Spin Dependent Drell Yan in QCD to O(αs2)O(\alpha_s^2) (I). (The Non-Singlet Sector)

A study of the order $\alpha_s^2$ corrections to the Drell Yan (non-singlet) cross section for incoming states of arbitrary longitudinal helicities is presented. The study is performed in the case of the transverse momentum distributions, $(q_T)$, of the lepton pair and extends the calculation of Ellis Martinelli and Petronzio (EMP) to the polarized case. We use the $\bar{MS}$ scheme and the t'Hooft-Veltman regularization for the helicity projectors. From our results one can obtain the bulk of the totally inclusive NNLO cross section for the production of a Drell Yan pair in the non-singlet sector by a simple integration over the heavy photon momentum. We show that in the $\bar{MS}$ helicity is not conserved, unless a finite renormalization is done to reenter into a physical scheme ($\bar{MS}_p$). This aspect of the calculation follows the same trend as in polarized production of single and double photon to $O(\alpha_s^2)$. In the unpolarized limit we reproduce all the results of EMP.Comment: 39 pages, 7 figures (included

The risk of overanticoagulation in patients with heart failure on coumarin anticoagulants

Heart failure has been identified as a risk factor for increased coumarin anticoagulant responsiveness in several small-scale experiments. Epidemiological studies quantifying the risk of overanticoagulation by heart failure in a non-selected population on coumarins are scarce. Therefore, we investigated whether patients with heart failure have an increased risk of overanticoagulation and determined the effect of incidental heart failure on coumarin dose requirements. A cohort study of all patients was performed from an outpatient anticoagulation clinic treated with acenocoumarol or phenprocoumon between 1 January 1990 and 1 January 2000. All cohort members were followed until the first occurrence of an international normalized ratio (INR) ≥6.0, the last INR assessment, death, loss to follow-up, or end of the study period. Of the 1077 patients in the cohort, 396 developed an INR ≥6.0. The risk of overanticoag

Family Unification in Five and Six Dimensions

In family unification models, all three families of quarks and leptons are grouped together into an irreducible representation of a simple gauge group, thus unifying the Standard Model gauge symmetries and a gauged family symmetry. Large orthogonal groups, and the exceptional groups $E_7$ and $E_8$ have been much studied for family unification. The main theoretical difficulty of family unification is the existence of mirror families at the weak scale. It is shown here that family unification without mirror families can be realized in simple five-dimensional and six-dimensional orbifold models similar to those recently proposed for SU(5) and SO(10) grand unification. It is noted that a family unification group that survived to near the weak scale and whose coupling extrapolated to high scales unified with those of the Standard model would be evidence accessible in principle at low energy of the existence of small (Planckian or GUT-scale) extra dimensions.Comment: 13 pages, 2 figures, minor corrections, references adde

New empirical fits to the proton electromagnetic form factors

Recent measurements of the ratio of the elastic electromagnetic form factors of the proton, G_Ep/G_Mp, using the polarization transfer technique at Jefferson Lab show that this ratio decreases dramatically with increasing Q^2, in contradiction to previous measurements using the Rosenbluth separation technique. Using this new high quality data as a constraint, we have reanalyzed most of the world e-p elastic cross section data. In this paper, we present a new empirical fit to the reanalyzed data for the proton elastic magnetic form factor in the region 0 < Q^2 < 30 GeV^2. As well, we present an empirical fit to the proton electromagnetic form factor ratio, G_Ep/G_Mp, which is valid in the region 0.1 < Q^2 < 6 GeV^2

Localization properties of groups of eigenstates in chaotic systems

In this paper we study in detail the localized wave functions defined in Phys. Rev. Lett. {\bf 76}, 1613 (1994), in connection with the scarring effect of unstable periodic orbits in highly chaotic Hamiltonian system. These functions appear highly localized not only along periodic orbits but also on the associated manifolds. Moreover, they show in phase space the hyperbolic structure in the vicinity of the orbit, something which translates in configuration space into the structure induced by the corresponding self--focal points. On the other hand, the quantum dynamics of these functions are also studied. Our results indicate that the probability density first evolves along the unstable manifold emanating from the periodic orbit, and localizes temporarily afterwards on only a few, short related periodic orbits. We believe that this type of studies can provide some keys to disentangle the complexity associated to the quantum mechanics of these kind of systems, which permits the construction of a simple explanation in terms of the dynamics of a few classical structures.Comment: 9 pages, 8 Postscript figures (low resolution). For high resolution versions of figs http://www.tandar.cnea.gov.ar/~wisniack/ To appear in Phys. Rev.

Discrete exterior calculus (DEC) for the surface Navier-Stokes equation

We consider a numerical approach for the incompressible surface Navier-Stokes equation. The approach is based on the covariant form and uses discrete exterior calculus (DEC) in space and a semi-implicit discretization in time. The discretization is described in detail and related to finite difference schemes on staggered grids in flat space for which we demonstrate second order convergence. We compare computational results with a vorticity-stream function approach for surfaces with genus 0 and demonstrate the interplay between topology, geometry and flow properties. Our discretization also allows to handle harmonic vector fields, which we demonstrate on a torus.Comment: 21 pages, 9 figure

Schmidt modes generated in parametric downconversion

This paper presents the general Schmidt decomposition of two-photon fields generated in spontaneous parametric down-conversion (SPDC). It discusses in particular the separation of the radial and azimuthal degrees of freedom, the role of projection in modal analysis, and the benefits of collinear phase mismatch. The paper is written in a review style and presents a wealth of numerical results. It aims at emphasising the physics beyond the mathematics, through discussions and graphical representations of key results.Comment: 11 pages, 13 figure

Polarized and Unpolarized Double Prompt Photon Production in Next to Leading Order QCD

We calculate $O(\alpha_s)$ corrections to inclusive and isolated double prompt photon production, both for the unpolarized case, and for longitudinal polarization of the incoming hadrons. The calculation is performed using purely analytical techniques for the inclusive case, and a combination of analytical and Monte Carlo techniques to perform the phase space integration in the isolated case. A brief phenomenological study is made of the process $pp\rightarrow \gamma \gamma X$ at CMS energies appropriate for the RHIC heavy ion collider.Comment: 47 pages, revtex, 12 ps figures, hep-ph Title corrected, no changes to the pape

Nucleon Charge and Magnetization Densities from Sachs Form Factors

Relativistic prescriptions relating Sachs form factors to nucleon charge and magnetization densities are used to fit recent data for both the proton and the neutron. The analysis uses expansions in complete radial bases to minimize model dependence and to estimate the uncertainties in radial densities due to limitation of the range of momentum transfer. We find that the charge distribution for the proton is significantly broad than its magnetization density and that the magnetization density is slightly broader for the neutron than the proton. The neutron charge form factor is consistent with the Galster parametrization over the available range of Q^2, but relativistic inversion produces a softer radial density. Discrete ambiguities in the inversion method are analyzed in detail. The method of Mitra and Kumari ensures compatibility with pQCD and is most useful for extrapolating form factors to large Q^2.Comment: To appear in Phys. Rev. C. Two new figures and accompanying text have been added and several discussions have been clarified with no significant changes to the conclusions. Now contains 47 pages including 21 figures and 2 table