arXiv subjects

Monika Randhawa

Publications and source records attributed to Monika Randhawa.

At least 19 recordsLinked to original sources

arXiv2026

Chiral-odd generalized parton distributions of spin-1/2 baryons

We present the tomographical structure of baryons by studying the nonforward matrix elements of lightlike correlation functions of the tensor current. At the leading twist, with the tensor current, four chiral-odd distributions are in count. We calculate these distributions in a diquark spectator model with light-front formalism by considering purely transverse momentum transfer, i.e., zero skewness. Predictions for the nucleons and light hyperons are studied, emphasizing the difference arising from their different quark flavors.

hep-ph↗

arXiv2025

Minimal structure for neutrino mass matrix

Taking clue from the minimal structure of texture 4-zero hermitian mass matrices, which are very successful in accommodating quark mixing data, we propose a form of texture 2-zero complex symmetric neutrino mass matrix with only one phase parameter. This minimal mass matrix not only accommodates the available neutrino oscillation data, but also makes interesting predictions for the unknown parameters like the lightest neutrino mass $m_{ν_1}$ (for normal ordering(NO)), Jarlskog's rephasing invariant $J_{CP}$, Dirac type CP violating phase $δ_{CP}$ and effective neutrino mass $\left< m_{ee} \right>$. We also explore the correlations between the parameters of the model, that lead us to minimizing the parameters further.

hep-ph↗

arXiv2024

Study of vector and axial-vector form factors and the decay parameters for the semileptonic hyperon decays

Using the standard parametrization of the dipole form, we have studied the vulnerability of $Q^2$ on the vector form factors ($f_i^{B_iB_f}(Q^2)$) and axial-vector form factors ($g_i^{B_iB_f}(Q^2)$), $i=1,2,3$ computed for the semileptonic $B_i \rightarrow B_f l \barν$ decays for hyperons in the framework of chiral constituent quark model ($χ$CQM). Both, strangeness changing as well as strangeness conserving decays have been examined. We also present the dependence of the ratio of hyperon semileptonic decay constants $g_1(Q^2)/f_1(Q^2)$ for these decays. Further, we calculate the CKM matrix elements $V_{ud}$ from strangeness conserving and $V_{us}$ from strangeness changing hyperon decays.

hep-ph↗

arXiv2023

Axial-vector form factors of the light, singly and doubly charmed baryons in the chiral quark constituent model

The axial-vector form factors of the light, singly and doubly charmed baryons are investigated in the framework of $SU(4)$ chiral constituent quark model. The axial-vector form factors having physical significance correspond to the generators of the $SU(4)$ group with flavor singlet $λ^{0}$, flavor isovector $λ^{3}$, flavor hypercharge $λ^{8}$ and flavor charmed $λ^{15}$ combinations of axial-vector current at zero momentum transfer. In order to further understand the $Q^2$ dependence of these charges, we have used the conventionally established dipole form of parametrization.

hep-ph↗

arXiv2023

Axial-vector charges of the spin $\frac{1}{2}^+$ and spin $\frac{3}{2}^+$ light and charmed baryons in the SU(4) chiral quark constituent model

Following the first clear evidence of the presence of intrinsic charm contribution in the proton, the axial-vector charges of the light and charmed baryons are investigated in the framework of $SU(4)$ chiral constituent quark model after including the explicit contributions from the $u\bar u $, $d\bar d $, $s\bar s $ and $c\bar c $ fluctuations. The axial-vector charges having physical significance correspond to the generators of the $SU(4)$ group with flavor singlet $λ^0$, flavor isovector $λ^3$, flavor hypercharge $λ^8$ and flavor charmed $λ^{15}$ combinations of axial-vector current at zero momentum transfer. In contemplation to further understand the $Q^2$ dependence of these charges, we have used the conventionally established dipole form of parametrization. The baryons considered here are the spin $\frac{1}{2}^+$ and spin $\frac{3}{2}^+$ multiplets decomposed further depending on the charm content of baryons.

hep-ph↗

arXiv2022

Minimizing the phase structure of quark mass matrices

Fritzsch-Xing matrices are a particular class of texture 4 zero hermitian quark mass matrices, known to be successful in accommodating the quark mixing data. In the present work, it is shown that these texture 4-zero matrices with only one phase parameter, unlike the usually considered two phase parameters, are not only consistent with the latest experimental quark mixing data, but also predict the CP violation parameters, $J$ and corresponding phase $δ$, in agreement with the recent global analyses. We also show that the mass matrix elements do not exhibit a strong hierarchy and there is a strong correlation between some of the mass matrix elements of up and down sector. A precision measurement of $δ$ as well as small quark masses would have the potential to constrain the phase structure of the matrices further.

hep-ph↗

arXiv2017

Electromagnetic and Axial-Vector Form Factors of the Quarks and Nucleon

In light of the improved precision of the experimental measurements and enormous theoretical progress, the nucleon form factors have been evaluated with an aim to understand how the static properties and dynamical behavior of nucleons emerge from the theory of strong interactions between quarks. We have analysed the vector and axial-vector nucleon form factors ($G^{p,n}_{E,M}(Q^2)$ and $G^{p,n}_{A}(Q^2)$) using the spin observables in the chiral constituent quark model ($χ$CQM) which has made a significant contribution to the unraveling of the internal structure of the nucleon in the nonperturbative regime. We have also presented a comprehensive analysis of the flavor decomposition of the form factors ($G^{q}_{E}(Q^2)$, $G^{q}_{M}(Q^2)$ and $G^{q}_{A}(Q^2)$for $q=u,d,s$) within the framework of $χ$CQM with emphasis on the extraction of the strangeness form factors which are fundamental to determine the spin structure and test the chiral symmetry breaking effects in the nucleon. The $Q^2$ dependence of the vector and axial-vector form factors of the nucleon has been studied using the conventional dipole form of parametrization. The results are in agreement with the available experimental data.

hep-ph↗

arXiv2016

Nucleon structure functions and longitudinal spin asymmetries in the chiral quark constituent model

We have analysed the phenomenological dependence of the spin independent ($F_1^{p,n}$ and $F_2^{p,n}$) and the spin dependent ($g_1^{p,n}$) structure functions of the nucleon on the the Bjorken scaling variable $x$ using the unpolarized distribution functions of the quarks $q(x)$ and the polarized distribution functions of the quarks $Δq(x)$ respectively. The chiral constituent quark model ($χ$CQM), which is known to provide a satisfactory explanation of the proton spin crisis and related issues in the nonperturbative regime, has been used to compute explicitly the valence and sea quark flavor distribution functions of $p$ and $n$. In light of the improved precision of the world data, the $p$ and $n$ longitudinal spin asymmetries ($A_1^p(x)$ and $A_1^n(x)$) have been calculated. The implication of the presence of the sea quarks has been discussed for ratio of polarized to unpolarized quark distribution functions for up and down quarks in the $p$ and $n$ $\frac{Δu^p(x)}{u^p(x)}$, $\frac{Δd^p(x)}{d^p(x)}$, $\frac{Δu^n(x)}{u^n(x)}$, and $\frac{Δd^n(x)}{d^n(x)}$. The ratio of the $n$ and $p$ structure functions $R^{np}(x)=\frac{F_2^n(x)}{F_2^p(x)}$ has also been presented. The results have been compared with the recent available experimental observations. The results on the spin sum rule have also been included and compared with data and other recent approaches.

hep-ph↗

arXiv2015

Magnetic moments of $J^P=\frac{3}{2}^+$ decuplet baryons using effective quark masses in chiral constituent quark model

The magnetic moments of $J^P=\frac{3}{2}^+$ decuplet baryons have been calculated in the chiral constituent quark model ($χ$CQM) with explicit results for the contribution coming from the valence quark polarizations, sea quark polarizations, and their orbital angular momentum. Since the $J^P=\frac{3}{2}^+$ decuplet baryons have short lifetimes, the experimental information about them is limited. The $χ$CQM has important implications for chiral symmetry breaking as well as SU(3) symmetry breaking since it works in the region between the QCD confinement scale and the chiral symmetry breaking scale. The predictions in the model not only give a satisfactory fit when compared with the experimental data but also show improvement over the other models. The effect of the confinement on quark masses has also been discussed in detail and the results of $χ$CQM are found to improve further with the inclusion of effective quark masses.

hep-ph↗

arXiv2014

Estimating matter induced CPT violation in Long-Baseline Neutrino Experiments

We examine matter induced CPT violation effects in long baseline electron neutrino appearance experiments in a low energy neutrino factory setup. Assuming CPT invariance in vacuum, the magnitude of CPT violating asymmetry in matter has been estimated using the exact expressions for the transition probabilities. The dependence of the asymmetry on the oscillation parameters like mixing angles, mass squared differences as well as on the Dirac CP violating phase has been investigated.

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↗

arXiv2013

Investigating texture six zero lepton mass matrices

Texture six zero Fritzsch like as well as non Fritzsch like hermitian lepton mass matrices (144 combinations in all) have been investigated for both Majorana and Dirac neutrinos for their compatibility with the current neutrino oscillation data, keeping in mind the hierarchy of neutrino masses. All the combinations considered here for Majorana neutrino masses are ruled out by the existing data in the case of inverted hierarchy and degenerate scenario. For Majorana neutrinos with normal hierarchy, only 16 combinations can accommodate the experimental data. Assuming neutrinos to be Dirac particles, normal hierarchy, inverted hierarchy as well as degenerate neutrinos are ruled out for all combinations of texture 6 zero hermitian mass matrices.

hep-ph↗

arXiv2010

Exploring the parameter space of texture 4 zero quark mass matrices

We have attempted to extend the parameter space of the elements of the texture 4 zero Hermitian quark mass matrices, to include the case of `weak hierarchy' amongst them along with the usually considered `strong hierarchy' case. This has been carried out by giving wide variation to the hierarchy defining parameters D_U and D_D, having implications for the structural features of the mass matrices. We find that not only the weakly hierarchical mass matrices are able to reproduce the strongly hierarchical mixing angles but also both the phases having their origin in the mass matrices have to be non zero to achieve compatibility of these matrices with recent quark mixing data. Further noting the difference between the exclusive and inclusive values of V_ub, we have carried out separate analyses corresponding to these.

hep-ph↗

arXiv2009

Texture specific mass matrices with Dirac neutrinos and their implications

Considering Dirac neutrinos and Fritzsch-like texture 6 zero and 5 zero mass matrices, detailed predictions for cases pertaining to normal/inverted hierarchy as well as degenerate scenario of neutrino masses have been carried out. All the cases considered here pertaining to inverted hierarchy and degenerate scenario of neutrino masses are ruled out by the existing data. For the normal hierarchy cases, the lower limit of m_nu_1 and of s_13 as well as the range of Dirac-like CP violating phase delta_l would have implications for the texture specific cases considered here.

hep-ph↗

arXiv2008

Texture 4 zero Fritzsch-like lepton mass matrices

For Majorana or Dirac neutrinos, using Fritzsch-like texture 4 zero mass matrices with parallel texture structures for the charged leptons and the Dirac neutrino mass matrix (M_{νD}), detailed predictions for cases pertaining to normal/inverted hierarchy as well as degenerate scenarios of neutrino masses have been carried out. The inverted hierarchy as well as degenerate scenarios seem to be ruled out at 3 σC.L. for both Majorana and Dirac neutrinos. For normal hierarchy, Jarlskog's rephasing invariant parameter J, the CP violating Dirac-like phase δand the effective neutrino mass m_{ee} have been calculated. For this case, lower limits of m_{ν_1} and θ_{13} would have implications for the nature of neutrinos.

hep-ph↗

arXiv2006

Implications of unitarity and precision measurements on CKM matrix elements

Unitarity along with precision measurements of sin2β, V_{us} and V_{cb} allows one to find a lower bound V_{ub}\geq 0.0035 which, on using the recently measured angle αof the unitarity triangle, translates to V_{ub}= 0.0035\pm 0.0002. This precise value, stable for a good deal of changes in α, along with CP violating phase δfound from unitarity allows the construction of a `precise' CKM matrix. The above unitarity based value of V_{ub} is in agreement with the latest exclusive value used as input by UTfit, CKMfitter, HFAG, however underlines the so called `tension' faced by the latest inclusive V_{ub}=0.00449 \pm 0.00033. Further, using this inclusive value of V_{ub} along with the latest sin2β, one finds δ=23 ^{\rm o}- 39 ^{\rm o}, again in conflict with δmeasured in B-decays. The calculated ranges of the elements of the CKM matrix are in excellent agreement with those obtained recently by UTfit, CKMfitter and HFAG. Also, the ratio \frac{V_{ts}}{V_{td}} is in agreement with its latest measured value, whereas there is some disagreement between the `measured' and the calculated V_{td} values.

hep-ph↗

arXiv2006

Constructing the CKM and PMNS matrices from mixing data

The CKM and PMNS matrices have been constructed based on the latest measurements, largely free from theoretical inputs as well as likely NP effects in the case of the former. To facilitate the construction of the CKM matrix in the PDG representation as well as in view of the comparatively large error in the measured value of the CP violating phase δ, the possibility of its construction from the tree level measured CKM elements has also been explored using the unitarity triangle. In view of the persistent difference between the |V_{ub}| exclusive and inclusive values, we have carried out separate analyses corresponding to these. The PMNS matrix has been constructed by incorporating the constraints due to solar and atmospheric neutrinos as well as by giving full variation to the Dirac-like CP violating phase δand considering different values of s_{13} having implications for different models of lepton mass matrices. Taking clue from quark mixing phenomenology, an analogous analysis of the leptonic unitarity triangle allows an estimate of the likely presence of CP violation in the leptonic sector.

hep-ph↗

arXiv2006

Implications of Fritzsch-like lepton mass matrices

Using seesaw mechanism and Fritzsch-like texture 6 zero and 5 zero lepton Dirac mass matrices, detailed predictions for cases pertaining to normal/inverted hierarchy as well as degenerate scenario of neutrino masses have been carried out. All the cases considered here pertaining to inverted hierarchy and degenerate scenario of neutrino masses are ruled out by the existing data. For the normal hierarchy cases, the lower limit of m_{ν1} and of s_{13} as well as the range of Dirac-like CP violating phase δwould have implications for the texture 6 zero and texture 5 zero cases considered here.

hep-ph↗