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Model-independent method for measuring the angular coefficients of B0→ D∗−τ+ντ decays

Journal of High Energy Physics volume 2019, Article number: 133 (2019) Cite this article

A preprint version of the article is available at arXiv.

Abstract

Reconstruction of the B0→ D∗−τ+ντ angular distribution is complicated by the strongly biasing effect of losing the neutrino information from both the B and τ decays. In this work, a novel method for making unbiased measurements of the angular coefficients while preserving the model independence of the angular technique is demonstrated. The twelve angular functions that describe the signal decay, in addition to background terms, are modelled in a multidimensional fit, using template probability density functions that encapsulate all resolution and acceptance effects. Sensitivities at the LHCb and Belle II experiments are estimated, and sources of systematic uncertainty are discussed, notably in the extrapolation to a measurement of R(D∗).

References

  1. BaBar collaboration, Evidence for an excess of \( \overline{B} \)→ D(∗)τ− \( \overline{\nu} \)τdecays, Phys. Rev. Lett.109 (2012) 101802 [arXiv:1205.5442] [INSPIRE].

  2. BaBar collaboration, Measurement of an excess of \( \overline{B} \)→ D(∗)τ− \( \overline{\nu} \)τdecays and implications for charged Higgs bosons, Phys. Rev.D 88 (2013) 072012 [arXiv:1303.0571] [INSPIRE].

  3. Belle collaboration, Measurement of the branching ratio of \( \overline{B} \)→ D(∗)τ− \( \overline{\nu} \)τrelative to \( \overline{B} \)→ D(∗) ℓ− \( \overline{\nu} \)ℓdecays with hadronic tagging at Belle, Phys. Rev.D 92 (2015) 072014 [arXiv:1507.03233] [INSPIRE].

  4. Belle collaboration, Measurement of the τ lepton polarization and R(D∗) in the decay \( \overline{B} \)→ D∗τ− \( \overline{\nu} \)τ , Phys. Rev. Lett.118 (2017) 211801 [arXiv:1612.00529] [INSPIRE].

  5. BELLE collaboration, Measurement of the τ lepton polarization and R(D∗ ) in the decay \( \overline{B} \)→ D∗τ− \( \overline{\nu} \)τwith one-prong hadronic τ decays at Belle, Phys. Rev.D 97 (2018) 012004 [arXiv:1709.00129] [INSPIRE].

  6. Belle collaboration, Measurement of ℛ(D) and ℛ(D∗ ) with a semileptonic tagging method, arXiv:1904.08794 [INSPIRE].

  7. LHCb collaboration, Measurement of the ratio of branching fractions ℬ (\( \overline{B} \)0→ D∗+ τ − \( \overline{\nu} \)τ)/ ℬ (\( \overline{B} \)0→ D∗+ μ− \( \overline{\nu} \)μ), Phys. Rev. Lett.115 (2015) 111803 [Erratum ibid.115 (2015) 159901] [arXiv:1506.08614] [INSPIRE].

  8. LHCb collaboration, Test of lepton flavor universality by the measurement of the B0→ D∗−τ+ντbranching fraction using three-prong τ decays, Phys. Rev.D 97 (2018) 072013 [arXiv:1711.02505] [INSPIRE].

  9. HFLAV collaboration, Averages of b-hadron, c-hadron and τ -lepton properties as of summer 2016, Eur. Phys. J.C 77 (2017) 895 [arXiv:1612.07233] [INSPIRE].

  10. P. Biancofiore, P. Colangelo and F. De Fazio, On the anomalous enhancement observed in B → D(∗)τ \( \overline{\nu} \)τdecays, Phys. Rev.D 87 (2013) 074010 [arXiv:1302.1042] [INSPIRE].

  11. M. Duraisamy and A. Datta, The Full B → D∗τ− \( \overline{\nu} \)τangular distribution and CP-violating triple products, JHEP09 (2013) 059 [arXiv:1302.7031] [INSPIRE].

    Google Scholar 

  12. S. Fajfer, J.F. Kamenik and I. Nisandzic, On the B → D∗τ \( \overline{\nu} \)τsensitivity to new physics, Phys. Rev.D 85 (2012) 094025 [arXiv:1203.2654] [INSPIRE].

  13. M. Tanaka, Charged Higgs effects on exclusive semitauonic B decays, Z. Phys.C 67 (1995) 321 [hep-ph/9411405] [INSPIRE].

  14. M. Tanaka and R. Watanabe, τ longitudinal polarization in B → Dτν and its role in the search for charged Higgs boson, Phys. Rev.D 82 (2010) 034027 [arXiv:1005.4306] [INSPIRE].

