Search results for "nuclear physics"
showing 10 items of 5307 documents
Quadrupole interaction of $^{8}$Li and $^{9}$Li in LiNbO$_{3}$ and the quadrupole moment of $^{9}$Li
1988
The quadrupole interaction of nuclear spin polarized8Li (I=2) and9Li (I=3/2) in LiNbO3 has been studied at room temperature. The polarization was achieved by optical pumping of a fast atomic beam with circularly polarized laser light. The atoms were implanted into a hexagonal LiNbO3 single crystal and the quadrupole splitting ofβ-NMR spectra was measured. A ratio of ¦Q(9Li)/Q(8Li)¦=0.88(4) for the nuclear quadrupole moments was deduced, yielding a new value of ¦Q(9Li)¦=25.3 (9) mb for the quadrupole moment of9Li.
Nuclear moments and laser spectroscopy
1990
Laser spectroscopy measurements have yielded a wealth of new information about the moments and charge radii of unstable isotopes. The procedures of evaluating these moments from the magnetic dipole and electric quadrupole terms of the hyperfine structure arew discussed. Examples are presented, with emphasis on the isotopic chains of odd-proton nuclei, and their essential features are put into the context of current theoretical model descriptions for spherical and deformed nuclei. Finally, new developments of extremely sensitive experimental techniques are discussed with regard to an application to nuclei very far from stability.
How to measure nuclear ground-state properties in simple systems such as 11Li or U91+?
2008
Abstract Atomic spectroscopy yields key information on properties of ground and isomeric states via a determination of the hyperfine structure and isotope shift. In order to deduce precise nuclear moments and charge radii, the electromagnetic fields produced by the electrons at the site of the nucleus must be known with high accuracy. This is presently possible only for simple systems with very few electrons. This contribution describes two scenarios for such experiments: the determination of the charge radius of the neutron-rich isotopes 8,9Li and of the halo nucleus 11Li at the on-line isotope separators at GSI and TRIUMF and the Highly charged Ion TRAP (HITRAP) facility which is under co…
Towards on-line production of N=Z94Ag at IGISOL
2008
Abstract A future study of the ground state and low-lying isomeric states of 94 Ag and 96 Ag at the Ion Guide Isotope Separator On-Line (IGISOL) facility, University of Jyvaskyla, requires the development of a low-energy beam of neutron-deficient silver. In order to attain the highest possible extraction efficiencies the coupling of a hot cavity graphite catcher device to the IGISOL mass-separator is planned. A heavy-ion fusion-evaporation reaction will produce the silver recoils which will be captured in the graphite catcher. Resonant laser ionization techniques will be applied to efficiently and selectively ionize the evaporated silver atoms. A simulation program has been written to study…
Measurement of the neutrino-oxygen neutral-current interaction cross section by observing nuclear deexcitation gamma rays
2014
We report the first measurement of the neutrino-oxygen neutral-current quasielastic (NCQE) cross section. It is obtained by observing nuclear deexcitation $\gamma$-rays which follow neutrino-oxygen interactions at the Super-Kamiokande water Cherenkov detector. We use T2K data corresponding to $3.01 \times 10^{20}$ protons on target. By selecting only events during the T2K beam window and with well-reconstructed vertices in the fiducial volume, the large background rate from natural radioactivity is dramatically reduced. We observe 43 events in the $4-30$ MeV reconstructed energy window, compared with an expectation of 51.0, which includes an estimated 16.2 background events. The background …
The experience of building and operating COMPASS RICH-1
2010
COMPASS RICH-1 is a large size gaseous Imaging Cherenkov Detector providing hadron identification in the range from 3 to 55 GeV/c, in the wide acceptance spectrometer of the COMPASS Experiment at CERN SPS. It uses a 3 m long C(4)F(10) radiator, a 21 m(2) large VUV mirror surface and two kinds of photon detectors: MAPMTs and MWPCs with CsI photocathodes, covering a total of 5.5 m(2). It is in operation since 2002 and its performance has increased in time thanks to progressive optimization and mostly to a major upgrade which was implemented in 2006. The main characteristics of COMPASS RICH-1 components are described and some specific aspects related to the radiator gas system, the mirror alig…
Higher order forward spin polarizability
2010
As a guideline for future experiments to extract the four (leading) spin polarizabilities of the nucleon, we have constructed the forward amplitude for polarized Compton scattering by dispersion integrals. These integrals have been saturated by recently measured helicity-dependent photoabsorption cross sections as well as predictions for pion photoproduction multipoles from several phenomenological descriptions and chiral perturbation theory. The comparison of these results corroborates the strategy to extract the spin polarizabilities by fitting them to polarized Compton data and fixing all higher order spin effects by dispersion relations based on pion photoproduction multipoles.
Measurement of the radiative K-e3 branching ratio
2005
We present a measurement of the relative branching ratio of the decay KL -> pi e nu gamma (Ke3gamma) with respect to KL-> pi e nu (gamma) (Ke3+Ke3gamma) decay. The result is based on observation of 19 000 Ke3gamma and 5.6 x 10^6 Ke3 decays. The value of the branching ratio is Br(Ke3gamma, Egamma^*>30 MeV,theta(e,gamma)^*>20^o)/Br(Ke3)= (0.964+-0.008+0.011-0.009)%. This result agrees with theoretical predictions but is at variance with a recently published result.
Proton-air cross section measurement with the ARGO-YBJ cosmic ray experiment
2009
The proton-air cross section in the energy range 1-100 TeV has been measured by the ARGO-YBJ cosmic ray experiment. The analysis is based on the flux attenuation for different atmospheric depths (i.e. zenith angles) and exploits the detector capabilities of selecting the shower development stage by means of hit multiplicity, density and lateral profile measurements at ground. The effects of shower fluctuations, the contribution of heavier primaries and the uncertainties of the hadronic interaction models, have been taken into account. The results have been used to estimate the total proton-proton cross section at center of mass energies between 70 and 500 GeV, where no accelerator data are …
Study of the electromagnetic background in the XENON100 experiment
2011
The XENON100 experiment, located at the Laboratori Nazionali del Gran Sasso (LNGS), aims to directly detect dark matter in the form of Weakly Interacting Massive Particles (WIMPs) via their elastic scattering off xenon nuclei. We present a comprehensive study of the predicted electronic recoil background coming from radioactive decays inside the detector and shield materials, and intrinsic contamination. Based on GEANT4 Monte Carlo simulations using a detailed geometry together with the measured radioactivity of all detector components, we predict an electronic recoil background in the WIMP-search energy range (0-100 keV) in the 30 kg fiducial mass of less than 10e-2 events/(kg-day-keV), co…