Searcharxiv⌕ Search

arXiv subjects

Ho-Meoyng Choi

Publications and source records attributed to Ho-Meoyng Choi.

At least 37 records · Page 2Linked to original sources
arXiv2019

Twist-2 Pseudoscalar and Vector Meson Distribution Amplitudes in Light-Front Quark Model with Exponential-type Confining Potential

We study the twist-2 distribution amplitudes (DAs) and the decay constants of pseudoscalar light ($π$, $K$) and heavy ($D$, $D_s$, $B$, $B_s$) mesons as well as the longitudinally and transversely polarized vector light ($ρ$, $K^*$) and heavy ($D^*$, $D_s^*$, $B^*$, $B_s^*$) mesons in the light-front quark model with the Coulomb plus exponential-type confining potential $V_{\rm {exp}} = a + b e^{αr}$ in addition to the hyperfine interaction. We first compute the mass spectra of ground state pseudoscalar and vector light and heavy mesons and fix the model parameters necessary for the analysis, applying the variational principle with the trial wave function up to the first three lowest order harmonic oscillator (HO) wave functions $Φ(x, \textbf{k}_\bot) = \sum_{n=1}^{3} c_n ϕ_{nS}$. We then obtain the numerical results for the corresponding decay constants of light and heavy mesons. We estimate the DAs, analyze their variation as a function of momentum fraction and compute the first six $ξ$-moments of the $B$ and $D$ mesons as well. We compare our results with the available experimental data as well as with the other theoretical model predictions.

hep-ph↗
arXiv2019

Beam Spin Asymmetry in Electroproduction of Pseudoscalar or Scalar Meson Production off the Scalar Target

We discuss the electroproduction of pseudoscalar ($0^{-+}$) or scalar ($0^{++}$) meson production off the scalar target. The most general formulation of the differential cross section for the $0^{-+}$ or $0^{++}$ meson production process involves only one or two hadronic form factors, respectively, on a scalar target. The Rosenbluth-type separation of the differential cross section provides the explicit relation between the hadronic form factors and the different parts of the differential cross section in a completely model-independent manner. The absence of the beam spin asymmetry for the pseudoscalar meson production provides a benchmark for the experimental data analysis. The measurement of the beam spin asymmetry for the scalar meson production may also provide a unique opportunity not only to explore the imaginary part of the hadronic amplitude in the general formulation but also to examine the significance of the chiral-odd generalized parton distribution (GPD) contribution in the leading-twist GPD formulation.

nucl-th↗
arXiv2019

The doubly virtual $(π^0,η,η')\toγ^*γ^*$ transition form factors in the light-front quark model

We report our investigation on the doubly virtual TFFs $F_{{\rm P}γ^*}(Q^2_1,Q^2_2)$ for the ${\rm P}\toγ^*(q_1)γ^*(q_2) \;({\rm P}=π^0,η,η')$ transitions using the light-front quark model (LFQM). Performing a LF calculation in the exactly solvable manifestly covariant Bethe-Salpeter (BS) model as the first illustration, we used $q^+_1=0$ frame and found that both LF and manifestly covariant calculations produce exactly the same results for $F_{{\rm P}γ^*}(Q^2_1,Q^2_2)$. This confirms the absence of the LF zero mode in the doubly virtual TFFs. We then mapped this covariant BS model to the standard LFQM using the more phenomenologically accessible Gaussian wave function provided by the LFQM analysis of meson mass spectra. For the numerical analyses of $F_{{\rm P}γ^*}(Q^2_1,Q^2_2)$, we compared our LFQM results with the available experimental data and the perturbative QCD (pQCD) and the vector meson dominance (VMD) model predictions. As $(Q^2_1, Q^2_2)\to\infty$, our LFQM result for doubly virtual TFF is consistent with the pQCD prediction, i.e. $F_{{\rm P}γ^*}(Q^2_1, Q^2_2)\sim 1/(Q^2_1 + Q^2_2)$, while it differs far from the result of VMD model which behaves $F^{\rm VMD}_{{\rm P}γ^*}(Q^2_1, Q^2_2)\sim 1/(Q^2_1 Q^2_2)$. Our LFQM prediction for $F_{η'γ^*}(Q^2_1,Q^2_2)$ shows an agreement with the very recent experimental data obtained from the BaBar collaboration for the ranges of $2< Q^2_1, Q^2_1 <60$ GeV$^2$.

