148 research outputs found
Reconciling and in Chiral Quark Model with one Gluon Generated Configuration Mixing
The spin polarization functions for proton
are calculated in the chiral quark model (QM) 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 as well as , 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?
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
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 (QM) are discussed in context of proton flavor and spin
structure as well as hyperon -decay data. Apart from reproducing the
success of QM with symmetry breaking, it is able to improve upon the
agreement with data in several cases such as,
dependent on spin polarization functions and (),
() and f_s involving the quark distribution
functions.Comment: 11 pages and 3 table
Strangeness Content of the Nucleon in the \chiCQM_{config}
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
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 QM with configuration mixing
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
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
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
In the light of refined and large reactor mixing angle , 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 and
Majorana phases and .Comment: 12 pages, 9 figure
Three flavor neutrino oscillations, LSND, SNP and ANP
The recently reanalysed LSND data is investigated in the context of three
flavor oscillations, with an emphasis on mass hierarchies and . 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.,
and .
In the first and second case, the calculated range of is in agreement
with the "LMA" solution of Akhmedov {\it et al.}, the lower limit on
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 found in the third case correspond to the value of 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 ,
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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