The implications of one gluon exchange generated configuration mixing in the Chiral Quark Model (χQM gcm ) with SU(3) and axial U(1) symmetry breakings are discussed in the context of proton flavor and spin structure as well as the hyperon β-decay parameters. We find that χQM gcm with SU(3) symmetry breaking is able to give a satisfactory unified fit for spin and quark distribution functions, with the symmetry breaking parameters α = .4, β = .7 and the mixing angle φ = 20 o , both for NMC and the most recent E866 data. In particular, the agreement with data, in the case of G A /G V , ∆ 8 , F, D, f s and f 3 /f 8 , is quite striking.It is well known that the chiral quark model (χQM) [1,2,3] with SU(3) symmetry is not only able to give a fair explanation of "proton spin crisis" [4] but is also able to account for theū −d asymmetry [5,6,7] as well as the existence of significant strange quark contents in the nucleon when the asymmetric octet singlet couplings are taken into account [8]. Further, χQM with SU(3) symmetry is also able to provide fairly satisfactory explanation for various quark flavor contributions to the proton spin [9], baryon magnetic moments [3,9] as well as the absence of polarizations of the antiquark sea in the nucleon [10,11] . However, in the case of hyperon decay parameters the predictions of the χQM are not in tune with the data [12], for example, in comparison to the experimental numbers .21 and 2.17 the χQM with SU(3) symmetry predicts f 3 /f 8 and ∆ 3 /∆ 8 to be 1 3 and 5 3 respectively. It has been shown [10,13] that when SU(3) breaking effects are taken into consideration within χQM, the predictions of the χQM regarding the above mentioned ratios have much better overlap with the data.It is well known that constituent quark model (CQM) with one gluon mediated configuration mixing gives a fairly satisfactory explanation of host of 1 low energy hadronic matrix elements [14,15,16]. Besides providing a viable explanation for some of the difficult cases of photohelicity amplitudes [17], it is well known that one gluon generated configuration mixing is also able to provide viable explanation for neutron form factor [16,18], which cannot be accomodated without configuration mixing in CQM. Therefore, it becomes interesting to examine, within the χQM, the implications of one gluon mediated configuration mixing for flavor and spin structure of nucleon. In particular, we would like to examine the nucleon spin polarizations and various hyperon β-decay parameters, violation of Gottfried sum rule, strange quark content in the nucleon, fractions of quark flavor etc. in the χQM with configuration mixing (χQM gcm ), with and without symmetry breaking. Further, it would be interesting to examine whether a unified fit could be effected for spin polarization functions as well as quark ditribution functions or not.For the sake of readability as well to facilitate the discussion, we detail the essentails of χQM gcm discussed earlier by Harleen and Gupta [19]. The basic process, in the χQM, is the em...

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

Magnetic moments of the low lying and charmed spin 1 2 + and spin 3 2 + baryons have been calculated in the SU(4) chiral constituent quark model (χCQM) by including the contribution from cc fluctuations. Explicit calculations have been carried out for the contribution coming from the valence quarks, "quark sea" polarizations and their orbital angular momentum. The implications of such a model have also been studied for magnetic moments of the low lying spin 3 2 + → 1 2 + and 1 2 + → 1 2 + transitions as well as the transitions involving charmed baryons. The predictions of χCQM not only give a satisfactory fit for the baryons where experimental data is available but also show improvement over the other models. In particular, for the case of µ(p), µ(Σ + ), µ(Ξ 0 ), µ(Λ), Coleman-Glashow sum rule for the low lying spin 1 2 + baryons and µ(∆ + ), µ(Ω − ) for the low lying spin 3 2 + baryons, we are able to achieve an excellent agreement with data. For the spin 1 2 + and spin 3 2 + charmed baryon magnetic moments, our results are consistent with the predictions of the QCD sum rules, Light Cone sum rules and Spectral sum rules. For the cases where "light" quarks dominate in the valence structure, the sea and orbital contributions are found to be fairly significant however, they cancel in the right direction to give the correct magnitude of the total magnetic moment. On the other hand, when there is an excess of "heavy" quarks, the contribution of the "quark sea" is almost negligible, for example, µ(Ω 0 c )

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Baryon octet magnetic moments when calculated within the chiral quark model, incorporating the orbital angular momentum as well as the quark sea contribution through the Cheng-Li mechanism, not only show improvement over the non relativistic quark model results but also gives a non zero value for the right hand side of Coleman-Glashow sum rule. When effects due to spin-spin forces between constituent quarks as well as 'mass adjustments' due to confinement are added, it leads to an excellent fit for the case of p, Σ + , Ξ o and violation of Coleman-Glashow sum rule, whereas in almost all the other cases the results are within 5% of the data.The EMC measurements [1] in the deep inelastic scattering had shown that only a small fraction of the proton's spin is carried by the valence quarks. This 'unexpected' conclusion from the point of view of non relativistic quark model (NRQM), usually referred to as 'proton spin crisis', becomes all the more intriguing when it is realized that NRQM is able to give a reasonably good description of magnetic moments using the assumption that magnetic moments of quarks are proportional to the spin carried by them. This issue regarding spin and magnetic moments further becomes difficult to understand when it is realized that the magnetic moments of baryons receive contribution not only from the magnetic moments carried by the valence quarks but also from various complicated effects, such as, orbital excitations [2], sea quark polarization [3][4][5][6], effects of the chromodynamic spin-spin forces [7,8], effect of the confinement on quark masses [9], pion cloud contributions [10], loop corrections [11], relativistic and exchange current effects [12], etc.. In the absence of any consistent way to calculate these effects simultaneously, even couple of these, it is very difficult to know their relative contributions. However, the success of NRQM, when viewed in this context, suggests that the various effects mentioned above contribute in a manner where large part of these is mutually cancelled making the understanding of the magnetic moments alongwith 'spin crisis' all the more difficult. The problem regarding magnetic moments gets further complicated when one realizes that Coleman-Glashow sum rule [13] (CGSR), valid in large variety of models [14,15], is convincingly violated by the data [16]. For example, the CGSR for the baryon magnetic moments is given asExperimentally ∆CG = 0.49 ± 0.05 [16], clearly depicting the violation of CGSR by ten standard deviations. As ∆CG=0, in most of the calculations, obtaining ∆CG = 0 alongwith the octet magnetic moments as well as resolution for 'spin crisis' and related issues could perhaps provide vital clues for the dynamics as well as the appropriate degrees of freedom required for understanding some of the non-perturbative aspects of QCD. In this context, it is interesting to note that the chiral quark model (χQM) [4,17] with SU(3) symmetry is not only able to give a fair explanation of 'proton spin crisis' [1] but is also able to give a fair acc...

