1,780 research outputs found
Baryonium, a common ground for atomic and high energy physics
Indications of the existence of quasi-bound states in the N-Nbar system are
presented. Measurements by BES discovered a broad enhancement close to the
p-pbar threshold in the S wave, isospin 0 state formed in radiative decays of
J/psi. Another enhancement located about 50 MeV below the threshold was found
in mesonic decays of J/psi. In terms of the Paris potential model it was shown
that these are likely to represent the same state. Antiprotonic atomic data
provide some support for this interpretation and indicate the existence of
another fairly narrow quasi-bound state in a P wave.Comment: 6 pages, 6 figures - Contribution to EXA2014 Vienna to appear in a
special edition of Hyperfine Interaction
K* resonance effects on direct CP violation in B -> pi pi K
Charged and neutral B decays into two charged pions and a charged or a
neutral kaon are analyzed within the QCD factorization scheme where final state
interactions before and after hadronization are included. The K*(892) and
K*(1430) resonance effects are taken into account using the presently known
pion-Kaon strange vector and scalar form factors. The weak decay amplitudes,
which are calculated at leading power in Lambda_QCD/m_b and at the
next-to-leading order in the strong coupling constant, include the hard
scattering and annihilation contributions. The end point divergences of these
weak final state interactions are controlled by two complex parameters
determined through a fit to the available effective mass and helicity angle
distribution, CP asymmetry and K*(892) branching ratio data. The predicted
K*(1430) branching ratios and the calculated direct CP violation asymmetries
are compared to the Belle and BABAR Collaboration data.Comment: Comments: 22 pages, 2 figures and 3 tables. In this new version, the
results are unchanged, but, the last paragraph of the Section "RESULTS AND
SUMMARY" (now called "RESULTS AND DISCUSSION") has been replaced by a new
Section "SUMMARY AND OUTLOOK". To appear in Physical Review
On the structure of the X(1835) baryonium
The measurement by the BES collaboration of J/psi -> gamma p pbar decays
indicates an enhancement at the p-pbar threshold. In another experiment BES
finds a peak in the invariant mass of pi-mesons produced in the possibly
related decay J/psi -> gamma pi+ pi- eta'. Using a semi-phenomenological
potential model which describes all the N-Nbar scattering data, we show that
the explanation of both effects may be given by a broad quasi-bound state in
the spin and isospin singlet S wave. The structure of the observed peak is due
to an interference of this quasi-bound state with a background amplitude and
depends on the annihilation mechanism.Comment: 7 pages, 7 figures, this version corresponds to the published paper
in Phys. Rev. C: minor corrections done and in section 5 suggestions of
experiments to confirm the link of the X(1835) to the antiproton-proton
syste
The Pion-Nucleon coupling constant from np charge exchange scattering
A novel extrapolation method has been used to deduce the charged Pion-Nucleon
coupling constant from backward differential scattering cross sections. We
applied it to new measurements performed at 162 MeV at the The Svedberg
Laboratory in Uppsala. In the angular range , the
carefully normalized data are steeper than those of most previous measurements.
The extracted value, , in good agreement with
the classical value, is higher than those determined in recent nucleon-nucleon
partial-wave analyses.Comment: 6 pages, 3 encapsulated figures, epsfig, menu97.cls (included
Pseudoscalar-scalar transition form factors in covariant light front dynamics
In an explicitly covariant light-front formalism, we analyze transition form
factors between pseudoscalar and scalar mesons. Application is performed in
case of the transition in the full available transfer momentum
range .Comment: 4 pages, 4 figures. Talk given at the XXXIII International Conference
on High Energy Physics, ICHEP06, Moscow, 26 July-02 Augus
Origin of the excitonic recombinations in hexagonal boron nitride by spatially resolved cathodoluminescence spectroscopy
The excitonic recombinations in hexagonal boron nitride (hBN) are
investigated with spatially resolved cathodoluminescence spectroscopy in the UV
range. Cathodoluminescence images of an individual hBN crystallite reveals that
the 215 nm free excitonic line is quite homogeneously emitted along the
crystallite whereas the 220 nm and 227 nm excitonic emissions are located in
specific regions of the crystallite. Transmission electron microscopy images
show that these regions contain a high density of crystalline defects. This
suggests that both the 220 nm and 227 nm emissions are produced by the
recombination of excitons bound to structural defects
The Effect of Particle Strength on the Ballistic Resistance of Shear Thickening Fluids
The response of shear thickening fluids (STFs) under ballistic impact has
received considerable attention due to its field-responsive nature. While
efforts have primarily focused on the response of traditional ballistic fabrics
impregnated with fluids, the response of pure STFs to penetration has received
limited attention. In the present study, the ballistic response of pure STFs is
investigated and the effect of fluid density and particle strength on ballistic
performance is isolated. The loss of ballistic resistance of STFs at higher
impact velocities is governed by particle strength, indicating the range of
velocities over which they may provide effective armor solutions.Comment: 4 pages, 4 figure
Form factors in B->f0(980) and D->f0(980) transitions from dispersion relations
Within the dispersion relation approach we give the double spectral
representation for space-like and time-like B-> f_0(980) and D-> f_0(980)
transition form factors in the full q^2 range. The spectral densities, being
the input of the dispersion relations, are obtained from a triangle diagram in
the relativistic quark model.Comment: Talk given at MESON 2006, Krakow, 9-13 June 200
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