Existence of theσmeson below 1 GeV and chiral symmetry

Abstract

On the basis of a simultaneous description of the isoscalar s-wave channel of the ππ scattering (from the threshold up to 1.9 GeV) and of the ππ → KK process (from the threshold to ∼ 1.4 GeV) in the model-independent approach, a confirmation of the σ-meson at ∼ 665 MeV and an indication for the glueball nature of the f 0 (1500) state are obtained. It is shown that the large ππ-background, usually obtained, combines, in reality, the influence of the left-hand branch-point and the contribution of a very wide resonance at ∼ 665 MeV. The coupling constants of the observed states with the ππ and KK systems and lengths of the ππ and KK scattering are obtained.

Vector meson production and nucleon resonance analysis in a coupled-channel approach for energiesmN<s<Penner1, Mosel2 2002Phys. Rev. C1428502View full textAdd to dashboardCite

“…The value for m σ is in line with the values found by Refs. [23] and [19], and also in the range of ππ calculations and predictions [33,34].…”

On lower scalar quark-antiquark nonets

“…According to the same arguments about the ππ background, it seems that a real evidence of the σ-meson below 1 GeV has been obtained only in our works [8,10]. However, in the σ-meson pole-cluster (see Table 2), the imaginary part of the pole on sheet III is too small (the pole cluster must be rather compact formation).…”

“…Earlier we have shown that a minimum scenario of the combined description of processes ππ → ππ, KK goes without the f 0 (1370) and f 0 (1710) resonances [8]. However, other analyses of these and other processes point to an existence of these two states [7].…”

“…KK molecule) and a qq bound state [8,17,38]. Just as in the 1-channel case, the existence of a particle bound state means the presence of a pole on the real axis under the threshold on the physical sheet, so in the 2-channel case, the existence of a particle bound state in channel 2 (KK molecule) that, however, can decay into channel 1 (ππ decay), would imply the presence of a pair of complex conjugate poles on sheet II under the secondchannel threshold without an accompaniment of the corresponding shifted pair of poles on sheet III.…”

“…For example, the actively discussed f 0 (600) meson is obtained in a number of analyses to be rather wide (see, e.g., [7], p. 010001-452), and even very wide (near to 1 GeV) [8][9][10][11][12] having properties of the σ-meson. This result and the obtained ππ-scattering length (in work [10] we obtain a 0 0 (ππ) ≈ 0.27[m −1 π + ]) suggest the linear realization of chiral symmetry, because the greatest value for a 0 0 (ππ), that one was able to obtain in the chiral perturbation theory, is 0.220 ± 0.005 [9].…”