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Search Results: 1 - 10 of 297442 matches for " J. Arvieux "
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Recent results from the G0 experiment
Real J.S.,Androi? D.,Armstrong D.S.,Arvieux J.
EPJ Web of Conferences , 2010, DOI: 10.1051/epjconf/20100303004
Abstract: We have measured parity violating asymmetries in elastic electron-proton and quasi-elastic electrondeuteron scattering at backward electron angle. These measurements have been done at two momentum transfers : Q2 = 0.22 and 0.63 (GeV/c)2 . Together with our previous forward angle measurement [1], we can extract strange quark contributions to the electromagnetic form factors of the nucleon, as well as nucleon axial form factor coming from the neutral weak interaction. The results indicate a strange quark magnetic contribution close to zero at these Q2 , and a possible non zero strange quark electric contribution for the high Q2 . The rst Q2 behavior measurement of the nucleon axial form factor in elastic electron scattering shows a good agreement with radiative corrections calculated at Q2 = 0 and with a dipole form using the axial mass determined in neutrino scattering.
C. Letoublon,Catherine Arvieux
Jurnalul de Chirurgie , 2005,
Abstract: The prognostic of the liver trauma is conditioned by the type of the hepatic injuries. Their anatomic and hemorhagic characteristics will influence the kind of treatment: emergency laparotomy or non-surgical treatment. The most important condition for a non-surgical treatment of the liver trauma is a stable patient. Operative option is indicated for unstable patients, when there are other visceral injuries or when the surgical unit hasn't accurate imagistics posssibilities. For optimal operative management of the liver trauma, some principles need to be followed: 1) the patient is positioned with the arms at right angles on arm boards, wich allowes better access to intravenous or intraarterial lines; 2) skin preparation is for a toarco-abdominal approach; 3) the primary incision is a midline one wich can be branched with a right transverse. After laparotomy there are two situations: liver injuries without or with active haemorrhage. For the first situation, evacuation of the hemoperitoneum, lavage and drainge are the only procedures indicated. For the second types of injuries we also describe favorable and unfavorable injuries. When the hand compression of the liver is effective and hepatic injury is anterior, the hemostasis after clampage of the hepatic pedicle (Pringle maneuver) is indicated. Perihepatic packing is indicated in case of choagulopaty. Hepatic resection it isn't recommended. The unfavorable situation is association of acidose-hypotermia and choagulopaty wich cause a "biological hemorrhage". In this cases are indicated"abbreviated laparotomy" with perihepatic packing (damage control) and planned reoperation or arterial embolisation (interventional radiology). When the clampage of the hepatic pedicle it isn't efficient, probably a hepatic vein is injured and a a perihepatic packing is also indicated. The unefficiency of the perihepatic packing, the clampage of the hepatic pedicle + inferior vena cava (under and above the liver) ± aorta it is necessary to stop the active bleeding. The closure of the laparotomy it is necessary to be made very fast, especially for the "abbreviated laparotomy". In the case of trauma of the main hepatic duct an external billiary drainage it is recommended. The reoperation it is indicated in some cases: intraabdominal hyperpression syndrome, perihepatic packing, other intraabdominal complications. Conclusion: The prognostic of the liver trauma depends by the anatomical type of the injuries. Operative management of the liver trauma is very difficult. The clampage of the hepatic pedicle (with or without vena cava
C. Letoublon,Catherine Arvieux
Jurnalul de Chirurgie , 2005,
Abstract: The most important condition for a conservative treatment of the liver trauma is a stable patient. Ultrasound and computerized tomography (CT) examinations are essential for the investigation of abdominal trauma. These explorations allow visualization of solid organ anatomy and have the ability to grade and quantify the livers' injuries (Mirvis classification). After the first exploration and the decision for initial non-operative approach, the patients will be followed in the intensive care unit (hemodynamic status, biological exploration, CT or ultrasonography). In this second survey period it is possible to appear complications (hemorrhage, peritonitis, intra-abdominal hyper-pressure syndrome etc.) and emergency laparotomy can be necessary. The overall mortality for non operative approach is about 9%, and direct mortality is under 1%. Secondary operations are necessary in 7-10% from these patients. Interventional radiology techniques and endoscopic procedures (such as endoscopic retrograde cholangio-pancreatography) allowed the reduction of the secondary surgical interventions. Hospital stay depends by the grade of the liver injury. Long term follow-up it is necessary; some cystic image can appear in the liver parenchyma at CT exam after months or years from the trauma, but without clinical significance.
