First Observation of CP Violation and Measurement of Polarization in B+ →ρ(770)0K∗(892)+ Decays

LHCb Collaboration; R. Aaij; C. Jayaweera; D. Johnson; C. Lazzeroni; M. J. Madurai; N. Sahoo; M. W. Slater; D. J. D. Thompson; F. C. Volle; N. K. Watson; E. Whiter

doi:10.1103/9zhl-kkwg

First Observation of CP Violation and Measurement of Polarization in B⁺ →ρ(770)⁰K^∗(892)⁺ Decays

LHCb Collaboration
, R. Aaij^*
, C. Jayaweera
, D. Johnson
, C. Lazzeroni
, M. J. Madurai
, N. Sahoo
, M. W. Slater
, D. J. D. Thompson
, F. C. Volle
, N. K. Watson
, E. Whiter

^*Corresponding author for this work

Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

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Abstract

An amplitude analysis of the B⁺→(π⁺π⁻)(K_S⁰π⁺) decay is performed in the mass regions 0.30 < m_π+π− < 1.10 GeV/c² and 0.75 < m_K_S0_π+ < 1.20 GeV/c², using pp collision data recorded with the LHCb detector corresponding to an integrated luminosity of 9 fb⁻¹. The polarization fractions and CP asymmetries for B⁺ →ρ(770)⁰K^∗(892)⁺ decays are measured. Violation of the CP symmetry in the decay B⁺ →ρ(770)⁰K^∗(892)⁺ is observed for the first time, with a significance exceeding 9 standard deviations. The CP asymmetry is measured to be A_CP = 0.507 ± 0.062(stat) ± 0.024(syst) and the CP-averaged longitudinal polarization fraction of f_L = 0.720 ± 0.028(stat) ± 0.009(syst). The measurements help to shed light on the polarization puzzle of B mesons decaying to two vector mesons.

Original language	English
Article number	021803
Number of pages	16
Journal	Physical Review Letters
Volume	136
Issue number	2
Early online date	14 Jan 2026
DOIs	https://doi.org/10.1103/9zhl-kkwg
Publication status	Published - 16 Jan 2026

Bibliographical note

Publisher Copyright:
© 2026 CERN.

ASJC Scopus subject areas

General Physics and Astronomy

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Cite this

@article{3a16dc225faf484c8cc6d085e9598696,

title = "First Observation of CP Violation and Measurement of Polarization in B+ →ρ(770)0K∗(892)+ Decays",

abstract = "An amplitude analysis of the B+→(π+π−)(KS0π+) decay is performed in the mass regions 0.30 < mπ+π− < 1.10 GeV/c2 and 0.75 < mKS0π+ < 1.20 GeV/c2, using pp collision data recorded with the LHCb detector corresponding to an integrated luminosity of 9 fb−1. The polarization fractions and CP asymmetries for B+ →ρ(770)0K∗(892)+ decays are measured. Violation of the CP symmetry in the decay B+ →ρ(770)0K∗(892)+ is observed for the first time, with a significance exceeding 9 standard deviations. The CP asymmetry is measured to be ACP = 0.507 ± 0.062(stat) ± 0.024(syst) and the CP-averaged longitudinal polarization fraction of fL = 0.720 ± 0.028(stat) ± 0.009(syst). The measurements help to shed light on the polarization puzzle of B mesons decaying to two vector mesons.",

author = "\{LHCb Collaboration\} and R. Aaij and C. Jayaweera and D. Johnson and C. Lazzeroni and Madurai, \{M. J.\} and N. Sahoo and Slater, \{M. W.\} and Thompson, \{D. J. D.\} and Volle, \{F. C.\} and Watson, \{N. K.\} and E. Whiter and William Rose",

note = "Publisher Copyright: {\textcopyright} 2026 CERN.",

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doi = "10.1103/9zhl-kkwg",

language = "English",

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T1 - First Observation of CP Violation and Measurement of Polarization in B+ →ρ(770)0K∗(892)+ Decays

AU - LHCb Collaboration

AU - Aaij, R.

AU - Jayaweera, C.

AU - Johnson, D.

AU - Lazzeroni, C.

AU - Madurai, M. J.

AU - Sahoo, N.

AU - Slater, M. W.

AU - Thompson, D. J. D.

AU - Volle, F. C.

AU - Watson, N. K.

AU - Whiter, E.

A2 - Rose, William

PY - 2026/1/16

Y1 - 2026/1/16

N2 - An amplitude analysis of the B+→(π+π−)(KS0π+) decay is performed in the mass regions 0.30 < mπ+π− < 1.10 GeV/c2 and 0.75 < mKS0π+ < 1.20 GeV/c2, using pp collision data recorded with the LHCb detector corresponding to an integrated luminosity of 9 fb−1. The polarization fractions and CP asymmetries for B+ →ρ(770)0K∗(892)+ decays are measured. Violation of the CP symmetry in the decay B+ →ρ(770)0K∗(892)+ is observed for the first time, with a significance exceeding 9 standard deviations. The CP asymmetry is measured to be ACP = 0.507 ± 0.062(stat) ± 0.024(syst) and the CP-averaged longitudinal polarization fraction of fL = 0.720 ± 0.028(stat) ± 0.009(syst). The measurements help to shed light on the polarization puzzle of B mesons decaying to two vector mesons.

AB - An amplitude analysis of the B+→(π+π−)(KS0π+) decay is performed in the mass regions 0.30 < mπ+π− < 1.10 GeV/c2 and 0.75 < mKS0π+ < 1.20 GeV/c2, using pp collision data recorded with the LHCb detector corresponding to an integrated luminosity of 9 fb−1. The polarization fractions and CP asymmetries for B+ →ρ(770)0K∗(892)+ decays are measured. Violation of the CP symmetry in the decay B+ →ρ(770)0K∗(892)+ is observed for the first time, with a significance exceeding 9 standard deviations. The CP asymmetry is measured to be ACP = 0.507 ± 0.062(stat) ± 0.024(syst) and the CP-averaged longitudinal polarization fraction of fL = 0.720 ± 0.028(stat) ± 0.009(syst). The measurements help to shed light on the polarization puzzle of B mesons decaying to two vector mesons.

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