@article{ji_choi_lundeen_bakker_2019, title={Beam spin asymmetry in the electroproduction of a pseudoscalar meson or a scalar meson off the scalar target}, volume={99}, ISSN={["2470-0029"]}, DOI={10.1103/PhysRevD.99.116008}, abstractNote={We discuss the electroproduction of scalar ($0^{++}$) or pseudoscalar ($0^{-+}$) 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 single spin asymmetry for the pseudoscalar meson production provides the benchmark for the experimental data analysis. The measurement of the single spin asymmetry for the scalar meson production may provide a clear criterion whether the leading-twist formulation of the generalized parton distribution is in agreement with the most general formulation of the hadronic tensor.}, number={11}, journal={PHYSICAL REVIEW D}, author={Ji, Chueng-Ryong and Choi, Ho-Meoyng and Lundeen, Andrew and Bakker, Bernard L. G.}, year={2019}, month={Jun} }
 @article{choi_ryu_ji_2019, title={Doubly virtual (pi(0),eta,eta ') -> gamma*gamma* transition form factors in the light-front quark model}, volume={99}, ISSN={["2470-0029"]}, DOI={10.1103/PhysRevD.99.076012}, abstractNote={We report our investigation on the doubly virtual TFFs $F_{{\rm P}\gamma^*}(Q^2_1,Q^2_2)$ for the ${\rm P}\to\gamma^*(q_1)\gamma^*(q_2) \;({\rm P}=\pi^0,\eta,\eta')$ 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 $F_{{\rm P}\gamma^*}(Q^2_1,Q^2_2)$. 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 $F_{{\rm P}\gamma^*}(Q^2_1,Q^2_2)$, 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. $F_{{\rm P}\gamma^*}(Q^2_1, Q^2_2)\sim 1/(Q^2_1 + Q^2_2)$, while it differs far from the result of VMD model which behaves $F^{\rm VMD}_{{\rm P}\gamma^*}(Q^2_1, Q^2_2)\sim 1/(Q^2_1 Q^2_2)$. Our LFQM prediction for $F_{\eta'\gamma^*}(Q^2_1,Q^2_2)$ 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$^2$.}, number={7}, journal={PHYSICAL REVIEW D}, author={Choi, Ho-Meoyng and Ryu, Hui-Young and Ji, Chueng-Ryong}, year={2019}, month={Apr} }
 @article{choi_frederico_ji_melo_2019, title={Pion off-shell electromagnetic form factors: Data extraction and model analysis}, volume={100}, ISSN={["2470-0029"]}, DOI={10.1103/PhysRevD.100.116020}, abstractNote={We investigate the pion electromagnetic half-off-shell form factors, which parametrize the matrix element of the charged pion electromagnetic current with one leg off mass shell and the other leg on mass shell, using an exactly solvable manifestly covariant model of a ($3+1$)- dimensional fermion field theory. The model provides a three-dimensional imaging of the two off-shell pion form factors ${F}_{1}$ and ${F}_{2}$ as a function of $({Q}^{2},t)$, which are related to each other, satisfying the Ward-Takahashi identity. The normalization of the renormalized charge form factor ${F}_{1}$ is fixed by ${F}_{1}({Q}^{2}=0,t={m}_{\ensuremath{\pi}}^{2})=1$, while the other form factor ${F}_{2}$ vanishes; i.e., ${F}_{2}({Q}^{2},t={m}_{\ensuremath{\pi}}^{2})=0$ for any value of ${Q}^{2}$ due to the time-reversal invariance of the strong interaction. We define the new form factor $g({Q}^{2},t)={F}_{2}({Q}^{2},t)/(t\ensuremath{-}{m}_{\ensuremath{\pi}}^{2})$ and find that $g({Q}^{2},t)$ can be measurable in the on-mass-shell limit. In particular, $g({Q}^{2}=0,t={m}_{\ensuremath{\pi}}^{2})$ is related with the pion charge radius. We also compare our form factors with the data extracted from the pion electroproduction reaction for both the off-shell region ($tl0$) and the on-shell limit ($t\ensuremath{\rightarrow}{m}_{\ensuremath{\pi}}^{2}$).}, number={11}, journal={PHYSICAL REVIEW D}, author={Choi, Ho-Meoyng and Frederico, T. and Ji, Chueng-Ryong and Melo, J. P. B. C.}, year={2019}, month={Dec} }
 @article{dhiman_dahiya_ji_choi_2019, title={Twist-2 pseudoscalar and vector meson distribution amplitudes in light-front quark model with exponential-type confining potential}, volume={100}, ISSN={["2470-0029"]}, DOI={10.1103/PhysRevD.100.014026}, abstractNote={We study the twist-2 distribution amplitudes (DAs) and the decay constants of pseudoscalar light ($\pi$, $K$) and heavy ($D$, $D_s$, $B$, $B_s$) mesons as well as the longitudinally and transversely polarized vector light ($\rho$, $K^*$) and heavy ($D^*$, $D_s^*$, $B^*$, $B_s^*$) mesons in the light-front quark model with the Coulomb plus exponential-type confining potential $V_{\rm {exp}} = a + b e^{\alpha r}$ 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 $\Phi(x, \textbf{k}_\bot) = \sum_{n=1}^{3} c_n \phi_{nS}$. 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 $\xi$-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.}, number={1}, journal={PHYSICAL REVIEW D}, author={Dhiman, Nisha and Dahiya, Harleen and Ji, Chueng-Ryong and Choi, Ho-Meoyng}, year={2019}, month={Jul} }
