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Phenomenological revisit of the $B \to π π$ decays by incorporating soft color-octet contributions

Yueling Yang , Bingbing Yang , and Junfeng Sun ^*

School of Physics, Henan Normal University, Xinxiang 453007, China

^*Contact author: sunjunfeng@htu.edu.cn

Phys. Rev. D 114, 096006 – Published 9 November, 2026

DOI: https://doi.org/10.1103/wrm3-6qwv

Abstract

Motivated by the long-standing “ $π π$ puzzle” in nonleptonic $B$ decays, we revisit the $B \to π π$ decays within the QCD factorization (QCDF) framework, now incorporating the soft color-octet matrix element (COME) contributions, an ingredient that has been largely overlooked in earlier QCDF studies. A comprehensive phenomenological analysis is performed under three distinct scenarios, with the free parameters determined via fits to the available experimental data using the $χ^{2}$ method. The goodness-of-fit is very poor for Scenario S1, which corresponds to the traditional QCDF case without the soft COME contributions, and for Scenario S2, which includes the soft COME contributions but omits the weak annihilation (WA) contributions. Scenario S3, in which both the COME and WA contributions are included simultaneously, achieves an excellent overall fit. In Scenario S3, the QCDF approach can accommodate almost all $B \to π π$ observables in a consistent and satisfactory manner, and the fitted parameters $ρ_{A} < 1$ (WA) and $ρ_{c} \sim 0.3$ (soft COME) are in good agreement with the QCDF power counting scheme and the factorization hypothesis.

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Phys. Rev. D 114, 096006– Published 9 November, 2026

Vol. 114, Iss. 9 — 1 November 2026

Received 3 September 2026
Accepted 23 October 2026

DOI: https://doi.org/10.1103/wrm3-6qwv

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

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Phenomenological revisit of the $B \to π π$ decays by incorporating soft color-octet contributions

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Phenomenological revisit of the B→ππ decays by incorporating soft color-octet contributions

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Phenomenological revisit of the $B \to π π$ decays by incorporating soft color-octet contributions