784 research outputs found

### Atmospheric waves and their utilization in soaring flight

In soaring flight, ascending air currents are utilized and the interesting question is raised whether there are such currents which extend to any considerable distance and which can be utilized practically

### Proton-deuteron asymmetry in Drell-Yan processes and polarized light-antiquark distributions

We discuss the relation between the ratio of the proton-deuteron (pd)
Drell-Yan cross section to the proton-proton (pp) one \Delta_{(T)}
\sigma_{pd}/2 \Delta_{(T)} \sigma_{pp} and the flavor asymmetry in polarized
light-antiquark distributions. Using a recent formalism of the polarized pd
Drell-Yan process, we show that the difference between the pp and pd cross
sections is valuable for finding not only the flavor asymmetry in
longitudinally polarized antiquark distributions but also the one in
transversity distributions. It is especially important that we point out the
possibility of measuring the flavor asymmetry in the transversity distributions
because it cannot be found in W production processes and inclusive lepton
scattering due to the chiral-odd property.Comment: 10 pages, LATEX2e with epsfig.sty, 4 eps figures. Complete postscript
file including the figures is available at http://www-hs.phys.saga-u.ac.jp .
Email: [email protected], [email protected]

### Multi-quark components in baryons

A brief review on some recent progresses in our understanding of multi-quark
components in baryons is presented. The multi-quark components in baryons seem
to be mainly in colored quark cluster configurations rather than in ``meson
cloud'' configurations or in the form of a sea of quark-antiquark pairs. The
colored quark cluster multi-quark picture gives a natural explanation of
empirical indications for a positive strangeness magnetic moment $\mu_s$ of the
proton and the longstanding mass-reverse problem of S11(1535) and $P11(1440) N*
resonances. A model-prediction for the$\mu_s$ of the proton is given.Comment: Contribution to the International Conference on QCD and Hadronic
Physics, June 16-20, 2005, Beijin

### Ultraslow light propagation in an inhomogeneously broadened rare-earth ion-doped crystal

We show that Coherent Population Oscillations effect allows to burn a narrow
spectral hole (26Hz) within the homogeneous absorption line of the optical
transition of an Erbium ion-doped crystal. The large dispersion of the index of
refraction associated with this hole permits to achieve a group velocity as low
as 2.7m/s with a ransmission of 40%. We especially benefit from the
inhomogeneous absorption broadening of the ions to tune both the transmission
coefficient, from 40% to 90%, and the light group velocity from 2.7m/s to
100m/s

### \bar u - \bar d asymmetry - a few remarks

We make a few remarks on possible sources of uncertainties of the $\bar d -
\bar u$ asymmetry obtained by different methods and comment on its possible
verification in the future. In addition we comment on its present
understanding.Comment: 3 pages, a talk at the 7th International Workshop on Deep Inelastic
Scattering and QCD (DIS99), Zeuthen, April 199

### Proton Sea Quark Flavour Asymmetry and Roper Resonance

We study the proton and the Roper resonance together with the meson cloud
model, by constructing a Hamiltonian matrix and solving the eigenvalue
equation. The proton sea quark flavour asymmetry and some properties of the
Roper resonance are thus reproduced in one scheme

