arXiv subjects

C. Bourrely

Publications and source records attributed to C. Bourrely.

27 records · Page 2Linked to original sources

arXiv1998

Polarized Quarks, Gluons and Sea in Nucleon Structure Functions

We perform a NLO analysis of polarized deep inelastic scattering data to test two different solutions to the so called spin crisis: one of them based on the axial gluon anomaly and consistent with the Bjorken sum rule and another one, where the defects in the spin sum rules and in the Gottfried sum rule are related. In this case a defect is also expected for the Bjorken sum rule. The first solution is slightly favoured by the SLAC E154 results, but both options seem to be consistent with the CERN SMC data.

hep-ph↗

arXiv1997

The $Q^2$ evolution of Soffer inequality

DGLAP evolution equations may be presented in a form completely analogous to the Boltzmann equation. This provides a natural proof of the positivity of the spin-dependent parton distributions, provided the initial distributions at $Q^2_0$ are also positive. In addition, the evolution to $Q^2 < Q^2_0$ may violate positivity, providing therefore a 'time arrow'. The positivity condition is just $|ΔP_{ij} (z)| \leq P_{ij} (z) $ for $z < 1$ for all types of partons, while the $'+'$prescription and terms containing $δ(1-z)$ do not affect positivity. This method allows one to complete immediately the existing proof of Soffer inequality at leading and next-to-leading order.

hep-ph↗

arXiv1997

A Numerical Study of Absorption by Multilayered Biperiodic Structures

We study the electromagnetic scattering by multilayered biperiodic aggregates of dielectric layers and gratings of conducting plates. We show that the characteristic lengths of such structures provide a good control of absorption bands. The influence of the physical parameters of the problem (sizes, impedances) is discussed.

physics.optics↗

arXiv1996

How to calibrate the polarization of a high energy proton beam? A theoretical prospect

In view of the realistic possibility for operating high-energy polarized proton beams in future collider machines, it is highly desirable to propose for such beams, an absolute calibration allowing to measure accurately their degree of polarization. We consider more specifically one practical method based on pp elastic scattering near the forward direction and we discuss its limitations.

hep-ph↗

arXiv1995

Improved version of the eikonal model for absorbing spherical particles

We present a new expression of the scattering amplitude, valid for spherical absorbing objects, which leads to an improved version of the eikonal method outside the diffraction region. Limitations of this method are discussed and numerical results are presented and compared successfully with the Mie theory.

hep-ph↗

arXiv1994

Fermi-Dirac Distributions for Quark Partons

We propose to use Fermi-Dirac distributions for quark and antiquark partons. It allows a fair description of the $x$-dependence of the very recent NMC data on the proton and neutron structure functions $F_2^p(x)$ and $F_2^n(x)$ at $Q^2=4$ GeV$^2$, as well as the CCFR antiquark distribution $x\overline q(x)$. We show that one can also use a corresponding Bose-Einstein expression to describe consistently the gluon distribution. The Pauli exclusion principle, which has been identified to explain the flavor asymmetry of the light-quark sea of the proton, is advocated to guide us for making a simple construction of the polarized parton distributions. We predict the spin dependent structure functions $g_1^p(x)$ and $g_1^n(x)$ in good agreement with EMC and SLAC data. The quark distributions involve some parameters whose values support well the hypothesis that the violation of the quark parton model sum rules is a consequence of the Pauli principle.

hep-ph↗

arXiv1994

Expanding Protons seen by HERA

We show that the rising total photoproduction cross section recently observed at HERA is entirely consistant with the impact-picture in the theory of expanding protons which was proposed more than twenty years ago. More accurate data, which is expected to be forthcoming soon, will give this prediction a stringent test.

hep-ph↗

arXiv1994

Experimental Evidence for Simple Relations between Unpolarized and Polarized Parton Distributions

The Pauli exclusion principle is advocated for constructing the proton and neutron deep inelastic structure functions in terms of Fermi-Dirac distributions that we parametrize with very few parameters. It allows a fair description of the recent NMC data on $F^p_2(x,Q^2)$ and $F^n_2(x,Q^2)$ at $Q^2=4 GeV^2$, as well as the CCFR neutrino data at $Q^2=3$ and $5 GeV^2$. We also make some reasonable and simple assumptions to relate unpolarized and polarized quark parton distributions and we obtain, with no additional free parameters, the spin dependent structure functions $xg^p_1(x,Q^2)$ and $xg^n_1(x,Q^2)$. Using the correct $Q^2$ evolution, we have checked that they are in excellent agreement with the very recent SMC proton data at $Q^2=10 GeV^2$ and the SLAC neutron data at $Q^2=2 GeV^2$.

hep-ph↗

arXiv1994

Impact Picture Model for Pbar-P Elastic Scattering

The predictions of an impact-picture model for proton-antiproton elastic scattering are compared with the new UA4 experimental data in the Coulomb interference region at the center-of-mass energy of $541 GeV$. The predicted differential cross section, the parameter $ρ$ and the forward slope are in very good agreement with the data.

hep-ph↗