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The width of the xi(2230) meson

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 Added by Lon-chang Liu
 Publication date 2002
  fields
and research's language is English
 Authors L. C. Liu




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A lower bound of 135 MeV for the width of the xi meson is obtained from analyzing the pp and pbar-p interactions by use of Regge theory. The pp data exclude a narrow xi as the latter would lead to total pbar-p cross sections far exceeding the measured ones. The broad width explains why the xi may not be seen in pbarp-p experiments.



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49 - L. C. Liu , Wei-hsing Ma 2000
We examine the possibility that the xi(2230) meson is a member of the Pomeron trajectory. A method of connecting the xi --> p pbar decay width and the pp cross sections through the Pomeron residue function is presented. We have used a relativistic, singularity-free form factor to make the analytic continuation of the residue function between crossed channels. We predict that if the xi(2230) meson is a Pomeron, then it should have a xi --> p pbar decay width of about 2 MeV.
We present a lattice QCD calculation of the $rho$ meson decay width via the $P$-wave scattering phase shift for the I=1 two-pion system. Our calculation uses full QCD gauge configurations for $N_f=2$ flavors generated using a renormalization group improved gauge action and an improved Wilson fermion action on a $12^3times24$ lattice at $m_pi/m_rho=0.41$ and the lattice spacing $1/a=0.92 {rm GeV}$. The phase shift calculated with the use of the finite size formula for the two-pion system in the moving frame shows a behavior consistent with the existence of a resonance at a mass close to the vector meson mass obtained in spectroscopy. The decay width estimated from the phase shift is consistent with the experiment, when the quark mass is scaled to the realistic value.
Using 13.4 $fb^{-1}$ of data collected with the CLEO detector at the Cornell Electron Storage Ring, we have observed 300 events for the two-photon production of ground-state pseudo-scalar charmonium in the decay $eta_c$ -> $K_S K^{mp} pi^{pm}$. We have measured the $eta_c$ mass to be (2980.4 +- 2.3 (stat) +- 0.6 (sys)) MeV and its full width as (27.0 +- 5.8 (stat) +- 1.4 (sys)) MeV. We have determined the two-photon partial width of the $eta_c$ meson to be (7.6 +- 0.8 (stat) +- 0.4 (sys) +- 2.3 (br)) keV, with the last uncertainty associated with the decay branching fraction.
Taking advantage of both the low-emittance proton-beam of the Cooler Synchrotron COSY and the high momentum precision of the COSY-11 detector system, the mass distribution of the eta meson was measured with a resolution of 0.33 MeV/c^2 (FWHM), improving the experimental mass resolution by almost an order of magnitude with respect to previous results. Based on the sample of more than 2300 reconstructed pp --> pp eta events the total width of the eta meson was determined to be 0.226 +- 0.017(stat.) +- 0.014(syst.) MeV/c^2.
We present preliminary results on the $rho$ meson decay width from $N_f=2+1$ full QCD configurations generated by PACS-CS Collaboration. The decay width is estimated from the $P$-wave scattering phase shift for the isospin $I=1$ two-pion system. The finite size formula presented by Luscher in the center of mass frame and its extension to non-zero total momentum frame by Rummukainen and Gottlieb are employed for the calculations of the phase shift. Our calculations are carried out at $m_pi=410 {rm MeV}$ ($m_pi/m_rho=0.46$) and $a=0.091 {rm fm}$ on a $32^3times 64$ ($La=2.9 {rm fm}$) lattice.
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