Color suppressed contributions to the decay modes B_{d,s} -> D_{s,d} D_{s,d}, B_{d,s} -> D_{s,d} D^*_{s,d}, and B_{d,s} -> D^*_{s,d} D^*_{s,d}

The amplitudes for decays of the type $B_{d,s} \to D_{s,d} D_{s,d}$, have no factorizable contributions, while $B_{d,s} \to D_{s,d} D^*_{s,d}$, and $B_{d,s} \to D^*_{s,d} D^*_{s,d}$ have relatively small factorizable contributions through the annihilation mechanism. The dominant contributions to the decay amplitudes arise from chiral loop contributions and tree level amplitudes which can be obtained in terms of soft gluon emissions forming a gluon condensate. We predict that the branching ratios for the processes $\bar B^0_d \to D_s^+ D_s^-$, $\bar B^0_d \to D_s^{+*} D_s^-$ and $\bar B^0_d \to D_s^+ D_s^{-*}$ are all of order $(2- 3) \times 10^{-4}$, while $\bar B^0_s \to D_d^+ D_d^-$, $\bar B^0_s \to D_d^{+*} D_d^-$ and $\bar B^0_s \to D_d^+ D_d^{-*}$ are of order $(4- 7) \times 10^{-3}$. We obtain branching ratios for two $D^*$'s in the final state of order two times bigger.Comment: 15 pages, 4 figure

The meaning of S-D dominance

The dominance of S and D pairs in the description of deformed nuclei is one of the facts that provided sustain to the Interacting Boson Approximation. In Ref.(J. Dukelsky and S. Pittel, Phys. Rev. Lett. 86, 4791, 2001.), using an exactly solvable model with a repulsive pairing interaction between bosons it has been shown that the ground state is described almost completely in terms of S and D bosons. In the present paper we study the excited states obtained within this exactly solvable hamiltonian and show that in order to obtain a rotational spectra all the other degrees of freedom are needed.Comment: Are S and D pairs enough to describe deformed nuclei

Micropattern gas detector technologies and applications, the work of the RD51 collaboration

The RD51 collaboration was founded in April 2008 to coordinate and facilitate efforts for development of micropattern gaseous detectors (MPGDs). The 75 institutes from 25 countries bundle their effort, experience and resources to develop these emerging micropattern technologies. MPGDs are already employed in several nuclear and high-energy physics experiments, medical imaging instruments and photodetection applications; many more applications are foreseen. They outperform traditional wire chambers in terms of rate capability, time and position resolution, granularity, stability and radiation hardness. RD51 supports efforts to make MPGDs also suitable for large areas, increase cost-efficiency, develop portable detectors and improve ease-of-use. The collaboration is organized in working groups which develop detectors with new geometries, study and simulate their properties, and design optimized electronics. Among the common supported projects are creation of test infrastructure such as beam test and irradiation facilities, and the production workshop.Comment: Submitted to the IEEE Nuclear Science Symposium 2010 Conference Recor

Antiferromagnetic s-d exchange coupling in GaMnAs

Measurements of coherent electron spin dynamics in Ga(1-x)Mn(x)As/Al(0.4)Ga(0.6)As quantum wells with 0.0006% < x < 0.03% show an antiferromagnetic (negative) exchange bewteen s-like conduction band electrons and electrons localized in the d-shell of the Mn2+ impurities. The magnitude of the s-d exchange parameter, N0 alpha, varies as a function of well width indicative of a large and negative contribution due to kinetic exchange. In the limit of no quantum confinement, N0 alpha extrapolates to -0.09 +/- 0.03 eV indicating that antiferromagnetic s-d exchange is a bulk property of GaMnAs. Measurements of the polarization-resolved photoluminescence show strong discrepancy from a simple model of the exchange enhanced Zeeman splitting, indicative of additional complexity in the exchange split valence band.Comment: 5 pages, 4 figures and one action figur

Chiral behavior of the B(s,d)-Bbar(s,d) mixing amplitude in the Standard Model and beyond

We compute the chiral logarithmic corrections to the Bd and Bs mixing amplitudes in the Standard Model and beyond. We then investigate the impact of the inclusion of the lowest-lying scalar heavy-light states to the decay constants and bag-parameters and show that this does not modify the pion chiral logarithms, but it does produce corrections which are competitive in size with the K- and eta-meson chiral logarithms. This conclusion is highly relevant to the lattice studies since the pion chiral logarithms represent the most important effect in guiding the chiral extrapolations of the lattice data for these quantities. Also important is to stress that the pion chiral logarithmic corrections are useful in guiding those extrapolations as long as Mpi << Delta, where Delta is the mass gap between the scalar and pseudoscalar heavy-light mesons.Comment: 16 pages, 5 figures (published version