Tue·Aug 22, 2017Tuesday·August 22, 2017

1. 01*

   Photoproduction prospects at the EIC

   Heikki Mäntysaari🇺🇸

   We discuss how photoproduction and electroproduction processes will provide a precise tool to study nuclear structure in the small-$x$ region in the future Electron-Ion Collider. In particular, we emphasize how exclusive vector meson production at the EIC can be used to accurately map the gluonic density profile of nuclei, including its event-by-event fluctuations. In addition, we show how measurements of the total diffractive cross section will be sensitive to saturation effects.

   nucl-exnucl-thCERN Proc.(2018)·1 citation
2. 02*

   Search for Jacobi shape transition in A $\sim 30$ nuclei

   Balaram Dey🇮🇳 · C. Ghosh🇮🇳 · Deepak Pandit🇮🇳 · A.K. Rhine Kumar🇮🇳 · S. Pal🇮🇳 · V. Nanal🇮🇳 · R.G. Pillay🇮🇳 · P. Arumugam🇮🇳 · S. De🇮🇳 · G. Gupta🇮🇳 · H. Krishnamoorthy🇮🇳 · E.T. Mirgule🇮🇳 · Surajit Pal🇮🇳 · P.C. Rout🇮🇳

   This paper reports the first observation of the Jacobi shape transition in ${}^{31}$P using high energy $\gamma$-rays from the decay of giant dipole resonance (GDR) as a probe. The measured GDR spectrum in the decay of ${}^{31}$P shows a distinct low energy component around 10 MeV, which is a clear signature of Corioli's splitting in a highly deformed rotating nucleus. Interestingly, a self-conjugate $\alpha$-cluster nucleus ${}^{28}$Si, populated at similar initial excitation energy and angular momentum, exhibits a vastly different GDR line shape. Even though the angular momentum of the compound nucleus ${}^{28}$Si is higher than the critical angular momentum required for the Jacobi shape transition, the GDR lineshape is akin to a prolate deformed nucleus. Considering the present results for ${}^{28}$Si and similar observation recently reported in ${}^{32}$S, it is proposed that the nuclear orbiting phenomenon exhibited by $\alpha$-cluster nuclei hinders the Jacobi shape transition. The present experimental results suggest a possibility to investigate the nuclear orbiting phenomenon using high energy $\gamma$-rays as a probe.

   nucl-exPRC(2018)·14 citations
3. 03*

   Dependencies of Lepton Angular Distribution Coefficients on the Transverse Momentum and Rapidity of$Z$ Bosons Produced in $pp$ Collisions at LHC

   Wen-Chen Chang🇹🇼 · Randall Evan McClellan🇺🇸 · Jen-Chieh Peng🇺🇸 · Oleg Teryaev🇷🇺

   High precision data of lepton angular distributions for ${\gamma }^{\ast }/Z$ production in $pp$ collisions at the LHC, covering broad ranges of dilepton transverse momenta ($q_T$) and rapidity ($y$), were recently reported. Strong $q_T$ dependencies were observed for several angular distribution coefficients, $A_i$, including $A_0-A_4$. Significant $y$ dependencies were also found for the coefficients $A_1$, $A_3$ and $A_4$, while $A_0$ and $A_2$ exhibit very weak rapidity dependence. Using an intuitive geometric picture we show that the $q_T$ and $y$ dependencies of the angular distributions coefficients can be well described.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2017)·17 citations
4. 04*

   Low Background Gamma Spectroscopy at the Boulby Underground Laboratory

   P.R. Scovell🇬🇧 · E. Meehan🇬🇧 · H.M. Araújo🇬🇧 · J. Dobson🇬🇧 · C. Ghag🇬🇧 · H. Kraus🇬🇧 · V.A. Kudryavtsev🇬🇧 · X-.R. Liu🇬🇧 · P. Majewski🇬🇧 · S.M. Paling🇬🇧 · R.M. Preece🇬🇧 · R. Saakyan🇬🇧 and 3 other authors

   The Boulby Underground Germanium Suite (BUGS) comprises three low background, high-purity germanium detectors operating in the Boulby Underground Laboratory, located 1.1 km underground in the north-east of England, UK. BUGS utilises three types of detector to facilitate a high-sensitivity, high-throughput radioassay programme to support the development of rare-event search experiments. A Broad Energy Germanium (BEGe) detector delivers sensitivity to low-energy gamma-rays such as those emitted by 210Pb and 234Th. A Small Anode Germanium (SAGe) well-type detector is employed for efficient screening of small samples. Finally, a standard p-type coaxial detector provides fast screening of standard samples. This paper presents the steps used to characterise the performance of these detectors for a variety of sample geometries, including the corrections applied to account for cascade summing effects. For low-density materials, BUGS is able to radio-assay to specific activities down to 3.6 mBq/kg for 234Th and 6.6 mBq/kg for 210Pb both of which have uncovered some significant equilibrium breaks in the 238U chain. In denser materials, where gamma-ray self-absorption increases, sensitivity is demonstrated to specific activities of 0.9 mBq/kg for 226Ra, 1.1 mBq/kg for 228 Ra, 0.3 mBq/kg for 224Ra, and 8.6 mBq/kg for 40K with all upper limits at a 90% confidence level. These meet the requirements of most screening campaigns presently under way for rare-event search experiments, such as the LUX-ZEPLIN (LZ) dark matter experiment. We also highlight the ability of the BEGe detector to probe the X-ray fluorescence region which can be important to identify the presence of radioisotopes associated with neutron production; this is of particular relevance in experiments sensitive to nuclear recoils.

