Transverse-momentum-dependent wave functions with Glauber gluons in $B \to \pi \pi$, $\rho \rho$ decays

TL;DR

This paper studies the impact of Glauber gluons on B meson decays to pions and rho mesons, showing that including transverse-momentum-dependent wave functions improves agreement with experimental data and helps resolve existing puzzles.

Contribution

It introduces a convolution of a universal Glauber phase with TMD meson wave functions in $k_T$ factorization, revealing significant effects on decay branching ratios and enhancing theoretical predictions.

Findings

Glauber gluons significantly modify decay branching ratios.

TMD wave functions with different $k_T$ falloff affect decay rates.

The approach improves agreement with experimental data.

Abstract

We investigate the Glauber-gluon effect on the $B \to \pi \pi$ and $\rho \rho$ decays, which is introduced via a convolution of a universal Glauber phase factor with transverse-momentum-dependent(TMD) meson wave functions in the $k_T$ factorization theorem. For an appropriate parametrization of the Glauber phase, it is observed that a TMD wave function for the pion ($\rho$ meson) with a weak (strong) falloff in parton transverse momentum $k_T$ leads to significant (moderate) modification of the $B^0 \to \pi^0 \pi^0$ ($B^0 \to \rho^0 \rho^0$) branching ratio: the former (latter) is enhanced (reduced) by about a factor of 2 (15\%). This observation is consistent with the dual role of the pion as a massless Nambu-Goldstone boson and as a $q \bar q$ bound state, which requires a tighter spatial distribution of its leading Fock state relative to higher Fock states. The agreement between the theoretical predictions and the data for all the $B \to \pi \pi$ and $\rho^0 \rho^0$ branching ratios is then improved simultaneously, and it is possible to resolve the $B \to \pi \pi$ puzzle.