Thu·Feb 25, 2016Thursday·February 25, 2016

1. 01*

   Baryon spectroscopy with polarization observables from CLAS

   Steffen Strauch (for the CLAS Collaboration)🇺🇸

   The spectrum of nucleon excitations is dominated by broad and overlapping resonances. Polarization observables in photoproduction reactions are key in the study of these excitations. They give indispensable constraints to partial-wave analyses and help clarify the spectrum. A series of polarized photoproduction experiments have been performed at the Thomas Jefferson National Accelerator Facility with the CEBAF Large Acceptance Spectrometer (CLAS). These measurements include data with linearly and circularly polarized tagged-photon beams, longitudinally and transversely polarized proton and deuterium targets, and recoil polarizations through the observation of the weak decay of hyperons. An overview of these studies and recent results will be given.

   nucl-exFew Body Syst.(2016)·0 citations
2. 02*

   Antineutrino emission and gamma background characteristics from a thermal research reactor

   V.M. Bui🇫🇷 · L. Giot🇫🇷 · M. Fallot🇫🇷 · V. Communeau🇫🇷 · S. Cormon🇫🇷 · M. Estienne🇫🇷 · M.Lenoir🇫🇷 · N. Peuvrel🇫🇷 · T. Shiba🇫🇷 · A. S. Cucoanes🇫🇷 · M. Elnimr🇫🇷 · J. Martino🇫🇷 and 7 other authors

   The detailed understanding of the antineutrino emission from research reactors is mandatory for any high sensitivity experiments either for fundamental or applied neutrino physics, as well as a good control of the gamma and neutron backgrounds induced by the reactor operation. In this article, the antineutrino emission associated to a thermal research reactor: the OSIRIS reactor located in Saclay, France, is computed in a first part. The calculation is performed with the summation method, which sums all the contributions of the beta decay branches of the fission products, coupled for the first time with a complete core model of the OSIRIS reactor core. The MCNP Utility for Reactor Evolution code was used, allowing to take into account the contributions of all beta decayers in-core. This calculation is representative of the isotopic contributions to the antineutrino flux which can be found at research reactors with a standard 19.75\% enrichment in ${}^{235}$U. In addition, the required off-equilibrium corrections to be applied to converted antineutrino energy spectra of uranium and plutonium isotopes are provided. In a second part, the gamma energy spectrum emitted at the core level is provided and could be used as an input in the simulation of any reactor antineutrino detector installed at such research facilities. Furthermore, a simulation of the core surrounded by the pool and the concrete shielding of the reactor has been developed in order to propagate the emitted gamma rays and neutrons from the core. The origin of these gamma rays and neutrons is discussed and the associated energy spectrum of the photons transported after the concrete walls is displayed.

   nucl-exhep-exphysics.ins-det3 citations
3. 03*

   QED Radiative Corrections to Low-Energy Moller and Bhabha Scattering

   Charles S. Epstein · Richard G. Milner🇺🇸

   We present a treatment of the next-to-leading-order radiative corrections to unpolarized Moller and Bhabha scattering without resorting to ultra-relativistic approximations. We extend existing soft-photon radiative corrections with new hard-photon bremsstrahlung calculations so that the effect of photon emission is taken into account for any photon energy. This formulation is intended for application in the OLYMPUS experiment and the upcoming DarkLight experiment, but is applicable to a broad range of experiments at energies where QED is a sufficient description.

   nucl-exPRD(2016)·15 citations
4. 04*

   Primordial $\alpha +d\to {}^6\mathrm{Li}+\gamma$ reaction and second Lithium puzzle

