arXiv subjects

Ishtiaq Ahmed

Publications and source records attributed to Ishtiaq Ahmed.

At least 37 records · Page 2Linked to original sources

arXiv2024

Probing New Physics in light of recent developments in $b \rightarrow c \ell ν$ transitions

The experimental studies of the observables associated with the $b \rightarrow c$ transitions in the semileptonic $B-$ meson decays at BaBar, Belle and LHCb have shown some deviations from the Standard Model (SM) predictions, consequently, providing a handy tool to probe the possible new physics (NP). In this context, we have first revisited the impact of recent measurements of $R({D^{(*)}})$ and $R(Λ_c)$ on the parametric space of the NP scenarios. In addition, we have included the $R(J/ψ)$ data in the analysis and found that their influence on the best-fit points and the parametric space is mild. Using the recent HFLAV data, after validating the well established sum rule of $R(Λ_c)$, we derived the similar sum rule for $R(J/ψ)$. Furthermore, according to the updated data, we have modified the correlation among the different observables, giving us their interesting interdependence. Finally, to discriminate the various NP scenarios, we have plotted the different angular observables and their ratios for $B \to D^* τν_τ$ against the transfer momentum square $\left(q^2\right)$, using the $1σ$ and $2σ$ parametric space of considered NP scenarios. By implementing the collider bounds on NP Wilson coefficients, we find that, in the parametric space of some NP WCs is significantly restrained. To see the clear influence of NP on the amplitude of the angular observables, we have also calculated their numerical values in different $q^2$ bins and shown them through the bar plots. We hope their precise measurements will help to discriminate various NP scenarios.

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arXiv2024

Signature decay modes of the compact doubly-heavy tetraquarks $T_{bb\bar{u} \bar{d}}$ and $T_{bc\bar{u} \bar{d}}$

Based on the expectations that the lowest-lying doubly-bottom tetraquark $T_{bb\bar u \bar d}$ ($J^P = 1^+$) and the bottom-charm tetraquark $T_{bc\bar u \bar d}$ ($J^P = 0^+$) are stable against strong and electromagnetic decays, we work out a number of semileptonic and non-leptonic weak decays of these hadrons, making use of the heavy quark symmetry. In doing this, we concentrate on the exclusive decays involving also tetraquarks in the final states, i.e., transitions such as $T_{bb\bar u \bar d} \to T_{bc\bar u \bar d}\, (\ell^- ν_\ell,\, h^-)$ and $T_{bc\bar u \bar d} \to T_{cc\bar u \bar d}\, (\ell^- ν_\ell,\, h^-)$, where $h^- = π^-, ρ^-, a_1^-, D^-_s, D^{*-}_s$. So far, only the $J^P = 1^+$ tetraquark $T_{cc\bar u \bar d}$ has been discovered, which we identify with the $I = 0$ $T_{cc}^+$ object, compatible with $J^P = 1^+$ and having the pole mass relative to the $D^{*+} D^0$ mass threshold and decay widths $δm = M (T_{cc}^+) - ( M (D^{*+}) + M (D^0) ) = - 360 \pm 40^{+4}_{-0}$ keV and $Γ(T_{cc}^+) = 48^{+2}_{-14}$ keV. Experimental discoveries of the transitions worked out here, and related ones involving doubly-heavy baryons, will quantify the diquark-antidiquark component of these tetraquarks.

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arXiv2024

Analysis of $b\rightarrow cτ\barν_τ$ anomalies using weak effective Hamiltonian with complex couplings

Recently, the experimental measurements of the branching ratios and different polarization asymmetries for the processes occurring through flavor-changing-charged current $b\rightarrow cτ\overlineν_τ$ transitions by BABAR, Belle, and LHCb show some sparkling differences with the corresponding SM predictions. Assuming the left handed neutrinos, we add the dimension-six vector, (pseudo-)scalar, and tensor operators with complex WCs to the SM WEH. Together with 60%, 30% and 10% constraints coming from the branching ratio of $B_{c}\toτ\barν_τ$, we analyze the parametric space of these new physics WCs accommodating the current anomalies in the purview of the most recent HFLAV data of $R_{τ/{μ,e}}\left(D\right)$, $R_{τ/{μ,e}}\left(D^*\right)$ and Belle data of $F_{L}\left(D^*\right)$ and $P_τ\left(D^*\right)$. Furthermore, we derive the sum rules which correlate these observables with $R_{τ/{μ,e}}\left(D\right)$ and $R_{τ/{μ,e}}\left(D^*\right)$. Using the best-fit points of the new complex WCs along with the latest measurements of $R_{τ/{μ,e}}\left(D^{(*)}\right)$, we predict the numerical values of the observable $R_{τ/\ell}\left(Λ_c\right)$, $R_{τ/μ}\left(J/ψ\right)$ and $R_{τ/\ell}\left(X_c\right)$ from the sum rules. Apart from finding the correlation matrix among the observables under consideration, we plot them graphically which is useful to discriminate different NP scenarios. Finally, we study the impact of these NP couplings on various angular and the CP triple product asymmetries, that could be measured in some ongoing and future experiments. The precise measurements of these observables are important to check the SM and extract the possible NP.

