arXiv subjects

Jun Hua

Publications and source records attributed to Jun Hua.

45 records · Page 3Linked to original sources

arXiv2021

Global determination of two-meson distribution amplitudes from three-body $B$ decays in the perturbative QCD approach

We perform a global analysis of three-body charmless hadronic decays $B\to VP_3\to P_1P_2P_3$ in the perturbative QCD (PQCD) approach, where $V$ denotes an intermediate vector resonance, and $P_i$, $i=1,2,3$, denote final-state pseudoscalar mesons. Fitting the PQCD factorization formulas at leading order in the strong coupling $α_s$ to measured branching ratios and direct $CP$ asymmetries, we determine the Gegenbauer moments in the two-meson distribution amplitudes (DAs) for the meson pairs $P_1P_2=ππ, Kπ, KK$. The fitted Gegenbauer moments are then employed to make predictions for those observables, whose data are excluded in the fit due to larger experimental uncertainties. A general consistency between our predictions and data is achieved, which hints the validity of the PQCD formalism for the above three-body $B$ meson decays and the universality of the nonperturbative two-meson DAs. The obtained two-meson DAs can be applied to PQCD studies of other multi-body $B$ meson decays involving the same meson pairs. We also attempt to determine the dependence of the Gegenbauer moments on the meson-pair invariant mass, and demonstrate that this determination is promising, when data become more precise.

hep-ph↗

arXiv2021

Global Analysis of hadronic two-body B decays in the perturbative QCD approach

Based on the flavor structure of four-quark effective operators, we develop an automatic computation program to calculate hadronic two-body $B$ meson decay amplitudes, and apply it to their global analysis in the perturbative QCD (PQCD) approach. Fitting the PQCD factorization formulas for $B\to PP,VP$ decays at leading order in the strong coupling $α_s$ to measured branching ratios and direct CP asymmetries, we determine the Gegenbauer moments in light meson light-cone distribution amplitudes (LCDAs). It is found that most of the fitted Gegenbauer moments of the twist-2 and twist-3 LCDAs for the pseudoscalar meson $P$ ($P=π$, $K$) and vector meson $V$ ($V=ρ$, $K^*$) agree with those derived in QCD sum rules. The shape parameter for the $B_s$ meson distribution amplitude and the weak phase $ϕ_3(γ)=(75.1\pm2.9)^\circ$ consistent with the value in Particle Data Group are also obtained. It is straightforward to extend our analysis to higher orders and higher powers in the PQCD approach, and to the global determination of LCDAs for other hadrons.

hep-ph↗

arXiv2020

Lattice-QCD Calculations of TMD Soft Function Through Large-Momentum Effective Theory

The transverse-momentum-dependent (TMD) soft function is a key ingredient in QCD factorization of Drell-Yan and other processes with relatively small transverse momentum. We present a lattice QCD study of this function at moderately large rapidity on a 2+1 flavor CLS dynamic ensemble with $a=0.098$ fm. We extract the rapidity-independent (or intrinsic) part of the soft function through a large-momentum-transfer pseudo-scalar meson form factor and its quasi-TMD wave function using leading-order factorization in large-momentum effective theory. We also investigate the rapidity-dependent part of the soft function---the Collins-Soper evolution kernel---based on the large-momentum evolution of the quasi-TMD wave function.

hep-lat↗

arXiv2019

The next-to-leading order corrections to rho meson electromagnetic form factors in the $k_T$ factorization approach

In this paper we calculate the next-to-leading-order (NLO) corrections to $ρ$-meson electromagnetic form factors by employing the $k_T$ factorization approach. We find that the NLO correction to $F_i (Q^2)(i=LT,TL)$ is around $30\%$ of the leading-order (LO) contributionin the region $Q^2>2GeV^2$. The NLO correction to $F_{LL}(Q^2)$ is close to $20\%$ of the LO one in the region $Q^2>3GeV^2$. The NLO radiative corrections to the electric, magnetic, and quadruple form factors $F_j(Q^2) (j=1,2,3)$ are sizeable in magnitude and agree with those from other approaches.

hep-ph↗

arXiv2018

The next-to-leading order corrections to $B \to ρ$ transition in the $k_T$ factorization

In this paper, we investigate the factorization hypothesis step by step for the exclusive process $B \to ρ$ at next-to-leading order (NLO) with the collinear factorization approach, and then we extend our results to the $k_T$ factorization frame. We show that the soft divergence from the specific NLO diagrams will cancel each other at the quark level, while the remaining collinear divergence can be absorbed into the NLO wave functions. The full NLO amplitudes can be factorized into two parts: the NLO $B$ and $ρ$ meson wave functions containing the collinear divergence and the leading order (LO) finite hard kernels. We give the general form of the nonlocal hadron matrix for the NLO $B$ and $ρ$ meson wave functions and all results of factorization for different twists' combinations.

