Heidelberg 2015 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 48: Poster

HK 48.12: Poster

Wednesday, March 25, 2015, 17:00–19:00, C/Foyer

Measurement of the Pion Polarizability with COMPASS — •Stefan Huber for the COMPASS collaboration — Technische Universiät München

Chiral Perturbation Theory predicts a precise value for the charged-pion polarisability. Experiments performed within the last decades are in tension with this value and also do not agree with each other. At the COMPASS experiment at CERN the pion polarisability is accessible through the Primakoff effect, where the quasi-real photons surrounding the nickel nuclei are used to measure pion-photon scattering. Studying the energy distribution of the outgoing photons, the polarisability value can be extracted. During the 2009 data taking COMPASS performed a first measurement based on about 60 000 exclusive events. In addition to the measurement with a pion beam a control measurement with a muon beam has been performed in order to control the systematics. The details of the measurement as well as the results will be discussed. Currently we are analysing a data set taken in 2012 which will allow us to study the value with better statistical and systematical precision.