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arXiv2024

Analysis of final state lepton polarization-dependent observables in $H\to \ell^{+}\ell^{-} γ$ in the SM at loop level

Recently, the CMS and ATLAS collaborations have announced the results for $H\rightarrow Z[\rightarrow \ell^{+}\ell^{-}]γ$ with $\ell=e$ or $μ$ \cite{CMS:2022ahq,CMS:2023mku}, where $H\rightarrow Zγ$ is a sub-process of $H\rightarrow \ell^{+} \ell^{-} γ$. This semi-leptonic Higgs decay receives loop induced resonant $H\rightarrow Z[\rightarrow \ell^{+}\ell^{-}]γ$ as well as non-resonant contributions. % as discussed in \cite{Kachanovich:2021pvx}. To probe further features coming from these contributions to $H\rightarrow \ell^{+} \ell^{-} γ$, we argue that the polarization of the final state leptons is also an important parameter. We show that the contribution from the interference of resonant and non-resonant terms plays an important role when the polarization of final state lepton is taken into account, which is negligible in the case of unpolarized leptons. For this purpose, we have calculated the polarized decay rates and the longitudinal ($P_L$), normal ($P_N$) and transverse ($P_T$) polarization asymmetries. We find that these asymmetries purely come from the loop contributions and are helpful to further investigate the resonant and non-resonant nature of $H\rightarrow Z[\rightarrow \ell^{+}\ell^{-}]γ$ decay. We observe that for $\ell=e,μ$, the longitudinal decay rate is highly suppressed around $m_{\ell\ell}\approx 60$GeV when the final lepton spin is $-\frac{1}{2}$, dramatically increasing the corresponding lepton polarization asymmetries. Furthermore, we analyze another observable, the ratio of decay rates $R^{\ell\ell'}_{i\pm}$, where $\ell$ and $\ell'$ refer to different final state lepton generations. Precise measurements of these observables at the HL-LHC and the planned $e^{+}e^{-}$ can provide a fertile ground to test not only the SM but also to examine the signatures of possible NP beyond the SM.

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arXiv2023

Radiative $B$ to axial-vector meson decays at NLO in Soft-Collinear Effective Theory

The rare decay $B\rightarrow Aγ$, with $A$ representing axial-vector mesons such as $K_1 (1270),\; K_1 (1400),\; b_1(1300),\; a_1(1260)$, is studied at next-to-leading order (NLO) in soft collinear effective theory (SCET). The large outgoing meson energy encourages the study of the decay with an appropriate factorization scheme that separates the factorizable and non-factorizable parts systematically. We have analyzed the leading-power and $\mathcal{O}(α_s)$ diagrams that contribute to matching to SCET$_I$. The new intermediate theory is matched onto SCET$_{II}$ and the running of SCET$_I$ operators is performed to sum large perturbative logarithms. The values of soft-overlap function $ζ_{\perp}$ for $K_1 (1270,\;1400), a_{1}$ and $b_{1}$ mesons are estimated from the light cone-sum-rules (LCSR), and later using it the corresponding branching fractions for $B \to \left(K_{1}(1270,\; 1400),\; a_{1},\; b_{1}\right)γ$ decays are calculated. We find that in case of $B \to K_{1}(1270,\; 1400)γ$ decays the results are in good agreement with their experimental measurements. Also the estimated values of the branching ratios of the $B \to (b_{1},\; a_1)γ$ decays are potentially large to be measured at the LHCb and future B-factories.