 @article{ryu_choi_ji_2018, title={Systematic twist expansion of (eta(c) ,eta(b)) -> gamma*gamma transition form factors in the light-front quark model}, volume={98}, ISSN={["2470-0029"]}, DOI={10.1103/PhysRevD.98.034018}, abstractNote={The light-front quark model analysis of the meson-photon transition form factor $F_{P\gamma} (Q^2)$ amenable both for the spacelike region ($Q^2 >0$) and the timelike region ($Q^2 <0$) provides a systematic twist expansion of $Q^2 F_{P\gamma} (Q^2)$ for the high $|Q^2|$ region. Investigating $F_{P\gamma} (Q^2) (P = \eta_c,\eta_b)$ for the entire kinematic regions of $Q^2$, we examine the twist-2 and twist-3 distribution amplitudes of $(\eta_c,\eta_b)$ mesons in the light-front quark model and quantify their contributions to $Q^2 F_{(\eta_c,\eta_b)\gamma}(Q^2)$. Our numerical results for the normalized transition form factor $F_{(\eta_c,\eta_b)\gamma}(Q^2)/F_{(\eta_c,\eta_b)\gamma}(0)$ and the decay width $\Gamma_{(\eta_c,\eta_b)\to\gamma\gamma}$ are compared with the available data checking the sensitivity of our model to the variation of the constituent quark masses.}, number={3}, journal={PHYSICAL REVIEW D}, author={Ryu, Hui-Young and Choi, Ho-Meoyng and Ji, Chueng-Ryong}, year={2018}, month={Aug} }
 @inproceedings{ji_bakker_choi_suzuki_2013, title={Ideas of four-fermion operators in hadron physics}, volume={6}, number={1}, booktitle={Light cone cracow 2012: modern approaches to nonperturbative gauge theories and their applications}, author={Ji, C. R. and Bakker, B. L. G. and Choi, H. M. and Suzuki, A. T.}, year={2013}, pages={117–123} }
 @article{choi_ji_2012, title={Light-Front Zero-Mode Issue for the Transition Form Factors Between Pseudoscalar and Vector Mesons}, volume={52}, ISSN={["1432-5411"]}, DOI={10.1007/s00601-011-0294-x}, number={3-4}, journal={FEW-BODY SYSTEMS}, author={Choi, Ho-Meoyng and Ji, Chueng-Ryong}, year={2012}, month={May}, pages={409–414} }
 @article{choi_ji_2009, title={Nonleptonic two-body decays of the B-c meson in the light-front quark model and the QCD factorization approach}, volume={80}, ISSN={["1550-2368"]}, DOI={10.1103/physrevd.80.114003}, abstractNote={We study exclusive nonleptonic two-body B{sub c}{yields}(D{sub (s)},{eta}{sub c},B{sub (s)})+F decays with F (pseudoscalar or vector mesons) factored out in the QCD factorization approach. The nonleptonic decay amplitudes are related to the product of meson decay constants and the form factors for semileptonic B{sub c} decays. As inputs in obtaining the branching ratios for a large set of nonleptonic B{sub c} decays, we use the weak form factors for the semileptonic B{sub c}{yields}(D{sub (s)},{eta}{sub c},B{sub (s)}) decays in the whole kinematical region and the unmeasured meson decay constants obtained from our previous light-front quark model. We compare our results for the branching ratios with those of other theoretical studies.}, number={11}, journal={PHYSICAL REVIEW D}, author={Choi, Ho-Meoyng and Ji, Chueng-Ryong}, year={2009}, month={Dec} }
 @article{ji_bakker_choi_2007, title={New developments in treacherous points of light-front dynamics}, volume={790}, ISSN={["0375-9474"]}, DOI={10.1016/j.nuclphysa.2007.03.099}, abstractNote={Light-front dynamics(LFD) plays an important role in hadron phenomenology. Last few years, however, it has been emphasized that treacherous points such as zero-mode contributions should be taken into account for successful LFD applications to hadron phenomenology. We discuss examples of treacherous points and present new progresses made last few years to handle them correctly.}, journal={NUCLEAR PHYSICS A}, author={Ji, Chueng-Ryong and Bakker, Bernard L. G. and Choi, Ho-Meoyng}, year={2007}, month={Jun}, pages={583C–587C} }
