Spin content ofΛin QCD sum rules

Abstract

We calculate the isoscalar axial-vector coupling constants of the Λ hyperon using the method of QCD sum rules. A determination of these coupling constants reveals the individual contributions of the u, d and the s quarks to the spin content of Λ. Our results for the light-quark contributions are in agreement with those from experiment assuming flavor SU(3). We also find that the flavor-SU(3)breaking effects are small and the contributions from the u and the d quarks to the Λ polarization are negatively polarized as in the flavor-SU(3) limit.

Manifestation of theP-wave diproton resonance in single-pion production inppcollisions

“…For the πNN vertex, we have chosen the valueΛ = 0.7 GeV, which was used in a number of previous calculations of single-pion production reactions [56,64]. This value of Λ is also consistent with the predictions of the lattice-QCD calculations [65,66].…”

Λ and Σ resonances coupled to vector and pseudoscalar mesons

“…Understanding meson-baryon interaction is an important aspect of exploring the strong interaction at low and intermediate energies. A lot of work has been done in this direction, especially in case of the low energy interaction of light pseudoscalar mesons and baryons, where several resonances in the baryon spectrum arise due to this interaction [1][2][3][4][5][6][7][8][9][10][11]. These states can be understood as weakly bound meson-baryon systems, whose existence originates directly from the characteristics of the theory of quantum chromodynamics (QCD), which leads to the generation of a quark-antiquark pair when the distance between the quarks increases.…”

Energy dependence of hadron polarization ine+e−→hXat high energies

“…There is not much progress on parameterizations of polarized FFs since DSV98 [49] besides some improvements for unpolarized FFs. There are however many phenomenological studies [6][7][8][9][10][11][12][13][14][15][16][17][18][19][50][51][52] using different models on hyperons polarization in different high energy reactions. We note in particular a series of analysis with the aids of the Monte-Carlo event generator such as PYTHIA based on Lund string fragmentation model [53,54] and another series [12][13][14][15][16][17][18] based on the Gribov relation [55] between PDFs and FFs.…”

“…With a Monte-Carlo event generator, one can analyze in detail the influence of different contributions. From these different phenomenological studies [6][7][8][9][10][11][12][13][14][15][16][17][18][19][50][51][52], we see that although there are distinct differences in different models, some features are common. Consistent with the data available [1][2][3][4][5], all models seem to suggest that polarization dependent FFs are important only in the large z region.…”