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arXiv2020

Interpretation of LHCb Hidden-Charm Pentaquarks within the Compact Diquark Model

The LHCb collaboration have recently updated their analysis of the resonant $J/ψ\, p$ mass spectrum in the decay $Λ_b^0 \to J/ψ\, p\, K^-$, making use of their combined Run~1 and Run~2 data. In the updated analysis, three narrow states, $P_c (4312)^+$, $P_c (4440)^+$, and $P_c (4457)^+$, are observed. The spin-parity assignments of these states are not yet known. We interpret these narrow resonances as compact hidden-charm diquark-diquark-antiquark pentaquarks. Using an effective Hamiltonian, based on constituent quarks and diquarks, we calculate the pentaquark mass spectrum for the complete $SU (3)_F$ lowest $S$- and $P$-wave multiplets, taking into account dominant spin-spin, spin-orbit, orbital and tensor interactions. The resulting spectrum is very rich and we work out the quark flavor compositions, masses, and $J^P$ quantum numbers of the pentaquarks. However, heavy quark symmetry restricts the observable states in $Λ_b$-baryon, as well as in the decays of the other weakly-decaying $b$-baryons, $Ξ_b$ and $Ω_b$. In addition, some of the pentaquark states are estimated to lie below the $J/ψ\, p$ threshold in $Λ_b$-decays (and corresponding thresholds in $Ξ_b$- and $Ω_b$-decays). They decay via $c \bar c$ annihilation into light hadrons or a dilepton pair, and are expected to be narrower than the $P_c$-states observed. We anticipate their discovery, as well as of the other pentaquark states present in the spectrum at the LHC, and in the long-term future at a Tera-$Z$ factory.

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arXiv2020

Probing new physics effects in $Λ_b \to Λ(\to pπ^-)\ell^+\ell^-$ decay via model independent approach

The New Physics (NP) effects are studied in the rare baryonic decay $Λ_b \to Λ(\to pπ^-)\ell^{+}\ell^{-}$, with unpolarized $Λ_b$ using most general model independent approach by introducing new axial(vector), (pseudo)scalar and tensor operators in the weak effective Hamiltonian corresponding to $b\to s$ transitions. Recently, for $Λ_b \to Λ(\to pπ^-)μ^{+}μ^{-}$ decay the LHCb collaboration has measured the branching ratio $(d\mathcal{B}/ds)$, lepton- and hadron-side forward-backward asymmetries, denoted by $A_{FB}^{\ell}$ and $A_{FB}^Λ$, respectively, and the longitudinal polarization fraction $F_L$ both in the low- and high-recoil regions. To see whether the new $VA$, $SP$ and $T$ couplings can accommodate the available experimental data of these observables, first we have examined their influence on these observables and later we have checked the imprints of these new couplings on a number of interesting but yet not measured observables. It is found that compared to the $VA$ the $SP$ couplings favor experimental data for all the four observables but still no individual coupling is able to accommodate all of the available data simultaneously. To achieve this goal, the pairs of new WCs are taken to check their range that simultaneously satisfy constraints of $B$-Physics and available LHCb data on $d\mathcal{B}/ds$, $F_L$, $A_{FB}^{\ell}$ and $A_{FB}^Λ$ in several bins for the decay channel under consideration. We find that most of the available data could be accommodated by the different pairs of $VA$ and $SP$ WCs giving more severe constraints on the parametric space of these WCs that is still satisfied with the $B$-physics data.

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arXiv2019

Mass spectrum of the hidden-charm pentaquarks in the compact diquark model

The LHCb collaboration have recently updated their analysis of the resonant $J/ψp$ mass spectrum in the decay $Λ_b^0 \to J/ψp K^-$, making use of their combined Run 1 and Run 2 data. In the updated analysis, three narrow states, $P_c (4312)^+$, $P_c (4440)^+$,and $P_c (4457)^+$, are observed. The spin-parity assignments of these states are not yet known. We interpret these narrow resonances as compact hidden-charm diquark-diquark-antiquark pentaquarks. Using an effective Hamiltonian, based on constituent quarks and diquarks, we calculate the pentaquark mass spectrum for the complete $SU (3)_F$ lowest $S$- and $P$-wave multiplets, taking into account dominant spin-spin, spin-orbit, orbital and tensor interactions. The resulting spectrum is very rich and we work out the quark flavor compositions, masses, and $J^P$ quantum numbers of the pentaquarks. However, heavy quark symmetry restricts the observable states in $Λ_b$-baryon, as well as in the decays of the other weakly-decaying $b$-baryons, $Ξ_b$ and $Ω_b$. In addition, some of the pentaquark states are estimated to lie below the $J/ψp$ threshold in $Λ_b$-decays (and corresponding thresholds in $Ξ_b$- and $Ω_b$-decays). They decay via $c \bar c$ annihilation into light hadrons or a dilepton pair, and are expected to be narrower than the $P_c$-states observed. We anticipate their discovery, as well as of the other pentaquark states present in the spectrum at the LHC, and in the long-term future at a Tera-$Z$ factory.

