CHIRAL QUARK MODEL (χ<font>QM</font>) AND THE NUCLEON SPIN

Dahiya, Harleen; Gupta, Manmohan

doi:10.1142/s0217751x04019949

Cited by 21 publications

(20 citation statements)

References 36 publications

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“…In the Table I, we have also presented the results of our calculations for the flavor singlet component of the spin of proton ∆Σ, however we have not discussed its implications for different cases. It has already been discussed earlier in χCQM [32] that ∆Σ receives contributions from various sources such as valence quarks, quark sea, gluon polarization etc.. In the context of χCQM, it seems that gluon anomaly not only contributes to the gluon polarization but also is responsible for the large mass of η ′ [20].…”

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confidence: 99%

Chiral Constituent Quark Model and the Coupling Strength of Η′

Dahiya

Gupta

Rana

2006

Int. J. Mod. Phys. A

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Using the latest data pertaining toū −d asymmetry and the spin polarization functions, detailed implications of the possible values of the coupling strength of the singlet Goldstone boson η ′ have been investigated in the χCQM with configuration mixing. Using ∆u, ∆3,ū−d andū/d, the possible ranges of the coupling parameters a, α 2 a, β 2 a and ζ 2 a, representing respectively the probabilities of fluctuations to pions, K, η and η ′ , are shown to be 0.10 < ∼ a < ∼ 0.14, 0.2 < ∼ α < ∼ 0.5, 0.2 < ∼ β < ∼ 0.7 and 0.10 < ∼ |ζ| < ∼ 0.70. To further constrain the coupling strength of η ′ , detailed fits have been obtained for spin polarization functions, quark distribution functions and baryon octet magnetic moments corresponding to the following sets of parameters: a = 0.1, α = 0.4, β = 0.7, |ζ| = 0.65 (Case I); a = 0.1, α = 0.4, β = 0.6, |ζ| = 0.70 (Case II); a = 0.14, α = 0.4, β = 0.2, ζ = 0 (Case III) and a = 0.13, α = β = 0.45, |ζ| = 0.10 (Case IV). Case I represents the calculations where a is fixed to be 0.1, in accordance with earlier calculations, whereas other parameters are treated free and the Case IV represents our best fit. The fits clearly establish that a small non-zero value of the coupling of η ′ is preferred over the higher values of η ′ as well as when ζ = 0, the latter implying the absence of η ′ from the dynamics of χCQM. Our best fit achieves an overall excellent fit to the data, in particular the fit for ∆u, ∆d, ∆8 as well as the magnetic moments µn, µ Σ − , µ Σ + and µ Ξ − is almost perfect, the µ Ξ − being a difficult case for most of the similar calculations.The chiral constituent quark model (χCQM), as formulated by Manohar and Georgi [1], has recently got good deal of attention [2][3][4][5] as it is successful in not only explaining the "proton spin crisis" [6] but is also able to account for theū −d asymmetry [7-9], existence of significant strange quark contents in the nucleon, various quark flavor contributions to the proton spin [2], baryon magnetic moments [2,3] and hyperon β−decay parameters etc.. Recently, it has been shown that configuration mixing generated by spin-spin forces [10][11][12], known to be compatible with the χCQM [13][14][15], improves the predictions of χCQM regarding the quark distribution functions and the spin polarization functions [16]. Further, χCQM with configuration mixing (henceforth to be referred as χCQM config ) when coupled with the quark sea polarization and orbital angular momentum (Cheng-Li mechanism [17]) as well as "confinement effects" is able to give an excellent fit [16] to the baryon magnetic moments and a perfect fit for the violation of Coleman Glashow sum rule [18].The key to understand the "proton spin problem", in the χCQM formalism [3], is the fluctuation process

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confidence: 99%

Chiral Constituent Quark Model and the Coupling Strength of Η′

Dahiya

Gupta

Rana

2006

Int. J. Mod. Phys. A

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“…The calculation of the magnetic moments in the χCQM with SU(3) broken symmetry requires the symmetry breaking parameters a, aα 2 , aβ 2 , and aζ 2 , representing, respectively, the probabilities of fluctuations of a constituent quark into pions, kaons, η, and η ′ . The best fit to the set of parameters obtained by carrying out a fine grained analysis of the spin and flavor distribution functions of the proton [21][22][23][24][25][30][31][32][33] gives a = 0.12 , α = β = 0.45 , ζ = −0.15 .…”

Section: Resultsmentioning

confidence: 99%

Magnetic moments of the low-lying $$\tfrac{1} {2}^ -$$ octet baryon resonances

et al. 2013

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The magnetic moments of the negative parity octet resonances with spin 1 2 : N * (1535), N * (1650), Σ * (1620), and Ξ * (1690) have been calculated within the framework of the chiral constituent quark model. In this approach, the presence of the polarized qq pairs (or the meson cloud, in other words) is considered by using the Lagrangian for Goldstone boson emission from the constituent quarks. Further, the explicit contributions coming from the spin and orbital angular momentum, including the effects of the configurations mixing between the states with different spins, are obtained. The motivation for these calculations comes from the recent interest in experimental measurement of the magnetic moment of the S 11 (1535) resonance and of similar calculations being done within lattice quantum chromodynamics approaches. Our results can be compared with those expected to come from these sources.

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“…where qq ′ + q ′ constitute the sea quarks [91][92][93][94][95][98][99][100][101][102][103][104][105][106][107][108]. The GB field can be expressed in terms of the GBs and their transition probabilities as…”

Section: Model (χCqm)mentioning

confidence: 99%

Electromagnetic and axial-vector form factors of the quarks and nucleon

Dahiya

Randhawa

2017

Int. J. Mod. Phys. A

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In light of the improved precision of the experimental measurements and enormous theoretical progress, the nucleon form factors have been evaluated with an aim to understand how the static properties and dynamical behavior of nucleons emerge from the theory of strong interactions between quarks. We have analysed the vector and axial-vector nucleon form factors (G p,n E,M (Q 2 ) and G p,n A (Q 2 )) using the spin observables in the chiral constituent quark model (χCQM) which has made a significant contribution to the unraveling of the internal structure of the nucleon in the nonperturbative regime. We have also presented a comprehensive analysis of the flavor decomposition of the form factors (G q E (Q 2 ), G q M (Q 2 ) and G q A (Q 2 )for q = u, d, s) within the framework of χCQM with emphasis on the extraction of the strangeness form factors which are fundamental to determine the spin structure and test the chiral symmetry breaking effects in the nucleon. The Q 2 dependence of the vector and axial-vector form factors of the nucleon has been studied using the conventional dipole form of parametrization. The results are in agreement with the available experimental data.

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CHIRAL QUARK MODEL (χQM) AND THE NUCLEON SPIN

Cited by 21 publications

References 36 publications

Chiral Constituent Quark Model and the Coupling Strength of Η′

Chiral Constituent Quark Model and the Coupling Strength of Η′

Magnetic moments of the low-lying $$\tfrac{1} {2}^ -$$ octet baryon resonances

Electromagnetic and axial-vector form factors of the quarks and nucleon

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