PEPPo Collaboration Meeting November 8-9, 2010, Newport News

Polarization Transfertin

Bremsstrahlung and Pair Creation

(i) Olsen & Maximon(ii) Kuraev et al.(iii) Physics case

Jonathan Dumasǂ*, Eric Voutierǂ

ǂ Laboratoire de Physique Subatomique et de Cosmologie

Grenoble, France* Thomas Jefferson National Accelerator Facility

Newport-News, Virginia, USA

Eric VoutierOlsen & Maximon

Bremsstrahlung

H. Olsen, L. Maximon, PR114 (1959) 887

The most currently used framework to evaluate polarization transferts for polarized bremsstrahlung and pair creation processes is the O&M work developped in the Born

approximation for relativistic particles and small scattering angles.

Newport News, November 8-9, 2010

The observed singularity reflectsthe known problem of unpolarized crosssections in the tip region: Coulombcorrections appear too strong forheavy nuclei, leading to negative crosssections.

Unphysical polarization transfertsremain even when neglecting Coulombcorrections.

The full screening case does notreflect any peculiar features.

2/5

Eric Voutier

Pair Creation

H. Olsen, L. Maximon, PR114 (1959) 887

Pair creation is obtained from bremsstrahlung expressions by kinematical substitutions

Some features of O&M calculationsare not valid

Unphysical polarization transfertsare observed at small energy over thefull kinematic range, independently ofCoulomb correction effects.

The full screening case does notreflect any peculiar features.

Newport News, November 8-9, 2010

Olsen & Maximon

3/5

Eric Voutier

BREMSSTRAHLUNG PAIR CREATION

Bremsstrahlung and Pair CreationRevisited…

E.A. Kuraev, Y.M. Bystritskiy, M. Shatnev, E. Tomasi-Gustafsson, PRC 81 (2010) 055208

These calculations, developpedwithout neglecting the electron mass,do not exhibit any unphysical features.

These calculations show a remarkablekinematic symmetry.

Significant differences with O&Mpersist at high photon energies.

Newport News, November 8-9, 2010

Kuraev et al.

4/5

Eric Voutier

PEPPo Physics

5/5Newport News, November 8-9, 2010

Physics Case

High energy point with small butstill sizeable differences betweentheoretical calculations. Easiest experimental point withsignificant asymmetries.

Medium energy point with largedifferences between theoreticalcalculations. Very difficult experimentalpoint because of no asymmetry.

Low energy point with thelargest differences betweentheoretical calculations. Difficult experimental pointbecause of thin target statistics.