Several spin and flavor dependent parameters characterizing the strangeness content of the nucleon have been calculated in the chiral constituent quark model with configuration mixing (χCQM config ) which is known to provide a satisfactory explanation of the "proton spin crisis" and related issues. In particular, we have calculated the strange spin polarization ∆s, the strangeness contribution to the weak axial vector couplings ∆ 8 etc., strangeness contribution to the magnetic moments µ(p) s etc., the strange quark flavor fraction f s , the strangeness dependent quark flavor whereas a recent phenomenology study with lattice inputs [7] also predicts a very small value for the strange magnetic moment, µ(p) s = −0.046 ± 0.19µ N . In the naive constituent quark model (CQM) [8,9,10], µ(p) s is predicted to be zero. The broader question of contribution of strangeness in the nucleon has also been discussed by several authors recently [11]. It is widely recognized that a knowledge about the strangeness content of the nucleon would undoubtedly provide vital clues to the non-perturbative aspects of QCD.The existence of strangeness in the nucleon has been indicated in the context of low energy experiments [12,13] whereas it has been observed in the deep inelastic scattering (DIS) experiments [14,15,16,17]. In the context of DIS, the strange spin polarization of the nucleon [18] looks to be well established through the measurements of polarized structure functions of the nucleon [15,16,17]. Apart from the observations of DIS data regarding strangeness dependent spin polarization functions, several interesting facts have also been revealed regarding the quark flavor distribution functions in the DIS experiments.In particular, the NuSea Collaboration −0.053 . In the context of low energy experiments, the large pion-nucleon sigma term value [13] indicating non zero strange quark flavor fraction f s is also indicative of the presence of strange quarks in the nucleon although there is no consensus regarding the various mechanisms which can contribute to f s [20]. Therefore, the indications of the strange quark degree of freedom in DIS as well as low energy experiments provide a strong motivation to examine the strangeness 2 contribution to the nucleon thereby giving vital clues to the non-perturbative effects of QCD.One may think that the strangeness content of the nucleon perhaps can be obtained through the generation of "quark sea" perturbatively from the quark-pair production by gluons. However, this kind of "sea" is symmetric w.r.t.ū andd [21], negated by the observed value ofū −d asymmetry [19]. Therefore, one has to consider the "quark sea" produced by the non-perturbative mechanism. One such model which can yield an adequate description of the "quark sea" generation through the chiral fluctuations is the chiral constituent quark model (χCQM) [22] which is not only successful in giving a satisfactory explanation of "proton spin crisis" [23] but is also able to account for the violation of Gottfried Sum Rule [21,2...

Background: Epilepsy is one of the most common problems in neurology clinical practice and currently we are in the midst of the coronavirus outbreak. The coronavirus pandemic is an epidemiological and psychological crisis, which is likely to affect persons with epilepsy. Objectives: This study was designed to evaluate the impact of COVID-19 pandemic on patients with epilepsy and effects on their mental health. Materials and Methods: This was a cross-sectional web-based survey carried out at the department of Neurology at a tertiary care hospital. A questionnaire was designed in the local language using Google Forms to assess basic knowledge regarding epilepsy, coronavirus, effects of COVID-19 and lockdown on epileptic patients and also effects on their mental health. The link to the online survey was distributed via WhatsApp messenger to epilepsy patients. Results: One hundred fifty-six cases were enrolled with 69.1% were below 34 years of age and male: female ratio was 1.2:1. Only 34.3% of the participants were employed and 50% of patients had an income of less than Rs. 3000 per month. Of the patients enrolled, 20.5% reported the “devil” and superstitions as a cause of epilepsy and only 10% of patients thought that tantric (holy priest) could treat the disease better than doctors. 53.8% of patients worried about getting COVID-19 and could not stop thoughts about being infected by coronavirus bothering them. 30.3% patients had increased seizure frequency during COVID-19 pandemic, of which the most common reason was that they forgot to take regular antiepileptic drugs (22.7%) or they had faced difficulty in obtaining medicine due to lockdown (12.1%). During the pandemic, 17% of patients reported depression symptoms and another 21% reported anxiety symptoms. Conclusion: The current COVID-19 pandemic negatively affected patients with epilepsy and increased seizure frequency, depression, anxiety, unemployment, and financial difficulty in obtaining medication.

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