Hadronic charmless B decays B-> AP

TL;DR

This paper analyzes hadronic B meson decays into pseudoscalar and axial-vector mesons using QCD factorization, evaluating light-cone distribution amplitudes and comparing theoretical predictions with experimental data.

Contribution

It provides new calculations of light-cone distribution amplitudes for axial-vector mesons and explores decay rate predictions, highlighting the importance of annihilation contributions and interference effects.

Findings

Predicted decay rates agree with data for several modes.

Discrepancies in expected ratios suggest need for improved measurements.

Sizable annihilation effects influence penguin-dominated decay rates.

Abstract

The two-body hadronic decays of B mesons into pseudoscalar and axial vector mesons are studied within the framework of QCD factorization. The light-cone distribution amplitudes (LCDAs) for $^3P_1$ and $^1P_1$ axial-vector mesons have been evaluated using the QCD sum rule method. Owing to the G-parity, the chiral-even two-parton light-cone distribution amplitudes of the $^3P_1$ ($^1P_1$) mesons are symmetric (antisymmetric) under the exchange of quark and anti-quark momentum fractions in the SU(3) limit. For chiral-odd LCDAs, it is other way around. The main results are the following: (i) The predicted rates for $a_1^\pm(1260)\pi^\mp$, $b_1^\pm(1235)\pi^\mp$, $b_1^0(1235)\pi^-$, $a_1^+K^-$ and $b_1^+K^-$ modes are in good agreement with the data. However, the naively expected ratios $Br(B^-\to a_1^0\pi^-)/Br(\ov B^0\to a_1^+\pi^-)\leq 1$, $Br(B^-\to a_1^-\pi^0)/Br(\ov B^0\to a_1^-\pi^+)\sim {1\over 2}$ and $Br(B^-\to b_1^0K^-)/Br(\ov B^0\to b_1^+K^-)\sim {1\over 2}$ are not borne out by experiment. This should be clarified by the improved measurements of these decays. (ii) Since the $\bar B\to b_1K$ decays receive sizable annihilation contributions, their rates are sensitive to the interference between penguin and annihilation terms. The measurement of $Br(\bar B^0\to b_1^+K^-)$ implies a destructive interference which in turn indicates that the form factors for $B\to b_1$ and $B\to a_1$ transitions are of opposite signs. (iii) Sizable power corrections such as weak annihilation are needed to account for the observed rates of the penguin-dominated modes $K_1^-(1270)\pi^+$ and $K_1^-(1400)\pi^+$.