Mass and width of the {sigma}(750) scalar meson from measurements of {pi}N{r_arrow}{pi}{sup {minus}}{pi}{sup +}N on polarized targets
- Department of Physics, Dawson College, Montreal, Quebec, H3Z 1A4 (CANADA)
The measurements of reactions {pi}{sup {minus}}p{sub {up_arrow}}{r_arrow}{pi}{sup {minus}}{pi}{sup +}n at 17.2 GeV/c and {pi}{sup +}n{sub {up_arrow}}{r_arrow}{pi}{sup +}{pi}{sup {minus}}p at 5.98 and 11.85 GeV/c on polarized targets at CERN provide model-independent and solution-independent evidence for a narrow scalar state {sigma}(750). The original {chi}{sup 2} minimization method and the recent Monte Carlo method for the amplitude analysis of data at 17.2 GeV/c are in excellent agreement. Both methods find that the mass distribution of the measured amplitude {vert_bar}{bar S}{vert_bar}{sup 2}{Sigma} with recoil transversity `up` resonates near 750 MeV while the amplitude {vert_bar}S{vert_bar}{sup 2}{Sigma} with recoil transversity `down` is large and nonresonating. The amplitude {vert_bar}S{vert_bar}{sup 2}{Sigma} contributes as a strong background to S-wave intensity I{sub S}=({vert_bar}S{vert_bar}{sup 2}+{vert_bar}{bar S}{vert_bar}{sup 2}){Sigma} and distorts the determinations of {sigma} resonance parameters from I{sub S}. To avoid this problem we perform a series of Breit-Wigner fits directly to the measured distribution {vert_bar}{bar S}{vert_bar}{sup 2}{Sigma}. The inclusion of various backgrounds causes the width of {sigma}(750) to become very narrow. Our best fit with a t-averaged coherent background yields m{sub {sigma}}=753{plus_minus}19MeV and {Gamma}{sub {sigma}}=108{plus_minus}53MeV. These values are in excellent agreement with the 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}{r_arrow}{pi}{pi}. We also show how data on polarized target invalidate essential assumptions of past determinations of {pi}{pi} phase shifts which explains the absence of {sigma}(750) in the conventional phase shift {delta}{sub 0}{sup 0}. (Abstract Truncated)
- OSTI ID:
- 562866
- Journal Information:
- Physical Review, D, Journal Name: Physical Review, D Journal Issue: 9 Vol. 55; ISSN 0556-2821; ISSN PRVDAQ
- Country of Publication:
- United States
- Language:
- English
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