arXiv subjects

Harleen Dahiya

Publications and source records attributed to Harleen Dahiya.

At least 109 records · Page 6Linked to original sources

arXiv2015

Transverse distortion of a relativistic composite system in impact parameter space

We investigate the Generalized Parton Distributions (GPDs) in impact parameter space using the explicit light front wave functions (LFWFs) for the two-particle Fock state of the electron in QED. The Fourier transform (FT) of the GPDs gives the distribution of quarks in the transverse plane for zero longitudinal momentum transfer ($ξ=0$). We study the relationship of the spin flip GPD $E(x,0,-\vecΔ_\perp^2)$ with the distortion of unpolarized quark distribution in the transverse plane when the target nucleon is transversely polarized and also determine the sign of distortion from the sign of anomalous magnetic moment. To verify the sign of distortion, we also compute it directly from the LFWFs by performing a FT in position space coordinate $\vec{f}_\perp$. The explicit relation between the deformation in the two spaces can also be obtained using the convolution integrals. To show the relation of the model LFWFs to a realistic model of nucleon physics, we have designed a specific weight function of our model LFWFs and integrated it over the mass parameter. Also we have simulated the form factor of the nucleon in the AdS/QCD holographic LFWFs model and studied the power-law behaviour at short distances.

hep-ph↗

arXiv2015

Generalized Parton Distributions of proton for non zero skewness in transverse and longitudinal position spaces

We investigate the Generalized Parton Distributions(GPDs) of proton by expressing them in terms of overlaps of light front wave functions (LFWFs) using a simulated model which is able to qualitatively improve the convergence near the end points of $x$. We study the spin non-flip $H(x, ζ, t)$ and spin flip $E(x, ζ, t)$ part of GPDs for the particle conserving $n \rightarrow n$ overlap in the DGLAP region $(ζ<x<1)$. The Fourier transform (FT) of the GPDs w.r.t. to the transverse momentum transfer as well the FT of the GPDs w.r.t. $ζ$ have also been obtained giving the distribution of partons in the transverse position space and the distribution in the longitudinal position space respectively. Diffraction pattern is obtained for both $ \mathcal{H}(x,σ,t)$ and $ \mathcal{E}(x,σ,t)$ in the longitudinal position space.

hep-ph↗

arXiv2014

Charge and magnetization densities in transverse coordinate and impact parameter space

Electromagnetic form factors obtained from the overlap of light front wave functions (LFWFs) have been used to study the transverse densities of charge and magnetization. The calculations have been carried out to develop a relation between the charge distribution of the quarks inside nucleon in the transverse coordinate space as well as in the impact parameter space. When a comparison is carried out, it is found that the transverse distribution in the impact parameter space, where the longitudinal momentum fraction $x$ can be fixed, falls off faster than the spatial distribution in the transverse coordinate space where there is some contribution from the longitudinal momentum as well. The anomalous magnetization density of the nucleon has also been discussed. Further, we have also presented the results of the QCD transverse AdS charge density inspired from the holographic QCD model.

hep-ph↗

arXiv2014

Impact parameter space and transverse distortion

We investigate the GPDs in impact parameter space using the explicit light front wave functions (LFWFs) for the two-particle Fock state of the electron in QED. The Fourier transform (FT) of the GPDs gives the distribution of quarks in the transverse plane for zero longitudinal momentum transfer ($ζ=0$). We study the relationship of the spin flip GPD with the distortion of unpolarized quark distribution in the transverse plane when the target nucleon is transversely polarized and also determine the sign of distortion from the sign of anomalous magnetic moment.

hep-ph↗

arXiv2014

Axial-vector form factors for the low lying octet baryons in the chiral quark constituent model

