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Angular analysis of \( {B}^0\to {D}^{\ast -}{D}_s^{\ast +} \) with \( {D}_s^{\ast +}\to {D}_s^{+}\gamma \) decays

A preprint version of the article is available at arXiv.

Abstract

The first full angular analysis of the \( {B}^0\to {D}^{\ast -}{D}_s^{\ast +} \) decay is performed using 6 fb1 of pp collision data collected with the LHCb experiment at a centre-of-mass energy of 13 TeV. The \( {D}_s^{\ast +}\to {D}_s^{+}\gamma \) and D*\( {\overline{D}}^0{\pi}^{-} \) vector meson decays are used with the subsequent \( {D}_s^{+} \)K+Kπ+ and \( {\overline{D}}^0 \)K+π decays. All helicity amplitudes and phases are measured, and the longitudinal polarisation fraction is determined to be fL = 0.578 ± 0.010 ± 0.011 with world-best precision, where the first uncertainty is statistical and the second is systematic. The pattern of helicity amplitude magnitudes is found to align with expectations from quark-helicity conservation in B decays. The ratio of branching fractions [ℬ(\( {B}^0\to {D}^{\ast -}{D}_s^{\ast +} \)) × ℬ(\( {D}_s^{\ast +}\to {D}_s^{+}\gamma \))]/ℬ(B0D*\( {D}_s^{+} \)) is measured to be 2.045 ± 0.022 ± 0.071 with world-best precision. In addition, the first observation of the Cabibbo-suppressed BsD*\( {D}_s^{+} \) decay is made with a significance of seven standard deviations. The branching fraction ratio ℬ(BsD*\( {D}_s^{+} \))/ℬ(B0D*\( {D}_s^{+} \)) is measured to be 0.049 ± 0.006 ± 0.003 ± 0.002, where the third uncertainty is due to limited knowledge of the ratio of fragmentation fractions.

References

  1. BaBar collaboration, Measurement of B0\( {D}_s^{\left(\ast \right)+}{D}^{\ast -} \) branching fractions and B0\( {D}_s^{\left(\ast \right)+}{D}^{\ast -} \) polarization with a partial reconstruction technique, Phys. Rev. D 67 (2003) 092003 [hep-ex/0302015] [INSPIRE].

  2. Particle Data collaboration, Review of particle physics, Prog. Theor. Exp. Phys. 2020 (2020) 083C01 [INSPIRE] and online at http://pdg.lbl.gov/.

  3. G. Kramer and W.F. Palmer, Branching ratios and CP asymmetries in the decay BVV, Phys. Rev. D 45 (1992) 193 [INSPIRE].

    Article  ADS  Google Scholar 

  4. CLEO collaboration, Measurements of B\( {D}_{(s)}^{\left(\ast \right)+}{D}^{\left(\ast \right)-} \) branching fractions, Phys. Rev. D 62 (2000) 112003 [hep-ex/0008015] [INSPIRE].

  5. CLEO collaboration, Measurement of the form-factors for \( {\overline{B}}^0\to {D}^{\ast +}{\mathrm{\ell}}^{-}\overline{\nu} \), Phys. Rev. Lett. 76 (1996) 3898 [INSPIRE].

  6. Z. Luo and J.L. Rosner, Factorization in color-favored B meson decays to charm, Phys. Rev. D 64 (2001) 094001 [hep-ph/0101089] [INSPIRE].

  7. M. Suzuki, Final-state interactions and s quark helicity conservation in BJ/ψK*, Phys. Rev. D 64 (2001) 117503 [hep-ph/0106354] [INSPIRE].

  8. LHCb collaboration, Test of Lepton Flavor Universality by the measurement of the B0D*τ+ντ branching fraction using three-prong τ decays, Phys. Rev. D 97 (2018) 072013 [LHCb-PAPER-2017-027] [CERN-EP-2017-256] [arXiv:1711.02505] [INSPIRE].

  9. D. Hill, M. John, W. Ke and A. Poluektov, Model-independent method for measuring the angular coefficients of B0D*τ+ντ decays, JHEP 11 (2019) 133 [arXiv:1908.04643] [INSPIRE].

    Article  ADS  Google Scholar 

  10. LHCb collaboration, Angular analysis of the B0K*0μ+μ decay using 3 fb1 of integrated luminosity, JHEP 02 (2016) 104 [LHCb-PAPER-2015-051] [CERN-PH-EP-2015-314] [arXiv:1512.04442] [INSPIRE].

  11. LHCb collaboration, Angular Analysis of the B+K*+μ+μ Decay, Phys. Rev. Lett. 126 (2021) 161802 [LHCb-PAPER-2020-041] [CERN-EP-2020-239] [arXiv:2012.13241] [INSPIRE].

  12. LHCb collaboration, The LHCb Detector at the LHC, 2008 JINST 3 S08005 [INSPIRE].

  13. LHCb collaboration, LHCb Detector Performance, Int. J. Mod. Phys. A 30 (2015) 1530022 [LHCB-DP-2014-002] [CERN-PH-EP-2014-290] [arXiv:1412.6352] [INSPIRE].

