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European Physical Journal A 37 (2008) 1-8
A new measurement of the structure functions $P_{LL}-P_{TT}/epsilon$ and $P_{LT}$ in virtual Compton scattering at $Q^2=$ 0.33 (GeV/c)$^2$
P. Janssens, L. Doria, P. Achenbach, C. Ayerbe Gayoso, D. Baumann, J. C. Bernauer, I. K. Bensafa1, R. Böhm, D. Bosnar, E. Burtin2, N. d'Hose2, X. Defaÿ, M. Ding, M. O. Distler, H. Fonvieille1, J. Friedrich, J. M. Friedrich, G. Laveissière1, M. Makek, J. Marroncle2, H. Merkel, U. Müller, L. Nungesser, B. Pasquini, J. Pochodzalla, O. Postavaru, M. Potokar, D. Ryckbosch, S. Sanchez Majos, B. S. Schlimme, M. Seimetz2, S. Sirca, G. Tamas, R. Van De Vyver, L. Van Hoorebeke, A. Van Overloop, Th. Walcher, M. Weinriefer
MAMI-A1 Collaboration(s)

The cross section of the $ep \to e' p' \gamma$ reaction has been measured at $Q^2 = 0.33$ (GeV/c)$^2$. The experiment was performed using the electron beam of the MAMI accelerator and the standard detector setup of the A1 Collaboration. The cross section is analyzed using the low-energy theorem for virtual Compton scattering, yielding a new determination of the two structure functions $P_LL}-P_{TT}/epsilon$ and $P_{LT}$ which are linear combinations of the generalized polarizabilities of the proton. We find somewhat larger values than in the previous investigation at the same $Q^2$. This difference, however, is purely due to our more refined analysis of the data. The results tend to confirm the non-trivial $Q^2$-evolution of the generalized polarizabilities and call for more measurements in the low-$Q^2$ region ($\le$ 1 (GeV/c)$^2$).
1 :  LPC-CLERMONT - Laboratoire de Physique Corpusculaire de Clermont-Ferrand
2 :  SPhN - Service de Physique Nucléaire
Physique/Physique Nucléaire Expérimentale

Physique/Physique des Hautes Energies - Expérience
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