The quark distributions in the Σ+ hyperon

We calculate the nucleon strangeness y N in the chiral quark model and the meson cloud model. With the internal relation between the sigma term of N ( N ) and y N , we present the results of N in these two models. Our calculations show that y N from the chiral quark model is significantly larger than that from the meson cloud model, whereas the difference of N between the two models is relatively small. We also present the results of KN and N , which could be determined by N and y N from their definition in the current algebra, and find that these two physical parameters are quite sensitive to y N . The results indicate the necessity to restrict the parameters of the two models from more precision measurements.

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“…The meson cloud model is very successful in explaining many nonperturbative properties of the nucleon [31][32][33][34][35][36].…”

Section: Meson Cloud Modelmentioning

confidence: 99%

Phenomenological analysis of nucleon strangeness and meson-nucleon sigma terms

Huang

Cao

2007

Phys. Rev. D

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“…In particular, this was discussed for 0 [24,25] and ± [26][27][28][29]. The 0 is charge neutral and has a short lifetime, but 0 fragmentation processes can be used to reveal its quark distributions, as discussed in Refs.…”

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confidence: 99%

“…The 0 is charge neutral and has a short lifetime, but 0 fragmentation processes can be used to reveal its quark distributions, as discussed in Refs. [23][24][25], while for the , Drell-Yan experiments with beams on protons and deuterium have been suggested [23,26,27,29].…”

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confidence: 99%

“…In order to distinguish between the predictions of the different models and to obtain a better understanding of the nonperturbative structure of QCD, new experiments are needed to measure the flavor asymmetry of hyperons. In particular, the flavor asymmetry of charged hyperons can be obtained from Drell-Yan experiments using charged hyperon beams on the proton [26,27] or by means of backward K ± electroproduction [48].…”

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confidence: 99%

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Flavor asymmetry of sea quarks in the unquenched quark model

Santopinto

Bijker

2010

Phys. Rev. C

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The flavor asymmetry of the nucleon sea is studied in the framework of the unquenched quark model in which the effects of quark-antiquark pairs (uū, dd, and ss) are taken into account via a microscopic, QCD-inspired, quark-antiquark creation mechanism. The inclusion of the qq pairs leads to an excess ofd overū, in agreement with the experimental data for the proton. In addition, the results for the flavor asymmetry of all ground-state octet and decuplet baryons are presented. The isospin symmetry leads to simple relations among the flavor asymmetries of octet and decuplet baryons. The flavor asymmetry of the + hyperon is predicted to be very similar to that of the proton and much larger than that for the 0 hyperon. A comparison with other approaches shows large differences in the predictions for the flavor asymmetries of the hyperons.Introduction. From an experimental point of view, the flavor asymmetry betweenū andd quarks in the proton is now well established [1-8]; for review, see also Refs. [9,10]. It is well known [11,12] that perturbative QCD is not able to account for this asymmetry. In fact, for quark-antiquark pairs created perturbatively, the sea quarks generated by leading twist evolution, i.e., from gluon splitting, are flavor symmetric with the same amount of uū as dd and ss. Thus the flavor asymmetry of the nucleon sea is assumed to have a nonperturbative origin, and since currently it is still a big challenge to perform calculations from the first principles of QCD in the nonperturbative region, one has to try to understand the situation with effective models of hadrons, in terms of constituent quark degrees of freedom and/or meson-baryon degrees of freedom.The flavor content of the nucleon sea provides an important test for models of the nucleon structure. The quark-parton model predicts a flavor symmetric sea that leads to the Gottfried sum rule S G = 1/3 [13], whereas any deviation from this value is an indication of thed/ū asymmetry of the nucleon sea, thus providing a clean evidence of the existence of nonperturbative higher Fock components (such as qqq-qq configurations) in the proton wave function. The first clear evidence of a flavor asymmetric sea and a related violation of the Gottfried sum rule came in 1991 from the New Muon Collaboration (NMC) [1], which was later confirmed in Drell-Yan experiments [4][5][6][7] that probe the ratioū/d, as well as in semi-inclusive deep-inelastic scattering (SIDIS) experiments [8]. All these experiments show evidence that there are morē d quarks in the proton than there areū quarks [10].Many phenomenological models have been applied to the flavor asymmetry of the nucleon sea, e.g., meson-cloud models [14-16] (see Ref.[17] for other references), chiral quark

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“…In previous articles applying meson cloud model to explain the light flavor sea asymmetry in the nucleon, a good description of the data was obtained for the distribution functions [8]. The dominant role is played by the pion, which provides that d(x)/u(x) either increases monotonically with x or turns back towards unity too slowly [8,9]. Many explanations have been applied to attack this problem [10,11,12,13], such as effects of ∆ [10,11,12], the influence of the Pauli exclusion principle [12], adjustment of parameters [13], but none of these explanations provides a satisfactory description of the ratio d(x)/u(x).…”

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confidence: 99%