Measurement of the charged-pion polarisability at COMPASS

by Jan Michael Friedrich (Technische Universitaet Muenchen (DE))

Tuesday 12 May 2015, 11:00 → 12:00 Europe/Zurich

500/1-001 - Main Auditorium (CERN)

For more than a decade, COMPASS has been tackling the measurement of the electromagnetic polarizability of the charged pion, which describes the stiffness of the pion against deformation in electromagnetic fields. Previous experiments date back to the 1980's in Serpukhov (Russia), where the Primakoff method for realizing interactions of charged pions with quasi-real photons was first employed. Later also other techniques in photon-nucleon and photon-photon collisions were carried out at different machines. The COMPASS measurement demonstrates that the charged-pion polarizability is significantly smaller than the previous results, roughly by a factor two, with the smallest uncertainties realized so far. The pion polarisability is of fundamental interest in the low-energy sector of quantum chromodynamics. It is directly linked to the quark-gluon substructure and dynamics of the pion, the lightest bound system of strong interaction.

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Poster poster.pdf

Slides friedrich_20150512.pdf

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