C. Letoublon,Catherine Arvieux
Jurnalul de Chirurgie , 2005,
Abstract: The liver is the largest solid abdominal organ with a relatively fixed position, which makes it prone to injury. The liver is the second most commonly injured organ in abdominal trauma, but damage to the liver is the most common cause of death after abdominal injury. The most common cause of liver injury is blunt abdominal trauma, which is secondary to motor vehicle accidents in most instances. In the past, most of these injuries were treated surgically. However, surgical literature confirms that many of liver injuries have stopped bleeding by the time surgical exploration is performed, and some operations performed for blunt abdominal trauma are nontherapeutic. Imaging techniques and non-operative management, have made a great impact on the treatment of patients with liver trauma, and use of these techniques has resulted in marked reduction in the number of patients requiring surgery and nontherapeutic operations
C. Létoublon,Catherine Arvieux
Jurnalul de Chirurgie , 2005,
Electroproduction of pseudoscalar mesons on the deuteron
Michail P. Rekalo,Egle Tomasi-Gustafsson,Jacques Arvieux
Physics , 2000,
Abstract: A general analysis of polarization phenomena for coherent meson electroproduction on deuterons, $e+ d\to e+ d +P^0$, where $P^0$ is a pseudoscalar $\pi ^0$ or $\eta$-meson, is presented. The spin structure of the electromagnetic current for $P^0$-production at threshold is parametrized in terms of specific (inelastic) threshold electromagnetic form factors which depend on the momentum transfer squared and the effective mass of the produced hadronic system. We give expressions for the structure functions of the reaction $e+\vec{d}\to e +d+ P^0$ (where the deuteron target is polarized) in terms of these threshold form factors. The spin and isospin structures of the $\gamma ^{*}+d\to d+P^0$ amplitudes (where $\gamma ^*$ is a virtual photon) is established in the framework of the impulse approximation and relationships between meson electroproduction on deuterons and on nucleons are given. The reaction of $\pi^0$ electroproduction on deuterons is investigated in detail both at threshold and in the region of $\Delta $-isobar excitation, using the effective Lagrangian approach for the calculation of the amplitudes of the elementary process $\gamma^*+N\to N+\pi$. Special attention is devoted to the analysis of all standard contributions to the exclusive cross section for $d(e,e\pi^0)d$, which are functions of the momentum transfer square, $k^2$, of the excitation energy of the produced hadrons and of the pion production angle, in a region of relatively large momentum transfer. The sensitivity of these contributions to different parametrizations of the $\gamma^*\pi\omega$ form factor as well as to the choice of $NN-$potential is discussed.
Neutral weak currents in pion electroproduction on the nucleon
Michail P. Rekalo,Jacques Arvieux,Egle Tomasi-Gustafsson
Physics , 2000, DOI: 10.1103/PhysRevC.65.035501
Abstract: Parity violating asymmetry in inclusive scattering of longitudinally polarized electrons by unpolarized protons with $\pi^0$ or $\pi^+$ meson production, is calculated as a function of the momentum transfer squared $Q^2$ and the total energy $W$ of the $\pi N$-system. This asymmetry, which is induced by the interference of the one-photon exchange amplitude with the parity-odd part of the $Z^0$-exchange amplitude, is calculated for the $\gamma^*(Z^*)+p\to N+\pi$ processes ($\gamma^*$ is a virtual photon and $Z^*$ a virtual Z-boson) considering the $\Delta$-contribution in the $s-$channel, the standard Born contributions and vector meson ($\rho$ and $\omega$) exchanges in the $t-$channel. Taking into account the known isotopic properties of the hadron electromagnetic and neutral currents, we show that the P-odd term is the sum of two contributions. The main term is model independent and it can be calculated exactly in terms of fundamental constants. It is found to be linear in $Q^2$. The second term is a relatively small correction which is determined by the isoscalar component of the electromagnetic current. Near threshold and in the $\Delta$-region, this isoscalar part is much smaller (in absolute value) than the isovector one: its contribution to the asymmetry depend on the polarization state (longitudinal or transverse) of the virtual photon.
G$^0$ Electronics and Data Acquisition (Forward-Angle Measurements)
D. Marchand,J. Arvieux,L. Bimbot,A. Biselli,J. Bouvier,H. Breuer,R. Clark,J. -C. Cuzon,M. Engrand,R. Foglio,C. Furget,X. Grave,B. Guillon,H. Guler,P. M. King,S. Kox,J. Kuhn,Y. Ky,J. Lachniet,J. Lenoble,E. Liatard,J. Liu,E. Munoz,J. Pouxe,G. Quéméner,B. Quinn,J. -S. Réal,O. Rossetto,R. Sellem
Physics , 2007, DOI: 10.1016/j.nima.2007.11.028
Abstract: The G$^0$ parity-violation experiment at Jefferson Lab (Newport News, VA) is designed to determine the contribution of strange/anti-strange quark pairs to the intrinsic properties of the proton. In the forward-angle part of the experiment, the asymmetry in the cross section was measured for $\vec{e}p$ elastic scattering by counting the recoil protons corresponding to the two beam-helicity states. Due to the high accuracy required on the asymmetry, the G$^0$ experiment was based on a custom experimental setup with its own associated electronics and data acquisition (DAQ) system. Highly specialized time-encoding electronics provided time-of-flight spectra for each detector for each helicity state. More conventional electronics was used for monitoring (mainly FastBus). The time-encoding electronics and the DAQ system have been designed to handle events at a mean rate of 2 MHz per detector with low deadtime and to minimize helicity-correlated systematic errors. In this paper, we outline the general architecture and the main features of the electronics and the DAQ system dedicated to G$^0$ forward-angle measurements.