 @article{choi_ji_2007, title={Perturbative QCD analysis of exclusive J/psi+eta(c) production in e(+)e(-) annihilation}, volume={76}, ISSN={["1550-2368"]}, DOI={10.1103/physrevd.76.094010}, abstractNote={We analyze the exclusive charmonium $J/\ensuremath{\psi}+{\ensuremath{\eta}}_{c}$ pair production in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation using the nonfactorized perturbative QCD and the light-front quark model (LFQM) that goes beyond the peaking approximation. We effectively include all orders of higher twist terms in the leading order of QCD coupling constant and compare our nonfactorized analysis with the usual factorized analysis in the calculation of the cross section. We also calculate the quark distribution amplitudes, the Gegenbauer moments, and the decay constants for $J/\ensuremath{\psi}$ and ${\ensuremath{\eta}}_{c}$ mesons using our LFQM. Our nonfactorized result enhances the nonrelativistic QCD result by a factor of $3\ensuremath{\sim}4$ at $\sqrt{s}=10.6\text{ }\text{ }\mathrm{GeV}$.}, number={9}, journal={PHYSICAL REVIEW D}, author={Choi, Ho-Meoyng and Ji, Chueng-Ryong}, year={2007}, month={Nov} }
 @article{ji_bakker_choi_2006, title={Revealing treacherous points for successful light-front phenomenological applications}, volume={161}, ISSN={["0920-5632"]}, DOI={10.1016/j.nuclphysbps.2006.08.011}, abstractNote={Light-front dynamics(LFD) plays an important role in hadron phenomenology as evidenced from recent development of generalized parton distributions and other quantities involving hadrons. For successful LFD applications to hadron phenomenology, however, treacherous points such as zero-mode contributions should be taken into account. For a concrete example of zero-mode contribution, we present Standard Model analysis of vector anomaly in the CP-even form factors of W^{\pm} gauge bosons. Main distinguished features of LFD is discussed in comparison with other Hamiltonian dynamics. We also present a power counting method to correctly pin down which hadron form factors receive the zero-mode contribution and which ones do not. Indications from our analysis to hadron phenomenology are discussed.}, journal={NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS}, author={Ji, Chueng-Ryong and Bakker, Bernard L. G. and Choi, Ho-Meoyng}, year={2006}, month={Nov}, pages={102–108} }
 @article{wakin_romberg_choi_baraniuk_2006, title={Wavelet-domain approximation and compression of piecewise smooth images}, volume={15}, ISSN={["1941-0042"]}, DOI={10.1109/TIP.2005.864175}, abstractNote={The wavelet transform provides a sparse representation for smooth images, enabling efficient approximation and compression using techniques such as zerotrees. Unfortunately, this sparsity does not extend to piecewise smooth images, where edge discontinuities separating smooth regions persist along smooth contours. This lack of sparsity hampers the efficiency of wavelet-based approximation and compression. On the class of images containing smooth C/sup 2/ regions separated by edges along smooth C/sup 2/ contours, for example, the asymptotic rate-distortion (R-D) performance of zerotree-based wavelet coding is limited to D(R) /spl lsim/1/R, well below the optimal rate of 1/R/sup 2/. In this paper, we develop a geometric modeling framework for wavelets that addresses this shortcoming. The framework can be interpreted either as 1) an extension to the "zerotree model" for wavelet coefficients that explicitly accounts for edge structure at fine scales, or as 2) a new atomic representation that synthesizes images using a sparse combination of wavelets and wedgeprints-anisotropic atoms that are adapted to edge singularities. Our approach enables a new type of quadtree pruning for piecewise smooth images, using zerotrees in uniformly smooth regions and wedgeprints in regions containing geometry. Using this framework, we develop a prototype image coder that has near-optimal asymptotic R-D performance D(R)/spl lsim/(logR)/sup 2//R/sup 2/ for piecewise smooth C/sup 2//C/sup 2/ images. In addition, we extend the algorithm to compress natural images, exploring the practical problems that arise and attaining promising results in terms of mean-square error and visual quality.}, number={5}, journal={IEEE TRANSACTIONS ON IMAGE PROCESSING}, author={Wakin, MB and Romberg, JK and Choi, H and Baraniuk, RG}, year={2006}, month={May}, pages={1071–1087} }