hep-ph↗

arXiv2018

Rho-pion transition form factors in the $k_T$ factorization formulism revisited

We revisit the evaluations for the spacelike and timelike $ρπ$ transition form factors $F_{ρπ}(Q^2)$ and $G_{ρπ}(Q^2)$ with the inclusion of the the next-to-leading order (NLO) QCD contributions in the framework of the $k_T$ factorization theorem. The infrared divergence is regularized by the transversal momentum carried by external valence quarks, and ultimately absorbed into the meson wave functions. In the region of $ Q^2 \leqslant 2 \, \textrm{GeV}^2 $, where PQCD factorization apporach applicable, the NLO contribution can bring no larger than $ 35\%$ enhancement to the spacelike form factor $F_{ρπ}(Q^2)$. For the timelike form factor derived under the kinematic exchanging symmetry, this contribution is also under control when the momentum transfer squared is large enough. We also prolong our prediction into the small $Q^2$ region by taking the Lattice QCD results into account, and subsequently obtain the coupling $g_{ρπγ} = G_{ρπ}(0)=0.596$.

hep-ph↗

arXiv2017

Revisiting the factorization theorem for $ργ^{*} \to π(ρ)$ at twist 3

We revisit the proof of the perturbative QCD factorization for the exclusive processes $ργ^{\star} \to π(ρ)$ at the two-parton twist-3 level. It is pointed out that the residual collinear divergences observed in the literature, which break the factorization of the above processes at the considered accuracy, are attributed to the improper insertion of the Fierz identity for factorizing the fermion flow. We show that the factorization theorem indeed holds at the two-parton twist-3 level after the mishandling is corrected.

hep-ph↗

arXiv2016

The perturbative QCD factorization of $ργ^{\star} \to ρ$

In this paper we firstly demonstrate step by step that the factorization hypothesis is valid at the next-to-leading order (NLO) for the exclusive process $ργ^{\star} \to ρ$ by employing the collinear factorization approach, and then extend this proof to the case of the $k_T$ factorization by taking into account the transversal momentum of the light external quark (anti-quark) lines in the $ρ$ meson. At the NLO level, we then show that the soft divergences from different sub-diagrams will be canceled each other in the quark level, while the remaining collinear divergences can be absorbed into the NLO meson wave functions. The full NLO amplitudes can therefore be factorized as the convolution of the NLO wave functions $ Φ^{(1)}_ρ$ and the infrared-finite leading order (LO) hard kernels $G^0_{X,IJ,kl}$ in the $k_T$ factorization. We also write down the polarized NLO $ρ$ meson wave functions in the form of nonlocal hadron matrix elements with the gauge factor integral path deviating from the light cone. These NLO $ρ$ meson wave functions can be used to calculate the NLO hard corrections to some relevant exclusive processes, such as $B \to ρ$ transition.

hep-ph↗

arXiv2015

The $ργ^* \to π(ρ)$ transition form factors in the Perturbative QCD factorization approach

In this paper, we studied the $ργ^* \to π$ and $ργ^*\to ρ$ transition processes and made the calculations for the $ρπ$ transition form factor $Q^4 F_{ρπ}(Q^2)$ and the $ρ$ meson electromagnetic form factors, $F_{\rm LL, LT,TT}(Q^2)$ and $F_{1,2,3}(Q^2)$, by employing the perturbative QCD (PQCD) factorization approach. For the $ργ^* \to π$ transition, we found that the contribution to form factor $Q^4 F_{ρπ}(Q)$ from the term proportional to the distribution amplitude combination $ϕ^T_ρ(x_1)ϕ^P_π(x_2)$ is absolutely dominant, and the PQCD predictions for both the size and the $Q^2$-dependence of this form factor $Q^4 F_{ρπ}(Q^2)$ agree well with those from the extended ADS/QCD models or the light-cone QCD sum rule. For the $ργ^* \to ρ$ transition and in the region of $Q^2\geq 3$ GeV$^2$, further more, we found that the PQCD predictions for the magnitude and their $Q^2$-dependence of the $F_1(Q^2)$ and $F_2(Q^2)$ form factors agree well with those from the QCD sum rule, while the PQCD prediction for $F_3(Q^2)$ is much larger than the one from the QCD sum rule.

hep-ph↗