148 research outputs found

    Reconciling GA/GV,<rn2>G_A/G_V, <r_n^2> and μp,n\mu_{p,n} in Chiral Quark Model with one Gluon Generated Configuration Mixing

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    The spin polarization functions (Δu, Δd, Δs)(\Delta u, ~\Delta d, ~\Delta s) for proton are calculated in the chiral quark model (χ\chiQM) with SU(3) symmetry breaking as well as configuration mixing generated by one gluon exchange forces for the NMC and the most recent E866 data. Besides reproducing the spin polarization functions Δu,Δd,Δs\Delta u,\Delta d, \Delta s as well as GA/GVG_A/G_V, it can accomodate nucleon magnetic moments and neutron charge radius as well, thus resolving the compatibility problem of these parameters which could not be achieved in constituent quark models.Comment: 10 latex pages with 2 tables, revised in the light of latest dat

    What is inside the nucleon?

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    We briefly review the structure of nucleon in the context of QCD, Constituent Quark Model and Chiral Quark Model.Comment: LateX, 23 pages, 3 figures and 5 Table

    Implications of Configuration Mixing in The Chiral Quark Model With SU(3) and Axial U(1) Breakings for Nucleon Spin-Flavor Structure

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    The implications of Chiral Quark Model with SU(3) and axial U(1) symmetry breakings as well as configuration mixing generated by one gluon exchange forces (χ\chiQMgcm_{gcm}) are discussed in context of proton flavor and spin structure as well as hyperon β\beta-decay data. Apart from reproducing the success of χ\chiQM with symmetry breaking, it is able to improve upon the agreement with data in several cases such as, GA/GV,Δ8,G_A/G_V, \Delta_8, dependent on spin polarization functions and (2sˉu+d\frac{2 \bar s}{u+d}), (2sˉuˉ+dˉ\frac{2 \bar s}{\bar u+\bar d}) and f_s involving the quark distribution functions.Comment: 11 pages and 3 table

    Strangeness Content of the Nucleon in the \chiCQM_{config}

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    Several parameters characterizing the strangeness content of the nucleon have been calculated in the chiral constituent quark model with configuration mixing (\chiCQM_{config}) which is known to provide a satisfactory explanation of the ``proton spin problem'' and related issues. In particular, we have calculated the strange spin polarization \Delta s, the strangeness contribution to the weak axial vector couplings \Delta_8 etc., strangeness contribution to the magnetic moments \mu(p)^s etc., the strange quark flavor fraction f_s, the strangeness dependent quark ratios \frac{2 \bar s}{u+d} and \frac{2 \bar s}{\bar u+\bar d} etc.. Our results show in general excellent agreement with the recent experimental observations.Comment: 14 pages, 3 table

    Constructing "Reference" Triangle through Unitarity of CKM Matrix

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    Motivated by the possibility of the low value of sin2\beta in the measurements of BABAR and BELLE collaborations, a reference unitarity triangle is constructed using the unitarity of the CKM matrix and the experimental values of the well known CKM elements, without involving any inputs from the processes which might include the new physics effects. The angles of the triangle are evaluated by finding the CP violating phase \delta through the Jarlskog's rephasing invariant parameter J. The present data and the unitarity of the CKM matrix gives for \delta the range 28^o to 152^o, which for sin2\beta translates to the range 0.21 to 0.88. This range is broadly in agreement with the recent BABAR and BELLE results. However, a value of sin2\beta \leq 0.2, advocated by Silva and Wolfenstein as a benchmark for new physics, would imply a violation in the three generation unitarity and would hint towards the existence of a fourth generation Further, the future refinements in the CKM elements will push the lower limit on sin2\beta still higher.Comment: Latex, 10 pages, 1 eps figur

    Octet magnetic moments and the violation of CGSR in χ\chiQM with configuration mixing

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    Octet baryon magnetic moments are calculated within \chiQM, respecting color spin spin forces (Szczepaniak et al., PRL 87, 072001(2001)), incorporating the orbital angular momentum as well as the quark sea contribution through the Cheng and Li mechanism (PRL 80, 2789(1998)). Using configuration mixing generated by color spin spin forces as well as the concept of ``effective'' quark mass to include the effects of confinement, we are able to get an excellent fit to the octet magnetic moments as well as the violation of Coleman Glashow Sum Rule (CGSR) without any further input except for the ones already used in \chiQM as well as in NRQM. Specifically, in the case of p, \Sigma^+, \Xi^o, and violation of CGSR we get a perfect fit whereas in almost all the other cases the results are within 5% of the data.Comment: 5 pages, 1 Table, RevTe

