at J-PARC. A total of $1.4\times 10^{12}$ ${\pi }^{-}$ was driven onto a ${}^6$Li target of 3.5-g/$\mathrm{c}{\mathrm{m}}^2$ thickness. No event was observed below the bound threshold, i.e., the mass of ${}_{\Lambda }^4$H + 2n, in the missing-mass spectrum of the ${}^6$Li(${\pi }^{-},K^{+}$)X reaction in the $2^{\circ }$ < ${\theta }_{\pi K}$ < $20^{\circ }$ angular range. Furthermore, no event was found up to 2.8 MeV/$c^2$ above the bound threshold. We obtained the the double-differential cross section spectra of the ${}^6$Li(${\pi }^{-},K^{+}$)X reaction in the angular range of $2^{\circ }$ < ${\theta }_{\pi K}$ < $14^{\circ }$. An upper limit of 0.56 nb/sr (90% C.L.) was obtained for the production cross section of the ${}_{\Lambda }^6$H hypernucleus bound state. In addition, not only the bound state region, but also the $\Lambda$ continuum region and part of the ${\Sigma }^{-}$ quasi-free production region of the ${}^6$Li(${\pi }^{-},K^{+}$)X reaction, were obtained with high statistics. The present missing-mass spectrum will facilitate the investigation of the ${\Sigma }^{-}$-nucleus optical potential for ${\Sigma }^{-}$-${}^5$He through spectrum shape analysis.

   nucl-exnucl-thPRC(2017)·16 citations
3. 03*

   Study of the 15N(p,n)15O reaction as a monoenergetic neutron source for the measurement of differential scattering cross sections

   Erik Poenitz · Ralf Nolte · Dankwart Schmidt🇺🇸 · Guochang Chen

   The 15N(p,n) reaction is a promising candidate for the production of monoenergetic neutrons with energies of up to 5.7 MeV at the facilities where the T(p,n)3He reaction cannot be used. The characteristic properties of this reaction were studied focusing on its suitability as a source of monoenergetic neutrons for the measurement of differential scattering cross sections in the neutron energy range of 2 MeV to 5 MeV. For this purpose differential and integral cross sections were measured and the choice of optimum target conditions was investigated. The reaction has already been used successfully to measure of elastic and inelastic neutron scattering cross sections for natPb in the energy range from 2 MeV to 4 MeV and for 209Bi and 181Ta at 4 MeV.

   nucl-exJINST(2017)·1 citation
4. 04*

   A new precision measurement of the {\alpha}-decay half-life of 190Pt

   Miháy Braun (1)🇷🇺 · Yordan M. Georgiev (2) · Tommy Schönherr (2) · Heinrich Wilsenach (3)🇩🇪 · Kai Zuber (3) ((1) Institute for Nuclear Research of the Hungarian Academy of Sciences (2) Institute of Ion Beam Physics and Materials Research (3) Institut für Kern- und Teilchenphysik, Technische Universität Dresden)🇩🇪

   A laboratory measurement of the $\alpha$-decay half-life of ${}^{190}$Pt has been performed using a low background Frisch grid ionisation chamber. A total amount of 216.60(17) mg of natural platinum has been measured for 75.9 days. The resulting half-life is $(4.97\pm 0.16)\times 10^{11}$ years, with a total uncertainty of 3.2%. This number is in good agreement with the half-life obtained using the geological comparison method.

   nucl-exphysics.ins-detPLB(2017)·14 citations
5. 05*

   PANDORA a New Facility for Interdisciplinary In-Plasma Physics

   D. Mascali🇮🇹 · A. Musumarra🇮🇹 · F. Leone🇮🇹 · F.P. Romano · A. Galatà🇮🇹 · S. Gammino🇮🇹 · C. Massimi🇮🇹

   PANDORA, Plasmas for Astrophysics, Nuclear Decays Observation and Radiation for Archaeometry, is planned as a new facility based on a state-of-the-art plasma trap confining energetic plasma for performing interdisciplinary research in the fields of Nuclear Astrophysics, Astrophysics, Plasma Physics and Applications in Material Science and Archaeometry: the plasmas become the environment for measuring nuclear decays rates in stellar-like condition (such as 7Be decay and beta-decay involved in s-process nucleosynthesis), especially as a function of the ionization state of the plasma ions. These studies are of paramount importance for addressing several astrophysical issues in both stellar and primordial nucleosynthesis environment (e.g. determination of solar neutrino flux and 7Li Cosmological Problem), moreover the confined energetic plasma will be a unique light source for high performance stellar spectroscopy measurements in the visible, UV and X-ray domains, offering advancements in observational astronomy. As to magnetic fields, the experimental validation of theoretical first and second order Landé factors will drive the layout of next generation polarimetric units for the high resolution spectrograph of the future giant telescopes. In PANDORA new plasma heating methods will be explored, that will push forward the ion beam output, in terms of extracted intensity and charge states. More, advanced and optimized injection methods of ions in an ECR plasma will be experimented, with the aim at optimizing its capture efficiency. This will be applied to the ECR-based Charge Breeding technique, that will improve the performances of the SPES ISOL-facility currently installed at Laboratori Nazionali di Legnaro-INFN. Finally, PANDORA will be suitable for energy conversion, making the plasma as a source of electromagnetic radiation, for applications in Material Science and Archaeometry.

