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FIZIKA B 17 (2008) 2, 313 - 320
 
PION POLARIZABILITIES MEASUREMENT AT COMPASS
ALEXEY GUSKOV
on behalf of the COMPASS collaboration
Joint Institute for Nuclear Research, Dzhelepov Laboratory of Nuclear Problems, Dubna, Russia
E-mail address: [email protected]
Received 23 October 2007; Accepted 20 February 2008
Online 20 June 2008
The electromagnetic structure of pions is probed in
p-+(A,Z)® p-+(A,Z)+g Compton scattering in inverse kinematics (Primakoff reaction) and described
by the electric ([`(ap)]) and the magnetic ([`(bp)]) polarizabilities that depend on the rigidity of pion's internal
structure as a composite particle. Values for pion polarizabilities can be
extracted from the comparison of the differential cross section for scattering
of pointlike pions with the measured cross section. The pion polarizability
measurement was performed with a p-
beam of 190 GeV. The high beam intensity, the good spectrometer resolution, the
high rate capability, the high acceptance and the possibility to use pion and
muon beams, unique to the COMPASS experiment, provide the tools to measure
precisely the pion polarizabilities in the Primakoff reaction. The preliminary
result for pion polarizabilities under the assumption of [`(ap)]+[`(bp)]=0 is [`(ap)]=-[`(bp)] = (2.5±1.7stat±0.6syst)×10-4 fm3.
PACS numbers: 25.80.Ek, 13.60.Fz
UDC 539.126
Keywords: pion, electromagnetic structure, polarizability, Compton
scattering, Primakoff reaction
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