Center Of Mass Correction Research Articles

The GOP analysis center: DORIS contribution to ITRF2020

The Geodetic Observatory Pecný (GOP) analysis center of the International DORIS Service (IDS) has participated in the ITRF2020 IDS DORIS data reprocessing. This participation followed previous contributions for the ITRF2014 and ITRF2008. The processing standards have changed since the ITRF2014 realization, in particular by switching to data processing based on RINEX observation files, keeping compatibility with the recent operational version of the IERS2010 conventions and with the IDS recommendations. The orbit parametrization and various models have been updated to reach the recent highest standards. The analysis strategy is completely independent of the auxiliary information from the data provider such as quality indicators and center of mass corrections. Several testing campaigns have been performed to optimize the strategy. Jason-1 data have been completely excluded, while SPOT-5 data have fully contributed. A specific strategy for handling the South Atlantic Anomaly was applied for the satellites SPOT-5 and Jason-3.When compared to the GOP solution for ITRF2014, changes in modeling and processing strategy resulted in several significant improvements in the solution statistics and the series of estimated parameters as the stability of the scale and the scattering of the translation series. The analysis of the WRMS of the station position residuals confirmed improvements in particular between mid-2002 and mid-2008 (reduction by more than 1 mm) and after mid-2008 (reduction by about 3 mm). The decrease of the standard deviations in the estimated pole coordinate series reaches 40 percent after adding of Jason-2 in mid-2008.

Electromagnetic Form Factors for 7,9,11Be Isotopes with Exact Center of Mass Correction

The shell model calculations with Cohen-Kurath (C-K) interaction were carried out to investigate form factors of elastic transverse electron scattering, and magnetic dipole-moments of odd 7,9,11Be isotopes. The effect of the exact value of center of mass correction was adopted to generate the magnetic form factors in Born approximation picture. The contribution of the higher 2p-shell configuration was included to reproduce the experimental data. A significant improvement was obtained in the present results with core-polarization (CP) effect through the effective g-factors. The occupancies percentage with respect to the valence nucleons was also calculated.

Study of the Exotic Structure of Neutron-Rich 14B and 17C Nuclei Using the Binary Cluster Model

The neutron, proton, and matter densities of the ground state of the 14B and 17C exotic nuclei are analyzed using the binary cluster model (BCM). Two density parameterizations are used in BCM calculations namely; Gaussian (GS) and harmonic oscillator (HO) parameterizations. According to the calculated results it found that, the BCM gives a good description of the nuclear structure for above neutron-rich exotic nuclei. The elastic form factors of theunstable 14B and 17C exotic nuclei and those of their stable isotopes 10B and 13C are determined using the plane-wave Born approximation. The main difference between the elastic form factors of unstable nuclei and their stable isotopes is due to the difference in the center of mass correction. Moreover, the Glauber model is used to calculate the matter rms radii and reaction cross section of these exotic nuclei. The calculate results of the mentioned nuclei give a good accordance with the experimental data.

Evaluation of CyberKnife® Fiducial Tracking Limitations to Assist Targeting Accuracy: A Phantom Study with Fiducial Displacement.

Introduction The underlying assumptions of the CyberKnife® (Accuray, Sunnyvale, CA, US) fiducial tracking system are: i) fiducial positions are accurately detected; ii) inter-fiducial geometry remains consistent (rigid); iii) inter-fiducial geometric array changes are detected and either accommodated with corrections or treatment is interrupted. However: i) soft-tissue targets are deformable & fiducial migration is possible; ii) the accuracy of the tracking system has not previously been examined with fiducial displacement; iii) treatment interruptions may occur due to inter-fiducial geometric changes, but there is little information available to assist subsequent troubleshooting. The purpose of this study was to emulate a clinical target defined with a two, three, or four-fiducial array where one fiducial is displaced to mimic a target deformation or fiducial migration scenario. The objectives: evaluate the fiducial positioning accuracy, array interpretation, & corresponding corrections of the CyberKnife system, with the aim of assisting troubleshooting following fiducial displacement.MethodsA novel solid-water phantom was constructed with three fixed fiducials (F1,F2,F3) & one moveable fiducial (F4), arranged as if placed to track an imaginary clinical target. Using either two fiducials (F1,F4), different combinations of three fiducials (F1,F2,F4; F1,F3,F4; F2,F3,F4) or four fiducials (F1,F2,F3,F4), repeat experiments were conducted where F4 was displaced inferiorly at 2-mm intervals from 0-16 mm. Data were acquired at each position of F4, including rigid body errors (RBE), fiducial x, y, & z coordinate displacements, six degrees of freedom (DOF) corrections, & robot center-of-mass (COM) translation corrections.ResultsMaximum positioning difference (mean±SD) between the reference and live x, y, & z coordinates for the three fixed fiducials was 0.08±0.30 mm, confirming good accuracy for fixed fiducial registration. For two fiducials (F1,F4), F4 registration was accurate to 14-mm displacement and the F4 x-axis coordinate change was 2.0±0.12 mm with each 2 mm inferior displacement validating the phantom for tracking evaluation. RBE was >5 mm (system threshold) at 6-14 mm F4 displacement: however, F1 was misidentified as the RBE main contributor. Further, F1/F4 false-lock occurred at 16 mm F4 displacement with corresponding RBE <3 mm & COM corrections >13 mm. For combinations of three fiducials, F4 registration was accurate to 10-mm displacement. RBE was >5 mm at 6-16 mm F4 displacement: however, F4 false-lock occurred at 12-16 mm with RBE 5-6 mm. For four fiducials, F4 registration was accurate to 4 mm displacement: however, F4 false-lock occurred at 6-16 mm displacement with concerning RBE <2 & <5 at 6 & 8-mm F4 displacement, respectively. False-locks were easily identified in the phantom but frequently uncorrectable.ConclusionsResults indicate fiducial positioning accuracy and system output following fiducial displacement depends on the number of fiducials correlated, displacement distance, and clinical thresholds applied. Displacements ≤4 mm were accurately located, but some displacements 6-16 mm were misrepresented, either by erroneous main contributor (two-fiducial array only) or by false-locks and misleading RBE, which underestimated displacement. Operator vigilance and implementation of our practical guidelines based on the study findings may help reduce targeting error and assist troubleshooting in clinical situations.

