Eikonal representation in the momentum-transfer space

By means of empirical fits to the differential cross section data on pp and p(bar)p elastic scattering, above 10 GeV (center-of-mass energy), we determine the eikonal in the momentum - transfer space (q^2- space). We make use of a numerical method and a novel semi-analytical method, through which the uncertainties from the fit parameters can be propagated up to the eikonal in the $q^2$- space. A systematic study of the effect of the experimental information at large values of the momentum transfer is developed and discussed in detail. We present statistical evidence that the imaginary part of the eikonal changes sign in the q^2- space and that the position of the zero decreases as the energy increases; after the position of the zero, the eikonal presents a minimum and then goes to zero through negative values. We discuss the applicability of our results in the phenomenological context, outlining some connections with nonperturbative QCD. A short review and a critical discussion on the main results concerning "model-independent" analyses are also presented.Comment: 18 pages, 17 figures, 4 tables, svjour.cls. Revised discussion on the proton's electromagnetic form factor and references added. To appear in Eur. Phys. J.

Evidence for eikonal zeros in the momentum transfer space

We present the results of fitting elastic $pp$ differential cross section data at 23.5 $\leq \sqrt{s} \leq$ 62.5 GeV with a novel analytic parametrization for the scattering amplitude. Making use of a fitting method, the errors from the free parameters are propagated to the imaginary part of the eikonal in the momentum transfer space. A novel systematic study of the effects coming from data at large momentum transfer is also performed. We find statistical evidence for the existence of eikonal zeros in the interval of momentum transfer 5-9 $GeV^{2}$.Comment: Text with 9 pages in Revtex (preprint form), 8 figures in PostScript. Replaced with small changes. Final version to be published in Physical Review

GPDs of the nucleons and elastic scattering at high energies

Taking into account the electromagnetic and gravitational form factors, calculated from a new set of $t$-dependent GPDs, a new model is built. The real part of the hadronic amplitude is determined only through complex $s$. In the framework of this model the quantitative description of all existing experimental data at $52.8 \leq \sqrt{s} \leq 1960 \$GeV, including the Coulomb range and large momentum transfers ($0.0008 \leq |t| \leq 9.75 \ $GeV$^2$), is obtained with only$3$fitting high energy parameters. The comparison with the preliminary data of the TOTEM Collaboration at an energy of$7$ TeV is made.Comment: 14 pages, 21 figures, minor corrections (slightly brush English and removed two misprint in numbering

Experimenting with Langevin Lattice QCD

We report on the status of our investigations of the effects of systematic errors upon the practical merits of Langevin updating in full lattice QCD. We formulate some rules for the safe use of this updating procedure and some observations on problems which may be common to all approximate fermion algorithms

On the chiral phase transition in two-flavor lattice QCD

We use a Langevin algorithm to simulate QCD with two light flavors on an 83× 4 lattice. We find metastability signals at a quark mass of 0.025 in lattice units, but not a quark mass of 0.1. These results are discussed in the light of other recent findings on the phase diagram of finite-temperature QCD and of the special significance of the two-flavor problem