hep-ph↗
arXiv2018

Systematic twist expansion of $(η_c,η_b)\toγ^*γ$ transition form factors in light-front quark model

The light-front quark model analysis of the meson-photon transition form factor $F_{Pγ} (Q^2)$ amenable both for the spacelike region ($Q^2 >0$) and the timelike region ($Q^2 <0$) provides a systematic twist expansion of $Q^2 F_{Pγ} (Q^2)$ for the high $|Q^2|$ region. Investigating $F_{Pγ} (Q^2) (P = η_c,η_b)$ for the entire kinematic regions of $Q^2$, we examine the twist-2 and twist-3 distribution amplitudes of $(η_c,η_b)$ mesons in the light-front quark model and quantify their contributions to $Q^2 F_{(η_c,η_b)γ}(Q^2)$. Our numerical results for the normalized transition form factor $F_{(η_c,η_b)γ}(Q^2)/F_{(η_c,η_b)γ}(0)$ and the decay width $Γ_{(η_c,η_b)\toγγ}$ are compared with the available data checking the sensitivity of our model to the variation of the constituent quark masses.

hep-ph↗
arXiv2017

Spacelike and timelike form factors for the $(π^0,η,η')\toγ^*γ$ transitions in the light-front quark model

We investigate the $(π^0,η,η')\toγ^*γ$ transitions both for the spacelike region and the timelike region using the light-front quark model (LFQM). In particular, we present the new direct method to explore the timelike region without resorting to mere analytic continuation from the spacelike region to the timelike region. Our direct calculation in timelike region shows the complete agreement not only with the analytic continuation result from the spacelike region but also with the result from the dispersion relation between the real and imaginary parts of the form factor. For the low energy regime, we compare our LFQM results of the transition form factors (TFFs) for the low timelike momentum transfer region and the slope parameters at $q^2=0$ with the recent experimental data from the Dalitz decays of $(π^0,η,η')$. For the high energy regime, we incorporate the QCD factorization in our LFQM to examine the asymptotic behavior of TFFs both for the spacelike region and the timelike region. We compare our results with the available experimental data.

hep-ph↗
arXiv2017

Two-particle twist-3 distribution amplitudes of the pion and kaon in the light-front quark model

We investigate the two-particle twist-3 distribution amplitudes (DAs) of the pseudoscalar mesons, in particular pseudoscalar ($ϕ^P_{3;M}(x)$) and pseudotensor ($ϕ^σ_{3;M}(x)$) DAs of the pion and kaon, in the light-front quark model based on the variational principle. We find that the behavior of the conformal symmetry in each meson distribution amplitude depends on the chiral limit characteristics of the light-front trial wave function taken in the variational principle. We specifically take the two different light-front trial wave functions, Gaussian vs. power-law type, and discuss their characteristics of the conformal symmetry in the chiral symmetry limit as well as their resulting degree of the conformal symmetry breaking in $ϕ^P_{3;M}(x)$ and $ϕ^σ_{3;M}(x)$ depending on the trial wave function taken in the computation. We present numerical results of transverse moments, Gegenbauer-moments and $ξ$-moments and compare them with other available model estimates. The SU(3) flavor-symmetry breaking effect is also quantified with the numerical computation.

hep-ph↗
arXiv2017

Twist-3 Distribution Amplitudes of Pion in the Light-Front Quark Model

We analyzed two twist-3 distribution amplitudes of pion, i.e. pseudoscalar $ϕ^P_{3;π}(x)$ and pseudotensor $ϕ^σ_{3;π}(x)$, within the LFQM. Our LFQM descriptions both for twist-3 $ϕ^P_{3;π}$ and $ϕ^σ_{3;π}$ not only satisfy the fundamental constraint required from the isospin symmetry, but also reproduce exactly the asymptotic forms anticipated from QCD's conformal limit.

