Search results for "visti"
showing 10 items of 759 documents
Azimuthally Differential Pion Femtoscopy in Pb-Pb Collisions at sNN=2.76 TeV
2017
We present the first azimuthally differential measurements of the pion source size relative to the second harmonic event plane in Pb-Pb collisions at a center-of-mass energy per nucleon-nucleon pair of √sNN = 2.76 TeV. The measurements have been performed in the centrality range 0%-50% and for pion pair transverse momenta 0.2 < kT < 0.7 GeV/c. We find that the Rside and Rout radii, which characterize the pion source size in the directions perpendicular and parallel to the pion transverse momentum, oscillate out of phase, similar to what was observed at the Relativistic Heavy Ion Collider. The final-state source eccentricity, estimated via Rside oscillations, is found to be significantly sma…
Observation of Direct-Photon Collective Flow inAu+AuCollisions atsNN=200 GeV
2012
The second Fourier component v(2) of the azimuthal anisotropy with respect to the reaction plane is measured for direct photons at midrapidity and transverse momentum (p(T)) of 1-12 GeV/c in Au + Au collisions at root s(NN) = 200 GeV. Previous measurements of this quantity for hadrons with p(T) 6 GeV/c a reduced anisotropy is interpreted in terms of a path-length dependence for parton energy loss. In this measurement with the PHENIX detector at the Relativistic Heavy Ion Collider we find that for p(T) > 4 GeV/c the anisotropy for direct photons is consistent with zero, which is as expected if the dominant source of direct photons is initial hard scattering. However, in the p(T) < 4 GeV/c re…
Survey on polarization observables in deuteron photodisintegration below pion-production threshold
1991
Polarization observables of deuteron photodisintegration with polarized photons and oriented deuterons are systematically investigated below π-production threshold with respect to their sensitivity to subnuclear degrees of freedom and relativistic effects, to the different electric and magnetic multipole contributions, and to various realistic potential models. In particular, a complete survey on all single- and double-polarization observables like beam and target asymmetries of the differential cross section, nucleon polarization and proton-neutron spin correlation is given.
Discreteness effects on a sine-Gordon breather
1991
We employ collective-variable theory to describe the dynamics of a breather excitation in its center-of-mass frame in continuous and discrete systems of one spatial dimension. The exact equations of motion for the collective variable and coupled phonon field are derived for any system which supports breatherlike excitations that have even spatial parity where the collective variable represents half the distance between the breather subkinks. We then specialize the theory to the sine-Gordon (SG) case. For the continuum SG system we derive the exact effective potential in terms of the collective variable and discuss the relativistic effects on the breather subkinks which are quite different t…
Local Lorentz invariance tests for photons and hadrons at the Gamma Factory
2021
High-precision tests of local Lorentz invariance, via monitoring of the sidereal time variation of the photon energies emitted by ultrarelativistic heavy-ion beams and of the beam momentum, are proposed. This paper includes descriptions of the physics ideas and the concept for the detector. The experiment results will allow high-precision tests of LLI via anisotropy of the maximum attainable speed of a photon and an ion. The projected accuracy for the asymmetries interpreted in the framework of the anisotropic relativistic mechanics corresponds to the limit on sidereal time variation of the one-way maximum attainable speed at the levels between $10^{-14}$ and $10^{-17}$.
On the convexity of Relativistic Hydrodynamics
2013
The relativistic hydrodynamic system of equations for a perfect fluid obeying a causal equation of state is hyperbolic (Anile 1989 {\it Relativistic Fluids and Magneto-Fluids} (Cambridge: Cambridge University Press)). In this report, we derive the conditions for this system to be convex in terms of the fundamental derivative of the equation of state (Menikoff and Plohr 1989 {\it Rev. Mod. Phys.} {\bf 61} 75). The classical limit is recovered.
Perturbations of spacetime: gauge transformations and gauge invariance at second order and beyond
1996
We consider in detail the problem of gauge dependence that exists in relativistic perturbation theory, going beyond the linear approximation and treating second and higher order perturbations. We first derive some mathematical results concerning the Taylor expansion of tensor fields under the action of one-parameter families (not necessarily groups) of diffeomorphisms. Second, we define gauge invariance to an arbitrary order $n$. Finally, we give a generating formula for the gauge transformation to an arbitrary order and explicit rules to second and third order. This formalism can be used in any field of applied general relativity, such as cosmological and black hole perturbations, as well …
First ionization potential of the heaviest actinide lawrencium, element 103
2016
The first ionization potential (IP1 ) of element 103, lawrencium (Lr), has been successfully determined for the first time by using a newly developed method based on a surface ionization process. The measured IP 1 value is 4.9630.08 0.07 eV. This value is the smallest among those of actinide elements and is in excellent agreement with the value of 4.963(15) eV predicted by state-of-the-art relativistic calculations also performed in this work. Our results strongly support that the Lr atom has an electronic configuration of [Rn]7s 2 5f 14 7p 1 1/2 , which is influenced by strong relativistic effects. The present work provides a reliable benchmark for theoretical calculations and also opens t…
Geometric Aspects of Mechanics
2010
In many respects, mechanics carries geometrical structures. This could be felt very clearly at various places in the first four chapters. The most important examples are the structures of the space–time continua that support the dynamics of nonrelativistic and relativistic mechanics, respectively. The formulation of Lagrangian mechanics over the space of generalized coordinates and their time derivatives, as well as of Hamilton–Jacobi canonical mechanics over the phase space, reveals strong geometrical features of these manifolds.
Integrated photoabsorption strength and sum rules for a bound Dirac particle
1985
Relativistic effects in the integrated total photoabsorption cross section are discussed using a simple model of a Dirac particle bound in a central potential of scalar or vector type. The integrated strength is calculated explicitly and compared to a new relativistic extension of the TRK-sum rule using positive energy projection and to predictions from dispersion relations. M1 and E2 sum rules are also considered. In all cases the integrated strength exceeds the classical sum rule up to a few percent. The dispersion sum rule cannot be compared directly to the integrated strength since it contains a negative contribution from pair production in the potential field which is of the order of a…