Ground-State Properties of C, O, and Ne Isotopes in Hartree-Fock-Bogoliubov Calculation with Gogny Interaction**The project supported by the Japanese Society for the Promotion of Science (JSPS) and National Natural Science Foundation of China (NSF) as the bilateral program between Japan and China, National Natural Science Foundation of China under Grant No. 10047001, the China Key Basic Research Development Program under

Ground-state properties of C, O, and Ne isotopes are described in the framework of Hartree–Fock–Bogoliubov theory with density-dependent finite-range Gogny interaction D1S. We include all the contributions to the Hartree–Fock and pairing field arising from Gogny and Coulomb interaction as well as the center of mass correction in the numerical calculations. These ground-state properties of C, O, and Ne isotopes are compared with available experimental results, Hartree–Fock plus BCS, shell model and relativistic Hartree–Bogoliubov calculations. The agreement between experiments and our theoretical results is pretty well. The predicted drip-line is dependent strongly on the model and effective interaction due to their sensitivity to various theoretical details. The calculations predict no evidence for halo structure predicted for C, O, and Ne isotopes in a previous RHB study.

Glauber model and the heavy ion reaction cross section

We reexamine the Glauber model and calculate the total reaction cross section as a function of energy in the low and intermediate energy range, where many of the corrections in the model are effective. The most significant effect in this energy range is by the modification of the trajectory due to the Coulomb field. The modification in the trajectory due to nuclear field is also taken into account in a self-consistent way. The energy ranges in which particular corrections are effective are quantified, and it is found that when the center of mass energy of the system becomes 30 times the Coulomb barrier, none of the trajectory modification to the Glauber model is really required. The reaction cross sections for light and heavy systems, from the Coulomb barrier to intermediate energies, have been calculated. The exact nuclear densities and free nucleon-nucleon (NN) cross sections have been used in the calculations. The center of mass correction, which is important for light systems, has also been taken into account. There is an excellent agreement between the calculations with the modified Glauber model and the experimental data. This suggests that the heavy ion reactions in this energy range can be explained by the Glauber model in terms of free NN cross sections without incorporating any medium modification.

Meson Cloud Effect on Δ(1232) Resonance Transition Properties with a Relativistic Quark Model Approach**The project supported by National Natural Science Foundations of China under Grant No. 10075056, Foundations of the Chinese Academy of Sciences (X-37), the Chinese Ministry of Education (B-22), and Institute of Theoretical Physics. Thanks also to the Knowledge Innovation Project of the Chinese Academy of Sciences (No.

Based on a relativistic quark model approach, the transition properties of the first nucleon resonance Δ(1232), and the coupling constants are investigated. Two different ways to remove the center of mass motion are considered. The results of the relativistic approaches with and without center of mass correction are compared with those of nonrelativistic constituent quark model. Moreover, pion meson cloud effect on these calculated observables is explicitly addressed. Better results are obtained by taking the pion meson cloud into account.

Nucleon Spin Content in a Relativistic Quark Potential Model Approach**The project supported by National Natural Science Foundation of China under Grant No. 10075056, and by Foundations of the Chinese Academy of Sciences (X-37), the Chinese Ministry of Education (B-22) and Institute of Theoretical Physics, the Chinese Academy of Sciences

Based on a relativistic quark model approach with an effective potential , the spin content of the nucleon is investigated. Pseudo-scalar interaction between quarks and Goldstone bosons is employed to calculate the couplings between the Goldstone bosons and the nucleon. Different approaches to deal with the center of mass correction in the relativistic quark potential model approach are discussed.

