Search results for " ELECTRODYNAMICS"
showing 10 items of 813 documents
Forward dihadron correlations in the Gaussian approximation of JIMWLK
2012
We compute forward dihadron azimuthal correlations in deuteron-gold collisions using a Gaussian approximation for the quadrupole operator. The double parton scattering contribution is found to be part of our dihadron calculation. We obtain a good description of the PHENIX data for the azimuthal-angle dependent away side peak and a relatively good estimate for the pedestal contribution.
Anisotropy of flow and the order of phase transition in relativistic heavy ion collisions
2005
Using a hydrodynamical model we study how the order of phase transition in the equation of state of strongly interacting matter affects single particle spectra, elliptic flow and higher order anisotropies in Au+Au collisions at RHIC (sqrt{s_NN}=200 GeV energy). We find that the single particle spectra are independent of the order of phase transition and that the fourth harmonic v_4(p_T) shows only a weak dependence in the p_T region where hydrodynamics is expected to work. The differential elliptic flow, v_2(p_T), of baryons shows the strongest dependence on equation of state. Surprisingly the closest fit to data was obtained when the equation of state had a strong first order phase transit…
Entropy development in ideal relativistic fluid dynamics with the Bag Model equation of state
2010
We consider an idealized situation where the Quark-Gluon Plasma (QGP) is described by a perfect, (3 + 1)-dimensional fluid dynamic model starting from an initial state and expanding until a final state where freeze-out and/or hadronization takes place. We study the entropy production with attention to effects of (i) numerical viscosity, (ii) late stages of flow where the Bag Constant and the partonic pressure are becoming similar, (iii) and the consequences of final freeze-out and constituent quark matter formation.
The Pion Velocity in Dense Skyrmion Matter
2003
We have developed a field theory formalism to calculate $in$-$medium$ properties of hadrons within a unified approach that exploits a single Lagrangian to describe simultaneously both matter background and meson fluctuations. In this paper we discuss the consequences on physical observables of a possible phase transition of hadronic matter taking place in the chiral limit. We pay special attention to the pion velocity $v_\pi$, which controls, through a dispersion relation, the pion propagation in the hadronic medium. The $v_\pi$ is defined in terms of parameters related to the matrix element in matter of the axial-vector current, namely, the in-medium pion decay constants, $f_t$ and $f_s$. …
Photon Scattering with the Lorentz Integral Transform Method
2011
The application of the Lorentz integral transform (LIT) method to photon scattering off nuclei is presented in general. As an example, elastic photon scattering off the deuteron in the unretarded dipole approximation is considered using the LIT method. The inversion of the integral transform is discussed in detail paying particular attention to the high-energy contributions in the resonance term. The obtained E1-polarizabilities are compared to results from the literature. The corresponding theoretical cross section is confronted with experimental results confirming, as already known from previous studies, that the E1-contribution is the most important one at lower energies.
Photoproduction of pions on 3He and 3H
1969
Abstract In this paper the photoproduction of pions on nuclei with three nucleons is considered in the “elastic” channels. The calculation is done using the impulse approximation and neglecting rescattering effects.
Violation of Siegert's theorem in the electro-excitation of the (1−, T = 0)-level at 7.117 MeV in 16O
1989
Abstract Cross sections are measured for the electro-excitation of the first 1−-level in 16O at extremely small momentum transfer. The model-independent interpretation with a Fourier-Bessel expansion of the transition charge density reveals an incompatibility with the life-time measurement at the photon point, i.e. a violation of Siegert's theorem.
Extended Thomas - Fermi expansion from nuclear linear response
1996
The coefficients of the successive orders of the extended Thomas - Fermi expansion of the kinetic energy density are obtained to the leading order in the density inhomogeneities. This is done by comparing the corresponding static polarizability with the exact value in two cases: a non-interacting nuclear infinite system and symmetric nuclear matter with a Skyrme interaction.
Threshold electro production of neutral pions at low q2 off the proton and off the deuteron
2000
Abstract The A1 Collaboration performs an extend program to measure threshold production of the neutral pion as test of Heavy Baryon Chiral Perturbation Theory. Starting with direct threshold measurements to extract the s wave amplitudes at threshold we continued with out of plane measurements with polarized beam to access the small p wave amplitudes. Coherent production off the deuteron is the first attempt to access the neutron amplitude in electro production.
Proton spin and the cheshire cat principle
1991
Abstract We discuss the proton matrix element of the flavor-singlet axial current (FSAC), often referred to as proton spin, in terms of the chiral bag model with due account of the axial anomaly and quantum number fractionation. We conclude that the contribution due to gluons is significant for large bag radii and that it is crucial in order to establish the Cheshire cat principle.