The semileptonic decay within the LCSR approach under heavy quark effective field theory *

Abstract

The heavy quark effective field theory (HQEFT) provides an effective way to deal with the heavy meson decays. In the paper, we adopt two different correlators to derive the light-cone sum rules of the B → π transition form factors (TFFs) within the framework of HQEFT. We label those two LCSR results as LCSR-U and LCSR-R, which are for conventional correlator and right-handed correlator, respectively. We observe that the correlation parameter |ρRU| for the branching ratio B(B → πlν l ) is ∼ 0.85, implying the consistency of the LCSRs under different correlators. Moreover, we obtain |V ub |LCSR−U = (3.45 +0.28 −0.20 ±0.13exp)×10 −3 and |V ub |LCSR−R = (3.38 +0.22 −0.16 ±0.12exp)×10 −3 . We then obtain Rπ|LCSR−U = 0.68 +0.10 −0.09 and Rπ|LCSR−R = 0.65 +0.13 −0.11 , both of them agree with the Lattice QCD predictions. Thus the HQEFT provides a useful framework for studying the B meson decays. Moreover, by using right-handed correlator, the twist-2 terms shall dominant the TFF f + (q 2 ), which approaches over ∼ 97% contribution in the whole q 2 -region; and the large twist-3 uncertainty for the conventional correlator is greatly suppressed. One can thus adopt the LCSR-R prediction to test the properties of the various models for the pion twist-2 distribution amplitudes.

Branching fractions and polarizations of D→Vℓνℓ within QCD light-cone sum rule

“…To further the understanding of the D → V semileptonic decay processes, the complete angular distribution and polarization information should be investigated, such as the longitudinal and transverse polarizations of the final charged lepton P L,T (q 2 ) and the final vector meson F L,T (q 2 ), the forward-backward asymmetry A FB (q 2 ), and the lepton-side convexity parameter C F (q 2 ). On the one hand, there is little theoretical research on that polarization information and even less experimental research, but one can find numerous experimental and theoretical studies for that of the B meson [26][27][28][29][30][31][32][33][34][35]. On the other hand, the QCD light-cone sum rule (LCSR) is an effective method to study the heavy meson to light meson decay processes that are actually an FCNC process of the heavy quark to light quark transition.…”

The ratio $\mathcal{R}(D_s)$ for $B_s \to D_s \ellν_\ell$ by using the QCD light-cone sum rules within the framework of heavy quark effective field theory

“…the QCD sum rules (QCDSR) [35], the constituent quark model (CQM) [36], the light-cone sum rules (LCSR) [37], the Bethe-Salpeter equation (BSE) [38], and the lattice QCD (LQCD) [30][31][32][33]. Different approaches are applicable in various energy scale regions, for example, the LCSR is applicable in the largest low and intermediate q 2 -region; and in the present paper, as the same as the previous treatment of B → π TFFs [39], we will adopt the LCSR approach within the framework of heavy quark effective field theory (HQEFT) [40][41][42][43][44][45] to calculate B s → D s TFFs. The HQEFT separates the non-perturbative longdistance terms from the short-distance dynamics via a systematic way, and the long-distance terms can be decreased to a series over the non-perturbative wave functions or transition form factors.…”

Branching fractions and polarizations of $D\to V(ω,ρ, K^*) \ell ν_\ell$ within QCD LCSR

“…But there are few theoretical research for those polarization information and even fewer experimental ones. Consider the numerous experimental and theoretical studies for that of the B-meson [28][29][30][31][32][33][34][35][36][37], we will study those observations for the semileptonic D → V + ν decays within the framework of QCD light-cone sum rules (LCSR).…”