Influence of Capillary Heterogeneity on Leakage of Co2 From a Borehole

We used a modified invasion percolation (MIP) model to examine the effect of capillary heterogeneity, buoyancy forces, and viscous forces on the surface area and saturation of a CO2 plume leaking into a shallow aquifer. The purpose of this study is to provide a better understanding of how CO 2 migrates from a borehole, which is essential in implementing effective simulation and monitoring regimes to accurately detect CO2 leakage from sequestration sites. The MIP model approach will simulate invasion of a light non-wetting fluid (e.g., CO2) into a medium initially saturated with a dense wetting fluid (water). The style of capillary heterogeneity, the strength of buoyancy and viscous forces, and the size of the CO2 source were systematically varied yielding 168 different simulation scenarios. We find that the interplay between capillary heterogeneity, buoyancy forces, and viscous forces controls the surface area and saturation of gaseous CO2 leaking into an aquifer system. In unstructured systems with the absence of buoyancy and viscous forces, the CO2 surface area and saturation are relatively large. In most cases, the CO 2 surface area decreases in weakly stratified systems, and as stratification increases, the CO2 surface area increases and the CO2 saturation decrease. Buoyancy forces stretch the invading CO2 into a narrower structure, resulting in a higher surface area and a lower saturation. Our model implements weak viscous forces which cause CO2 to pool around the leak source until, at a radial distance, either buoyancy or capillary forces begin to dominate CO2 invasion. The dissolution rate of gaseous CO2 into groundwater is proportional to the surface area of the CO2 phase. Our study shows that variations in the style of capillary heterogeneity and the strength of buoyancy and viscous forces can lead to large differences in CO2 dissolution rates

Measurements of branching fraction ratios and CP-asymmetries in suppressed B^- -> D(-> K^+ pi^-)K^- and B^- -> D(-> K^+ pi^-)pi^- decays

We report the first reconstruction in hadron collisions of the suppressed decays B^- -> D(-> K^+ pi^-)K^- and B^- -> D(-> K^+ pi^-)pi^-, sensitive to the CKM phase gamma, using data from 7 fb^-1 of integrated luminosity collected by the CDF II detector at the Tevatron collider. We reconstruct a signal for the B^- -> D(-> K^+ pi^-)K^- suppressed mode with a significance of 3.2 standard deviations, and measure the ratios of the suppressed to favored branching fractions R(K) = [22.0 \pm 8.6(stat)\pm 2.6(syst)]\times 10^-3, R^+(K) = [42.6\pm 13.7(stat)\pm 2.8(syst)]\times 10^-3, R^-(K)= [3.8\pm 10.3(stat)\pm 2.7(syst]\times 10^-3, as well as the direct CP-violating asymmetry A(K) = -0.82\pm 0.44(stat)\pm 0.09(syst) of this mode. Corresponding quantities for B^- -> D(-> K^+ pi^-)pi^- decay are also reported.Comment: 8 pages, 1 figure, accepted by Phys.Rev.D Rapid Communications for Publicatio

Search for B_s --> mu+mu- and B_d --> mu+mu- Decays with CDF II

A search has been performed for B_s --> mu+mu- and B_d --> mu+mu- decays using 7/fb of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron collider. The observed number of B_d candidates is consistent with background-only expectations and yields an upper limit on the branching fraction of BF(B_d-->mu+mu-) < 6.0E-9 at 95% confidence level. We observe an excess of B_s candidates. The probability that the background processes alone could produce such an excess or larger is 0.27%. The probability that the combination of background and the expected standard model rate of B_s --> mu+mu- could produce such an excess or larger is 1.9%. These data are used to determine BF(B_s-->mu+mu-) = (1.8^{+1.1}_{-0.9})E-8 and provide an upper limit of BF(B_s -->mu+mu-) < 4.0E-8 at 95% confidence level.Comment: 7 pages, 1 figure; version accepted by PR

Description and performance of track and primary-vertex reconstruction with the CMS tracker

A description is provided of the software algorithms developed for the CMS tracker both for reconstructing charged-particle trajectories in proton-proton interactions and for using the resulting tracks to estimate the positions of the LHC luminous region and individual primary-interaction vertices. Despite the very hostile environment at the LHC, the performance obtained with these algorithms is found to be excellent. For tbar t events under typical 2011 pileup conditions, the average track-reconstruction efficiency for promptly-produced charged particles with transverse momenta of pT > 0.9GeV is 94% for pseudorapidities of |η| < 0.9 and 85% for 0.9 < |η| < 2.5. The inefficiency is caused mainly by hadrons that undergo nuclear interactions in the tracker material. For isolated muons, the corresponding efficiencies are essentially 100%. For isolated muons of pT = 100GeV emitted at |η| < 1.4, the resolutions are approximately 2.8% in pT, and respectively, 10μm and 30μm in the transverse and longitudinal impact parameters. The position resolution achieved for reconstructed primary vertices that correspond to interesting pp collisions is 10–12μm in each of the three spatial dimensions. The tracking and vertexing software is fast and flexible, and easily adaptable to other functions, such as fast tracking for the trigger, or dedicated tracking for electrons that takes into account bremsstrahlung