6,640 research outputs found
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 Decays in the Standard Model
With SU(3) symmetry one only needs 13 hadronic parameters to describe 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 can be predicted. In this talk we
present SU(3) predictions of branching ratios and CP asymmetries for
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 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 flavor () symmetry. One is
the irreducible approach (IRA), which depends on the irreducible
representation of the effective Hamiltonian. The other is the
topological-diagram approach (TDA), where the decays are drawn to consist of
-boson emission and -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 might cause theoretical difficulties. With the
symmetry breaking, we explain . It is
found that a specific -boson exchange topology denoted by only appears
in , by which we explain . In addition, we predict for future
measurements to test if can be a significant contribution.Comment: 13 pages, 7 tables, 1 figure, introduction rephrased, reference
added, typos correcte
Pictorial approach for two-body weak decays
We explore two-body non-leptonic weak decays of into final
states and , where denotes an
octet (a decuplet) baryon, and represents a pseudoscalar (vector) meson.
Based on the flavor symmetry, we depict and parameterize
the -emission and -exchange processes using the topological diagram
approach, establishing strict relations for possible decay channels.
We identify dominant topological parameters, determined by available data,
allowing us to explain the experimental ratios , , and . We also calculate the branching fractions of the
Cabibbo-allowed decays, such as . In particular, we establish
approximate isospin relations: and , where
is accessible
to the Belle and LHCb experiments.Comment: 16 pages, 3 tables, 2 figure
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