Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spin Information from Vector-Meson Decay in Photoproduction   For the photoproduction of vector mesons, all single and double spin
observables involving vector meson two-body decays are defined consistently in
the $\gamma N$ center of mass. These definitions yield a procedure for
extracting physically meaningful single and double spin observables that are
subject to known rules concerning their angle and energy evolution. As part of
this analysis, we show that measuring the two-meson decay of a photoproduced
$\rho$ or $\phi$ does not determine the vector meson's vector polarization, but
only its tensor polarization. The vector meson decay into lepton pairs is also
insensitive to the vector meson's vector polarization, unless one measures the
spin of one of the leptons. Similar results are found for all double spin
observables which involve observation of vector meson decay. To access the
vector meson's vector polarization, one therefore needs to either measure the
spin of the decay leptons, make an analysis of the background interference
effects or relate the vector meson's vector polarization to other accessible
spin observables.

18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
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The categories of this paper are: q-fin
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The categories of this paper are: supr-con
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The categories of this paper are: math
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-lat