 @article{choi_ji_2001, title={Exploring the time-like region for the elastic form factor in the light-front quantization}, volume={679}, ISSN={["0375-9474"]}, DOI={10.1016/S0375-9474(00)00376-6}, abstractNote={Even though the Drell–Yan–West formulation is the most rigorous and well-established framework to compute the exclusive processes, its utility has been limited only to the space-like region because of the intrinsic kinematic constraint q+=0. We present an explicit example demonstrating how one may obtain the necessary information (i.e. nonvalence or so called Z-graph contribution) in the time-like region of exclusive process without encountering a formidable task of direct calculation that has hindered so far the progress in this area. In the analysis of qQ bound state form factors using an exactly solvable model of (3+1)-dimensional scalar field theory interacting with gauge fields, the results analytically continued from the space-like region coincide exactly with the direct results in the time-like region. This example verifies that the method of analytic continuation is capable of yielding the effect of complicate nonvalence contributions. The meson peaks analogous to the vector meson dominance (VMD) phenomena are also generated at the usual VMD positions.}, number={3-4}, journal={NUCLEAR PHYSICS A}, author={Choi, HM and Ji, CR}, year={2001}, month={Jan}, pages={735–750} }
 @article{choi_ji_2001, title={Higher-Fock states and the covariance of the light-front quark model}, volume={16}, DOI={10.1142/S0217751X01006929}, abstractNote={ The light-front quark model has been successful in describing various meson properties. We apply the model to the meson weak decays and discuss the covariance of the model. We find that the inclusion of the higher-Fock state (i.e. nonvalence or so called Z-graph) contributions is necessary to recover the covariance of the light-front quark model. We present the possibility of the effective calculation of the higher-Fock state contributions to restore the covariance in the light-front model. }, number={2001 Oct}, journal={International Journal of Modern Physics. A}, author={Choi, H. M. and Ji, Chueng-Ryong}, year={2001}, pages={357–359} }
 @article{ji_choi_2001, title={New effective treatment of the light-front nonvalence contribution in timelike exclusive processes}, volume={513}, ISSN={["0370-2693"]}, DOI={10.1016/S0370-2693(01)00481-6}, abstractNote={We discuss a necessary nonvalence contribution in timelike exclusive processes. Following a Schwinger–Dyson type of approach, we relate the nonvalence contribution to an ordinary light-front wave function that has been extensively tested in the spacelike exclusive processes. A complicate four-body energy denominator is exactly cancelled in summing the light-front time-ordered amplitudes. Applying our method to Kℓ3 and D0→K−ℓ+νl where a rather substantial nonvalence contribution is expected, we find not only an improvement in comparing with the experimental data but also a covariance (i.e., frame-independence) of existing light-front constituent quark model.}, number={3-4}, journal={PHYSICS LETTERS B}, author={Ji, CR and Choi, HM}, year={2001}, month={Aug}, pages={330–336} }
 @article{kisslinger_choi_ji_2001, title={Pion form factor and quark mass evolution in a light-front Bethe-Salpeter model - art. no. 113005}, volume={6311}, number={11}, journal={Physical Review. D, Particles and Fields}, author={Kisslinger, L. S. and Choi, H. M. and Ji, C. R.}, year={2001}, pages={3005-} }
 @article{choi_ji_kisslinger_2001, title={Skewed quark distribution of the pion in the light-front quark model - art. no. 093006}, volume={6409}, number={9}, journal={Physical Review. D, Particles and Fields}, author={Choi, H. M. and Ji, C. R. and Kisslinger, L. S.}, year={2001}, pages={3006-} }
 @article{ji_choi_2000, title={B-physics phenomenology with emphasis on the light-cone}, volume={90}, ISSN={["0920-5632"]}, DOI={10.1016/S0920-5632(00)00879-3}, abstractNote={Theoretical overviews on the B-physics are presented with an emphasis on the light-cone degrees of freedom. Our new treatment of the embedded states seems to give an encouraging result.}, number={2000 Dec}, journal={NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS}, author={Ji, CR and Choi, HM}, year={2000}, month={Dec}, pages={93–99} }
 @article{choi_ji_1999, title={Kaon electroweak form factors in the light-front quark model - art. no. 034001}, volume={5903}, number={3}, journal={Physical Review. D, Particles and Fields}, author={Choi, H. M. and Ji, C. R.}, year={1999}, pages={4001-} }
