Search results for "electrodynamics"
showing 10 items of 820 documents
Cranked Relativistic Hartree-Bogoliubov Theory: Formalism and Application to the Superdeformed Bands in the $A\sim 190$ region
2000
Cranked Relativistic Hartree-Bogoliubov theory without and with approximate particle number projection by means of the Lipkin-Nogami method is presented in detail as an extension of Relativistic Mean Field theory with pairing correlations to the rotating frame. Pairing correlations are taken into account by a finite range two-body force of Gogny type. The applicability of this theory to the description of rotating nuclei is studied in detail on the example of superdeformed bands in even-even nuclei of the $A\sim 190$ mass region. Different aspects such as the importance of pairing and particle number projection, the dependence of the results on the parametrization of the RMF Lagrangian and …
Moments of inertia of nuclei in the rare earth region: A relativistic versus nonrelativistic investigation
2000
A parameter free investigation of the moments of inertia of ground state rotational bands in well deformed rare-earth nuclei is carried out using Cranked Relativistic Hartree-Bogoliubov (CRHB) and non-relativistic Cranked Hartree-Fock-Bogoliubov (CHFB) theories. In CRHB theory, the relativistic fields are determined by the non-linear Lagrangian with the NL1 force and the pairing interaction by the central part of finite range Gogny D1S force. In CHFB theory, the properties in particle-hole and particle-particle channels are defined solely by Gogny D1S forces. Using an approximate particle number projection before variation by means of the Lipkin Nogami method improves the agreement with the…
The RMS charge radius of the proton and Zemach moments
2010
On the basis of recent precise measurements of the electric form factor of the proton, the Zemach moments, needed as input parameters for the determination of the proton rms radius from the measurement of the Lamb shift in muonic hydrogen, are calculated. It turns out that the new moments give an uncertainty as large as the presently stated error of the recent Lamb shift measurement of Pohl et al.. De Rujula's idea of a large Zemach moment in order to reconcile the five standard deviation discrepancy between the muonic Lamb shift determination and the result of electronic experiments is shown to be in clear contradiction with experiment. Alternative explanations are touched upon.
Generalized polarizabilities of the proton in a constituent quark model revisited
2001
We study low-energy virtual Compton scattering off the proton within the framework of a nonrelativistic constituent quark model. The Compton tensor is divided into two separately gauge-invariant contributions. The first consists of the groundstate propagation in the direct and crossed channels together with an appropriately chosen term to satisfy gauge invariance. The residual part contains the relevant structure information characterized by the so-called generalized polarizabilities. We discuss two different schemes to obtain the generalized polarizabilities from the residual term. Explicit predictions for the generalized polarizabilities are presented for the Isgur-Karl model. Our results…
Quadrupole collective inertia in nuclear fission: Cranking approximation
2010
Collective mass tensor derived from the cranking approximation to the adiabatic time-dependent Hartree-Fock-Bogoliubov (ATDHFB) approach is compared with that obtained in the Gaussian Overlap Approximation (GOA) to the generator coordinate method. Illustrative calculations are carried out for one-dimensional quadrupole fission pathways in 256Fm. It is shown that the collective mass exhibits strong variations with the quadrupole collective coordinate. These variations are related to the changes in the intrinsic shell structure. The differences between collective inertia obtained in cranking and perturbative cranking approximations to ATDHFB, and within GOA, are discussed.
Event-by-event distributions of azimuthal asymmetries in ultrarelativistic heavy-ion collisions
2012
Relativistic dissipative fluid dynamics is a common tool to describe the space-time evolution of the strongly interacting matter created in ultrarelativistic heavy-ion collisions. For a proper comparison to experimental data, fluid-dynamical calculations have to be performed on an event-by-event basis. Therefore, fluid dynamics should be able to reproduce, not only the event-averaged momentum anisotropies, $$, but also their distributions. In this paper, we investigate the event-by-event distributions of the initial-state and momentum anisotropies $\epsilon_n$ and $v_n$, and their correlations. We demonstrate that the event-by-event distributions of relative $v_n$ fluctuations are almost eq…
Fluctuating parts of nuclear ground state correlation energies
2013
Background: Heavy atomic nuclei are often described using the Hartree-Fock-Bogoliubov (HFB) method. In principle, this approach takes into account Pauli effects and pairing correlations while other correlation effects are mimicked through the use of effective density-dependent interactions. Purpose: Investigate the influence of higher order correlation effects on nuclear binding energies using Skyrme's effective interaction. Methods: A cut-off in relative momenta is introduced in order to remove ultraviolet divergences caused by the zero-range character of the interaction. Corrections to binding energies are then calculated using the quasiparticle-random-phase approximation (QRPA) and secon…
Analysis of enhancedβeffects in minimal flavor violation GUT scenarios
2006
Long-range forces between macroscopic objects are mediated by light particles that interact with the electrons or nucleons, and include spin-dependent static components as well as spin- and velocity-dependent components. We parametrize the long-range potential between two fermions assuming rotational invariance, and find 16 different components. Applying this result to electrically neutral objects, we show that the macroscopic potential depends on 72 measurable parameters. We then derive the potential induced by the exchange of a new gauge boson or spinless particle, and compare the limits set by measurements of macroscopic forces to the astrophysical limits on the couplings of these partic…
Dispersion relation formalism for virtual Compton scattering of the proton
2001
We present in detail a dispersion relation formalism for virtual Compton scattering (VCS) off the proton from threshold into the $\Delta(1232)$-resonance region. Such a formalism can be used as a tool to extract the generalized polarizabilities of the proton from both unpolarized and polarized VCS observables over a larger energy range. We present calculations for existing and forthcoming VCS experiments and demonstrate that the VCS observables in the energy region between pion production threshold and the $\Delta(1232)$-resonance show an enhanced sensitivity to the generalized polarizabilities.
Single Spin Asymmetry Parameter from Deeply Virtual Compton Scattering of Hadrons up to Twist-3 accuracy: I. Pion case
2002
The study of deeply virtual Compton scattering has shown that electromagnetic gauge invariance requires, to leading order, not only twist two but additional twist three contributions. We apply this analysis and, using the Ellis-Furmanski-Petronzio factorization scheme, compute the single (electron) spin asymmetry arising in the collision of longitudinally polarized electrons with hadrons up to twist 3 accuracy. In order to simplify the kinematics we restrict the actual calculation to pions in the chiral limit. The process is described in terms of the generalized parton distribution functions which we obtain within a bag model framework.