Energy scale determination and energy resolution in positron total cross section measurements

Abstract

We compare the recent values of positron total cross sections in benzene, cyclohexane and aniline by Zecca et al. with our previous measurements [Karwasz et al. Acta Phys. Pol. A, 107 (2005) 666] on the same apparatus. An apparent discrepancy disappears if Zecca's data are shifted by +0.2 eV; then their data can be approximated by the modified effective range theory, as well. This observation induced us to compare recent Trento data with other experiments and theories for polar targets, H2O and HCOOH. The evidence points out towards the need of a careful energy calibration in positron experiments.