Douglas Wright

Cosmic-ray shower generator (CRY) for Monte Carlo transport codes

The CRY software library generates correlated cosmic-ray particle shower distributions at one of three elevations (sea level, 2100 m, and 11300 m) for use as input to transport and detector simulation codes. Our simulation is based on precomputed input tables derived from full MCNPX simulations of primary cosmic rays on the atmosphere and benchmarked against published cosmic-ray measurements. Our simulation provides all particle production (muons, neutrons, protons, electrons, photons, and pions) with the proper flux within a user-specified area and altitude. The code generates individual showers of secondary particles sampling the energy, time of arrival, zenith angle, and multiplicity with basic correlations, and has user controls for latitude (geomagnetic cutoff) and solar cycle effects. We provide a function library, callable from C, C++, and Fortran, and interfaces to popular Monte Carlo transport codes (MCNP, MCNPX, COG, Geant4). The software library and examples can be downloaded from http://nuclear.llnl.gov/simulation.

Calculating gamma-ray signatures from aged mixtures of heavy nuclides

We have created and distributed an open-source software package, RadSrc, that calculates the intrinsic gamma- ray spectrum from the nuclear decay of a mixture of radioisotopes. It implements the Bateman solution of the standard equations of radioactive-series growth and decay to determine isotope concentrations at a user selectable age and processes a database of decay energy lines to generate gamma-ray intensities from all decay chains. We provide an interactive program for studying complete spectra, a function library (callable from C, C++, and Fortran), and interfaces to popular Monte Carlo transport codes (MCNP, MCNPX, COG, and Geant4) so that the gamma rays can be sampled and tracked directly by the parent code. The RadSrc Suite can be downloaded from http://nuclear.llnl.gov/simulation.

Proton radiography as a means of material characterization

We describe how protons with energies of 800 MeV or greater can be used as radiographic probes for material characterization. A feature which distinguishes protons from x-rays is their charge, which results in multiple Coulomb scattering effects in proton radiographs. Magnetic lensing can ameliorate these effects and even allow mixed substances to be disentangled. We illustrate some of these effects using 800 MeV protons radiographs of a composite step wedge composed of Aluminum, Foam, and Graphite. We discuss how proton radiographs must be manipulated in order to use standard tomographic reconstruction algorithms. We conclude with a brief description of an upcoming experiment, which will be performed at Brookhaven National Laboratory at 25 GeV.

Measurement of sin2β with BABAR

We present updated results on time-dependent CP -violating asymmetries in neutral B decays to several CP eigenstates containing charmonium. In the Standard Model, the amplitude of these asymmetries is proportional to sin2 β . We measure sin2 β = 0.741 ± 0.067 (stat) ± 0.034 (syst) from a data sample of about 88 million γ(4 S ) → B B ¯ decays collected with the BaBa R detector at the PEP-II asymmetric-energy B Factory at SLAC. We have also measured CP -violating asymmetries in open charm, and penguin modes sensitive to sin2 β , which provide important consistency tests of the Standard Model.