hep-ph↗
arXiv2016

Light-Front Quark Model Analysis of Meson-Photon Transition Form Factor

We discuss $(π^0,η,η')\toγ^*γ$ transition form factors using the light-front quark model. Our discussion includes the analysis of the mixing angles for $η-η'$. Our results for $Q^2 F_{(π^0,η,η')\toγ^*γ}(Q^2)$ show scaling behavior for high $Q^2$ consistent with pQCD predictions.

hep-ph↗
arXiv2015

Update on the Light-Front Quark Model and Mass Spectrum Calculations for Ground State Pseudoscalar and Vector Mesons

We present an update on the meson mass spectra calculation with the light-front quark model constrained by the variational principle for the QCD-motivated effective Hamiltonian. By smearing out the Dirac delta function in the hyperfine interaction, we were able to avoid the negative infinity that one encounters when using variational principle for the entire Hamiltonian. We obtained a better fitting for the mass spectra of ground state pseudoscalar and vector mesons from $π$ to $Υ$, compared to the previous calculation that handled the hyperfine interaction as a perturbation rather than including it in the parameterization process. Our new parameters are further tested in decay constant calculation. We showed that by taking a larger harmonic oscillator basis in our trial wave function, the decay constants calculated from our model can be improved to agree reasonably well with the experimental data.

hep-ph↗
arXiv2015

Variational Analysis of Mass Spectra and Decay Constants for Ground State Pseudoscalar and Vector Mesons in Light-Front Quark Model

Using the variational principle, we compute mass spectra and decay constants of ground state pseudoscalar and vector mesons in the light-front quark model (LFQM) with the QCD-motivated effective Hamiltonian including the hyperfine interaction. By smearing out the Dirac delta function in the hyperfine interaction, we avoid the issue of negative infinity in applying the variational principle to the computation of meson mass spectra and provide analytic expressions for the meson mass spectra. Our analysis with the smeared hyperfine interaction indicates that the interaction for the heavy meson sector including the bottom and charm quarks gets more point-like. We also consider the flavor mixing effect in our analysis and determine the mixing angles from the mass spectra of $(ω,ϕ)$ and $(η,η')$. Our variational analysis with the trial wave function including the two lowest order harmonic oscillator basis functions appears to improve the agreement with the data of meson decay constants and the heavy meson mass spectra over the previous computation handling the hyperfine interaction as perturbation.

hep-ph↗
arXiv2015

Light-Front Quark Model Phenomenology Consistent with Chiral Symmetry

We discuss the link between the chiral symmetry of QCD and the numerical results of the light-front quark model, analyzing both the twist-2 and twist-3 distribution amplitudes of a pion. In particular, we exhibit that the pion twist-3 distribution amplitude can flip the sign of curvature as the cutoff scale for the transverse momentum gets lower than a typical scale of around 1 GeV.

hep-ph↗
arXiv2015

Consistency of the light-front quark model with chiral symmetry in the pseudoscalar meson analysis

We discuss the link between the chiral symmetry of QCD and the numerical results of the light-front quark model (LFQM), analyzing both the two-point and three-point functions of a pseudoscalar meson from the perspective of the vacuum fluctuation consistent with the chiral symmetry of QCD. The two-point and three-point functions are exemplified in this work by the twist-2 and twist-3 distribution amplitudes of a pseudoscalar meson and the pion elastic form factor, respectively. The present analysis of the pseudoscalar meson commensurates with the previous analysis of the vector meson two-point function and fortifies our observation that the light-front quark model with effective degrees of freedom represented by the constituent quark and antiquark may provide the view of effective zero-mode cloud around the quark and antiquark inside the meson. Consequently, the constituents dressed by the zero-mode cloud may be expected to satisfy the chiral symmetry of QCD. Our results appear consistent with this expectation and effectively indicate that the constituent quark and antiquark in the LFQM may be considered as the dressed constituents including the zero-mode quantum fluctuations from the vacuum.

