414 research outputs found
Next--to--Leading Order Corrections to Meson Masses in the Heavy Quark Effective Theory
We use the QCD sum rule approach to calculate the splitting between vector
and pseudoscalar mesons containing one light and one heavy quark, and the
kinetic energy of the heavy quark. Our result for the splitting induced by the
chromomagnetic interaction agrees to the experimental data on charm and beauty
mesons. For the matrix element of the kinetic energy operator, we obtain the
value .Comment: 33 ps., PS figures included, requires REVTEX.3 and psfig,
TUM-T31-42/93/R (additional contribution to kinetic energy taken into
account, marginal changes in the results
Charmed Strange Pentaquarks in the Large Limit
The properties of pentaquarks containing a heavy anti-quark and strange
quarks are studied in the bound state picture. In the flavor SU(3) limit, there
are many pentaquark states with the same binding energy. When the SU(3)
symmetry breaking effects are included, however, three states become
particularly stable due to a ``Gell-Mann--Okubo mechanism''. They are the and states discussed by Lipkin, and a a previously
unstudied state. These states will have and
their masses are estimated. These states, if exist, may be seen in experiments
in the near future.Comment: 12 pages in REVTeX, no figure
Structural and dielectric properties of SrTiO from first principles
We have investigated the structural and dielectric properties of
SrTiO,the first member of the SrTiO
Ruddlesden-Popper series, within density functional theory. Motivated by recent
work in which thin films of SrTiO were grown by molecular beam
epitaxy (MBE) on SrTiO substrates, the in-plane lattice parameter was
fixed to the theoretically optimized lattice constant of cubic SrTiO
(n=), while the out-of-plane lattice parameter and the internal
structural parameters were relaxed. The fully relaxed structure was also
investigated. Density functional perturbation theory was used to calculate the
zone-center phonon frequencies, Born effective charges, and the electronic
dielectric permittivity tensor. A detailed study of the contribution of
individual infrared-active modes to the static dielectric permittivity tensor
was performed. The calculated Raman and infrared phonon frequencies were found
to be in agreement with experiment where available. Comparisons of the
calculated static dielectric permittivity with experiments on both ceramic
powders and epitaxial thin films are discussed.Comment: 11 pages, 1 figure, 8 tables, submitted to Phys. Rev.
Polarized Hydrogen Gas Target in the Cooler
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Radiation Hydrodynamical Instabilities in Cosmological and Galactic Ionization Fronts
Ionization fronts, the sharp radiation fronts behind which H/He ionizing
photons from massive stars and galaxies propagate through space, were
ubiquitous in the universe from its earliest times. The cosmic dark ages ended
with the formation of the first primeval stars and galaxies a few hundred Myr
after the Big Bang. Numerical simulations suggest that stars in this era were
very massive, 25 - 500 solar masses, with H II regions of up to 30,000
light-years in diameter. We present three-dimensional radiation hydrodynamical
calculations that reveal that the I-fronts of the first stars and galaxies were
prone to violent instabilities, enhancing the escape of UV photons into the
early intergalactic medium (IGM) and forming clumpy media in which supernovae
later exploded. The enrichment of such clumps with metals by the first
supernovae may have led to the prompt formation of a second generation of
low-mass stars, profoundly transforming the nature of the first protogalaxies.
Cosmological radiation hydrodynamics is unique because ionizing photons coupled
strongly to both gas flows and primordial chemistry at early epochs,
introducing a hierarchy of disparate characteristic timescales whose relative
magnitudes can vary greatly throughout a given calculation. We describe the
adaptive multistep integration scheme we have developed for the self-consistent
transport of both cosmological and galactic ionization fronts.Comment: 6 pages, 4 figures, accepted for proceedings of HEDLA2010, Caltech,
March 15 - 18, 201
Installation of the Polarized Hydrogen Target and Detector System in the Cooler A-Region
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Polarization Measurements of a Storage Cell Target
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Flavourful hadronic physics
We review theoretical approaches to form factors that arise in heavy-meson
decays and are hadronic expressions of non-perturbative QCD. After motivating
their origin in QCD factorisation, we retrace their evolution from quark-model
calculations to non-perturbative QCD techniques with an emphasis on
formulations of truncated heavy-light amplitudes based upon Dyson-Schwinger
equations. We compare model predictions exemplarily for the B\to\pi transition
form factor and discuss new results for the g_{D*D\pi} coupling in the hadronic
D* decay.Comment: Based on a talk given at Light Cone 2009: Relativistic Hadronic And
Particle Physics, 8-13 July 2009, Sao Jose dos Campos, Sao Paulo, Brazi
Spin Correlation Coefficients in pp Elastic Scattering at 200 MeV
This research was sponsored by the National Science Fooundation Grant NSF PHY-931478
Chiral Multiplets of Heavy-Light Mesons
The recent discovery of a narrow resonance in D_s+pi^0 by the BABAR
collaboration is consistent with the interpretation of a heavy J^P(0+,1+) spin
multiplet. This system is the parity partner of the groundstate (0-,1-)
multiplet, which we argue is required in the implementation of SU(3)_L x
SU(3)_R chiral symmetry in heavy-light meson systems. The (0+,1+)->(0-,1-)+pi
transition couplings satisfy a Goldberger-Treiman relation, g_pi =
Delta(M)/f_pi, where Delta(M) is the mass gap. The BABAR resonance fits the 0+
state, with a kinematically blocked principal decay mode to D+K. The allowed
D_s+pi, D_s+2pi and electromagnetic transitions are computed from the full
chiral theory and found to be suppressed, consistent with the narrowness of the
state. This state establishes the chiral mass difference for all such
heavy-quark chiral multiplets, and precise predictions exist for the analogous
B_s and strange doubly-heavy baryon states.Comment: 10 pages; minor editorial revisions; recomputed M1 transitio
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