We give a pedagogical analysis on K-matrix models describing theπN scattering amplitude,in S11 channel at low energies.We show how the correct use of analyticity in the s-channel and crossing symmetry in t-and u-chan...We give a pedagogical analysis on K-matrix models describing theπN scattering amplitude,in S11 channel at low energies.We show how the correct use of analyticity in the s-channel and crossing symmetry in t-and u-channels leads to a much improved analytic behavior in the negative s region,in agreement with the prediction from chiral perturbation amplitudes in its validity region.The analysis leads again to the conclusion that a genuine N^*(890)resonance exists.展开更多
Extensive dynamical N/D calculations are conducted in the study of S_(11) channel low energy πN scatterings,based on various phenomenological model inputs of left cuts at the tree level.The subtleties of the singular...Extensive dynamical N/D calculations are conducted in the study of S_(11) channel low energy πN scatterings,based on various phenomenological model inputs of left cuts at the tree level.The subtleties of the singular behavior of the partial wave amplitude,at the origin of the complex s plane,are analysed in detail.Furthermore,it is found that the dispersion representation for the phase shift,δ,must be modified in the case of πN scatterings.An additional contribution from the dispersion integral exists,which approximately cancels the contribution of the two virtual poles located near the end points of the segment cut,induced by u channel nucleon exchanges.With limited reliance on the details of the dynamical inputs,the subthreshold resonance N*(890)survives.展开更多
The recently proposed N^(*)(890)1/2^(-)baryon is studied in a flavor SU(3) scheme with K-matrix unitarization,by fitting to low-energy cross section and phase shift data.It is found that N^(*)(890) co-exists with low-...The recently proposed N^(*)(890)1/2^(-)baryon is studied in a flavor SU(3) scheme with K-matrix unitarization,by fitting to low-energy cross section and phase shift data.It is found that N^(*)(890) co-exists with low-lying poles in other channels,which have been extensively discussed in the literature,though they belong to different octets in the SU(3) limit.Hence,the existence of N^(*)(890) is further verified.展开更多
We present a dispersive representation of the γN→πN partial-wave amplitude based on unitarity and analyticity.In this representation,the right-hand-cut contribution responsible for πN final-state-interaction effec...We present a dispersive representation of the γN→πN partial-wave amplitude based on unitarity and analyticity.In this representation,the right-hand-cut contribution responsible for πN final-state-interaction effects is taken into account via an Omnes formalism with elastic πN phase shifts as inputs,while the left-hand-cut contribution is estimated by invoking chiral perturbation theory.Numerical fits are performed to pin down the involved subtraction constants.Good fit quality can be achieved with only one free parameter,and the experimental data regarding the multipole amplitude E0+ in the energy region below the △(1232) are well described.Furthermore,we extend the γN →μN partial-wave amplitude to the second Riemann sheet to extract the couplings of the N*(890).The modulus of the residue of the multipole amplitude E0+(S11pE) is 2.41 mfm·GeV2,and the partial width of N*(890)→ yN at the pole is approximately 0.369 MeV,which is almost the same as that of the N*(1535) resonance,indicating that N*(890) strongly couples to the πN system.展开更多
基金supported in part by the National Nature Science Foundations of China under contract numbers 11975028 and 10925522by the Sino-German CRC 110(Grant No.TRR110)。
文摘We give a pedagogical analysis on K-matrix models describing theπN scattering amplitude,in S11 channel at low energies.We show how the correct use of analyticity in the s-channel and crossing symmetry in t-and u-channels leads to a much improved analytic behavior in the negative s region,in agreement with the prediction from chiral perturbation amplitudes in its validity region.The analysis leads again to the conclusion that a genuine N^*(890)resonance exists.
基金Support in part by National Nature Science Foundations of China (11975028, 10925522)the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)(196253076-TRR 110)
文摘Extensive dynamical N/D calculations are conducted in the study of S_(11) channel low energy πN scatterings,based on various phenomenological model inputs of left cuts at the tree level.The subtleties of the singular behavior of the partial wave amplitude,at the origin of the complex s plane,are analysed in detail.Furthermore,it is found that the dispersion representation for the phase shift,δ,must be modified in the case of πN scatterings.An additional contribution from the dispersion integral exists,which approximately cancels the contribution of the two virtual poles located near the end points of the segment cut,induced by u channel nucleon exchanges.With limited reliance on the details of the dynamical inputs,the subthreshold resonance N*(890)survives.
基金Supported in part by National Nature Science Foundations of China (11975028,10925522)。
文摘The recently proposed N^(*)(890)1/2^(-)baryon is studied in a flavor SU(3) scheme with K-matrix unitarization,by fitting to low-energy cross section and phase shift data.It is found that N^(*)(890) co-exists with low-lying poles in other channels,which have been extensively discussed in the literature,though they belong to different octets in the SU(3) limit.Hence,the existence of N^(*)(890) is further verified.
基金Supported by National Nature Science Foundations of China(NSFC)(11905258,11975028,10925522)by the Fundamental Research Funds for the Central Universities(531118010379)。
文摘We present a dispersive representation of the γN→πN partial-wave amplitude based on unitarity and analyticity.In this representation,the right-hand-cut contribution responsible for πN final-state-interaction effects is taken into account via an Omnes formalism with elastic πN phase shifts as inputs,while the left-hand-cut contribution is estimated by invoking chiral perturbation theory.Numerical fits are performed to pin down the involved subtraction constants.Good fit quality can be achieved with only one free parameter,and the experimental data regarding the multipole amplitude E0+ in the energy region below the △(1232) are well described.Furthermore,we extend the γN →μN partial-wave amplitude to the second Riemann sheet to extract the couplings of the N*(890).The modulus of the residue of the multipole amplitude E0+(S11pE) is 2.41 mfm·GeV2,and the partial width of N*(890)→ yN at the pole is approximately 0.369 MeV,which is almost the same as that of the N*(1535) resonance,indicating that N*(890) strongly couples to the πN system.