### Chiral constituent quark model and the coupling strength of eta'

Using the latest data pertaining to \bar u-\bar d asymmetry and the spin
polarization functions, detailed implications of the possible values of the
coupling strength of the singlet Goldstone boson \eta' have been investigated
in the \chiCQM with configuration mixing. Using \Delta u, \Delta_3, \bar u-\bar
d and \bar u/\bar d, the possible ranges of the coupling parameters a, \alpha^
2, \beta^ 2 and \zeta^ 2, representing respectively the probabilities of
fluctuations to pions, K, \eta and \eta^{'}, are shown to be 0.10 \lesssim a
\lesssim 0.14, 0.2\lesssim \alpha \lesssim 0.5, 0.2\lesssim \beta \lesssim 0.7
and 0.10 lesssim |\zeta| \lesssim 0.70. To constrain the coupling strength of
\eta', detailed fits have been obtained for spin polarization functions, quark
distribution functions and baryon octet magnetic moments corresponding to the
following sets of parameters: a=0.1, \alpha=0.4, \beta=0.7, |\zeta|=0.65 (Case
I); a=0.1, \alpha=0.4, \beta=0.6, |\zeta|=0.70 (Case II); a=0.14, \alpha=0.4,
\beta=0.2, \zeta=0 (Case III) and a=0.13, \alpha=\beta=0.45, |\zeta|=0.10 (Case
IV). Case I represents the calculations where a is fixed to be 0.1, in
accordance with earlier calculations, whereas other parameters are treated free
and the Case IV represents our best fit. The fits clearly establish that a
small non-zero value of the coupling of \eta' is preferred over the higher
values of \eta' as well as when \zeta=0, the latter implying the absence of
\eta' from the dynamics of \chiCQM. Our best fit achieves an overall excellent
fit to the data, in particular the fit for \Delta u, \Delta d, \Delta_8 as well
as the magnetic moments \mu_{n}, \mu_{\Sigma^-}, \mu_{\Sigma^+} and \mu_{\Xi^-}
is almost perfect, the \mu_{\Xi^-} being a difficult case for most of the
similar calculations.Comment: 8 RevTeX pages, 2 Tables, Revised version to appear in Int.J.Mod.Phys

### The role of five-quark components in gamma decay of the $\Delta(1232)$

An admixture of 10-20 % of qqqq\bar q components in the Delta(1232) resonance
is shown to reduce the well known underprediction for the decay width for
Delta(1232)->N gamma decay by about half and that of the corresponding helicity
amplitudes from a factor ~ 1.7 to ~ 1.5. The main effect is due to the
quark-antiquark annihilation transitions qqqq\bar q -> qqq gamma, the
consideration of which brings the ratio A_{3/2}/A_{1/2} and consequently the
E2/M1 ratio R_{EM} into agreement with the empirical value. Transitions between
qqqq\bar q components in the resonance and the nucleon qqqq\bar q->qqqq\bar q
gamma are shown to enhance the calculated width by only a few percent, as long
as the probability of the qqqq\bar q component of the Delta(1232) and the
proton is at most ~ 20 %. The transitions qqqq\bar q->qqqq\bar q gamma between
the qqqq\bar q components in the Delta(1232) and the proton do not lead to a
nonzero value for R_{EM}

### Omega Meson Cloud and the Proton's Light Anti-Quark Distribution

We use the meson cloud model of the nucleon to calculate distribution
functions for $(\bar {d} - \bar{u})$ and $\bar{d}/\bar{u}$ in the proton.
Including the effect of the omega meson cloud, with a coupling constant
$g_\omega^2/4\pi\approx 8$, allows a reasonably good description of the data.Comment: 6 pages, 2 figures, LaTe

### Follow-up of a panel restoration procedure through image correlation and finite element modeling

International audienceResidual stress estimation is an important question for structural integrity. Since residual stresses are self-balanced stress fields, a classical way to obtain information on them is to remove a part of the structure, and observe the structure displacement field arising from the stress redistribution. The hole- drilling method is such an approach. In some cases, as for the present one concerning a painted panel of cultural heritage, the hole-drilling method is not suited (a structure with a complex geometry, few tests allowed) but one can take advantage of structural modifications if they are monitored (here, a restoration act). We therefore describe in this article a model updating approach, focusing on the residual stress estimation and not on the material parameter identification. This study couples an optical non-invasive shape measurement (digital image correlation, using a projected speckle pattern on the painted panel, with luminance compensation) and a numerical approach (3D finite elements) for the model updating. The 3D stereo-correlation is used to measure a partial displacement field between three different states of the structure (at three different times of the restoration act). The numerical part concerns stress evaluation, once the model and the experiments are compared using a geometric mapping and a spatial projection of discrete fields. Using modeling and identification, the simulation is used to obtain the residual stresses in the panel, before and after the restoration

- â€¦