   ↳ physics.ins-detnucl-exAstropart.Phys.(2018)·40 citations
5. 05*

   Yrast band of 109Ag described by tilted axis cranking covariant density functional theory with a separable pairing force

   Yakun Wang

   A separable form of the Gogny pairing force is implemented in tilted axis cranking covariant density functional theory for the description of rotational bands in open shell nuclei. The developed method is used to investigate the yrast sequence of 109Ag for an example. The experimental energy spectrum, angular momenta, and electromagnetic transition probabilities are well reproduced by taking into account pairing correlations with the separable pairing force. An abrupt transition of the rotational axis from the long-intermediate plane to the long-short one is obtained and discussed in detail.

   ↳ nucl-thnucl-exPRC(2017)·31 citations
6. 06*

   Partial dynamical symmetries and shape coexistence in nuclei

   A. Leviatan🇮🇱 · N. Gavrielov🇮🇱

   We present a symmetry-based approach for shape coexistence in nuclei, founded on the concept of partial dynamical symmetry (PDS). The latter corresponds to a situation when only selected states (or bands of states) of the coexisting configurations preserve the symmetry while other states are mixed. We construct explicitly critical-point Hamiltonians with two or three PDSs of the type U(5), SU(3), $\overline{\mathrm{SU}(3)}$ and SO(6), appropriate to double or triple coexistence of spherical, prolate, oblate and $\gamma$-soft deformed shapes, respectively. In each case, we analyze the topology of the energy surface with multiple minima and corresponding normal modes. Characteristic features and symmetry attributes of the quantum spectra and wave functions are discussed. Analytic expressions for quadrupole moments and $E2$ rates involving the remaining solvable states are derived and isomeric states are identified by means of selection rules.

   ↳ nucl-thnucl-exquant-phPhys.Scripta(2017)·17 citations
7. 07*

   Neutron response of PARIS phoswich detector

   Balaram Dey🇮🇳 · C Ghosh🇮🇳 · S. Pal🇮🇳 · V. Nanal🇮🇳 · R.G. Pillay🇮🇳 · K.V. Anoop🇮🇳 · M.S. Pose🇮🇳

   We have studied neutron response of PARIS phoswich [LaBr${}_3$(Ce)-NaI(Tl)] detector which is being developed for measuring the high energy (E${}_{\gamma }$ = 5 - 30 MeV) $\gamma$ rays emitted from the decay of highly collective states in atomic nuclei. The relative neutron detection efficiency of LaBr${}_3$(Ce) and NaI(Tl) crystal of the phoswich detector has been measured using the time-of-flight (TOF) and pulse shape discrimination (PSD) technique in the energy range of E${}_n$ = 1 - 9 MeV and compared with the GEANT4 based simulations. It has been found that for E${}_n$ $>$ 3 MeV, $\sim$ 95 \% of neutrons have the primary interaction in the LaBr${}_3$(Ce) crystal, indicating that a clear n-$\gamma$ separation can be achieved even at $\sim$15 cm flight path.

   ↳ physics.ins-detnucl-exSpringer Proc.Phys.(2018)·1 citation
8. 08*

   Dark Photons from Nuclear Transitions

   Jonathan Kozaczuk🇺🇸

   Light new particles can be emitted in decays of excited nuclear states. Experiments analyzing such transitions and incorporating high-resolution detectors can be sensitive to new MeV-scale physics at a level competitive with upcoming collider and other fixed target experiments, provided sufficient luminosity. We demonstrate this in the case of the ${}^8\text{Be}$ system, showing that searches targeting the reported anomaly in ${}^8\text{Be}$ nuclear transitions can also be sensitive to currently unexplored regions of the canonical dark photon parameter space with 1 MeV $\lesssim m_{A^{\prime }}\lesssim 18$ MeV and ${\epsilon }^2\gtrsim 10^{-7}$. These experiments could be performed on a short timescale, at low cost, and directly probe both the hadronic and leptonic couplings of light hidden particles.

   ↳ hep-phnucl-exPRD(2018)·18 citations
9. 09*

   Search for axion-like dark matter through nuclear spin precession in electric and magnetic fields

   C. Abel🇬🇧 · N.J. Ayres🇬🇧 · G. Ban🇫🇷 · G. Bison🇨🇭 · K. Bodek🇵🇱 · V. Bondar🇧🇪 · M. Daum🇨🇭 · M. Fairbairn🇬🇧 · V.V. Flambaum🇦🇺 · P. Geltenbort🇫🇷 · K. Green🇬🇧 · W.C. Griffith🇬🇧 and 36 other authors

   We report on a search for ultra-low-mass axion-like dark matter by analysing the ratio of the spin-precession frequencies of stored ultracold neutrons and ${}^{199}$Hg atoms for an axion-induced oscillating electric dipole moment of the neutron and an axion-wind spin-precession effect. No signal consistent with dark matter is observed for the axion mass range $10^{-24}\text{eV}\le m_a\le 10^{-17}\text{eV}$. Our null result sets the first laboratory constraints on the coupling of axion dark matter to gluons, which improve on astrophysical limits by up to 3 orders of magnitude, and also improves on previous laboratory constraints on the axion coupling to nucleons by up to a factor of 40.

   ↳ hep-phastro-ph.COnucl-exnucl-th+1PRX(2017)·331 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.