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arXiv2019

Vertex renormalization and hard scattering symmetry breaking corrections to $B$ to axial vector meson form factors at large recoil

The symmetries arise due to heavy quark and large energy limit help us to reduce the number of independent form factors in the heavy-to-light $B$-meson decays. It is expected that these symmetry relations are not exact and are broken by the perturbative effects, namely, the vertex corrections and the hard-spectator scatterings. The former are included in the form factors via vertex renormalization whereas the later are calculated through light-cone distribution amplitudes. We first calculate these symmetry breaking corrections to the form factors involved in semileptonic $B$-meson to an axial-vector $(K_{1})$-meson decay. Later, by using these form factors we see their effect on the physical observables such as the zero-position of the forward-backward $(\mathcal{A}_{FB})$ asymmetry and the longitudinal lepton polarization ($P_L$) asymmetry in $B\rightarrow K_1(1270) μ^+μ^-$ decay. We find that as a result of these corrections to the form factors, the zero-position of the forward-backward asymmetry is shifted by $10\%$ from its SM value while the effects on $P_L$ are rather insignificant.

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arXiv2019

Testing Leptoquark and $Z^{\prime}$ Models via $B\to K_{1}(1270,1400)μ^{+}μ^{-}$ Decays

The measurements of $R_{K^{(*)}}=\mathcal B(B\to K^{(*)}μ^{+}μ^{-})/\mathcal B(B\to K^{(*)}e^{+}e^{-})$ in recent years have hinted lepton flavor non-universality and thus drawn widespread attentions. If these anomalies are induced by new physics (NP), deviations from the SM predictions may also be found in other channels via the same process at the quark level. In this work, we study in $B\to K_{1}(1270,1400)μ^{+}μ^{-}$ decays the effects of two popular classes of NP models which can address the $b\to s$ anomalies, i.e. the leptoquark models and the $Z^{\prime}$ models. By assuming that NP only affects the $b\to sμ^+μ^-$ transition, we find that the unpolarized and polarized lepton flavor universality (LFU) ratios $R_{K_1^{(L,T)}(1270)}$ are useful to distinguish among the NP models (scenarios) and the SM because they are sensitive to the NP effects and insensitive to the mixing angle $θ_{K_1}$, while the $R_{K_1^{(L,T)}(1400)}$ are sensitive to both NP and $θ_{K_1}$. Another ratio $R_μ(K_1)=\mathcal B(B\to K_1(1400)μ^+μ^-)/\mathcal B(B\to K_1(1270)μ^+μ^-)$ is shown to depend weekly on the effects from the NP models (scenarios) under consideration, and thus can be used to determine the $θ_{K_1}$ and complement the $R_{K_1^{(L,T)}}$ in the probe for NP.

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arXiv2018

LHCb anomaly in $\boldsymbol{B\to K^*μ^+ μ^-}$ optimised observables and potential of $\boldsymbol{Z^\prime}$ Model

Over the last few years LHCb with present energies found some discrepancies in $b\to s\ell^+\ell^-$ FCNC transitions including anomalies in the angular observables of $B\to K^*μ^+μ^-$, particularly in $P_5^\prime$, in low dimuon mass region. Recently, these anomalies are confirmed by Belle, CMS and ATLAS. As the direct evidence of physics beyond-the-SM is absent so far, therefore, these anomalies are being interpreted as indirect hint of new physics. In this context, we study the implication of non universal family of $Z^\prime$ model to the angular observables $P_{1,2,3}$, $P^{\prime}_{4,5,6}$ and newly proposed lepton flavor universality violation observables, $Q_{4,5}$, in $B\to K^*(\to Kπ)μ^+ μ^-$ decay channel in the low dimuon mass region. To see variation in the values of these observables from their standard model values, we have chosen the different scenarios of the $Z^\prime$ model. It is found that these angular observables are sensitive to the values of the parameters of $Z^\prime$ model. We have also found that with the present parametric space of $Z^\prime$ model, the $P_5^\prime$-anomaly could be accommodated. However, more statistics on the anomalies in the angular observables are helpful to reveal the status of the considered model and, in general, the nature of new physics.

