ργ*→π(ρ)transition form factors in the perturbative QCD factorization approach

Abstract

In this paper, we studied the ργ * → π and ργ * → 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 LL,LT,TT (Q 2 ) and F 1,2,3 (Q 2 ), by employing the perturbative QCD (PQCD) factorization approach. For the ργ * → 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 * → ρ transition and in the region of Q 2 ≥ 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.

Charmless two-body B meson decays in the perturbative QCD factorization approach*

“…Annihilation amplitudes are more important than emission amplitudes when the strong destructive interaction between the color suppressed tree amplitude and the penguin amplitude becomes true. The NLO QCD corrections to the naive factorizable annihilation amplitudes have been calculated to improve the PQCD precision for relevant B meson decays [57][58][59][60][61]. The most important contribution of this type of NLO correction is the timelike form factors, as depicted in the second row of Fig.…”

“…One part of these NLO correlations is included in the effective Wilson coefficients, whereas the other parts provide the independent decay amplitudes for certain channels. The second type of NLO QCD corrections carries the dynamics from the scale to the hadronic scale, which are manifested by means of heavy-to-light transition form factors [55,56], the timelike form factors of final light mesons [57][58][59][60][61], Glauber effects in the hard scattering spectator and annihilation amplitudes [62][63][64], and other possible corrections that have not been studied in detail [65]. Besides the QCD correction at NLO, the sub-leading power corrections from high twist light cone distribution amplitudes (LC-DAs) were recently studied for pion form factors and the radiative leptonic decay in the PQCD approach [66][67][68].…”

The next-to-leading order corrections to ρ meson electromagnetic form factors in the k factorization approach

“…where the expressions for the the Sudakov factor S ρ (x i ; b i ; Q; µ) and the hard function h(x 2 , x 1 , b 2 , b 1 ) can be found in Ref. [9]. The NLO correction of F T T (Q 2 ) is the result of both the initial and final states taking the twist-3 meson distribution amplitudes, whose power-law behavior is the same as the one combining twist-2 with twist-4 meson distribution amplitudes [46].…”

“…For light meson, their electromagnetic and transition form factors have been studied extensively due to their significance in phenomenology. Over the past decades, the collinear and k T factorization for light meson form factors have been demonstrated [1][2][3][4][5][6] and calculated [7][8][9][10] based on the Perturbative QCD (PQCD) factorization approach. For the pseudoscalar mesons such as the pion, the form factors are well understood up to NLO accuracy [7,8].…”