41,824 research outputs found
Final stare interaction enhancement effect on the near threshold p\bar p system in B^\pm\to p\bar p \p^\pm decay
We discuss the low-mass enhancement effect in the baryon-antibaryon invariant
mass in three-body baryonic B decays using final state interactions in the
framework of Regge theory. We show that the rescattering between baryonic pair
can reproduce the observed mass spectrum.Comment: 7 pages, 11 figure
Nondecoupling of Heavy Fermions and a Special Yukawa Texture
Talk based on work entitled ``Yukawa textures, new physics and
nondecoupling,'' done in collaboration with G. C. Branco and J. I.
Silva-Marcos, arXiv:hep-ph/0612252, to appear in Phys. Rev. D. In this work we
pointed out that New Physics can play an important r\^ ole in rescuing some of
the Yukawa texture zero ans\" atze which would otherwise be eliminated by the
recent, more precise measurements of . We have shown that the presence
of an isosinglet vector-like quark which mixes with standard quarks, can render
viable a particularly interesting four texture zero Yukawa ansatz. The crucial
point is the nondecoupling of the effects of the isosinglet quark, even for
arbitrary large values of its mass.Comment: Invited talk at CTP Symposium on Supersymmetry at LHC: Theoretical
and Experimental Prospectives, Cairo, Egypt, 11-14 Mar 200
Systematic study of the symmetry energy coefficient in finite nuclei
The symmetry energy coefficients in finite nuclei have been studied
systematically with a covariant density functional theory (DFT) and compared
with the values calculated using several available mass tables. Due to the
contamination of shell effect, the nuclear symmetry energy coefficients
extracted from the binding energies have large fluctuations around the nuclei
with double magic numbers. The size of this contamination is shown to be
smaller for the nuclei with larger isospin value. After subtracting the shell
effect with the Strutinsky method, the obtained nuclear symmetry energy
coefficients with different isospin values are shown to decrease smoothly with
the mass number and are subsequently fitted to the relation . The resultant volume and
surface coefficients from axially deformed covariant DFT calculations are
and MeV respectively. The ratio is in good
agreement with the value derived from the previous calculations with the
non-relativistic Skyrme energy functionals. The coefficients and
corresponding to several available mass tables are also extracted. It is shown
that there is a strong linear correlation between the volume and surface
coefficients and the ratios are in between for all
the cases.Comment: 16 pages, 6 figure
Intrinsic interface exchange coupling of ferromagnetic nanodomains in a charge ordered manganite
We present a detailed magnetic study of the Pr1/3Ca2/3MnO3 manganite, where
we observe the presence of small ferromagnetic (FM) domains (diameter ~ 10A)
immersed within the charge-ordered antiferromagnetic (AFM) host. Due to the
interaction of the FM nanodroplets with a disordered AFM shell, the
low-temperature magnetization loops present exchange bias (EB) under cooling in
an applied magnetic field. Our analysis of the cooling field dependence of the
EB yields an antiferromagnetic interface exchange coupling comparable to the
bulk exchange constant of the AFM phase. We also observe training effect of the
EB, which is successfully described in terms of a preexisting relaxation model
developed for other classical EB systems. This work provides the first evidence
of intrinsic interface exchange coupling in phase separated manganites.Comment: 7 pages, 6 figure
The structure of electronic polarization and its strain dependence
The \phi(\kpp)\sim \kpp relation is called polarization structure. By
density functional calculations, we study the polarization structure in
ferroelectric perovskite PbTiO, revealing (1) the \kpp point that
contributes most to the electronic polarization, (2) the magnitude of
bandwidth, and (3) subtle curvature of polarization dispersion. We also
investigate how polarization structure in PbTiO is modified by compressive
inplane strains. The bandwidth of polarization dispersion in PbTiO is shown
to exhibit an unusual decline, though the total polarization is enhanced. As
another outcome of this study, we formulate an analytical scheme for the
purpose of identifying what determine the polarization structure at arbitrary
\kpp points by means of Wannier functions. We find that \phi(\kpp) is
determined by two competing factors: one is the overlaps between neighboring
Wannier functions within the plane {\it perpendicular} to the polarization
direction, and the other is the localization length {\it parallel} to the
polarization direction. Inplane strain increases the former while decreases the
latter, causing interesting non-monotonous effects on polarization structure.
Finally, polarization dispersion in another paradigm ferroelectric BaTiO is
discussed and compared with that of PbTiO.Comment: 5 Figure
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