72 research outputs found
Multipole Amplitudes of Pion Photoproduction on Nucleons up to 2GeV within Dispersion Relations and Unitary Isobar Model
Two approaches for analysis of pion photo- and electroproduction on nucleons
in the resonance energy region are checked at using the results of
GWU(VPI) partial-wave analysis of photoproduction data. The approaches are
based on dispersion relations and unitary isobar model. Within dispersion
relations good description of photoproduction multipoles is obtained up to
. Within unitary isobar model, modified with increasing energy by
incorporation of Regge poles, and with unified Breit-Wigner parametrization of
resonance contributions, good description of photoproduction multipoles is
obtained up to .Comment: 23 pages, LaTe
A dispersion theoretical approach to the threshold amplitudes of pion photoproduction
We give predictions for the partial wave amplitudes of pion photoproduction
near threshold by means of dispersion relations at fixed t. The free parameters
of this approach are determined by a fit to experimental data in the energy
range 160 MeV 420 MeV. The observables near threshold are
found to be rather sensitive to the amplitudes in the resonance region, in
particular to the (1232) and (1440). We obtain a good agreement
with the existing threshold data for both charged and neutral pion production.
Our predictions also agree well with the results of chiral perturbation theory,
except for neutral pion production off the neutron.Comment: 16 pages LATEX including 4 postscript figure
The position and the residues of the delta resonance pole in pion photoproduction
We have analyzed the and multipole
amplitudes of pion photoproduction in the framework of fixed- dispersion
relations. Applying the speed plot technique to our results for these
multipoles, we have determined the position and the residues of the
(1232) resonance pole. The pole is found at total energy MeV on the second Riemann sheet, and the ratio of the electric and
magnetic residues is , resulting in an E2/M1
ratio for the "dressed" delta resonance of .Comment: 16 pages LATEX including 5 postscript figures in a self-extracting
uufile archiv
A unitary isobar model for pion photo- and electroproduction on the proton up to 1 GeV
A new operator for pion photo- and electroproduction has been developed for
nuclear applications at photon equivalent energies up to 1 GeV. The model
contains Born terms, vector mesons and nucleon resonances (,
, , , , and
). The resonance contributions are included taking into account
unitarity to provide the correct phases of the pion photoproduction multipoles.
The dependence of electromagnetic resonance vertices is described with
appropriate form factors in the electromagnetic helicity amplitudes. Within
this model we have obtained good agreement with the experimental data for pion
photo- and electroproduction on the nucleon for both differential cross
sections and polarization observables. The model can be used as a starting
point to predict and analyze forthcoming data.Comment: 32 pages LaTeX including 23 postscript figures (a few misprints have
been corrected
The P_33(1232) resonance contribution into the amplitudes M_{1+}^{3/2},E_{1+}^{3/2},S_{1+}^{3/2} from an analysis of the p(e,e'p)\pi^0 data at Q^2 = 2.8, 3.2, and 4 (GeV/c)^2 within dispersion relation approach
Within the fixed-t dispersion relation approach we have analysed the TJNAF
and DESY data on the exclusive p(e,e'p)\pi^0 reaction in order to find the
P_{33}(1232) resonance contribution into the multipole amplitudes
M_{1+}^{3/2},E_{1+}^{3/2},S_{1+}^{3/2}. As an input for the resonance and
nonresonance contributions into these amplitudes the earlier obtained solutions
of the integral equations which follow from dispersion relations are used. The
obtained values of the ratio E2/M1 for the \gamma^* N \to P_{33}(1232)
transition are: 0.039\pm 0.029, 0.121\pm 0.032, 0.04\pm 0.031 for Q^2= 2.8,
3.2, and 4 (GeV/c)^2, respectively. The comparison with the data at low Q^2
shows that there is no evidence for the presence of the visible pQCD
contribution into the transition \gamma N \to P_{33}(1232) at Q^2=3-4 GeV^2.
