Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Isospin Symmetry Breaking in the Quark Condensates, $< \bar dd>\not= <
  \bar uu>$, as Estimated from QCD Sum Rules   Isospin symmetry breaking in the quark condensates, $< \bar dd> \not= < \bar
uu>$, is a fundamental parameter in both the QCD sum rule studies and the
chiral perturbation theory. In this article, we apply the QCD sum rule method
to treat the hyperon mass difference ${1\over
2}(m_{\Sigma^-}+m_{\Sigma^0})-m_{\Sigma^+}$ in order to obtain a reasonable
estimate on such isospin symmetry breaking parameter $\gamma$ defined as $(<
\bar dd>-< \bar uu>)/ < \bar uu>$. Note that the electromagnetic contributions
to the particular mass difference are expected to cancel almost completely.
Using the light-quark mass difference $m_d-m_u=4\pm 1$ MeV and the experimental
data ${1\over 2}(m_{\Sigma^-}+m_{\Sigma^0})-m_{\Sigma^+}$$=5.62\pm 0.13$ MeV,
we obtain $\gamma= -0.011\pm 0.001$, a value which is slightly larger than the
commonly adopted value and is of smaller uncertainty.

11
The categories of this paper are: hep-lat
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
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The categories of this paper are: astro-ph
27
The categories of this paper are: comp-gas
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The categories of this paper are: cond-mat
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn