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Determination of quantum numbers for several excited charmed mesons observed in B−→D*+π−π− decays

R. Aaij et al. (LHCb Collaboration)
Phys. Rev. D 101, 032005 – Published 20 February 2020
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  • INTRODUCTION
  • LHCb DETECTOR
  • SELECTION REQUIREMENTS
  • THE B−→D*+π−π− DALITZ PLOT
  • BACKGROUND AND EFFICIENCY
  • AMPLITUDE ANALYSIS
  • FITS TO THE DATA USING…
  • FIT RESULTS
  • MEASUREMENT OF THE BRANCHING FRACTIONS
  • SUMMARY
  • ACKNOWLEDGMENTS
    • References

    Abstract

    A four-body amplitude analysis of the B−→D*+π−π− decay is performed, where fractions and relative phases of the various resonances contributing to the decay are measured. Several quasi-model-independent analyses are performed aimed at searching for the presence of new states and establishing the quantum numbers of previously observed charmed meson resonances. In particular the resonance parameters and quantum numbers are determined for the D1(2420), D1(2430), D0(2550), D1*(2600), D2(2740) and D3*(2750) states. The mixing between the D1(2420) and D1(2430) resonances is studied and the mixing parameters are measured. The dataset corresponds to an integrated luminosity of 4.7  fb−1, collected in proton-proton collisions at center-of-mass energies of 7, 8 and 13 TeV with the LHCb detector.

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    • Received 15 November 2019
    • Accepted 23 January 2020

    DOI:https://doi.org/10.1103/PhysRevD.101.032005

    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.

    © 2020 CERN, for the LHCb Collaboration

    Physics Subject Headings (PhySH)

    1. Research Areas
    Particle decays
    Particles & Fields

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    Issue

    Vol. 101, Iss. 3 — 1 February 2020

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    Images

    • Figure 1
      Figure 1

      Distribution of (a) m(K−π+πs+)−m(K−π+)+mD0PDG and (b) D*+π−π− invariant masses for candidates after the selection on the χ2/ndf from the fit to the B− decay tree.

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    • Figure 2
      Figure 2

      Mass distribution for D*+π−π− candidates after the selection R>0.5. The full (red) line is the result from the fit while the dotted (blue) line describes the background. The vertical dashed lines indicate the signal region.

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    • Figure 3
      Figure 3

      Dalitz plot distribution for B−→D*+π−π− candidates in Run 2 data.

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    • Figure 4
      Figure 4

      Distribution of m(D*+π−)low for the total dataset.

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    • Figure 5
      Figure 5

      Definition of the angles (a) θH, (b) θ and (c) γ.

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    • Figure 6
      Figure 6

      Two-dimensional distribution of cosθH vs m(D*+π−)low. The vertical lines indicate the positions of the D1(2420) and D2*(2460) resonances.

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    • Figure 7
      Figure 7

      Distribution for low/high-purity selection (filled black/open red points) for (a) m(D*+π−)low and (c) cosθ. Signal-subtracted distributions for (b) m(D*+π−)low and (d) cosθ with superimposed fit curves described in the text.

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    • Figure 8
      Figure 8

      Interpolated efficiency as a function of log(m(D*+π−)/MeV) and cosθ for (a) Run 1 and (b) Run 2 data. The line indicates the regions where log(m(D*+π−)/MeV) is taken as log(m(D*+π−)low/MeV) (left side of the line) and as log(m(D*+π−)high/MeV) (right side of the line).

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    • Figure 9
      Figure 9

      (a) Magnitude and (b) phase of the 1+S amplitude from the QMI method. The red circles indicate the mass bin where the complex amplitude has been fixed.

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    • Figure 10
      Figure 10

      (a) Magnitude and (b) phase of the JP=0− amplitude from the QMI method. The red circle indicates the mass bin where the complex amplitude has been fixed. The curves are the result from the fit described in the text.

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    • Figure 11
      Figure 11

      (a) Magnitude and (b) phase of the JP=1− amplitude from the QMI method. The red circle indicates the mass bin where the complex amplitude has been fixed. The curves represent the Breit–Wigner function describing the D1*(2600) resonance.

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    • Figure 12
      Figure 12

      (a) Magnitude and (b) phase of the JP=1+D amplitude from the QMI method. The red circle indicates the mass bin where the complex amplitude has been fixed. The curves represent the Breit–Wigner function describing the D1(2420) resonance.

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    • Figure 13
      Figure 13

      (a) Magnitude and (b) phase of the JP=2+ amplitude from the QMI method. The red circle indicates the mass bin where the complex amplitude has been fixed. The curves represent the Breit–Wigner function describing the D2*(2460) resonance.

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    • Figure 14
      Figure 14

      Projections of the fit to Run 2 data from the QMI fitting model. The background contribution is shown in gray. Data are represented with filled dots and the line is the results from the fit.

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    • Figure 15
      Figure 15

      Projections of the fit to the total dataset from the QMI fitting model with (a,b) all amplitude contributions and (c) the significant interference terms.

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    • Figure 16
      Figure 16

      Legendre polynomial moments YL0(cosθ) as functions of m(D*+π−) for Run 2 data. The data are represented by filled dots and the superimposed histograms result from the amplitude analysis described in the text.

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    • Figure 17
      Figure 17

      Distributions of the Legendre polynomial moments (a) Y2H(cosθH) and (b) Y2γ(cosγ) as a function of m(D*+π−) for Run 2 data. The data are represented by filled dots while the superimposed histograms result from the amplitude analysis described in the text. The vertical lines indicate the positions of the D1(2420), D2*(2460) and D1*(2600) resonances.

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