B_s decays at Belle

We report recent results obtained with the Belle detector using a 23.6 fb^{-1} data sample collected on the Y(5S) resonance at the KEKB asymmetric energy e^+ e^- collider. Inclusive semileptonic B_s^0 -> X^+ l^- \nu decays are studied for the first time and the branching fraction is measured. Combining the electron and muon channels, we obtain Bf(B_s^0 -> X^+ l^- \nu) = (10.2 \pm 0.8 \pm 0.9)%. Also, the radiative penguin decay B_s^0 -> \phi \gamma is observed for the first time, and an improved upper limit for the decay B_s^0 \to \gamma \gamma is obtained.Comment: Proceedings of the EPS/HEP 2007 Conference, Manchester, England, July 2007 (on behalf of the Belle collaboration), 3 pages, 2 figure

Bounds on quark mass matrices elements due to measured properties of the mixing matrix and present values of the quark masses

We obtain constraints on possible structures of mass matrices in the quark sector by using as experimental restrictions the determined values of the quark masses at the $M_Z$ energy scale, the magnitudes of the quark mixing matrix elements $V_{\rm ud}$, $V_{\rm us}$, $V_{\rm cd}$, and $V_{\rm cs}$, and the Jarlskog invariant $J(V)$. Different cases of specific mass matrices are examined in detail. The quality of the fits for the Fritzsch and Stech type mass matrices is about the same with $\chi^2/{\rm dof}=4.23/3=1.41$ and $\chi^2/{\rm dof}=9.10/4=2.28$, respectively. The fit for a simple generalization (one extra parameter) of the Fritzsch type matrices, in the physical basis, is much better with $\chi^2/{\rm dof}=1.89/4=0.47$. For comparison we also include the results using the quark masses at the 2 GeV energy scale. The fits obtained at this energy scale are similar to that at $M_Z$ energy scale, implying that our results are unaffected by the evolution of the quark masses from 2 to 91 GeV.Comment: Evolution effects include

SPSA-Based Tracking Method for Single-Channel-Receiver Array

A novel tracking method in the phased antenna array with a single-channel receiver for the moving signal source is presented in this paper. And the problems of the direction-of-arrival track and beamforming in the array system are converted to the power maximization of received signal in the free-interference conditions, which is different from the existing algorithms that maximize the signal to interference and noise ratio. The proposed tracking method reaches the global optimum rather than local by injecting the extra noise terms into the gradient estimation. The antenna beam can be steered to coincide with the direction of the moving source fast and accurately by perturbing the output of the phase shifters during motion, due to the high efficiency and easy implementation of the proposed beamforming algorithm based on the simultaneous perturbation stochastic approximation (SPSA). Computer simulations verify that the proposed tracking scheme is robust and effective

Tensor coupling effects on spin symmetry in anti-Lambda spectrum of hypernuclei

The effects of $\bar\Lambda\bar\Lambda\omega$-tensor coupling on the spin symmetry of $\bar{\Lambda}$ spectra in $\bar{\Lambda}$-nucleus systems have been studied with the relativistic mean-field theory. Taking $^{12}$C+$\bar{\Lambda}$ as an example, it is found that the tensor coupling enlarges the spin-orbit splittings of $\bar\Lambda$ by an order of magnitude although its effects on the wave functions of $\bar{\Lambda}$ are negligible. Similar conclusions has been observed in $\bar{\Lambda}$-nucleus of different mass regions, including $^{16}$O+$\bar{\Lambda}$, $^{40}$Ca+$\bar{\Lambda}$ and $^{208}$Pb+$\bar{\Lambda}$. It indicates that the spin symmetry in anti-lambda-nucleus systems is still good irrespective of the tensor coupling.Comment: 12 pages, 3 figures

Core Polarization and Tensor Coupling Effects on Magnetic Moments of Hypernuclei

The effects of core polarization and tensor coupling on the magnetic moments in $^{13}_\Lambda$C, $^{17}_\Lambda$O, and $^{41}_\Lambda$Ca $\Lambda$-hypernuclei are studied in the Dirac equation with scalar, vector and tensor potentials. It is found that the effect of core polarization on the magnetic moments is suppressed by $\Lambda$ tensor coupling. The $\Lambda$ tensor potential reduces the spin-orbit splitting of $p_\Lambda$ states considerably. However, almost the same magnetic moments are obtained using the hyperon wave function obtained via the Dirac equation either with or without the $\Lambda$ tensor potential in the electromagnetic current vertex. The deviations of magnetic moments for $p_\Lambda$ states from the Schmidt values are found to increase with nuclear mass number.Comment: 10 pages, 2 figures, 2 table

The unit of electric charge and the mass hierarchy of heavy particles

We propose some empirical formulae relating the masses of the heaviest particles in the standard model (the W,Z,H bosons and the t quark) to the charge of the positron $e$ and the Higgs condensate v. The relations for the masses of gauge bosons m_W = (1+e)v/4 and m_Z=sqrt{(1+e^2)/2}*(v/2) are in excellent agreement with experimental values. By requiring the electroweak standard model to be free from quadratic divergencies at the one-loop level, we find: m_t=v/sqrt{2} and m_H=v/sqrt{2e}, or the very simple ratio (m_t/m_H)^2=e.Comment: 6 page