hep-ph↗
arXiv2014

Self-consistent covariant description of vector meson decay constants and chirality-even quark-antiquark distribution amplitudes up to twist-3 in the light-front quark model

Although the meson decay amplitude described by a two-point function may be regarded as one of the simplest possible physical observable, it is interesting that this apparently simple amplitude bears abundant fundamental informations on QCD vacuum dynamics and chiral symmetry. The light-front zero-mode issue of the vector meson decay constant $f_V$ is in this respect highly non-trivial and deserves careful analyses. We discuss the zero-mode issue in the light-front quark model (LFQM) prediction of $f_V$ from the perspective of the vacuum fluctuation consistent with the chiral symmetry of QCD. We extend the exactly solvable manifestly covariant Bethe-Salpeter model calculation to the more phenomenologically accessible realistic LFQM and present a self-consistent covariant description of $f_V$ analyzing the twist-2 and twist-3 quark-antiquark distribution amplitudes with even chirality.

hep-ph↗
arXiv2013

Light-front zero-mode issue on the vector meson decay constant

We discuss the light-front zero-mode issue in the light-front quark model (LFQM) prediction of a vector meson decay constant from the perspective of the vacuum fluctuation consistent with the chiral symmetry of QCD. We extend the exactly solvable manifestly covariant Bethe-Salpeter model calculation to the more phenomenologically accessible realistic LFQM and present a self-consistent covariant description of the vector meson decay constant analyzing the twist-2 and twist-3 quark-antiquark distribution amplitudes with even chirality.

hep-ph↗
arXiv2013

Ideas of Four-Fermion Operators in Electromagnetic Form Factor Calculations

Four-fermion operators have been utilized in the past to link the quark-exchange processes in the interaction of hadrons with the effective meson-exchange amplitudes. In this paper, we apply the similar idea of a Fierz rearrangement to the electromagnetic processes and focus on the electromagnetic form factors of the nucleon and the electron. We explain the motivation of using four-fermion operators and discuss the advantage of this method in computing electromagnetic processes.

hep-ph↗
arXiv2012

Relativistic Covariance of Light-Front Few-Body Systems in Hadron Physics

We study the light-front covariance of a vector-meson decay constant using a manifestly covariant fermion field theory model in $(3+1)$ dimensions. The light-front zero-mode issues are analyzed in terms of polarization vectors and method of identifying the zero-mode operator and of obtaining the light-front covariant decay constant is discussed.

hep-ph↗
arXiv2011

Light-front dynamic analysis of transition form factors in the process of $P\to V\ellν_{\ell}$

We investigate the light-front zero-mode contribution to the weak transition form factors between pseudoscalar and vector mesons using a covariant fermion field theory model in $(3+1)$ dimensions. In particular, we discuss the form factors $a_-(q^2)$ and $f(q^2)$ which have been suspected to have the zero-mode contribution in the $q^+=0$ frame. While the zero-mode contribution in principle depends on the form of the vector meson vertex $Γ^μ=γ^μ- (2k-P_V)^μ/D$, the form factor $f(q^2)$ is found to be free from the zero mode if the denominator $D$ contains the term proportional to the light-front longitudinal momentum fraction factor $(1/x)^n$ of the struck quark with the power $n>0$. Although the form factor $a_-(q^2)$ is not free from the zero mode, the zero-mode contribution comes only either from the simple vertex $Γ^μ=γ^μ$ term or from the other term just with a constant $D$ (i.e. $n=0$), but not with the momentum-dependent denominator (i.e. $D\sim (1/x)^n$ with $n>0$). We identify the zero-mode contribution to $a_-(q^2)$ and incorporate it as a convolution of the zero-mode operator with the initial and final state light-front wave functions. The covariance (i.e. frame independence) of our model has been checked by performing the light-front calculations both in the $q^+=0$ and $q^+\neq 0$ frames. We present our numerical result for the $B\toρ$ transition for an explicit demonstration of our findings.

hep-ph↗