  14. T. Sjöstrand, S. Mrenna and P.Z. Skands, A Brief Introduction to PYTHIA 8.1, Comput. Phys. Commun. 178 (2008) 852 [arXiv:0710.3820] [INSPIRE].

  15. T. Sjöstrand, S. Mrenna and P.Z. Skands, PYTHIA 6.4 Physics and Manual, JHEP 05 (2006) 026 [hep-ph/0603175] [INSPIRE].

  16. LHCb collaboration, Handling of the generation of primary events in Gauss, the LHCb simulation framework, J. Phys. Conf. Ser. 331 (2011) 032047 [INSPIRE].

  17. D.J. Lange, The EvtGen particle decay simulation package, Nucl. Instrum. Meth. A 462 (2001) 152 [INSPIRE].

    Article  ADS  Google Scholar 

  18. N. Davidson, T. Przedzinski and Z. Was, PHOTOS interface in C++: Technical and Physics Documentation, Comput. Phys. Commun. 199 (2016) 86 [arXiv:1011.0937] [INSPIRE].

    MathSciNet  Article  ADS  Google Scholar 

  19. J. Allison et al., Geant4 developments and applications, IEEE Trans. Nucl. Sci. 53 (2006) 270 [INSPIRE].

    Article  ADS  Google Scholar 

  20. GEANT4 collaboration, GEANT4 — a simulation toolkit, Nucl. Instrum. Meth. A 506 (2003) 250 [INSPIRE].

  21. LHCb collaboration, The LHCb simulation application, Gauss: Design, evolution and experience, J. Phys. Conf. Ser. 331 (2011) 032023 [INSPIRE].

  22. D. Müller, M. Clemencic, G. Corti and M. Gersabeck, ReDecay: A novel approach to speed up the simulation at LHCb, Eur. Phys. J. C 78 (2018) 1009 [LHCb-DP-2018-004] [arXiv:1810.10362] [INSPIRE].

  23. G.A. Cowan, D.C. Craik and M.D. Needham, RapidSim: an application for the fast simulation of heavy-quark hadron decays, Comput. Phys. Commun. 214 (2017) 239 [arXiv:1612.07489] [INSPIRE].

    Article  ADS  Google Scholar 

  24. W.D. Hulsbergen, Decay chain fitting with a Kalman filter, Nucl. Instrum. Meth. A 552 (2005) 566 [physics/0503191] [INSPIRE].

  25. LHCb collaboration, Precise measurement of the fs/fd ratio of fragmentation fractions and of \( {B}_s^0 \) decay branching fractions, arXiv:2103.06810 [LHCb-PAPER-2020-046] [CERN-EP-2021-027] [INSPIRE].

  26. T. Skwarnicki, A study of the radiative cascade transitions between the Upsilon-prime and Upsilon resonances, Ph.D. Thesis, Institute of Nuclear Physics, Krakow Poland (1986).

  27. LHCb collaboration, Measurement of C P observables in B±D(*)K± and B±D(*)π± decays, Phys. Lett. B 777 (2018) 16 [LHCb-PAPER-2017-021] [CERN-EP-2017-195] [arXiv:1708.06370] [INSPIRE].

  28. LHCb collaboration, Measurement of CP observables in B±D(*)K± and B±D(*)π± decays using two-body D final states, JHEP 04 (2021) 081 [LHCb-PAPER-2020-036] [CERN-EP-2020-225] [arXiv:2012.09903] [INSPIRE].

  29. M. Pivk and F.R. Le Diberder, SPlot: A Statistical tool to unfold data distributions, Nucl. Instrum. Meth. A 555 (2005) 356 [physics/0402083] [INSPIRE].

  30. J. Eschle, A. Puig Navarro, R. Silva Coutinho and N. Serra, zfit: scalable pythonic fitting, SoftwareX 11 (2020) 100508 [arXiv:1910.13429] [INSPIRE].

  31. C. Langenbruch, Parameter uncertainties in weighted unbinned maximum likelihood fits, arXiv:1911.01303 [INSPIRE].

  32. LHCb collaboration, Measurement of polarization amplitudes and CP asymmetries in B0ϕK*(892)0, JHEP 05 (2014) 069 [CERN-PH-EP-2014-038] [LHCb-PAPER-2014-005] [arXiv:1403.2888] [INSPIRE].

  33. BaBar collaboration, Measurements of branching fractions, polarizations, and direct CP-violation asymmetries in B+ρ0K*+ and B+f0(980)K*+ decays, Phys. Rev. D 83 (2011) 051101 [arXiv:1012.4044] [INSPIRE].

  34. Belle collaboration, Measurements of branching fractions and polarization in BK*ρ decays, Phys. Rev. Lett. 95 (2005) 141801 [hep-ex/0408102] [INSPIRE].

  35. LHCb collaboration, First observation of the decay \( {B}_s^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0} \), Phys. Lett. B 709 (2012) 50 [CERN-PH-EP-2011-183] [LHCb-PAPER-2011-012] [arXiv:1111.4183] [INSPIRE].

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