The Origin of C IV Absorption Systems at Redshifts z<1---Discovery of Extended C IV Envelopes Around Galaxies

(Abridged) We report the discovery of extended CIV gaseous envelopes around galaxies of a wide range of luminosity and morphological type. First, we show that CIV absorption systems are strongly clustered around galaxies on velocity scales of v < 250 km/s and impact parameter scales of rho < 100 h^{-1} kpc but not on larger velocity or impact parameter scales. Next, adopting measurements of galaxy properties presented in previous papers, we examine how properties of the CIV absorption systems depend on properties of the galaxies. On the basis of 14 galaxy and absorber pairs and 36 galaxies that do not produce corresponding CIV absorption lines to within sensitive upper limits, we find that: (1) Galaxies of a range of morphological type and luminosity appear to possess extended CIV gaseous envelopes of radius R ~ 100 h^{-1} kpc, with abrupt boundaries between the CIV absorbing and non-absorbing regions. (2) The extent of CIV-absorbing gas around galaxies scales with galaxy B-band luminosity as R \propto L_B^{0.5 +/- 0.1} but does not depend strongly on galaxy surface brightness, redshift, or morphological type. And (3) the covering factor of CIV clouds within ~ 100 h^{-1} kpc of galaxies is nearly unity, but there is a large scatter in the mean number of clouds encountered along the line of sight. The most significant implication of the study is that galaxies of a wide range of luminosity and morphological type are surrounded by chemically enriched gas that extends for at least ~ 100 h^{-1} kpc. We consider various scenarios that may have produced metals at large galactic distance and conclude that accreting satellites are most likely to be responsible for chemically enriched gas at large galactic distances to regular looking galaxies.Comment: 19 pages, 3 figures, to appear in ApJ, July 20 200

Efficient orthogonal control of tunnel couplings in a quantum dot array

Electrostatically-defined semiconductor quantum dot arrays offer a promising platform for quantum computation and quantum simulation. However, crosstalk of gate voltages to dot potentials and inter-dot tunnel couplings complicates the tuning of the device parameters. To date, crosstalk to the dot potentials is routinely and efficiently compensated using so-called virtual gates, which are specific linear combinations of physical gate voltages. However, due to exponential dependence of tunnel couplings on gate voltages, crosstalk to the tunnel barriers is currently compensated through a slow iterative process. In this work, we show that the crosstalk on tunnel barriers can be efficiently characterized and compensated for, using the fact that the same exponential dependence applies to all gates. We demonstrate efficient calibration of crosstalk in a quadruple quantum dot array and define a set of virtual barrier gates, with which we show orthogonal control of all inter-dot tunnel couplings. Our method marks a key step forward in the scalability of the tuning process of large-scale quantum dot arrays.Comment: 8 pages, 7 figure

SU(3) Predictions of B→PPB\to PP Decays in the Standard Model

With SU(3) symmetry one only needs 13 hadronic parameters to describe $B\to PP$ decays in the Standard Model. When annihilation contributions are neglected, only 7 hadronic parameters are needed. These parameters can be determined from existing experimental data and some unmeasured branching ratios and CP asymmetries of the type $B\to PP$ can be predicted. In this talk we present SU(3) predictions of branching ratios and CP asymmetries for $B\to PP$ decays in the Standard Model.Comment: 4 pages, no figure. Talk present at the 5th International Conference on Hyperons, Charm and Beauty Hadrons, Vancouver, June 200

Equivalent SU(3)fSU(3)_f approaches for two-body anti-triplet charmed baryon decays

For the two-body anti-triplet charmed baryon decays, there exist two theoretical analyses based on the $SU(3)$ flavor ($SU(3)_f$) symmetry. One is the irreducible $SU(3)_f$ approach (IRA), which depends on the irreducible $SU(3)_f$ representation of the effective Hamiltonian. The other is the topological-diagram approach (TDA), where the decays are drawn to consist of $W$-boson emission and $W$-boson exchange topologies. We demonstrate that IRA and TDA can be equivalent, such that the IRA parameters can be seen to mix with the TDA topologies. The current observations of $\Xi_c^0\to \Xi^-\pi^+,\Xi^- K^+,\Lambda^0\bar K^0$ might cause theoretical difficulties. With the $SU(3)_f$ symmetry breaking, we explain ${\cal B}(\Xi_c^0\to\Xi^-\pi^+,\Xi^-K^+)$. It is found that a specific $W$-boson exchange topology denoted by $E_M$ only appears in $\Xi_c^0\to{\bf B}M$, by which we explain ${\cal B}(\Xi_c^0\to\Lambda^0\bar K^0)$. In addition, we predict ${\cal B}(\Xi_c^0\to\Sigma^0\bar K^0,\Sigma^+ K^-)= (5.8^{+4.7}_{-3.5},5.4^{+4.9}_{-3.4})\times 10^{-3}$ for future measurements to test if $E_M$ can be a significant contribution.Comment: 13 pages, 7 tables, 1 figure, introduction rephrased, reference added, typos correcte

Pictorial SU(3)fSU(3)_f approach for two-body Ωc\Omega_c weak decays

We explore two-body non-leptonic weak decays of $\Omega_c^0$ into final states ${\bf B}^{(*)}M$ and ${\bf B}^{(*)}V$, where ${\bf B}^{(*)}$ denotes an octet (a decuplet) baryon, and $M(V)$ represents a pseudoscalar (vector) meson. Based on the $SU(3)$ flavor $[SU(3)_f]$ symmetry, we depict and parameterize the $W$-emission and $W$-exchange processes using the topological diagram approach, establishing strict $SU(3)_f$ relations for possible decay channels. We identify dominant topological parameters, determined by available data, allowing us to explain the experimental ratios ${\cal B}(\Omega_c^0\to\Xi^{*0}\bar K^{*0})/{\cal B}(\Omega_c^0\to\Omega^-\rho^+)=0.28\pm 0.11$, ${\cal B}(\Omega_c^0\to\Xi^-\pi^+)/{\cal B}(\Omega_c^0\to\Xi^{0}\bar K^{0})=0.10\pm 0.02$, and ${\cal B}(\Omega_c^0 \to \Omega^- K^+)/{\cal B}(\Omega_c^0 \to \Omega^- \pi^+)=0.06\pm 0.01$. We also calculate the branching fractions of the Cabibbo-allowed decays, such as ${\cal B}(\Omega_c^0 \to \Xi^{* 0} \bar{K}^{0})=(9.8\pm1.3)\times 10^{-4}$. In particular, we establish approximate isospin relations: ${\cal B}(\Omega_c^0 \to \Xi^{(*)-} \pi^+)\simeq 2{\cal B}(\Omega_c^0 \to \Xi^{(*)0} \pi^0)$ and ${\cal B}(\Omega_c^0 \to \Xi^{(*)-} \rho^+)\simeq 2{\cal B}(\Omega_c^0 \to \Xi^{(*)0} \rho^0)$, where ${\cal B}(\Omega_c^0 \to \Xi^0 \pi^0)=(2.3\pm0.2)\times 10^{-4}$ is accessible to the Belle and LHCb experiments.Comment: 16 pages, 3 tables, 2 figure