Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: $b \to s(d) \gamma$ with a Vector-like Quark as Fourth-generation   We study the implications of a vector-like quark, especially a down-type
vector-like quark in $b \rightarrow s(d) \gamma$ including the neutral Higgs in
the calculation. After analyzing some possible constraints for the mixing, the
contribution may be significant for the $b \rightarrow d \gamma$, but not for
the $b \rightarrow s \gamma$. We also find that the FCNC among ordinary quarks
vanishes for a special form of down-type quark mass matrix.

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The categories of this paper are: gr-qc
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The categories of this paper are: eess
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The categories of this paper are: math
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The categories of this paper are: quant-ph
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The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-lat
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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: q-fin
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The categories of this paper are: supr-con
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The categories of this paper are: q-bio
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The categories of this paper are: astro-ph
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The categories of this paper are: adap-org
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The categories of this paper are: ao-sci