arXiv subjects

Jai More

Publications and source records attributed to Jai More.

17 recordsLinked to original sources

arXiv2025

Features of Charged Lepton Flavor Violation in an $A_4$ Symmetric Neutrino Mass Model

Neutrino flavour oscillations imply that there must be charged lepton flavour violation (CLFV) also. Different neutrino mass models predict different patterns of CLFV decays. Neutrino mass generation through standard see-saw mechanisms leads to the prediction that the branching ratios of meson CLFV decays will always be smaller than the corresponding radiative CLFV decays. In this work, we analyse an interesting neutrino mass model, based on $A_4$ symmetry, in which the symmetry and the symmetry-breaking pattern lead the neutrino mixing matrix to be of tri-bimaximal (TBM) form. In this model, we find that the meson CLFV decay amplitudes are not correlated to the corresponding radiative CLFV amplitudes, unlike in the case of see-saw models. The branching ratios of radiative CLFV decays are predicted to be negligibly small in this model, but those of the meson CLFV decays can be large enough to be observable in the near future.

hep-ph↗

arXiv2024

Charged Lepton Flavour Violating Meson Decays in Seesaw Models

The occurrence of neutrino oscillations demands the existence of flavour violation in charged lepton sector. The relation between the branching ratios of different charged lepton flavour violating (CLFV) decay modes depends on the details of the neutrino mass model. In this work, we consider the three types of simple seesaw mechanisms of neutrino masses and study the correlation between the radiative CLFV decays and the meson CLFV decays. We find that the meson CLFV decay branching ratios are negligibly small in type-II seesaw mechanism whereas they are constrained to be at least three (two) orders of magnitude smaller than the radiative CLFV decay branching ratios in the case of type-I (type-III) seesaw mechanism. Thus the relationship between these two modes of CLFV decays helps in distinguishing between different types of seesaw mechanism. If, the branching ratios of CLFV decays of mesons are larger than those of radiative CLFV decays, it provides a strong hint that the neutrino mass generating mechanism is more complicated than simple seesaw.

hep-ph↗

arXiv2023

Dynamics of heavy quarks in the Fock space

This paper concerns a method of describing hadrons that starts with the canonical front form Hamiltonian of QCD. The method is developed in the relatively simple context of QCD with only heavy quarks. We regulate its canonical Hamiltonian by introducing a vanishingly small gluon mass $m_g$. For positive $m_g$, the small-$x$ gluon divergences become ultraviolet and hence they are renormalized in the same way the ultraviolet transverse divergences are. This is done using the renormalization group procedure for effective particles. Up to the second order of expansion of the renormalized Hamiltonian in powers of the quark-gluon coupling constant $g$, only the quark mass-squared and gluon-exchange divergences require counter terms. In these circumstances, we calculate an effective potential between quarks in heavy quarkonia in an elementary way, replacing all the quarkonium-state components with gluons of mass $m_g$ by only one component with just one gluon that is assigned a mass $m_G$, comparable to or exceeding the scale of typical relative momenta of bound quarks. In the limit of $m_g \to 0$ and large $m_G$ two results are obtained. (1) While the color-singlet quarkonium mass eigenvalue stays finite and physically reasonable in that limit, the eigenvalues for single quarks and octet quarkonia are infinite. (2) The effective quark-antiquark potential is quadratic as a function of the distance and spherically symmetric for typical separations between quarks but becomes logarithmic and no longer spherically symmetric for large separations. Our conclusion indicates how to systematically improve upon the approximations made in this paper.

hep-ph↗

arXiv2023

Sum rules for the Gravitational Form Factors using light-front dressed quark state

We consider a light-front dressed quark state, per se, instead of a proton state, we consider a simple composite spin-1/2 state of a quark dressed with a gluon. This perturbative model incorporates gluonic degrees of freedom, which enable us to evaluate the gravitational form factors (GFFs) of the quark as well as the gluon in this model \cite{More:2021stk, More:2023pcy}. We employ the Hamiltonian framework and choose the light-front gauge $A^+=0$. We calculate the four GFFs and corroborate the sum rules that GFFs satisfy. The GFF $D$ is attributed to information like pressure, shear, and energy distributions. We analyze some of these distributions for a dressed quark state at one loop in QCD.