Normal Point Algorithm For Reduction Of Two Colour Slr Observations

Two colour laser ranging to artificial satellites is an attractivetechnique, which is capable to provide refraction corrected ranges without the need of an atmospheric model by measuring the dispersive delay of laser pulses of different wavelength. Although the required accuracy of the detection scheme is stringent, the technique has matured so far, that routine two colour observationsbecame feasible.The present paper describes a normal point procedure reducing two colour laser range observations with respect to the dispersive delay,exploiting the knowledge of satellite response signatures in conjunction with detector characteristics and the appropriate center of mass correction models.Moreover the dispersion model of the atmosphere is briefly reviewed, paying attention to the wavelength domains provided by modern twocolour ranging lasers, e.g., the Ti:SAP laser.Preliminary data is presented and compared to both, normal point data reduced with a standard procedure and zenith path equivalent meteorological parameters.

Procedure for calculating the structure of hypernuclei

A simple procedure is described for determining the structure of hypernuclei. This procedure allows for complete flexibility in the hyperon wave function, while eliminating spurious center of mass components. The method is applied to $_{\ensuremath{\Lambda}}^{6}\mathrm{Li}$, $_{\ensuremath{\Lambda}}^{7}\mathrm{L}$, and $_{\ensuremath{\Lambda}}^{16}\mathrm{O}$. Center of mass corrections are large for the $_{\ensuremath{\Lambda}}^{6}\mathrm{Li}$ and $_{\ensuremath{\Lambda}}^{7}\mathrm{Li}$ $p$ states and still substantial for $_{\ensuremath{\Lambda}}^{16}\mathrm{O}$. Spectra and selected transition and formation rates are calculated. Comparison is made with the recently measured ${\frac{5}{2}}^{+}\ensuremath{\rightarrow}{\frac{1}{2}}^{+}$ gamma-ray energy in $_{\ensuremath{\Lambda}}^{7}\mathrm{Li}$. Large changes are seen in the ${l}_{\ensuremath{\Lambda}}=1$ wave functions between $_{\ensuremath{\Lambda}}^{6}\mathrm{Li}$ and $_{\ensuremath{\Lambda}}^{16}\mathrm{O}$. The ${l}_{\ensuremath{\Lambda}}=1$ levels inferred from (${\mathrm{K}}^{\ensuremath{-}}$,${\ensuremath{\pi}}^{\ensuremath{-}}$) are well reproduced. The ground state $_{\ensuremath{\Lambda}}^{16}\mathrm{O}$ is overbound, suggesting that a two-body $\ensuremath{\Lambda}\mathrm{N}$ interaction must be modified in the nuclear interior.

Investigation of microscopic form factors for the (p, α) reaction

Microscopic form factors for the three-nucleon transfer (p, α) reaction are described, with special emphasis on their comparison with conventional cluster form factors. Considerable differences in shape of these form factors is found, especially in the surface region. An extension of the earlier zero-range descriptions of the microscopic form factor to include finite-range effects, is formulated and tested. Center of mass corrections, the α-particle size parameter, and non-local corrections in the single-particle states, all have a strong influence on the shape of the microscopic form factor. The implications of these observations for the extraction of nuclear structure information is discussed, especially as this affects the commonly used procedure of replacing the microscopic form factor with a cluster form factor, in the actual DWBA calculation.

Isobars and the medium-energy (γ,p) reaction

Recently, precise experimental measurements have been obtained for the reaction $^{16}\mathrm{O}$($\ensuremath{\gamma}$,$p$)$^{15}\mathrm{N}$ for photon energies 50-350 MeV. For photon energies greater than 100 MeV, isobar photoproduction is expected to provide an important part of the ($\ensuremath{\gamma}$,${p}_{0}$) reaction. We evaluate the isobar contribution to the ($\ensuremath{\gamma}$,$p$) reaction, and we add this amplitude to a term which corresponds to direct knockout of the proton by the photon. We compare our results in detail with the experimental data from Glasgow and Bates on $^{16}\mathrm{O}$. Our calculation uses coupling constants and nuclear wave functions determined from independent experiments, and we neglect the isobar-nucleus interaction. Agreement with the experimental data is quite reasonable, and isobar photoproduction provides a very large contribution to the nuclear photoeffect in $^{16}\mathrm{O}$, for photon energies above about 100 MeV. We consider the effects of various corrections to our formalism, such as the effect of distortion of the outgoing nucleon by the nuclear force, center of mass corrections, and the inclusion of $\ensuremath{\rho}$ mesons in addition to pions at the isobar decay vertex. None of these corrections alters the qualitative features of the isobar amplitude and its importance in the nuclear photoeffect at medium energies.NUCLEAR REACTIONS, photonuclear reactions, nuclear photoeffect, medium energies, isobars, isobar current, ($\ensuremath{\gamma}$,$p$) reactions.

Elastic electron scattering with short range correlations in 4He and 16O

The form factors of 4He and 16O have been calculated in the oscillator model including short range correlations and corrections due to the non-self consistency of the single particle model. Various nucleon-nucleon potentials have been used. With realistic potentials and the center of mass correction it is not possible to fit the experimental data.

Dispersion corrections in electron scattering

The lowest order dispersion correction is calculated using the harmonic oscillator model of the nucleus. Large contributions are found from highly excited nuclear states. The results depend strongly on the nuclear excitation energy and center of mass corrections.