Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Radiative corrections to pion-nucleus bremsstrahlung   We calculate the one-photon loop radiative corrections to virtual pion
Compton scattering $\pi^- \gamma^* \to \pi^- \gamma$, that subprocess which
determines in the one-photon exchange approximation the pion-nucleus
bremsstrahlung reaction $\pi^- Z\to \pi^- Z \gamma$. Ultraviolet and infrared
divergencies of the loop integrals are both treated by dimensional
regularization. Analytical expressions for the ${\cal O}(\alpha)$ corrections
to the virtual Compton scattering amplitudes, $A(s,u,Q)$ and $B(s,u,Q)$, are
derived with their full dependence on the (small) photon virtuality $Q$ from 9
classes of contributing one-loop diagrams. Infrared finiteness of these virtual
radiative corrections is achieved (in the standard way) by including soft
photon radiation below an energy cut-off $\lambda$. In the region of low $\pi^-
\gamma$ center-of-mass energies, where the pion-nucleus bremsstrahlung process
is used to extract the pion electric and magnetic polarizabilities, we find
radiative corrections up to about -3% for $\lambda=5 $MeV. Furthermore, we
extend our calculation of the radiative corrections to virtual pion Compton
scattering $\pi^-\gamma^* \to \pi^- \gamma$ by including the leading pion
structure effect in form of the polarizability difference $\alpha_\pi -
\beta_\pi$. Our analytical results are particularly relevant for analyzing the
data of the COMPASS experiment at CERN which aims at measuring the pion
electric and magnetic polarizabilities with high statistics using the Primakoff
effect.

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The categories of this paper are: funct-an
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The categories of this paper are: chem-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: eess
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The categories of this paper are: bayes-an
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The categories of this paper are: cmp-lg
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The categories of this paper are: astro-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: math
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The categories of this paper are: hep-th
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The categories of this paper are: adap-org
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The categories of this paper are: alg-geom
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The categories of this paper are: dg-ga
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-th