CPV on charmless B→hhh decays

Charmless three body B decays

Last Update: Feb. 5, 2017

About the Analysis

B mesons decays to three-body charmless final states offer a good environment to study CP violation phenomena.
They also provide important insight into the dynamics of hadronic B decays.

The LHCb Bu→hhh Rio Group has been studying charmless three-body B decays since the beginning of LHCb data taking in 2009.
The first analysis was a measurement of the relative branching fractions of B±→K±K±K- and B±→ppK± decays with respect to the reference mode B±→K±π±π-.
The analysis was performed using 34 pb-1 of 2010 data, and was reported in the public note LHCb-CONF-2011-059.
The branching ratios relative to B±→K±π±π- are found to be

  • ℬℛ(B±→K±K±K-)ℬℛ(B±→K±π±π-)= 0.52 ± 0.003(stat) ± 0.01(syst)
  • ℬℛ(B±→ppK±)ℬℛ(B±→K±π±π-) = 0.19 ± 0.02(stat) ± 0.02(syst)

With the bigger dataset of 3 fb-1 of 2011 and 2012 LHCb data, we measured the direct CP asymmetries of four charmless decay modes.
We found for the the first evidences of CP violation in these modes, as well as localised asymmetries much larger than the integrated ones in some regions of phase space.
The results are listed below in the LHCb Collaboration Results. The inclusive CP asymmetries (ACP) of these modes are measured to be

  • ACP(B±→K±π±π-) = +0.025 ± 0.004 ± 0.004 ± 0.007
  • ACP(B±→K±K±K-) = -0.036 ± 0.004 ± 0.002 ± 0.007
  • ACP(B±→π±π±π-) = +0.058 ± 0.008 ± 0.009 ± 0.007
  • ACP(B±→K±K±π-) = -0.123 ± 0.017 ± 0.012 ± 0.007

In addition, a measurement of the forward-backward asymmetry (AFB) of the light meson in the pp rest frame are measured to be

  • AFB(ppK+, mpp < 2.85 GeV/c2) = 0.495 ± 0.012(stat) ± 0.007(syst)
  • AFB(ppπ+, mpp < 2.85 GeV/c2) = -0.409 ± 0.033(stat) ± 0.006(syst)

and the branching fraction of the decay B+Λ(1520)p is measured to be

  • ℬℛ (B+Λ(1520)p) = (3.15 ± 0.48(stat) ± 0.07(syst) ± 0.26(BF))×10-7

where BF denotes the uncertainty on secondary branching fractions.

The phase space of three-body decays is the Dalitz plot, and its complete understanding is achieved by a complex amplitude analysis.
However, such an amplitude analysis is model dependent.
The CBPF group proposed in 2009 a model-independent method for a CP anisotropy measurement in the Dalitz plot.
This “Mirandizing” method performs a direct measurement of the diference between particles and antiparticles in the Dalitz plot.
Although qualitative, the method can be used as a guide to locate the decay channels and the Dalitz plot regions with large asymmetry, thus aiding the choice of a future amplitude analysis model.

Irina Nasteva and Fernando Rodrigues
Last update: April 8, 2015


LHCb Collaboration Results
A list of all the LHCb public results that the Bu→hhh Rio Group directly participated.

Results from LHCb Run I dataset (2009 → 2012)

About the Bu→hhh Group

Current members from UFRJ:

Jose Helder, Juan Otalora, Irina Nasteva, Fernando Rodrigues

in collaboration with:

Centro Brasileiro de Pesquisas Físicas: Ignacio Bediaga, Jussara Miranda, Alberto Reis, Ana Cavalcante, Lais Soares

Universidade Católica do Rio de Janeiro: Melissa Cruz, Carla Gobel

Universidade Federal do Triângulo Mineiro: Alvaro Gomes

University of Bristol: Jeremy Dalseno, Jonas Rademacker

University of Warwick: Thomas Latham, Timothy Gershon, John Back, Daniel O’Hanlon

Group meeting

Wednesday at 15:00 (BRT/BRST) — Vidyo


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