Measurement of the Transverse Beam Spin Asymmetry in Elastic Electron Proton Scattering and the Inelastic Contribution to the Imaginary Part of the Two-Photon Exchange Amplitude
F. E. Maas,K. Aulenbacher,S. Baunack,L. Capozza,J. Diefenbach,B. Gl?ser,Y. Imai,T. Hammel,D. von Harrach,E. -M. Kabub,R. Kothe,J. H. Lee,A. Sanchez-Lorente,E. Schilling,D. Schwaab,G. Stephan,G. Weber,C. Weinrich,I. Altarev,J. Arvieux,M. Elyakoubi,R. Frascaria,R. Kunne,M. Morlet,S. Ong,J. Vandewiele,S. Kowalski,R. Suleiman,S. Taylor
Physics , 2004, DOI: 10.1103/PhysRevLett.94.082001
Abstract: We report on a measurement of the asymmetry in the scattering of transversely polarized electrons off unpolarized protons, A$_\perp$, at two Q$^2$ values of \qsquaredaveragedlow (GeV/c)$^2$ and \qsquaredaveragedhighII (GeV/c)$^2$ and a scattering angle of $30^\circ < \theta_e < 40^\circ$. The measured transverse asymmetries are A$_{\perp}$(Q$^2$ = \qsquaredaveragedlow (GeV/c)$^2$) = (\experimentalasymmetry alulowcorr $\pm$ \statisticalerrorlow$_{\rm stat}$ $\pm$ \combinedsyspolerrorlowalucor$_{\rm sys}$) $\times$ 10$^{-6}$ and A$_{\perp}$(Q$^2$ = \qsquaredaveragedhighII (GeV/c)$^2$) = (\experimentalasymme tryaluhighcorr $\pm$ \statisticalerrorhigh$_{\rm stat}$ $\pm$ \combinedsyspolerrorhighalucor$_{\rm sys}$) $\times$ 10$^{-6}$. The first errors denotes the statistical error and the second the systematic uncertainties. A$_\perp$ arises from the imaginary part of the two-photon exchange amplitude and is zero in the one-photon exchange approximation. From comparison with theoretical estimates of A$_\perp$ we conclude that $\pi$N-intermediate states give a substantial contribution to the imaginary part of the two-photon amplitude. The contribution from the ground state proton to the imaginary part of the two-photon exchange can be neglected. There is no obvious reason why this should be different for the real part of the two-photon amplitude, which enters into the radiative corrections for the Rosenbluth separation measurements of the electric form factor of the proton.
Measurement of Strange Quark Contributions to the Vector Form Factors of the Proton at Q**2=0.22 (GeV/c)**2
S. Baunack,K. Aulenbacher,D. Balaguer Ríos,L. Capozza,J. Diefenbach,B. Gl?ser,D. v. Harrach,Y. Imai,E. M. Kabu?,R. Kothe,J. H. Lee,H. Merkel,M. C. Mora Espí,U. Müller,E. Schilling,G. Stephan,C. Weinrich,J. Arvieux,M. A. El-Yakoubi,R. Kunne,F. E. Maas,M. Morlet,S. Ong,J. van de Wiele,S. Kowalski,Y. Prok,S. Taylor
Physics , 2009, DOI: 10.1103/PhysRevLett.102.151803
Abstract: A new measurement of the parity violating asymmetry in elastic electron scattering on hydrogen at backward angles and at a four momentum transfer of Q^2=0.22 (GeV/c)^2 is reported here. The measured asymmetry is A_LR=(-17.23 +- 0.82_stat +-0.89_syst) ppm. The Standard Model prediction assuming no strangeness is A_0=(-15.87 +- 1.22) ppm. In combination with previous results from measurements at forward angles, it it possible to disentangle for the first time the strange electric and magnetic form factors at this momentum transfer, G_E^s(0.22)=0.050 +- 0.038 +- 0.019 and G_M^s(0.22)=-0.14 +- 0.11 +- 0.11.
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