hep-ph↗

arXiv2023

Baryon masses estimate in heavy flavor QCD

We apply the renormalization group procedure for effective particles (RGPEP) to the QCD eigenvalue problem for only heavy quarks. We derive the effective Hamiltonian that acts on the Fock space by solving the RGPEP equation up to second order in powers of the coupling constant. The eigenstates that contain three quarks and two or more gluons are eliminated by inserting a gluon-mass term in the component with one gluon and formulate the eigenvalue problem for baryons. We estimate masses for $bbb$ and $ccc$ states and find that the results match the estimates obtained in lattice QCD and in quark models.

hep-ph↗

arXiv2023

Gluon contribution to the mechanical properties of a dressed quark in light-front Hamiltonian QCD

We calculate the contribution to the gravitational form factors (GFFs) from the gluon part of the energy-momentum tensor in QCD. We take a simple spin $1/2$ composite state, namely a quark dressed with a gluon. We use the light-front Hamiltonian QCD approach in the light-front gauge. We also present the effect of the gluon on the mechanical properties like the pressure, shear and energy distributions of the dressed quark state.

hep-ph↗

arXiv2022

Constraints on the Doublet Left-Right Symmetric Model from Higgs data

We study the constraints on the doublet left-right symmetric model (DLRSM) arising due to the Higgs data. The $SU(2)_L$ symmetry of this model is broken by three vacuum expectation values, $\kappa_1$, $\kappa_2$, and $v_L$. Most studies of this model assume that the ratios $r = \kappa_2/\kappa_1$ and $w = v_L/\kappa_1$ are very small. In this work, we study the constraints imposed on $r$ and $w$ by the Higgs data from LHC. We consider the most general scalar potential and calculate the masses of the CP-even scalars and the couplings of the lightest of these scalars to itself, to $W$ and $Z$ gauge bosons, and to the third generation quarks. We find that there is no lower bound on either $r$ or $w$. Equating the mass of the lightest CP-even scalar to $125$ GeV leads to an upper limit $w < 6.7$. The requirement that the Yukawa coupling of the quarks to the Higgs bidoublet of the model should be perturbative yields the upper bounds $r < 0.8$ and $w < 3.5$. The Yukawa coupling of the bottom quark to the lightest CP-even scalar strongly disfavours value of $r, w < 0.1$ and shows a marked preference for values of $w \sim \mathcal{O}(1)$.

hep-ph↗

arXiv2021

Gravitational form factors and mechanical properties of a quark at one loop in light-front Hamiltonian QCD

We calculate the gravitational form factors (GFFs) and pressure, shear and energy distributions for a quark state dressed with a gluon at one loop in QCD. We use the light-front Hamiltonian approach. In the light-front gauge, we use a two-component formalism to eliminate the constrained fields. The state may be thought of as a perturbative model for a relativistic spin $1/2$ composite system having a gluonic degree of freedom. We compare the results with model calculations for a nucleon.

hep-ph↗

arXiv2021

Signatures of $A_4$ symmetry in the charged lepton flavour violating decays in a neutrino mass model

We study the charged lepton flavour violation in a popular neutrino mass model with $A_4$ discrete symmetry. This symmetry requires the presence of multiple Higgs doublets in the model and it also dictates the flavour violating Yukawa couplings of the additional neutral scalars of the model. Such couplings lead to the decays of the neutral mesons, the top quark and the $τ$ lepton into charged leptons of different flavours at tree level. The $A_4$ symmetry of the model leads to certain characteristic signatures in these decays. We discuss these signatures and predict the rates for the most favourable charged lepton flavour violating modes.

hep-ph↗

arXiv2018

Approximate Hamiltonian for baryons in heavy-flavor QCD

Aiming at relativistic description of gluons in hadrons, the renormalization group procedure for effective particles (RGPEP) is applied to baryons in QCD of heavy quarks. The baryon eigenvalue problem is posed using the Fock-space Hamiltonian operator obtained by solving the RGPEP equations up to second order in powers of the coupling constant. The eigenstate components that contain three quarks and two or more gluons are heuristically removed at the price of inserting a gluon-mass term in the component with one gluon. The resulting problem is reduced to the equivalent one for the component of three quarks and no gluons. Each of the three quark-quark interaction terms thus obtained consists of a spin-dependent Coulomb term and a spin-independent harmonic oscillator term. Quark masses are chosen to fit the lightest spin-one quarkonia masses most accurately. The resulting estimates for bbb and ccc states match estimates obtained in lattice QCD and in quark models. Masses of ccb and bbc states are also estimated. The corresponding wave functions are invariant with respect to boosts. In the ccb states, charm quarks tend to form diquarks. The accuracy of our approximate Hamiltonian can be estimated through comparison by including components with two gluons within the same method.

