16,591 research outputs found

    Bs0Bˉs0B_s^0 - \bar B_s^0 mixing and bsb \to s transitions in isosinglet down quark model

    Full text link
    The recent observation of the mass difference in BsB_s system seems to be not in complete agreement with the corresponding standard model value. We consider the model with an extra vector like down quark to explain this discrepancy and obtain the constraints on the new physics parameters. Thereafter, we show that with these new constraints this model can successfully explain other observed deviations associated with bsb \to s transitions, namely, BsψϕB_s \to \psi \phi, BKπB\to K \pi and BϕKsB\to \phi K_s.Comment: 19 pages, 6 figure

    The B -> pi pi, pi K Puzzles: Implications for Hadron Physics, New Physics and Rare Decays

    Full text link
    The B-meson system is an interesting probe for the exploration of strong interactions, the quark-flavour sector of the Standard Model, and the search for new physics. In this programme, non-leptonic B decays, which are particularly challenging from the point of view of QCD, play a key role. After discussing strategies to deal with the corresponding hadronic matrix elements of four-quark operators and popular avenues for new physics to manifest itself in B decays, we focus on puzzling patterns in the B-factory data for B -> pi pi, pi K decays; we explore their implications for hadron physics, new physics and rare K and B decays.Comment: 10 pages, 2 figures, plenary talk at the International Conference on QCD and Hadronic Physics, Peking University, Beijing, China, 16-20 June 2005, to appear in the Proceeding

    Correlations between plasma variables and the deposition process of Si films from chlorosilanes in low pressure RF plasma of argon and hydrogen

    Get PDF
    The dissociation of chlorosilanes to silicon and its deposition on a solid substrate in a RF plasma of mixtures of argon and hydrogen were investigated as a function of the macrovariables of the plasma. The dissociation mechanism of chlorosilanes and HCl as well as the formation of Si in the plasma state were studied by sampling the plasma with a quadrupole mass spectrometer. Macrovariables such as pressure, net RF power input and locations in the plasma reactor strongly influence the kinetics of dissociation. The deposition process of microcrystalline silicon films and its chlorine contamination were correlated to the dissociation mechanism of chlorosilanes and HCl

    Fast CP Violation

    Get PDF
    BB flavor tagging will be extensively studied at the asymmetric BB factories due to its importance in CP asymmetry measurements. The primary tagging modes are the semileptonic decays of the bb (lepton tag), or the hadronic bc(s)b \to c (\to s) decays (kaon tag). We suggest that looking for time dependent CP asymmetries in events where one BB is tagged leptonically and the other one is tagged with a kaon could result in an early detection of CP violation. Although in the Standard Model these asymmetries are expected to be small, 1\sim 1%, they could be measured with about the same amount of data as in the ``gold-plated'' decay BdψKSB_d \to \psi K_S. In the presence of physics beyond the Standard Model, these asymmetries could be as large as 5\sim 5%, and the first CP violation signal in the BB system may show up in these events. We give explicit examples of new physics scenarios where this occurs.Comment: 9 pages, revtex, no figures. Discussion of new physics effects on CP violation with two lepton tags expanded. Factors of 2 correcte

    The photon polarization in B -> X gamma in the standard model

    Full text link
    The standard model prediction for the BXs,dγB\to X_{s,d}\gamma decay amplitude with a right-handed photon is believed to be tiny, suppressed by ms,d/mbm_{s,d}/m_b, compared to the amplitude with a left-handed photon. We show that this suppression is fictitious: in inclusive decays, the ratio of these two amplitudes is only suppressed by gs/(4π)g_s/(4\pi), and in exclusive decays by ΛQCD/mb\Lambda_{QCD}/m_b. The suppression is not stronger in BXdγB\to X_d\gamma decays than it is in BXsγB\to X_s\gamma. We estimate that the time dependent CP asymmetries in BKγB\to K^*\gamma, ργ\rho\gamma, KSπ0γK_S\pi^0\gamma, and π+πγ\pi^+\pi^-\gamma are of order 0.1 and that they have significant uncertainties.Comment: Clarifications in the exclusive section, references adde

    Microphysical, microchemical and adhesive properties of lunar material. 3: Gas interaction with lunar material

    Get PDF
    Knowledge of the reactivity of lunar material surfaces is important for understanding the effects of the lunar or space environment upon this material, particularly its nature, behavior and exposure history in comparison to terrestrial materials. Adsorptive properties are one of the important techniques for such studies. Gas adsorption measurements were made on an Apollo 12 ultrahigh vacuum-stored sample and Apollo 14 and 15 N2-stored samples. Surface area measurements were made on the latter two. Adsorbate gases used were N2, A, O2 and H2O. Krypton was used for the surface area determinations. Runs were made at room and liquid nitrogen temperature in volumetric and gravimetric systems. It was found that the adsorptive/desorptive behavior was in general significantly different from that of terrestrial materials of similar type and form. Specifically (1) the UHV-stored sample exhibited very high initial adsorption indicative of high surface reactivity, and (2) the N2-stored samples at room and liquid nitrogen temperatures showed that more gas was desorbed than introduced during adsorption, indicative of gas release from the samples. The high reactivity is a scribed cosmic ray track and solar wind damage

    Constraining the CKM Parameters using CP Violation in semi-leptonic B Decays

    Get PDF
    We discuss the usefulness of the CP violating semi-leptonic asymmetry a_{SL} not only as a signal of new physics, but also as a tool in constraining the CKM parameters. We show that this technique could yield useful results in the first years of running at the B factories. We present the analysis graphically in terms of M_{12}, the dispersive part of the B-Bbar mixing amplitude. This is complementary to the usual unitarity triangle representation and often allows a cleaner interpretation of the data.Comment: 15 pages REVTEX, 7 figure

    Fractal dimensions of the Q-state Potts model for the complete and external hulls

    Full text link
    Fortuin-Kastelyn clusters in the critical QQ-state Potts model are conformally invariant fractals. We obtain simulation results for the fractal dimension of the complete and external (accessible) hulls for Q=1, 2, 3, and 4, on clusters that wrap around a cylindrical system. We find excellent agreement between these results and theoretical predictions. We also obtain the probability distributions of the hull lengths and maximal heights of the clusters in this geometry and provide a conjecture for their form.Comment: 9 pages 4 figure

    Stress effects on the Raman spectrum of an amorphous material: theory and experiment on a-Si:H

    Get PDF
    Strain in a material induces shifts in vibrational frequencies, which is a probe of the nature of the vibrations and interatomic potentials, and can be used to map local stress/strain distributions via Raman microscopy. This method is standard for crystalline silicon devices, but due to lack of calibration relations, it has not been applied to amorphous materials such as hydrogenated amorphous silicon (a-Si:H), a widely studied material for thin-film photovoltaic and electronic devices. We calculated the Raman spectrum of a-Si:H \ab initio under different strains ϵ\epsilon and found peak shifts Δω=(460±10 cm1)Tr ϵ\Delta \omega = \left( -460 \pm 10\ \mathrm{cm}^{-1} \right) {\rm Tr}\ \epsilon. This proportionality to the trace of the strain is the general form for isotropic amorphous vibrational modes, as we show by symmetry analysis and explicit computation. We also performed Raman measurements under strain and found a consistent coefficient of 510±120 cm1-510 \pm 120\ \mathrm{cm}^{-1}. These results demonstrate that a reliable calibration for the Raman/strain relation can be achieved even for the broad peaks of an amorphous material, with similar accuracy and precision as for crystalline materials.Comment: 12 pages, 3 figures + supplementary 8 pages, 4 figure
    corecore