 @article{choi_ji_1999, title={Light-front quark model analysis of exclusive 0(-) -> 0(-) semileptonic heavy meson decays}, volume={460}, ISSN={["1873-2445"]}, DOI={10.1016/S0370-2693(99)00817-5}, abstractNote={We present the analysis of exclusive $0^{-}$$\to$$0^{-}$ semileptonic heavy meson decays using the constituent quark model based on the light-front quantization. Our model is constrained by the variational principle for the well-known linear plus Coulomb interaction motivated by QCD. Our method of analytic continuation to obtain the weak form factors avoids the difficulty associated with the contribution from the nonvalence quark-antiquark pair creation. Our numerical results for the heavy-to-heavy and heavy-to-light meson decays are in a good agreement with the available experimental data and the lattice QCD results. In addition, our model predicts the two unmeasured mass spectra of $^{1}S_{0}(b\bar{b})$ and $^{3}S_{1}(b\bar{s})$ systems as $M_{b\bar{b}}$=9657 MeV and $M_{b\bar{s}}$= 5424 MeV.}, number={3-4}, journal={PHYSICS LETTERS B}, author={Choi, HM and Ji, CR}, year={1999}, month={Aug}, pages={461–466} }
 @article{choi_ji_1999, title={Mixing angles and electromagnetic properties of ground state pseudoscalar and vector meson nonets in the light-cone quark model - art. no. 074015}, volume={5907}, number={7}, journal={Physical Review. D, Particles and Fields}, author={Choi, H. M. and Ji, C. R.}, year={1999}, pages={4015} }
 @article{ji_choi_1998, title={Mixing angles and electromagnetic properties of ground statepseudoscalar and vector meson nonets in the light-cone quarkmodel}, volume={29}, number={11}, journal={Acta Physica Polonica. B}, author={Ji, C. R. and Choi, H. M.}, year={1998}, pages={3363–3366} }
 @article{choi_ji_1998, title={Nonvanishing zero modes in the light-front current - art. no.071901}, volume={5807}, number={7}, journal={Physical Review. D, Particles and Fields}, author={Choi, H. M. and Ji, C. R.}, year={1998}, pages={1901} }
 @article{choi_ji_1997, title={Light-cone quark model predictions for radiative meson decays}, volume={618}, ISSN={["0375-9474"]}, DOI={10.1016/S0375-9474(97)00052-3}, abstractNote={We investigate the radiative decay of pseudoscalar (π, K, η, η′), vector (ϱ, K∗, ω, ƒ) and axial-vector (A1) mesons using a simple relativistic constituent quark model. For both simplicity and relativity, we take advantage of the distinguished features in the light-cone quantization method: (1) the Fock state expansion of meson wave functions are not contaminated by the vacuum fluctuation, (2) the problem of assigning quantum numbers JPC to mesons is circumvented by the Melosh transformation. Except the well-known constituent quark masses of (u, d, s) quarks and the spin-averaged meson masses, the only parameter in the model is the Gaussian parameter β which determines the broadness (or sharpness) of the radial wave function. Our overall predictions of pseudoscalar, vector and axial-vector meson radiative decay processes are in remarkably good agreement with the experimental data.}, number={3}, journal={NUCLEAR PHYSICS A}, author={Choi, HM and Ji, CR}, year={1997}, month={Jun}, pages={291–316} }
 @article{choi_ji_1997, title={Relations among the light-cone quark models with the invariant meson mass scheme and the model prediction of the eta-eta' mixing angle}, volume={56}, ISSN={["0556-2821"]}, DOI={10.1103/physrevd.56.6010}, abstractNote={We analyze the relations among the light-cone quark models which are based on the invariant meson mass scheme. We find that the difference from the Jacobi factor in model wave functions is substantially reduced in the numerical predictions for the physical observables once the best fit parameters are chosen. The difference in the choice of radial wave function [e.g., harmonic oscillator (HO) wave function versus power-law wave function] is, however, still appreciable even though the best fit parameters are used. We also observe an excellent agreement between the HO model predictions and the experimental data on the radiative decays of pseudoscalar (P) and vector (V) mesons and P{r_arrow}{gamma}{gamma} processes, if we use the constraint obtained by the axial anomaly plus partial conservation of axial-vector current relations and choose the {eta}-{eta}{sup {prime}} mixing angle {theta}{sub SU(3)} {approx}{minus}19{degree}. {copyright} {ital 1997} {ital The American Physical Society}}, number={9}, journal={PHYSICAL REVIEW D}, author={Choi, HM and Ji, CR}, year={1997}, month={Nov}, pages={6010–6013} }