Incompatibility of modulated checkerboard patterns with the neutron scattering resonance peak in cuprate superconductors

Checkerboard patterns have been proposed in order to explain STM experiments on the cuprates BSCCO and Na-CCOC. However the presence of these patterns has not been confirmed by a bulk probe such as neutron scattering. In particular, simple checkerboard patterns are inconsistent with neutron scattering data, in that they have low energy incommsensurate (IC) spin peaks rotated 45 degrees from the direction of the charge IC peaks. However, it is unclear whether other checkerboard patterns can solve the problem. In this paper, we have studied more complicated checkerboard patterns ("modulated checkerboards") by using spin wave theory and analyzed noncollinear checkerboards as well. We find that the high energy response of the modulated checkerboards is inconsistent with neutron scattering results, since they fail to exhibit a resonance peak at (pi,pi), which has recently been shown to be a universal feature of cuprate superconductors. We further argue that the newly proposed noncollinear checkerboard also lacks a resonance peak. We thus conclude that to date no checkerboard pattern has been proposed which satisfies both the low energy constraints and the high energy constraints imposed by the current body of experimental data in cuprate superconductors.Comment: 5 pages, 5 figures, Fig.2 update

The effect of Mach number on unstable disturbances in shock/boundary-layer interactions

The effect of Mach number on the growth of unstable disturbances in a boundary layer undergoing a strong interaction with an impinging oblique shock wave is studied by direct numerical simulation and linear stability theory (LST). To reduce the number of independent parameters, test cases are arranged so that both the interaction location Reynolds number (based on the distance from the plate leading edge to the shock impingement location for a corresponding inviscid flow) and the separation bubble length Reynolds number are held fixed. Small-amplitude disturbances are introduced via both white-noise and harmonic forcing and, after verification that the disturbances are convective in nature, linear growth rates are extracted from the simulations for comparison with parallel flow LST and solutions of the parabolized stability equations (PSE). At Mach 2.0, the oblique modes are dominant and consistent results are obtained from simulation and theory. At Mach 4.5 and Mach 6.85, the linear Navier-Stokes results show large reductions in disturbance energy at the point where the shock impinges on the top of the separated shear layer. The most unstable second mode has only weak growth over the bubble region, which instead shows significant growth of streamwise structures. The two higher Mach number cases are not well predicted by parallel flow LST, which gives frequencies and spanwise wave numbers that are significantly different from the simulations. The PSE approach leads to good qualitative predictions of the dominant frequency and wavenumber at Mach 2.0 and 4.5, but suffers from reduced accuracy in the region immediately after the shock impingement. Three-dimensional Navier-Stokes simulations are used to demonstrate that at finite amplitudes the flow structures undergo a nonlinear breakdown to turbulence. This breakdown is enhanced when the oblique-mode disturbances are supplemented with unstable Mack modes

A comparative study of the electronic and magnetic properties of BaFe_2As_2 and BaMn_2As_2 using the Gutzwiller approximation

To elucidate the role played by the transition metal ion in the pnictide materials, we compare the electronic and magnetic properties of BaFe_{2}As_{2} with BaMn_{2}As_{2}. To this end we employ the LDA+Gutzwiller method to analyze the mass renormalizations and the size of the ordered magnetic moment of the two systems. We study a model that contains all five transition metal 3d orbitals together with the Ba-5d and As-4p states (ddp-model) and compare these results with a downfolded model that consists of Fe/Mn d-states only (d-model). Electronic correlations are treated using the multiband Gutzwiller approximation. The paramagnetic phase has also been investigated using LDA+Gutzwiller method with electron density self-consistency. The renormalization factors for the correlated Mn 3d orbitals in the paramagnetic phase of BaMn_{2}As_{2} are shown to be generally smaller than those of BaFe_{2}As_{2}, which indicates that BaMn_{2}As_{2} has stronger electron correlation effect than BaFe_{2}As_{2}. The screening effect of the main As 4p electrons to the correlated Fe/Mn 3d electrons is evident by the systematic shift of the results to larger Hund's rule coupling J side from the ddp-model compared with those from the d-model. A gradual transition from paramagnetic state to the antiferromagnetic ground state with increasing J is obtained for the models of BaFe_{2}As_{2} which has a small experimental magnetic moment; while a rather sharp jump occurs for the models of BaMn_{2}As_{2}, which has a large experimental magnetic moment. The key difference between the two systems is shown to be the d-level occupation. BaMn_{2}As_{2}, with approximately five d-electrons per Mn atom, is for same values of the electron correlations closer to the transition to a Mott insulating state than BaFe_{2}As_{2}. Here an orbitally selective transition, required for a system with close to six electrons only occurs at significantly larger values for the Coulomb interactions

Tree FCNC and non-unitarity of CKM matrix

We discuss possible signatures of the tree level FCNC, which results from the non-unitarity of CKM matrix. We first define the unitaity step-by-step, and possible test of the non-unitaity through the 4-value-KM parametrization. We, then, show how the phase angle of the unitary triangle would change in case of the vector-like down quark model. As another example of tree FCNC, we investigate the leptophobic $Z'$ model and its application to the recent $B_s$ mixing measurements.Comment: Talk given at Neutrino Masses and Mixings 2006 (NMM2006), Shizuoka, Japan (December 2006