# 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)$^2$

Abstract : 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)$^2$).
Document type :
Journal articles
Domain :

http://hal.in2p3.fr/in2p3-00261506
Contributor : Jeanine Pellet <>
Submitted on : Friday, March 7, 2008 - 11:47:39 AM
Last modification on : Monday, February 10, 2020 - 6:12:40 PM

### Citation

P. Janssens, L. Doria, P. Achenbach, C. Ayerbe Gayoso, D. Baumann, et al.. 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)$^2$. European Physical Journal A, EDP Sciences, 2008, 37, pp.1-8. ⟨10.1140/epja/i2008-10609-3⟩. ⟨in2p3-00261506⟩

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