   ↳ physics.ins-detnucl-exEPJA(2017)·16 citations
6. 06*

   Evaluation of commercial nickel-phosphorus coating for ultracold neutron guides using a pinhole bottling method

   R. W. Pattie Jr🇺🇸 · E. Adamek🇺🇸 · T. Brenner🇫🇷 · A. Brandt🇺🇸 · L. J. Broussard🇺🇸 · N. B. Callahan🇺🇸 · S. M. Clayton🇺🇸 · C. Cude-Woods🇺🇸 · S. A. Currie🇺🇸 · P. Geltonbort🇫🇷 · T. Ito🇺🇸 · T. Lauer🇩🇪 and 15 other authors

   We report on the evaluation of commercial electroless nickel phosphorus (NiP) coatings for ultracold neutron (UCN) transport and storage. The material potential of 50~$\mu$m thick NiP coatings on stainless steel and aluminum substrates was measured to be $V_F=213(5.2)$~neV using the time-of-flight spectrometer ASTERIX at the Lujan Center. The loss per bounce probability was measured in pinhole bottling experiments carried out at ultracold neutron sources at Los Alamos Neutron Science Center and the Institut Laue-Langevin. For these tests a new guide coupling design was used to minimize gaps between the guide sections. The observed UCN loss in the bottle was interpreted in terms of an energy independent effective loss per bounce, which is the appropriate model when gaps in the system and upscattering are the dominate loss mechanisms, yielding a loss per bounce of $1.3(1)\times 10^{-4}$. We also present a detailed discussion of the pinhole bottling methodology and an energy dependent analysis of the experimental results.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2017)·17 citations
7. 07*

   New estimation for neutron-neutron scattering length: charge symmetry and charge independence breaking revisited

   E.S. Konobeevski · S.V. Zuyev · V.I. Kukulin🇷🇺 · V.N. Pomerantsev🇷🇺

   Recent experimental results for neutron-neutron scattering length are reanalyzed from the point of view of three-nucleon force contribution. We found that the limiting value of $a_{nn}=-15.8\pm 0.5$~fm must be free of any implicit three-body force contribution. We have also shown that the difference between the above experimental value of $a_{nn}$ and the well established value of neutron-proton scattering length $a_{np}$ can be explained by differences in the one-pion exchange potentials.

   ↳ nucl-thnucl-ex3 citations
8. 08*

   Calibration Of Proton Accelerator Beam Energy

   Dan Cohen · Moshe Friedman🇺🇸 · Michael Paul🇮🇱

   When studying the 7Li(p,n)7Be reaction with a RF accelerator, it is difficult to define the precise energy of the beam and its energy distribution, which together fully define the beam, for our purpose. What we do know is the difference between two given energies. We resolve this problem by finding a reference energy and then finding another energy by examining the data, relative to the reference energy. From the difference between them we can approximate the energy distribution for a given energy, and since we know the energy threshold of the reaction (E_threshold for 7Li(p,n)7Be is about 1880.4-1880.8 (keV)) we can calibrate the beam energy. We then determine the energy which produce the maximum yield derivative as the reference and record the energy whose neutron yield is 5% of the reference energy. The data is collected by simulating this reaction using SimLit. Since this is a simulation we know the real energy distribution so we make a linear fit for energy distribution as function of energy difference. We tested the theory on experimental data for which we approximate the energy distribution by other means, and found our new method to be accurate and satisfactory for our needs.

   ↳ physics.ins-detnucl-ex0 citations
9. 09*

   Collective flow and hydrodynamics in large and small systems at the LHC

   Huichao Song🇨🇳 · You Zhou🇩🇰 · Katarina Gajdosova🇩🇰

   In this article, we briefly review the recent progress on collective flow and hydrodynamics in large and small systems at the Large Hadron Collider (LHC), which includes the following topics: extracting the QGP viscosity from the flow data, initial state fluctuations and final state correlations in 2.76 A TeV Pb--Pb collisions, correlations and collective flow in high energy p--Pb and p--p collisions.

   ↳ nucl-thhep-phnucl-exNucl.Sci.Tech.(2017)·154 citations
10. 10*

    Heavy and light flavor jet quenching at RHIC and LHC energies

    Shanshan Cao🇺🇸 · Tan Luo🇨🇳 · Guang-You Qin🇨🇳 · Xin-Nian Wang🇨🇳

    The Linear Boltzmann Transport (LBT) model coupled to hydrodynamical background is extended to include transport of both light partons and heavy quarks through the quark-gluon plasma (QGP) in high-energy heavy-ion collisions. The LBT model includes both elastic and inelastic medium-interaction of both primary jet shower partons and thermal recoil partons within perturbative QCD (pQCD). It is shown to simultaneously describe the experimental data on heavy and light flavor hadron suppression in high-energy heavy-ion collisions for different centralities at RHIC and LHC energies. More detailed investigations within the LBT model illustrate the importance of both initial parton spectra and the shapes of fragmentation functions on the difference between the nuclear modifications of light and heavy flavor hadrons. The dependence of the jet quenching parameter $\hat{q}$ on medium temperature and jet flavor is quantitatively extracted.

    ↳ nucl-thhep-phnucl-exPLB(2018)·173 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.