hep-ph↗

arXiv2018

Wigner Distributions For Gluons

We investigate the gluon Wigner distributions for unpolarized, longitudinally polarized and transversely polarized target state. Instead of a nucleon, we take the target state to be a quark dressed with a gluon at one loop and investigate the gluon Wigner distributions at leading twist. Better numerical convergence is obtained compared to an earlier study, that removes the regulator dependence of the results. We present a first calculation of the Wigner distribution for the transversely polarized target and linearly polarized gluon. We study the spin densities in momentum and impact parameter space. We also investigate the quark and gluon helicity and orbital angular momentum distributions at small-$x$.

hep-ph↗

arXiv2018

Three Dimensional Imaging of the Nucleon

We study the Wigner distributions of quarks and gluons in light-front dressed quark model using the overlap of light front wave functions (LFWFs). We take the target to be a dressed quark, this is a composite spin $-1/2$ state of quark dressed with a gluon. This state allows us to calculate the quark and gluon Wigner distributions analytically in terms of LFWFs using Hamiltonian perturbation theory. We analyze numerically the Wigner distributions of quark and gluon and report their nature in the contour plots. We use an improved numerical technique to remove the cutoff dependence of the Fourier transformed integral over ${\bf Δ}_\perp$.

hep-ph↗

arXiv2017

Renormalized quark-antiquark Hamiltonian induced by a gluon mass ansatz in heavy-flavor QCD

In response to the growing need for theoretical tools that can be used in QCD to describe and understand the dynamics of gluons in hadrons in the Minkowski space-time, the renormalization group procedure for effective particles (RGPEP) is shown in the simplest available context of heavy quarkonia to exhibit a welcome degree of universality in the first approximation it yields once one assumes that beyond perturbation theory gluons obtain effective mass. Namely, in the second-order terms, the Coulomb potential with Breit-Fermi spin couplings in the effective quark-antiquark component of a heavy quarkonium, is corrected in one-flavor QCD by a spin-independent harmonic oscillator term that does not depend on the assumed effective gluon mass or the choice of the RGPEP generator. The new generator we use here is much simpler than the ones used before and has the advantage of being suitable for studies of the effective gluon dynamics at higher orders than the second and beyond the perturbative expansion.

hep-ph↗

arXiv2017

Wigner Distributions of Quarks and Gluons

We present a recent calculation of Wigner distributions of quarks and gluons for a quark target state dressed with a gluon, using overlaps of light-front wave functions.

hep-ph↗

arXiv2017

Quark Wigner Distributions Using Light-Front Wave Functions

The quasi-probabilistic Wigner distributions are the quantum mechanical analog of the classical phase-space distributions. We investigate quark Wigner distributions for a quark state dressed with a gluon, which can be thought of as a simple composite and relativistic spin-1/2 state with a gluonic degree of freedom. We calculate various polarization configurations, namely unpolarized, longitudinally polarized and transversely polarized quark and the target state using light-front wave functions in this model. At leading twist, one can define 16 quark Wigner distributions, however, we obtain only 8 independent non-zero Wigner distributions in our model. We compare our results with other model calculations for the proton.

hep-ph↗

arXiv2016

Wigner distributions of quarks for different polarizations

We calculate quark Wigner distributions using the light-front wave functions in a dressed quark model. In this model, a proton target is replaced by a simplified spin-1/2 state, namely a quark dressed with a gluon. We calculate the Wigner distributions for different polarization configuration of quark and the target state in this model.

hep-ph↗

arXiv2015

Application of Coherent State Approach for the cancellation of Infrared divergences to all orders in LFQED

We sketch an all order proof of cancellation of infrared (IR) divergences in Light Front Quantum Electrodynamics (LFQED) using a coherent state formalism. In this talk, it has been shown that the true IR divergences in fermion self energy are eliminated to all orders in a light-front time-ordered perturbative calculation if one uses coherent state basis instead of the usual Fock basis to calculate the Hamiltonian matrix elements.

hep-th↗