Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Cross Section Evaluation by Spinor Integration I: The massless case in
  4D   To get the total cross section of one interaction from its amplitude ${\cal
M}$, one needs to integrate $|{\cal M}|^2$ over phase spaces of all out-going
particles. Starting from this paper, we will propose a new method to perform
such integrations, which is inspired by the reduced phase space integration of
one-loop unitarity cut developed in the last few years. The new method reduces
one constrained three-dimension momentum space integration to an
one-dimensional integration, plus one possible Feynman parameter integration.
There is no need to specify a reference framework in our calculation, since
every step is manifestly Lorentz invariant by the new method. The current paper
is the first paper of a series for the new method. Here we have exclusively
focused on massless particles in 4D. There is no need to carve out a
complicated integration region in the phase space for this particular simple
case because the integration region is always simply $[0,1]$.

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The categories of this paper are: q-bio
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-th
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The categories of this paper are: math
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-alg
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The categories of this paper are: physics
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-lat
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The categories of this paper are: cs
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The categories of this paper are: ao-sci
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: adap-org