Combined analysis of theπ−p→K0Λ,ηnreactions in a chiral quark model

Abstract

A combined analysis of the reactions π − p → K 0 Λ and ηn is carried out with a chiral quark model. The data in the center-of-mass (c.m.) energy range from threshold up to W ≃ 1.8 GeV are reasonably described. For π − p → K 0 Λ, it is found that N(1535)S 11 and N(1650)S 11 paly crucial roles near threshold. The N(1650)S 11 resonance contributes to the reaction through configuration mixing with N(1535)S 11 . The constructive interference between N(1535)S 11 and N(1650)S 11 is responsible for the peak structure around threshold in the total cross section. The n-pole, u-and t-channel backgrounds provide significant contributions to the reaction as well. While, for the π − p → ηn process, the "first peak" in the total cross section is dominant by N(1535)S 11 , which has a sizeable destructive interference with N(1650)S 11 . Around P π ≃ 1.0 GeV/c (W ≃ 1.7 GeV), there seems to be a small bump structure in the total cross section, which might be explained by the interference between the u-channel and N(1650)S 11 . The N(1520)D 13 resonance notably affects the angle distributions of the cross sections, although less effects are seen in the total cross section. The role of P-wave state N(1720)P 13 should be further confirmed by future experiments. If N(1720)P 13 has a narrow width of Γ ≃ 120 MeV as found in our previous work by a study of the π 0 photoproduction processes, obvious evidence should be seen in the π − p → K 0 Λ and ηn processes as well.

Quark model study of the πN→πN reactions up to the N(1440) resonance region

“…By a combined analysis of these reactions, we hope (i) to further test the validity of the chiral quark model and obtain a better understanding of the reaction mechanism for the πN scattering; (ii) to confirm the properties of ∆(1232)P 33 extracted from the π 0 -meson photoproduction processes in our previous work [36]; (iii) to extract some reliable information of N(1440)P 11 . In our previous quark model analyses of the π − p → ηn, K + Λ [34,35] and γN → ηN, π 0 N [36, 37] reactions, no obvious evidence of N(1440)P 11 is found.…”

“…For the main resonances ∆(1232)P 33 and N(1440)P 11 , we vary their masses and widths in a proper range to better describe the data. To be consistent with our previous study, we take the masses and widths of N(1535)S 11 and N(1520)D 13 from [34], where the resonances parameters of N(1535)S 11 and N(1520)D 13 are well constrained. The other resonances have few effects on the reactions, thus, their masses and widths are taken from the PDG [4], or the constituent quark model predictions [54][55][56] if no experimental data are available.…”

“…The t-channel backgrounds might play an important role in the reactions, thus, the t-channel contributions of vector exchange and the scalar exchange are considered in this work. The vector meson-quark and scalar meson-quark interactions are adopted by [34]…”

“…Furthermore, in some literature the N(1535)S 11 resonance is suggested to be a dynamically generated resonance by analyzing the πN reactions [29][30][31][32][33]. Recently, according to our chiral quark model study of the π − p → ηn, K + Λ [34,35], and γN → ηN, π 0 N reactions [36,37], the N(1535)S 11 resonance can be explained as a mixing three-quark state between representations of [70, 2 8] and [70, 4 8]. To deepen our understanding of the resonance properties from the πN reactions, more partial wave analyses are needed.…”

“…The chiral quark model has been well developed and successfully applied to pseudoscalar-meson photoproduction reactions [36,37,[39][40][41][42][43][44][45][46][47][48][49][50]. Recently, this model has been extended to π − p [34,35] and K − p [51][52][53] reactions as well, which provides some novel insights into the observables measured in these reactions.…”