Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Test of CP Symmetry in Positronium   The aim of this CP symmetry test in positronium is to measure the CP
violation amplitude parameter \ccp. This is derived from the measurement of the
asymmetry in an angular distribution of the photons from the decay of the
ortho-positronium in a magnetic field. The Standard Model prediction for \ccp\
is a value of the order of $10^{-9}$. Thus the observation of a larger \ccp\
value would be signal of physics beyond the Standard Model. A previous
measurement has found \ccp consistent with zero, with an uncertainty of $\sim
10^{-2}$. We have investigated the possibility of using the existing
ETHZ-INRM-IN2P3 BGO crystal detector, set-up for positronium physics studies,
to improve the sensitivity on the \ccp measurement. Preliminary calculations
indicate that, using such an apparatus, with some modification, in a magnetic
field of 4 kGauss, \ccp could be measured with an uncertainty in the range
between $\sim 10^{-4}$ and $\sim 10^{-3}$, depending mainly on the uncertainty
in the asymmetry measurement and the angular resolution of the photon
detectors. If \ccp is less than $\sim 10^{-4}$, the experimental technique
outlined here appears to be inadequate to observe a CP violating effect and new
techniques or different observables must be exploited for better sensitivity.

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The categories of this paper are: eess
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The categories of this paper are: math-ph
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The categories of this paper are: solv-int
2
The categories of this paper are: math
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The categories of this paper are: nucl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: adap-org
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The categories of this paper are: nlin
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The categories of this paper are: econ
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The categories of this paper are: ao-sci
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The categories of this paper are: chao-dyn
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The categories of this paper are: bayes-an
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The categories of this paper are: astro-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: stat