SU(4) chiral quark model with configuration mixing

Abstract

Chiral quark model with configuration mixing and broken SU(3)×U(1) symmetry has been extended to include the contribution from cc fluctuations by considering broken SU(4) instead of SU(3). The implications of such a model have been studied for quark flavor and spin distribution functions corresponding to E866 and the NMC data. The predicted parameters regarding the charm spin distribution functions, for example, ∆c, There has been considerable interest in estimating the possible size of the intrinsic charm content of the nucleon [1][2][3][4][5]. Detailed investigations have been carried out regarding the size and implications of intrinsic charm contribution for nucleon [6] in a version of chiral quark model (χQM) [7][8][9][10][11][12][13] which is quite successful in giving a satisfactory explanation of "proton spin crisis" [14] including the violation of Gottfried sum rule [15][16][17]. Further, the same model is also able to account for the existence of significant strange quark contents [18,19] The successes of χQM in resolving the "proton spin crisis" and related issues strongly suggest that constituent quarks and the weakly interacting Goldstone bosons (GBs) provide the appropriate degrees of freedom in the nonperturbative regime of QCD. Thus the quantum fluctuations generated by broken chiral symmetry in χQM gcm should be able to provide a viable estimate of the heavier quark flavor, for example, cc, bb and tt. However, it is known that these flavor fluctuations are much suppressed in the case of bb and tt as compared to the cc because the intrinsic heavy quark contributions scale as 1/M 2 q , where M q is the mass of the heavy quark [1,30]. Therefore, regarding the intrinsic charm flavor content of the nucleon one should estimate only the contribution of cc fluctuations and for that one should be considering the extension of SU(3) symmetry in χQM to SU(4).The purpose of the present communication, on the one hand, is to extend χQM gcm with broken SU(3)×U(1) symmetry to broken SU(4)×U(1) symmetry. On the other hand, using the NMC [16] and the latest E866 data [17], we intend to study the implications of such a model for quark flavor and spin distribution functions, in particular the charm quark flavor and spin distribution functions.The details of χQM gcm within the SU(3) framework have already been discussed in Ref.[32], here we discuss the essentials of its extension to SU(4) χQM gcm . To begin with, the basic process in the χQM is the emission of a GB which further splits into qq pair, for example,wherein qq ′ pairs and q ′ constitute the "quark sea" with q ′ having opposite helicity as that of q. The effective Lagrangian describing interaction between quarks and the mesons in the SU(4) case iswhere g 15 is the coupling constant, 1

Radiative decays of decuplet baryons,Λ(1405)andΛ(1520)hyperons in the chiral quark model

“…On the other hand, a series of interesting work about the chiral quark model [15,16,17,18] indicates that the constituent quarks and internal Goldstone bosons can offer an adequate description of flavor and spin structure of baryons in the low Q 2 1 GeV 2 region. Within the same framework, the octet and decuplet magnetic moments, ΣΛ transition magnetic moments and the explanation of the violation of the Coleman-Glashow sum rule are in remarkably good agreement with experimental data [19,20]. So it is interesting to explore whether we can make reliable predictions of other important observables using the chiral quark model.…”

QCD sum rules for 70 - plet baryons

“…QCD sum rules remain essentially the same [9,10] (only with γ 5 inside, to change baryon parity) while NRQM gives μ 70 [1] and references therein). We propose a way to arrive at the desired QCD sum rules in accord with the NRQM limit [11] with the help of quark-diquark model which has led previously to Eq.(3).…”

“…We propose a way to arrive at the desired QCD sum rules in accord with the NRQM limit [11] with the help of quark-diquark model which has led previously to Eq.(3). Let us take quark wave functions of the 70-plet baryon [1] (and we take Σ 0 ) as (subindices 1,2 mean ↑,↓, correspondingly):…”

“…(ψ (0 + ) and ψ " (0 + ) are spatial wave functions [1]). To obtain Λ wave functions, and also to control the formulae, we use relations with the exchange of quarks:…”

“…In the quark model these baryons are assigned usually to the 70-plet representation of SU (6), in contrast to the 1/2 + baryons of the 56-plet (see [1,2] and the references therein).…”