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arXiv2017

A New Look at the $Y$ Tetraquarks and $Ω_c$ Baryons in the Diquark Model

We analyze the hidden charm $P$-wave tetraquarks in the diquark model, using an effective Hamiltonian incorporating the dominant spin-spin, spin-orbit and tensor interactions. We compare with other $P$-wave system such as $P$-wave charmonia and the newly discovered $Ω_c$ baryons, analysed recently in this framework. Given the uncertain experimental situation on the $Y$ states, we allow for different spectra and discuss the related parameters in the diquark model. In addition to the presently observed ones, we expect many more states in the supermultiplet of $L=1$ diquarkonia, whose $J^{PC}$ quantum numbers and masses are worked out, using the parameters from the currently preferred $Y$-states pattern. The existence of these new resonances would be a decisive footprint of the underlying diquark dynamics.

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arXiv2017

Mass spectrum of spin-1/2 pentaquarks with a $c\bar{c}$ component and their anticipated discovery modes in $b$-baryon decays

The LHCb discovery of the two baryonic states $P_c^+(4380)$ and $P_c^+(4450)$, having $J^{P}=3/2^-$ and $J^{P}=5/2^+$, respectively, in the process $pp \to b \bar{b} \to Λ_b X$, followed by the decay $Λ_b \to J/ψ\; p\; K^-$, has motivated a number of theoretical models. Interpreting them as compact $\{\bar{c}\; [c u] \; [ud]; L_{\mathcal{P}}=0,1\}$ objects, the mass spectroscopy of the $J^P=3/2^-$ and $J^P=5/2^+$ pentaquarks was worked out by us for the pentaquarks in the $SU(3)_F$ multiplets, using an effective Hamiltonian based on constituent diquarks and quarks. Their possible discovery modes in $b$-baryon decays were also given using the heavy quark spin symmetry. In this paper, we calculate the mass spectrum of the hidden $c\bar{c}$ pentaquarks having $J^{P}=\frac{1}{2}^\pm$ for the $SU(3)_F$ multiplets and their anticipated discovery modes in $b$-baryon decays. Some of the $P_c^+(J^P=1/2^\pm$) pentaquarks, produced in the $Λ_{b}$ decays may have their masses just below the $J/ψ\, p$ threshold, in which case they should be searched for in the modes $ P_c^+(J^P=1/2^\pm) \to η_c\; p,\;\; μ^+ μ^- \;p,\;\; e^+ e^-\; p$.

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arXiv2016

Heavy quark symmetry and weak decays of the $b$-baryons in pentaquarks with a $c\bar{c}$ component

The discovery of the baryonic states $P_c^+(4380)$ and $P_c^+(4450)$ by the LHCb collaboration has evoked a lot of theoretical interest. These states have the minimal quark content $c \bar{c} u u d$. Interpreted as hidden charm diquark-diquark-antiquark baryons, the assigned spin and angular momentum quantum numbers are $P_c^+(4380)= \{\bar{c} [cu]_{s=1} [ud]_{s=1}; L_{\mathcal{P}}=0, J^{\rm P}=\frac{3}{2}^- \}$ and $P_c^+(4450)= \{\bar{c} [cu]_{s=1} [ud]_{s=0}; L_{\mathcal{P}}=1, J^{\rm P}=\frac{5}{2}^+ \}$, where $s=0,1$ are the spins of the diquarks and $L_{\mathcal{P}}=0,1$ are the orbital angular momentum quantum numbers of the pentaquarks. We point out that heavy quark symmetry allows only the higher mass pentaquark state $P_c^+(4450)$ having $[ud]_{s=0}$ to be produced in $Λ_b^0$ decays, whereas the lower mass state $P_c^+(4380)$ having $[ud]_{s=1}$ is disfavored. Pentaquark spectrum is rich enough to accommodate a $J^P=\frac{3}{2}^-$ state, which has the correct light diquark spin $\{\bar{c} [cu]_{s=1} [ud]_{s=0}; L_{\mathcal{P}}=0, J^{\rm P}=\frac{3}{2}^- \}$ to be produced in $Λ_b^0$ decays. Assuming that the orbital mass difference between the charmed pentaquarks is similar to the corresponding mass difference in the charmed baryons, we estimate the mass of the lower pentaquark $J^P=3/2^-$ state to be about 4110 MeV and suggest to reanalyze the LHCb data to search for this third state. We present the spectroscopy of the $S$- and $P$-wave pentaquark states having a $c\bar{c}$ pair and three light quarks using an effective Hamiltonian approach. Some of these pentaquarks can be produced in weak decays of the $b$-baryons. Combining heavy quark symmetry and the $SU(3)_F$ symmetry results in strikingly simple relations among the decay amplitudes which are presented here.