   A. M. Mukhamedzhanov · Shubhchintak🇺🇸 · C. A. Bertulani🇺🇸

   During the Big Bang, ${}^6\mathrm{Li}$ was synthesized via the ${}^2\mathrm{H}(\alpha ,\gamma ){}^6\mathrm{Li}$ reaction. After almost 25 years of the failed attempts to measure the ${}^2\mathrm{H}(\alpha ,\gamma ){}^6\mathrm{Li}$ reaction in the lab at the Big Bang energies, just recently the LUNA collaboration presented the first successful measurements at two different Big Bang energies [M. Anders {\it et al.}, Phys. Rev. Lett. {\bf 113}, 042501 (2014)]. In this paper we will discuss how to improve the accuracy of the direct experiment. To this end the photon's angular distribution is calculated in the potential model. It contains contributions from electric dipole and quadrupole transitions and their interference, which dramatically changes the photon's angular distribution. The calculated distributions at different Big Bang energies have a single peak at $\sim 50^{\circ }$. These calculations provide the best kinematic conditions to measure the ${}^2\mathrm{H}(\alpha ,\gamma ){}^6\mathrm{Li}$ reaction. The expressions for the total cross section and astrophysical factor are also derived by integrating the differential cross section over the photon's solid angle. The LUNA data are in excellent agreement with our calculations using a potential approach combined with a well established asymptotic normalization coefficient for ${}^6\mathrm{Li}\to \alpha +d$. Comparisons of the available experimental data for the $S_{24}$ astrophysical factor and different calculations are presented. The Big Bang lithium isotopic ratio ${}^6\mathrm{Li}{/}^7\mathrm{Li}=(1.5\pm 0.3)\times 10^{-5}$ following from the LUNA data and the present analysis are discussed in the context of the disagreement between the observational data and the standard Big Bang model, which constitutes the second Lithium problem.

   ↳ nucl-thnucl-exPRC(2016)·41 citations
5. 05*

   A CaMoO4 Crystal Low Temperature Detector for the AMoRE Neutrinoless Double Beta Decay Search

   G.B. Kim🇰🇷 · S. Choi🇰🇷 · F.A. Danevich🇺🇦 · A. Fleischmann🇩🇪 · C.S. Kang🇰🇷 · H.J. Kim🇰🇷 · S.R. Kim🇰🇷 · Y.D. Kim🇰🇷 · Y.H. Kim🇰🇷 · V.A. Kornoukhov🇷🇺 · H.J. Lee🇰🇷 · J.H. Lee🇰🇷 and 4 other authors

   We report the development of a CaMoO4 crystal low temperature detector for the AMoRE neutrinoless double beta decay (0{\nu}\b{eta}\b{eta}) search experiment. The prototype detector cell was composed of a 216 g CaMoO4 crystal and a metallic magnetic calorimeter. An over-ground measurement demonstrated FWHM resolution of 6-11 keV for full absorption gamma peaks. Pulse shape discrimination was clearly demonstrated in the phonon signals, and 7.6 {\sigma} of discrimination power was found for the {\alpha} and \b{eta}/{\gamma} separation. The phonon signals showed rise-times of about 1 ms. It is expected that the relatively fast rise-time will increase the rejection efficiency of two-neutrino double beta decay pile-up events which can be one of the major background sources in 0{\nu}\b{eta}\b{eta} searches.

   ↳ physics.ins-detnucl-exAdv.High Energy Phys.(2015)·44 citations
6. 06*

   Trilateration-based reconstruction of ortho-positronium decays into three photons with the J-PET detector

   A. Gajos🇵🇱 · D. Kamińska🇵🇱 · E. Czerwiński🇵🇱 · D. Alfs🇵🇱 · T. Bednarski🇵🇱 · P. Białas🇵🇱 · B. Głowacz🇵🇱 · M. Gorgol🇵🇱 · B. Jasińska🇵🇱 · Ł. Kapłon🇵🇱 · G. Korcyl🇵🇱 · P. Kowalski🇵🇱 and 19 other authors

   This work reports on a new reconstruction algorithm allowing to reconstruct the decays of ortho-positronium atoms into three photons using the places and times of photons recorded in the detector. The method is based on trilateration and allows for a simultaneous reconstruction of both location and time of the decay. Results of resolution tests of the new reconstruction in the J-PET detector based on Monte Carlo simulations are presented, which yield a spatial resolution at the level of 2 cm (FWHM) for X and Y and at the level of 1 cm (FWHM) for Z available with the present resolution of J-PET after application of a kinematic fit. Prospects of employment of this method for studying angular correlations of photons in decays of polarized ortho-positronia for the needs of tests of CP and CPT discrete symmetries are also discussed. The new reconstruction method allows for discrimination of background from random three-photon coincidences as well as for application of a novel method for determination of the linear polarization of ortho-positronium atoms, which is also introduced in this work.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2016)·54 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.