Cosmogenic 11C production and sensitivity of organic scintillator detectors to pep and CNO neutrinos

Several possible background sources determine the detectability of pep and CNO solar neutrinos in organic liquid scintillator detectors. Among such sources, the cosmogenic 11C nuclide plays a central role. 11C is produced underground in reactions induced by the residual cosmic muon flux. Experimental data available for the effective cross section for 11C by muons indicate that 11C will be the dominant source of background for the observation of pep and CNO neutrinos. 11C decays are expected to total a rate 2.5 (20) times higher than the combined rate of pep and CNO neutrinos in Borexino (KamLAND) in the energy window preferred for the pep measurement, between 0.8 and 1.3 MeV. This study examines the production mechanism of 11C by muon-induced showers in organic liquid scintillators with a novel approach: for the first time, we perform a detailed ab initio calculation of the production of a cosmogenic nuclide, 11C, taking into consideration all relevant production channels. Results of the calculation are compared with the effective cross sections measured by target experiments in muon beams. This paper also discusses a technique for reduction of background from 11C in organic liquid scintillator detectors, which allows to identify on a one-by-one basis and remove from the data set a large fraction of 11C decays. The background reduction technique hinges on an idea proposed by Martin Deutsch, who suggested that a neutron must be ejected in every interaction producing a 11C nuclide from 12C. 11C events are tagged by a three-fold coincidence with the parent muon track and the subsequent neutron capture on protons.Comment: 11 pages, 6 figures; added one section detailing comparison with previous estimates; added reference

Conformal moduli of symmetric circular quadrilaterals with cusps

We investigate moduli of planar circular quadrilaterals that are symmetric with respect to both coordinate axes. First we develop an analytic approach that reduces this problem to ODEs and then devise a numerical method to find out the accessory parameters. This method uses the Schwarz equation to determine a conformal mapping of the unit disk onto a given circular quadrilateral. We also give an example of a circular quadrilateral for which the value of the conformal modulus can be found in analytic form. This example is used to validate the numeric calculations. We also apply another method, the so called hpFEM, for the numerical calculation of the moduli. These two different approaches provide results agreeing with high accuracy

Atomic and electronic structures of amorphous ZrO2 and HfO2 films

Atomic and electronic structures of ZrO2 and HfO2 films deposited using sputtering technique were studied by X-ray diffraction (XRD), EXAFS spectroscopy, photoemission (with X-ray and ultraviolet excitation sources) and electron energy loss spectroscopy (EELS). XRD results indicated that the as-deposited films were amorphous and a monoclinic phase was detected after annealing them in ambient at 800 degrees C. Photoemission results indicated that the ZrO2 valence band consists of two bands separated by an ionic gap of 6 eV. The lower band of 10 eV width is occupied mainly by 0 2s states. EELS results indicated that the bandgap of ZrO2 and HfO2 films are 4.7 and 5.7 eV, respectively. (c) 2005 Published by Elsevier B.V

A new low voltage fast SONOS memory with high-k dielectric

Abstract The comparison of simulated write/erase characteristics of silicon-oxide-nitride-oxide-silicon (SONOS) nonvolatile memory with different oxides SiO 2 , Al 2 O 3 and ZrO 2 as a top dielectric was made. We demonstrate, that an application of high-k dielectrics allows to decrease the write/erase programming voltage amplitude or programming time from 1 ms to 10 ls. The ZrO 2 suppresses parasitic electron injection from polysilicon gate. Also the design of SONOS memory based on high-k dielectrics is promising for terabit scale using hot carriers injection EEPROM and DRAM memory