We have calculated the axial-vector form factors of the low lying octet baryons ($N$, $Σ$, $Ξ$ and $Λ$) in the chiral constituent quark model ($χ$CQM). In particular, we have studied the implications of chiral symmetry breaking and SU(3) symmetry breaking for the singlet ($g^0_{A}$) and non-singlet ($g^3_{A}$ and $g^8_{A}$) axial-vector coupling constants expressed as combinations of the spin polarizations at zero momentum transfer. The conventional dipole form of parametrization has been used to analyse the $Q^2$ dependence of the axial-vector form factors ($G^0_{A}(Q^2)$, $G^3_{A}(Q^2)$ and $G^8_{A}(Q^2)$). The total strange singlet and non-singlet contents ($G_s^0(Q^2)$, $G_s^3(Q^2)$ and $G_s^8(Q^2)$) of the nucleon determining the strange quark contribution to the nucleon spin ($Δs$) have also been discussed.

hep-ph↗

arXiv2014

Electromagnetic and gravitational form factors in simulated QED and Yukawa model

The light-cone Fock state representation of composite systems has number of remarkable properties and for systems such as hadrons they have exact representation for angular momentum, energy momentum tensor. We investigate the electromagnetic and gravitational form factors with zero momentum transfer in QED and Yukawa theory. To improve the convergence near the end points of $x$ qualitatively as well as to check the consistency of the model, we differentiate the wavefunction w.r.t. bound state mass. We test the behaviour of the anomalous gravitomagnetic moment, which follows directly from the Lorentz boost properties of the light-cone Fock representation, for the simulated model as well as the Yukawa model. We also discuss the Pauli form factor obtained from the spin-flip matrix element.

hep-ph↗

arXiv2013

Quadrupole moments of low lying baryons with spin 1/2^+, spin 3/2^+, and spin 3/2^+ \to 1/2^+ transitions

The chiral constituent quark model (\chiCQM) with general parameterization (GP) method has been formulated to calculate the quadrupole moments of the spin 3/2^+ decuplet baryons and spin 3/2^+ \to 1/2^+ transitions. The implications of such a model have been investigated in detail for the effects of symmetry breaking and GP parameters pertaining to the two- and three-quark contributions. It is found that the \chiCQM is successful in giving a quantitative and qualitative description of the quadrupole moments.

hep-ph↗

arXiv2013

Magnetic moments of the low-lying {1/2}^- octet baryon resonances

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 $q\bar{q}$ 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.

hep-ph↗

arXiv2012

Magnetic moments of the low-lying $J^P=\,1/2^-$, $3/2^-$ $Λ$ resonances within the framework of the chiral quark model

The magnetic moments of the low-lying spin-parity $J^P=$ $1/2^-$, $3/2^-$ $Λ$ resonances, like, for example, $Λ(1405)$ $1/2^-$, $Λ(1520)$ $3/2^-$, as well as their transition magnetic moments, are calculated using the chiral quark model. The results found are compared with those obtained from the nonrelativistic quark model and those of unitary chiral theories, where some of these states are generated through the dynamics of two hadron coupled channels and their unitarization.

nucl-th↗

arXiv2011

Strangeness magnetic moments of $N$ and $Δ$

We have calculated the strangeness contribution to the magnetic moments of the nucleon and $Δ$ decuplet baryons in the chiral constituent quark model with configuration mixing ($χ$CQM$_{\rm config}$) which is known to provide a satisfactory explanation of the proton spin crisis and related issues. Our results are consistent with the recent experimental observations.

hep-ph↗

arXiv2011

Electromagnetic form factors of the nucleon in the chiral constituent quark model

The electromagnetic form factors have attracted lot of theoretical and experimental attention recently as they encode extensive information on the internal structure of the hadron. An understanding of the form factors is necessary to describe the strong interactions as they are sensitive to the pion cloud and provide a test for the QCD inspired effective field theories based on the chiral symmetry. In view of the very exciting recent developments in the field, we propose to apply the techniques of chiral constituent quark model to measure the electromagnetic form factors of the nucleon.The results obtained are comparable to the latest experimental studies and also show improvement over some theoretical interpretations.

