938 research outputs found
Omega-3 Fatty Acid, Selenium, and Mercury Content of Aquaculture Products in Hawaii
The purpose of this study was to gather baseline data on the fatty acid profile and selenium and mercury concentration of aquaculture products in Hawaii
Mass enhancements and band shifts in strongly hole overdoped Fe-based pnictide superconductors: KFeAs and CsFeAs
The interplay of high and low-energy mass renormalizations with band-shifts
reflected by the positions of van Hove singularities (VHS) in the normal state
spectra of the highest hole-overdoped and strongly correlated AFeAs
(A122) with A = K, Cs is discussed phenomenologically based on ARPES data and
GGA band-structure calculations with full spin-orbit coupling. The big increase
of the Sommerfeld coefficient from K122 to Cs122 is ascribed to an
enhanced coupling to low-energy bosons in the vicinity of a quantum critical
point to an unknown, yet incommensurate phase different from the commensurate
Mott one. We find no sizeable increase in correlations for Cs122 in contrast to
F. Eilers et al., PRL v. 116, 237003 (2016) [3]. The empirical (ARPES) VHS
positions as compared with GGA-predictions point even to slightly weaker
correlations in Cs122 in accord with low- magnetic susceptibility
data and a decreasing Wilson ratio .Comment: 8 pages, 7 figures, updated references, and a Note for arXiv-reader
Meson Decay Constants from Isospin Mass Splittings in the Quark Model
Decay constants of and mesons are estimated within the framework of a
heavy-quark approach using measured isospin mass splittings in the , ,
and states to isolate the electromagnetic hyperfine interaction between
quarks. The values MeV and MeV are
obtained. Only experimental errors are given; possible theoretical ambiguities,
and suggestions for reducing them, are noted.Comment: 7 pages, LaTeX, EFI-92-3
Born Effective Charges and Infrared Response of LiBC
Calculations of the zone center optical mode frequencies (including LO-TO
splitting), Born effective charges Z for each atom,
dielectric constants and , and the dielectric
response in the infrared, using density functional linear response theory, are
reported. Calculated Raman modes are in excellent agreement with experimental
values (170 cm and 1170 cm), while it will require better
experimental data to clarify the infrared active mode frequencies. The Born
effective charges Z (i) have surprisingly different values
for B and C, and (ii) show considerable anisotropy. Relationships between the
effective charges and LO-TO splitting are discussed, and the predicted
reflectivity in the range 0 -- 1400 cm is presented. These results hold
possible implications for Li removal in LiBC, and C substition for B in
MgB.Comment: 6 pages, 3 figure
Theoretical overview of atomic parity violation. Recent developments and challenges
Recent advances in interpreting the most accurate to-date measurement of
atomic parity violation in Cs are reviewed. The inferred nuclear weak charge,
Q_W = - 72.65(28)_expt (36)_theor, agrees with the prediction of the standard
model at 1 sigma level. Further improved interpretation is limited by an
accuracy of solving basic correlation problem of atomic structure. We report on
our progress in solving this problem within the relativistic coupled-cluster
formalism. We include single-, double- and triple- electronic excitations in
the coupled-cluster expansion. Numerical results for energies, electric-dipole
matrix elements, and hyperfine-structure constants of Cs are presented.Comment: PAVI'06 proceedings + EJPA; refs + SM Qw fixe
Framework for Identification of Neutral B Mesons
We introduce a method for the study of CP-violating asymmetries in tagged
states of neutral mesons with arbitrary coherence properties. A set of
time-dependent measurements is identified which completely specifies the
density matrix of the initial state in a two-component space with basis vectors
and , and permits a determination of phases in the
Cabibbo-Kobayashi-Maskawa matrix. For a given tagging configuration, the
measurement of decays both to flavor eigenstates and to CP eigenstates provides
the necessary information.Comment: Submitted to Phys. Rev. Letters. 8 pages, LaTeX, Technion-PH-93-31 /
EFI 93-3
QCD sum rules study of the meson Z^+(4430)
We use QCD sum rules to study the recently observed meson ,
considered as a molecule with . We consider the
contributions of condensates up to dimension eight and work at leading order in
. We get m_Z=(4.40\pm0.10) \GeV in a very good agreement with the
experimental value. We also make predictions for the analogous mesons
and considered as and molecules respectively. For
we predict , which is above the
threshold, indicating that it is probably a very broad state and,
therefore, difficult to be experimentally seen. For we predict
, in agreement with quark model
predictions.Comment: 2 new figures included. version accepted for publication in Phys.
Lett.
Identification of Neutral B Mesons Using Correlated Hadrons
The identification of the flavor of a neutral meson can make use of
hadrons produced nearby in phase space. Examples include the decay of
``'' resonances or the production of hadrons as a result of the
fragmentation process. Some aspects of this method are discussed, including
time-dependent effects in neutral decays to flavor states, to eigenstates
of CP and to other states, and the effects of possible coherence between
and in the initial state. We study the behavior of the leading
hadrons in -quark jets and the expected properties of resonances.
These are extrapolated from the corresponding resonances, of whose
properties we suggest further studies.Comment: To be submitted to Phys. Rev. D. 26 pages, LaTeX, figures not
included (available upon request). Technion-PH-93-32 / EFI 93-4
Photoemission and x-ray absorption study of MgC_(1-x)Ni_3
We investigated electronic structure of MgC_(1-x)Ni_3 with photoemission and
x-ray absorption spectroscopy. Both results show that overall band structure is
in reasonable agreement with band structure calculations including the
existence of von Hove singularity (vHs)near E_F. However, we find that the
sharp vHs peak theoretically predicted near the E_F is substantially
suppressed. As for the Ni core level and absorption spectrum, there exist the
satellites of Ni 2p which have a little larger energy separation and reduced
intensity compared to the case of Ni-metal. These facts indicate that
correlation effects among Ni 3d electrons may be important to understand
various physical properties.Comment: 12 pages, 4 figure
Model of the Quark Mixing Matrix
The structure of the Cabibbo-Kobayashi-Maskawa (CKM) matrix is analyzed from
the standpoint of a composite model. A model is constructed with three families
of quarks, by taking tensor products of sufficient numbers of spin-1/2
representations and imagining the dominant terms in the mass matrix to arise
from spin-spin interactions. Generic results then obtained include the familiar
relation , and a less frequently
seen relation . The magnitudes of
and come out naturally to be of the right order. The phase in
the CKM matrix can be put in by hand, but its origin remains obscure.Comment: Presented by Mihir P. Worah at DPF 92 Meeting, Fermilab, November,
1992. 3 pages, LaTeX fil
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