Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mass and width of sigma(750) scalar meson from measurements of
  piN->pi(-)pi(+)N on polarized targets   The measurements of reactions $\pi^- p_\uparrow \to \pi^- \pi^+ n$ at 17.2
GeV/c and $\pi^+ n_\uparrow \to \pi^+ \pi^- p$ at 5.98 and 11.85 GeV/c made at
CERN with polarized targets provide a model-independent and
solution-independent evidence for a narrow scalar state sigma(750). The
original chi^2 minimization method and the recent Monte Carlo method for
amplitude analysis of data at 17.2 GeV/c are in excellent agreement. Both
methods find that the mass distribution of the measured amplitude $|\overline S
|^2\Sigma$ with recoil transversity ``up'' resonates near 750 MeV while the
amplitude $|S|^2\Sigma$ with recoil transversity ``down'' is large and
nonresonating. The amplitude $|S|^2\Sigma$ contributes as a strong background
to S-wave intensity I_S = (|S|^2 + |\overline S |^2)\Sigma$ and distorts the
determinations of $\sigma$ resonance parameters from $I_S$. To avoid this
problem we perform a series of Breit-Wigner fits directly to the measured
distribution $|\overline S |^2\Sigma$. The inclusion of various backgrounds
causes the width of sigma(750) to become very narrow. Our best fit with
$t$-averaged coherent background yields $m_\sigma = 753 \pm 19$ MeV and
$\Gamma_\sigma = 108 \pm 53$ MeV. These values are in excellent agreement with
Ellis-Lanik theorem for the width of scalar gluonium. The gluonium
interpretation of $\sigma(750)$ is also supported by the absence of
$\sigma(750)$ in reactions $\gamma\gamma \to \pi\pi$. We also show how data on
polarized target invalidate essential assumptions of past determinations of
$\pi\pi$ phase shifts .

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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: q-fin
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The categories of this paper are: eess
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The categories of this paper are: nlin
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The categories of this paper are: plasm-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-th
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The categories of this paper are: quant-ph
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The categories of this paper are: stat
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The categories of this paper are: astro-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: math
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The categories of this paper are: cond-mat
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The categories of this paper are: cmp-lg
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The categories of this paper are: adap-org