Wed·Nov 25, 2015Wednesday·November 25, 2015

1. 01*

   Direct Dark Matter Search with XMASS-I

   Masaki Yamashita (for the XMASS collaboration)🇯🇵

   XMASS-I uses single phase liquid xenon technology for aiming at the direct detection of dark matter. The detector observes only scintillation light by 2 inch 642 PMTs which are placed in sphere shape around an active volume. With its large mass target and high photoelectron yield, we conducted a search for dark matter by annual modulation with 832 kg $\times$ 359.2 days exposure of data. We find no modulation signal in the data so that we set an upper limit 4.3$\times 10^{-41}{\mathrm{cm}}^2$ at WIMP mass of 8 GeV/$c^2$ which excluded an interpreted DAMA/LIBRA allowed region.

   ↳ astro-ph.COhep-exnucl-exphysics.ins-det4 citations
2. 02*

   Recent developments in the theory of electromagnetic probes in relativistic heavy-ion collisions

   Chun Shen (McGill U.)🇨🇦

   The theoretical developments in the study of electromagnetic radiation in relativistic heavy-ion collisions are reviewed. The recent progress in the rates for photon and lepton pair production is discussed. Together with the improvements in the hydrodynamic descriptions of the bulk medium, the combined effort is discussed to resolve the "direct photon flow puzzle" in the RHIC and the LHC experiments. Further prediction of the direct photon production in high multiplicity proton-nucleus collisions at the LHC energy can serve as a signature of the quark gluon plasma formation in these small systems. Phenomenological study of dilepton production at finite net baryon density is highlighted at the collision energies available for the RHIC beam energy scan program.

   ↳ nucl-thhep-phnucl-exNucl.Part.Phys.Proc.(2016)·14 citations
3. 03*

   A VUV detection system for the direct photonic identification of the first excited isomeric state of ${}^{229}$Th

   Benedict Seiferle · Lars von der Wense · Mustapha Laatiaoui · Peter G. Thirolf🇷🇴

   With an expected energy of 7.6(5) eV, ${}^{229}$Th possesses the lowest excited nuclear state in the landscape of all presently known nuclei. The energy corresponds to a wavelength of about 160 nm and would conceptually allow for an optical laser excitation of a nuclear transition. We report on a VUV optical detection system that was designed for the direct detection of the isomeric ground-state transition of ${}^{229}$Th. ${}^{229(m)}$Th ions originating from a ${}^{233}$U $\alpha$-recoil source are collected on a micro electrode that is placed in the focus of an annular parabolic mirror. The latter is used to parallelize the UV fluorescence that may emerge from the isomeric ground-state transition of ${}^{229}$Th. The parallelized light is then focused by a second annular parabolic mirror onto a CsI-coated position-sensitive MCP detector behind the mirror exit. To achieve a high signal-to-background ratio, a small spot size on the MCP detector needs to be achieved. Besides extensive ray-tracing simulations of the optical setup, we present a procedure for its alignment, as well as test measurements using a D${}_2$ lamp, where a focal-spot size of $\approx$100 $\mu$m has been achieved. Assuming a purely photonic decay, a signal-to-background ratio of $\approx$7000:1 could be achieved.

   ↳ physics.ins-detnucl-exEur.Phys.J.D(2016)·6 citations
4. 04*

   UCN sources at external beams of thermal neutrons. An example of PIK reactor

   E.V. Lychagin · V.A. Mityukhlyaev · A.Yu. Muzychka · G.V. Nekhaev · V.V. Nesvizhevsky🇫🇷 · M.S. Onegin🇷🇺 · E.I. Sharapov🇷🇺 · A.V. Strelkov

   We consider ultracold neutron (UCN) sources based on a new method of UCN production in superfluid helium (4He). The PIK reactor is chosen as a perspective example of the application of this idea, which consists of installing a 4He UCN source in a beam of thermal or cold neutrons and surrounding the source with a moderator-reflector, which plays the role of a source of cold neutrons (CNs) feeding the UCN source. The CN flux in the source can be several times larger than the incident flux, due to multiple neutron reflections from the moderator-reflector. We show that such a source at the PIK reactor would provide an order of magnitude larger density and production rate than an analogous source at the ILL reactor. We estimate parameters of a 4He source with solid methane (CH4) or/and liquid deuterium (D2) moderator-reflector. We show that such a source with CH4 moderator-reflector at the PIK reactor would provide the UCN density of ~1x10^5 1/cm^3, and the UCN production rate of ~2x10^7 1/s. These values are respectively 1000 and 20 times larger than those for the most intense UCN user source. The UCN density in a source with D2 moderator-reflector would reach the value of ~2x10^5 1/cm^3, and the UCN production rate would be equal ~8x10^7 1/s. Installation of such sources in beams of CNs with equal flux would slightly increase the density and production rate.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2016)·7 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.