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arXiv2016

Asymmetries in $B \to K^\ast \ell^+ \ell^-$ Decays and Two Higgs Doublet Model

The study of polarized branching ratio and different lepton polarization asymmeteries in the exclusive rare decays $B\rightarrow K^{\ast}\ell^{+}\ell^{-}$ ($\ell=μ, τ$) have been made in the standard model (SM) and in type III of the THDM. It has been found that the effects arise from the THDM are quite promising in the longitudinal and transverse polarized branching ratios $(\mathcal{B}_{L, T})$. Likewise, in case of $μ$'s as final state leptons, the polarized branching ratios have an order of magnitude difference from their SM results. Similar trends have also been observed both in the longitudinal and normal lepton polarization asymmetries $P_{L, N}$ as well as their average values. We hope that the possible signatures of these observables in $B\rightarrow K^{\ast}\ell^{+}\ell^{-}$ decays at different on going and future experiments will serve as a good tool in the indirect searches of an extra Higgs boson doublet.

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arXiv2015

Polarized forward-backward asymmetries of lepton pair in $B\rightarrow K_{1}\ell^{+}\ell^{-}$ decay in the presence of New physics

Double polarized forward-backward asymmetries in $B\rightarrow K_{1}(1270,1400)\ell^{+}\ell^{-}$ with $\ell=μ, τ$ decays are studied, using most general non-standard local four-fermi interactions, where the mass eigenstates $K_{1}(1270)$ and $K_{1}(1400)$ are the mixture of $^{1}{P}_{1}$ and $^{3}{P}_{1}$ states with the mixing angle $θ_{K}$. We have calculated the expressions of nine doubly polarized forward-backward asymmetries and it is presented that the polarized lepton pair forward-backward asymmetries are greatly influenced by the new physics. Therefore, these asymmetries are interesting tool to explore the status of new physics in near future, specially at LHC.

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arXiv2015

Analysis of Forward-Backward and Lepton Polarization Asymmetries in $B\to K_{1}\ell^{+}\ell^{-}$ Decays in the Two-Higgs-doublet Model

The exclusive semileptonic $B\to K_{1}(1270) \ell^{+}\ell^{-}$ ($\ell=μ, τ$) decays are analyzed in variants of two Higgs double models (THDMs). The mass eigenstates $K_{1}(1270)$ and $K_{1}(1400)$ are the mixture of two axial-vector SU(3) $^{1}{P}_{1}$ and $^{3}{P}_{1}$ states with the mixing angle $θ_{K}$. Making use of the form factors calculated in the Light Cone QCD approach and by taking the mixing angle $θ_{K}=-34^{\circ}$, the impact of the parameters of the THDMs on different asymmetries in above mentioned semileptonic $B$ meson decays are studied. In this context the forward-backward asymmetry and different lepton polarization asymmetries have been analyzed. We have found comprehensive effects of the parameters of the THDMs on the above mentioned asymmetries. Therefore, the precise measurements of these asymmetries at the LHC and different $B$ factories, for the above mentioned processes, can serve as a good tool to put some indirect constraints on the parametric space of the different versions of THDM.

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arXiv2015

Pseudoscalar mesons with symmetric bound state vertex functions on the light front

We study the electromagnetic form factors, decay constants and charge radii of the pion and kaon within the framework of light-front field theory formalism where we use an ansatz for the quark-meson interaction bound-state function which is symmetric under exchange of quark and antiquark momentum. The above mentioned observables are evaluated for the $+$ component of the electromagnetic current, $J^+$, in the Breit frame. We also check the invariance of these observables in other frames, whereby both the valance and the non-valence contributions have to be taken into account, and study the sensitivity of the electromagnetic form factors and charge radius to the model's parameters; namely, the quark masses, $m_u=m_d$, $m_{\bar s}$, and the regulator mass, $m_R$. It is found that after a fine tuning of the regulator mass, i.e. $m_R=0.6$ GeV, the model is suitable to fit the available experimental data within the theoretical uncertainties of both the pion and kaon.

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