Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic excitation in relativistic heavy ion collisions   In this note we study the conversion of nucleons into deltas induced by a
strong magnetic field in ultraperipheral relativistic heavy ion collisions. The
interaction Hamiltonian couples the magnetic field to the spin operator, which,
acting on the spin part of the wave function, converts a spin 1/2 into a spin
3/2 state. We estimate this transition probability and calculate the cross
section for delta production. This process can in principle be measured, since
the delta moves close to the beam and decays almost exclusively into pions.
Forward pions may be detected by forward calorimeters.

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The categories of this paper are: atom-ph
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The categories of this paper are: nlin
1
The categories of this paper are: cs
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The categories of this paper are: alg-geom
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The categories of this paper are: gr-qc
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The categories of this paper are: econ
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The categories of this paper are: q-bio
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: funct-an
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The categories of this paper are: chao-dyn
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The categories of this paper are: acc-phys
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The categories of this paper are: bayes-an
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The categories of this paper are: math