If the fourth generation fermions exist, the new quarks could influence the branching ratio of the rare B → K * ν ¯ ν decay. Two possible solutions of the fourth generation CKM factor (V * ´ ts V ´ tb) (±) are obtained as a function of the new´t-quark mass (m ´ t) from the experimental results of the B → X s γ together with the semileptonic decay B → X c ℓ¯ ν. The branching ratio of the decay B...

The experiments presented here investigate the competing photodissociation pathways for allyl chloride upon excitation of the nominally pp*~CvC! transition at 193 nm. The measured photofragment velocity distributions evidence C–Cl bond fission and HCl elimination. The recoil kinetic energy distribution for the HCl products is bimodal, indicating two primary processes for HCl elimination. The ex...

We study the two-body and three-body charmful baryonic B decays: B 0 → Λc p̄ and B → Λc p̄ π(ρ). The factorizable W -exchange contribution to B 0 → Λc p̄ is negligible. Applying the bag model to evaluate the baryon-to-baryon weak transition matrix element, we find B(B → Λc p̄) <∼ 2.5 × 10−5|gB0pΣ+b /8| 2 with gB0pΣ+ b being a strong coupling for the decay Σb → B 0 p and hence the predicted branchin...

Recent developments in the theory of weak decays of heavy flavours are reviewed. Applications to exclusive semileptonic B decays, the semileptonic branching ratio and charm counting, beauty lifetimes, and hadronic B decays are discussed. Invited talk presented at the International Europhysics Conference on High Energy Physics Jerusalem, Israel, 19–26 August 1997 CERN-TH/98-2 January 1998 19: He...

Precise β-branching-ratio measurements are required in order to determine ft-values as part of our program to test the Electroweak Standard Model via unitarity of the Cabibbo-Kobayashi-Moskawa matrix. For the measurements to be useful in this test, their precision must be close to 0.1%. In a branching-ratio measurement, we position the radioactive sample between a thin plastic scintillator used...

We describe the modeling and fabrication of waveguide grating couplers with theoretical outcoupling efficiencies into a single diffracted order nearing 100%. Termed single leakage-channel grating couplers (or SLCGC's), these devices utilize a high-reflectivity dielectric stack to reflect the outcoupled beam diffracted toward the substrate and back up into the air region, where it constructively...

Measurement of the Ratio of B[+ over c] Branching Fractions to J/[superscript +] and J[superscript +][subscript ] Final States. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Measurement of the ratio of B þ c branching fractions to J=ψπ þ and J=ψμ þ ν μ final states R. Aaij et al. The first measurement that relates semilept...