hep-ph↗

arXiv2011

Strangeness and meson-nucleon sigma terms

The chiral constituent quark model ($χ$CQM) has been extended to calculate the flavor structure of the nucleon through the meson-nucleon sigma terms which have large contributions from the quark sea and are greatly affected by chiral symmetry breaking and SU(3) symmetry breaking. The hidden strangeness component in the nucleon has also been investigated and its significant contribution is found to be consistent with the recent available experimental observations.

hep-ph↗

arXiv2011

Charge radii of octet and decuplet baryons

The charge radii of the octet and decuplet baryons have been calculated in the framework of chiral constituent quark model ($χ$CQM) using a general parameterization (GP) method. Our results are comparable with the latest experimental studies as well as with other phenomenological models. The effects of SU(3) symmetry breaking and GP parameters pertaining to the one-, two- and three-quark contributions have also been investigated in detail.

hep-ph↗

arXiv2010

Strangeness and Chiral Symmetry Breaking

The implications of chiral symmetry breaking and SU(3) symmetry breaking have been studied in the chiral constituent quark model ($χ$CQM). The role of hidden strangeness component has been investigated for the scalar matrix elements of the nucleon with an emphasis on the meson-nucleon sigma terms. The $χ$CQM is able to give a qualitative and quantitative description of the "quark sea" generation through chiral symmetry breaking. The significant contribution of the strangeness is consistent with the recent available experimental observations.

hep-ph↗

arXiv2010

Chiral symmetry breaking and electromagnetic structure of the nucleon

The electromagnetic form factors are the most fundamental quantities to describe the internal structure of the nucleon and are related to the charge radii of the baryons. We have calculated the charge radii of octet baryons in the framework of chiral constituent quark model with the inclusion of the spin-spin generated configuration mixing. This model is quite successful in predicting the low energy hadron matrix elements. The results obtained in the case of charge radii are also comparable to the latest experimental studies and show improvement over some theoretical interpretations.

hep-ph↗

arXiv2010

Quadrupole moment of the nucleon in chiral constituent quark model

The electromagnetic form factors are the most fundamental quantities to describe the internal structure of the nucleon and the shape of a spatially extended particle is determined by its {\it intrinsic} quadrupole moment which is first order moment of the charge density operator. With some experimental indications of a deformed nucleon, we have calculated the {\it intrinsic} quadrupole moment of the octet and decuplet baryons in the framework of chiral constituent quark model \chiCQM which is quite successful in explaining some of the important baryon properties in the nonperturbative regime.

hep-ph↗

arXiv2010

Nonperturbative Quark Sea Asymmetries

The effects of nonperturbatively generated ``quark sea'' have been investigated to determine the flavor structure of the octet baryons. The chiral constituent quark model ($χ$CQM), which is known to provide a satisfactory explanation of the proton spin and related issues in the nonperturbative regime, is able to explain the qualitative generation of the requisite amount of quark sea. The importance of quark sea has been studied at different values of the Bjorken scaling variable $x$ by including it phenomenologically in the sea quark distribution functions. The results for the quark sea asymmetries like $\bar d(x)-\bar u(x)$, $\bar d(x)/\bar u(x)$ and Gottfried integral for the octet baryons strengthen the significance of quark sea at lower values of $x$.

hep-ph↗

arXiv2010

Quark sea asymmetries of the octet baryons

The effects of "quark sea" in determining the flavor structure of the octet baryons have been investigated in the chiral constituent quark model (\chiCQM). The \chiCQM is able to qualitatively generate the requisite amount of quark sea and is also known to provide a satisfactory explanation of the proton spin and related issues in the nonperturbative regime. The Bjorken scaling variable x has been included phenomenologically in the sea quark distribution functions to understand its implications on the quark sea asymmetries like \bar d(x)-\bar (x), \bar d(x)/\bar u(x) and Gottfried integral for the octet baryons. The results strengthen the importance of quark sea at lower values of x.

hep-ph↗