    Strangeness in the Nucleon

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    There are several different experimental indications, such as the strangeness contribution to the magnetic moment of the proton, sigma_{\pi N} term, strange spin polarization, ratio of strange and non strange quark flavor distributions which suggest that the nucleon contains a hidden strangeness component which is contradictory to the naive constituent quark model. Chiral constituent quark model with configuration mixing (\chiCQM_{{\rm config}}) is known to provide a satisfactory explanation of the ``proton spin problem'' and related issues. In the present work, we have extended the model to carry out the calculations for the parameters pertaining to the strange quark content of the nucleon, for example, the strange spin polarization \Delta s, strange components of the weak axial vector form factors \Delta \Sigma and \Delta_8 as well as F and D, strangeness magnetic moment of the proton \mu_p^s, the strange quark content in the nucleon f_s coming from the \sigma_{\pi N} term, the ratios between strange and non-strange quarks \frac{2 s}{u+d} and \frac{2 s}{\bar u+ \bar d}, contribution of strangeness to angular momentum sum rule etc.. Our result demonstrates the broad consistency with the experimental observations as well as other theoretical considerations.Comment: 4 pages, To appear in the Proceedings of International Workshop on Theoretical High Energy Physics, 15-20 March 2007, Roorkee, Indi

    Flavor mixings and textures of the fermion mass matrices

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    A comprehensive review of several aspects of fermion mixing phenomenon and texture specific mass matrices have been presented. Regarding fermion mixings, implications of unitarity and certain new developments for the CKM paradigm have been discussed. In the leptonic sector, the question of possibility of CP violation has been discussed in detail from the unitarity triangle perspective. In the case of texture specific mass matrices, the issues of viability of Fritzsch-like as well as non Fritzsch-like mass matrices have been detailed for both the quark and leptonic sectors. The relationship of textures, naturalness and weak basis rotations has also been looked into. The issue of the compatibility of texture specific mass matrices with the SO(10) based GUT mass matrices has also been discussed.Comment: 100 pages, 19 figure

    Revisiting the texture zero neutrino mass matrices

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    In the light of refined and large reactor mixing angle θ13\theta_{13}, we have revisited the texture three and two zero neutrino mass matrices in the flavor basis. For Majorana neutrinos, it has been explicitly shown that all the texture three zero mass matrices remain ruled out. Further, for both normal and inverted mass ordering, for the texture two zero neutrino mass matrices one finds interesting constraints on the Dirac-like CP violating phase δ\delta and Majorana phases ρ\rho and σ\sigma.Comment: 12 pages, 9 figure

    Three flavor neutrino oscillations, LSND, SNP and ANP

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    The recently reanalysed LSND data is investigated in the context of three flavor oscillations, with an emphasis on mass hierarchies and s13s_{13}. The resultant mass hierarchies and oscillation angles are tested with regard to "key" features of solar neutrinos and atmospheric neutrinos, e.g., "average" survival probability in the case of solar neutrinos, and zenith angle dependence and up-down asymmetry in the case of high energy atmospheric neutrinos. We find there are three distinct mass hierarchies, e.g., Δm<<ΔM,Δm<ΔM\Delta m << \Delta M, \Delta m < \Delta M and ΔmΔM\Delta m \simeq \Delta M. In the first and second case, the calculated range of s13s_{13} is in agreement with the "LMA" solution of Akhmedov {\it et al.}, the lower limit on s13s_{13} in these cases is also in agreement with the recent analysis of Garcia {\it et al.} based on the constraints of SNP, ANP and CHOOZ, therefore, strongly supporting the neutrino oscillations observed at LSND. Further, the solutions of s13s_{13} found in the third case correspond to the value of s13s_{13} found by Akhmedov {\it et al.} in the case of "SMA" and "LOW" solutions. A rough estimate of the possibility of the existence of CP violation in the leptonic sector is also carried out for different possible ranges of s13s_{13}, indicating that the CP asymmetries may be measureable even in the case of LSND.Comment: 16 pages, LaTex, 1 eps figure, Minor changes in the tex
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