Singlet GB contributions in the chiral constituent quark model

The implications of the latest data pertaining to ū−d̄ asymmetry and the spin polarization functions on the contributions of singlet Goldstone Boson η′ within χCQM with configuration mixing for explaining the “proton spin problem” have been investigated. It is found that the present data favors smaller values of the coupling of singlet Goldstone Boson η′ as compared to the corresponding contributions from π, K and η Goldstone bosons. It seems that a small non-zero value of the coupling of η′ (ζ 6= 0) is preferred over ζ = 0 phenomenologically. The chiral constituent quark model (χCQM), as formulated by Manohar and Georgi [1, 2], has recently got good deal of attention [3, 4, 5, 6] as it is successful in not only explaining the “proton spin crisis” [7, 8, 9, 10] through the emission of a Goldstone boson (GB) but is also able to account for the ū − d̄ asymmetry [11, 12, 13], existence of significant strange quark content s̄ in the nucleon, various quark flavor contributions to the proton spin [3], baryon magnetic moments [3, 4] and hyperon β−decay parameters etc.. Recently, it has been shown that configuration mixing generated by spinspin forces [14, 15, 16], known to be compatible with the χCQM [17, 18, 19],