Brookhaven National Laboratory

About: Brookhaven National Laboratory is a facility organization based out in Upton, New York, United States. It is known for research contribution in the topics: Quantum chromodynamics & Scattering. The organization has 18828 authors who have published 39450 publications receiving 1782061 citations. The organization is also known as: BNL.

Independent Measurement of the Total Active 8B Solar Neutrino Flux Using an Array of 3He Proportional Counters at the Sudbury Neutrino Observatory

Abstract: The Sudbury Neutrino Observatory (SNO) used an array of He3 proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active (x) B8 solar neutrino flux. This technique is independent of previous methods employed by SNO. The total flux is found to be 5.54-0.31+0.33(stat)-0.34+0.36(syst)106cm-2s-1, in agreement with previous measurements and standard solar models. A global analysis of solar and reactor neutrino results yields m2=7.59-0.21+0.1910-5eV2 and =34.4-1.2+1.3 degrees. The uncertainty on the mixing angle has been reduced from SNO's previous results.

Spatially modulated 'Mottness' in La2-xBaxCuO4

Abstract: Competition between magnetism and the kinetic energy of mobile carriers (typically holes) in doped antiferromagnets may lead to ‘stripe’ phases1,2,3,4, which are charged rivers separating regions of oppositely phased antiferromagnetism. In copper oxides the main experimental evidence for such coexisting static spin and charge order comes from neutron scattering in La1.48Nd0.4Sr0.12CuO4 (LNSCO; ref. 5) and La1.875Ba0.125CuO4 (LBCO; ref. 6). However, as a neutron is neutral, it does not detect charge but rather its associated lattice distortion7, so it is not known whether the stripes involve ordering of the doped holes. Here we present a study of the charge order in LBCO with resonant soft X-ray scattering (RSXS). We observe giant resonances near the Fermi level as well as near the correlated gap8,9, demonstrating significant modulation in both the doped-hole density and the ‘Mottness’, or the degree to which the system resembles a Mott insulator10. The peak-to-trough amplitude of the valence modulation is estimated to be 0.063 holes, which suggests11 an integrated area of 0.59 holes under a single stripe, close to the expected 0.5 for half-filled stripes.

Action spectrum for DMA damage in alfalfa lowers predicted impact of ozone depletion

Abstract: DEPLETION of stratospheric ozone will increase the intensity of solar mid-ultraviolet (280–320 nm) radiation reaching the biosphere1. Predictions of increases in biologically effective ultraviolet radiation require knowledge of both the solar spectral intensity and the wavelength-dependent sensitivity (action spectrum) for damaging the biological target2. A generalized action spectrum for plant damage encompassing wavelengths from 280 to 313 nm3–5 has been widely used to predict the consequences of ozone depletion. Calculations6 based on this spectrum and new satellite measurements of atmospheric ozone suggest that plants will be among those organisms most severely affected. Here we report an absolute action spectrum for cyclobutyl pyrimidine dimer induction in DNA in intact alfalfa seedlings, which reveals damage by wavelengths as long as 365 nm. Calculations based on this new action spectrum predict significantly smaller increases in biologically effective ultraviolet radiation resulting from ozone depletion, particularly at high latitudes, than calculations based on either the generalized plant action spectrum or the action spectrum for damaging unshielded DNA.

Search for nearly massless, weakly coupled particles by optical techniques.

Abstract: We have searched for light scalar and/or pseudoscalar particles that couple to two photons by studying the propagation of a laser beam ($\ensuremath{\lambda}=514$ nm) through a transverse magnetic field A limit of 35\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}10}$ rad was set on a possible optical rotation of the beam polarization for an effective path length of 22 km in a 325 T magnetic field We find that the coupling ${g}_{\ensuremath{\alpha}\ensuremath{\gamma}\ensuremath{\gamma}}l36\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$ Ge${\mathrm{V}}^{\ensuremath{-}1}$ at the 95% confidence level, provided ${m}_{a}l{10}^{\ensuremath{-}3}$ eV Similar limits can be set from the absence of ellipticity in the transmitted beam We also searched for photon regeneration in a magnetic field and found the limit ${g}_{\ensuremath{\alpha}\ensuremath{\gamma}\ensuremath{\gamma}}l67\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$ Ge${\mathrm{V}}^{\ensuremath{-}1}$ for the same range of particle mass