Towards an amplitude analysis of the decay \( {\varLambda}_b^0\to {pK}^{-}\gamma \)


The helicity formalism applied to the radiative decay \( {\varLambda}_b^0\to {pK}^{-}\gamma \) is presented for the first time in this paper. The aim is to provide the necessary formalism to be able to resolve the resonant pK structures at the photon pole by means of an amplitude analysis. Experimental effects, such as resolution, are also discussed.

A preprint version of the article is available at ArXiv.


  1. [1]

    LHCb collaboration, Test of lepton universality using B+→ K++decays, Phys. Rev. Lett.113 (2014) 151601 [arXiv:1406.6482] [LHCb-PAPER-2014-024].

  2. [2]

    LHCb collaboration, Test of lepton universality with B0→ K∗0+decays, JHEP08 (2017) 055 [arXiv:1705.05802] [LHCb-PAPER-2017-013].

  3. [3]

    LHCb collaboration, Test of lepton universality with \( {\Lambda}_b^0\to {pK}^{-}{\mathrm{\ell}}^{+}{\mathrm{\ell}}^{-} \)decays, JHEP20 (2020) 040 [arXiv:1912.08139] [INSPIRE].

  4. [4]

    LHCb collaboration, Observation of J/ψp resonances consistent with pentaquark states in \( {\Lambda}_b^0\to J/\psi {K}^{-}p \)decays, Phys. Rev. Lett.115 (2015) 072001 [arXiv:1507.03414] [INSPIRE].

  5. [5]

    M. Jacob and G.C. Wick, On the general theory of collisions for particles with spin, Annals Phys.7 (1959) 404 [INSPIRE].

    ADS  MathSciNet  Article  Google Scholar 

  6. [6]

    S.U. Chung, Spin formalisms, CERN-1971-008 (1971).

  7. [7]

    J.D. Richman, An experimenter’s guide to the helicity formalism, Technical Report CALT-68-1148 (1984).

  8. [8]

    Particle Data Group collaboration, Review of particle physics, Phys. Rev.D 98 (2018) 030001 [INSPIRE].

  9. [9]

    J.M. Blatt and V.F. Weisskopf, Theoretical nuclear physics, Springer, Germany (1952).

  10. [10]

    F. Von Hippel and C. Quigg, Centrifugal-barrier effects in resonance partial decay widths, shapes and production amplitudes, Phys. Rev.D 5 (1972) 624 [INSPIRE].

    ADS  Google Scholar 

  11. [11]

    JPAC collaboration, Dalitz-plot decomposition for three-body decays, Phys. Rev.D 101 (2020) 034033 [arXiv:1910.04566] [INSPIRE].

  12. [12]

    R.H. Dalitz, On the analysis of τ -meson data and the nature of the τ -meson, Phil. Mag. Ser.44 (1953) 1068.

    Article  Google Scholar 

  13. [13]

    LHCb collaboration, Angular analysis of the B0→ K∗0μ+μdecay using 3 fb1of integrated luminosity, LHCb-PAPER-2015-051 (2015).

  14. [14]

    Ya. Azimov, Quantum interference of particles and resonances, J. Phys.G 37 (2010) 023001 [arXiv:0904.1376] [INSPIRE].

    ADS  Article  Google Scholar 

  15. [15]

    A. Dery, M. Ghosh, Y. Grossman and S. Schacht, SU(3)Fanalysis for beauty baryon decays, JHEP03 (2020) 165 [arXiv:2001.05397] [INSPIRE].

    Article  Google Scholar 

  16. [16]

    Q. Wang, X.-H. Liu and Q. Zhao, Photoproduction of hidden charm pentaquark states \( {P}_c^{+} \) (4380) and \( {P}_c^{+} \) (4450), Phys. Rev.D 92 (2015) 034022 [arXiv:1508.00339] [INSPIRE].

    ADS  Google Scholar 

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Correspondence to Carla Marin Benito.

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Albrecht, J., Amhis, Y., Beck, A. et al. Towards an amplitude analysis of the decay \( {\varLambda}_b^0\to {pK}^{-}\gamma \). J. High Energ. Phys. 2020, 116 (2020).

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  • Heavy Quark Physics
  • Beyond Standard Model