The ratio S_{1+}^{3/2}/M_{1+}^{3/2} for the resonance parts of multipoles is:
-0.049\pm 0.029, -0.099\pm 0.041, -0.085\pm 0.021 for Q^2= 2.8, 3.2, and 4
(GeV/c)^2, respectively. Our results for the transverse form factor G_T(Q^2) of
the \gamma^* N \to P_{33}(1232) transition are lower than the values obtained
from the inclusive data. With increasing Q^2, Q^4G_T(Q^2) decreases, so there
is no evidence for the presence of the pQCD contribution here too
Multipole analysis of pion photoproduction based on fixed t dispersion relations and unitarity
We have analysed pion photoproduction imposing constraints from fixed t
dispersion relations and unitarity. Coupled integral equations for the S and P
wave multipoles were derived from the dispersion relations and solved by the
method of Omnes and Muskhelishvili. The free parameters were determined by a
fit to the most recent data for \pi^{+} and \pi^{0} production on the proton as
well as \pi^{-} production on the neutron, in the energy We have analysed pion
photoproduction imposing constraints from fixed t dispersion relations and
unitarity. Coupled integral equations for the S and P wave multipoles were
derived from the dispersion relations and solved by the method of Omnes and
Muskhelishvili. The free parameters were determined by a fit to the most recent
data for \pi^{+} and \pi^{0} production on the proton as well as \pi^{-}
production on the neutron, in the energy range 160 MeV \leq E_{\gamma} \leq 420
MeV. The lack of high precision data on the neutron and of polarization
observables leads to some limitations of our results. Especially the multipole
M_{1-} connected with the Roper resonance P_{11}(1440) cannot be determined to
the required precision. Our predictions for the threshold amplitudes are in
good agreement with both the data and chiral perturbation theory. In the region
of the \Delta(1232) we have determined the ratio of electric quadrupole and
magnetic dipole excitation. The position of the resonance pole is obtained in
excellent agreement with pion-nucleon scattering, and the complex residues of
the multipoles are determined with the speed-plot technique.Comment: 46 pages LATEX including 29 postscript figure
Awareness of health effects of cooking smoke among women in the Gondar Region of Ethiopia: a pilot survey
This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens
Effective Lagrangian Approach to the Theory of Eta Photoproduction in the Region
We investigate eta photoproduction in the resonance region
within the effective Lagrangian approach (ELA), wherein leading contributions
to the amplitude at the tree level are taken into account. These include the
nucleon Born terms and the leading -channel vector meson exchanges as the
non-resonant pieces. In addition, we consider five resonance contributions in
the - and - channel; besides the dominant , these are:
and . The amplitudes for the
and the photoproduction near threshold have significant
differences, even as they share common contributions, such as those of the
nucleon Born terms. Among these differences, the contribution to the
photoproduction of the -channel excitation of the is the most
significant. We find the off-shell properties of the spin-3/2 resonances to be
important in determining the background contributions. Fitting our effective
amplitude to the available data base allows us to extract the quantity
, characteristic of the
photoexcitation of the resonance and its decay into the
-nucleon channel, of interest to precise tests of hadron models. At the
photon point, we determine it to be from
the old data base, and from a
combination of old data base and new Bates data. We obtain the helicity
amplitude for to be from the old data base, and from the combination of the old data base and new Bates
data, compared with the results of the analysis of pion photoproduction
yielding , in the same units.Comment: 43 pages, RevTeX, 9 figures available upon request, to appear in
Phys. Rev.
Indoor air quality in a restaurant kitchen using margarine for deep-frying
Indoor air quality has a great impact on human health. Cooking, in particular frying, is one of the most important sources of indoor air pollution. Indoor air CO, CO2, particulate matter (PM), and volatile organic compound (VOC) concentrations, including aldehydes, were measured in the kitchen of a small establishment where a special deep-frying margarine was used. The objective was to assess occupational exposure concentrations for cooks of such restaurants. While individual VOC and PM2.5 concentrations were measured before, during, and after frying events using active sampling, TVOC, PM10, CO, CO2, temperature, and relative humidity were continuously monitored through the whole period. VOC and aldehyde concentrations did not increase to considerable levels with deep-frying compared to the background and public indoor environment levels, whereas PM10 increased significantly (1.85 to 6.6 folds). The average PM2.5 concentration of the whole period ranged between 76 and 249 μg/m3. Hence, considerable PM exposures could occur during deep-frying with the special margarine, which might be sufficiently high to cause health effects on cooks considering their chronic occupational exposures.Dokuz Eylul University (BAP-2011.KB.SAG.017
Brain iron accumulation in unexplained fetal and infant death victims with smoker mothers-The possible involvement of maternal methemoglobinemia
<p>Abstract</p> <p>Background</p> <p>Iron is involved in important vital functions as an essential component of the oxygen-transporting heme mechanism. In this study we aimed to evaluate whether oxidative metabolites from maternal cigarette smoke could affect iron homeostasis in the brain of victims of sudden unexplained fetal and infant death, maybe through the induction of maternal hemoglobin damage, such as in case of methemoglobinemia.</p> <p>Methods</p> <p>Histochemical investigations by Prussian blue reaction were made on brain nonheme ferric iron deposits, gaining detailed data on their localization in the brainstem and cerebellum of victims of sudden death and controls. The Gless and Marsland's modification of Bielschowsky's was used to identify neuronal cell bodies and neurofilaments.</p> <p>Results</p> <p>Our approach highlighted accumulations of blue granulations, indicative of iron positive reactions, in the brainstem and cerebellum of 33% of victims of sudden death and in none of the control group. The modified Bielschowsky's method confirmed that the cells with iron accumulations were neuronal cells.</p> <p>Conclusions</p> <p>We propose that the free iron deposition in the brain of sudden fetal and infant death victims could be a catabolic product of maternal methemoglobinemia, a biomarker of oxidative stress likely due to nicotine absorption.</p
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