  15. Y. Sakaki and H. Tanaka, Constraints on the charged scalar effects using the forward-backward asymmetry on B−→ D(∗)τ ν−τ , Phys. Rev.D 87 (2013) 054002 [arXiv:1205.4908] [INSPIRE].

  16. A. Datta, M. Duraisamy and D. Ghosh, Diagnosing New Physics in b → cτντdecays in the light of the recent BaBar result, Phys. Rev.D 86 (2012) 034027 [arXiv:1206.3760] [INSPIRE].

  17. M.A. Ivanov, J.G. Körner and C.T. Tran, Exclusive decays B → ℓ − \( \overline{\nu} \)and B → D(∗)ℓ − \( \overline{\nu} \)in the covariant quark model, Phys. Rev.D 92 (2015) 114022 [arXiv:1508.02678] [INSPIRE].

  18. D. Becirevic, S. Fajfer, I. Nisandzic and A. Tayduganov, Angular distributions of \( \overline{B} \)→ D(∗) ℓ\( \overline{\nu} \)ℓdecays and search of New Physics, Nucl. Phys.B 946 (2019) 114707 [arXiv:1602.03030] [INSPIRE].

    Article  Google Scholar 

  19. R. Alonso, A. Kobach and J. Martin Camalich, New physics in the kinematic distributions of \( \overline{B} \)→ D(∗)τ− (→ℓ \( \overline{\nu} \)−ν̄ ντ ) \( \overline{\nu} \)τ , Phys. Rev.D 94 (2016) 094021 [arXiv:1602.07671] [INSPIRE].

  20. A.K. Alok, D. Kumar, S. Kumbhakar and S.U. Sankar, D∗polarization as a probe to discriminate new physics in \( \overline{B} \)→ D∗τ \( \overline{\nu} \), Phys. Rev.B 95 (2017) 115038 [arXiv:1606.03164] [INSPIRE].

    Google Scholar 

  21. D. Bardhan, P. Byakti and D. Ghosh, A closer look at the RD and RD∗ anomalies, JHEP01 (2017) 125 [arXiv:1610.03038] [INSPIRE].

    ADS  Article  Google Scholar 

  22. M.A. Ivanov, J.G. Körner and C.-T. Tran, Probing new physics in \( \overline{B} \)0→ D(∗) τ − \( \overline{\nu} \)τusing the longitudinal, transverse and normal polarization components of the tau lepton, Phys. Rev.D 95 (2017) 036021 [arXiv:1701.02937] [INSPIRE].

  23. R. Alonso, J. Martin Camalich and S. Westhoff, τ properties in B → Dτν from visible final-state kinematics, Phys. Rev.D 95 (2017) 093006 [arXiv:1702.02773] [INSPIRE].

  24. P. Asadi, M.R. Buckley and D. Shih, Asymmetry observables and the origin of RD(∗) anomalies, Phys. Rev.D 99 (2019) 035015 [arXiv:1810.06597] [INSPIRE].

  25. P. Colangelo and F. De Fazio, Scrutinizing \( \overline{B} \)→ D∗ (Dπ) ℓ-\( \overline{\nu} \)ℓand \( \overline{B} \)→ D∗ (Dγ) ℓ − \( \overline{\nu} \)ℓin search of new physics footprints, JHEP06 (2018) 082 [arXiv:1801.10468] [INSPIRE].

    ADS  Article  Google Scholar 

  26. Belle collaboration, Measurement of the D∗−polarization in the decay B0→ D∗−τ+ντ , talk given at the 10thInternational Workshop on the CKM Unitarity Triangle (CKM 2018), September 17–21, Heidelberg, Germany (2018), arXiv:1903.03102 [INSPIRE].

  27. M. Tanaka and R. Watanabe, New physics in the weak interaction of \( \overline{B} \)→ D(∗) τ \( \overline{\nu} \), Phys. Rev.D 87 (2013) 034028 [arXiv:1212.1878] [INSPIRE].

  28. Z.-R. Huang et al., Footprints of new physics in b → cτν transitions, Phys. Rev.D 98 (2018) 095018 [arXiv:1808.03565] [INSPIRE].

  29. S. Bhattacharya, S. Nandi and S. Kumar Patra, b → cτντdecays: a catalogue to compare, constrain and correlate new physics effects, Eur. Phys. J.C 79 (2019) 268 [arXiv:1805.08222] [INSPIRE].

  30. D. Bečirević, M. Fedele, I. Nišanďzić and A. Tayduganov, Lepton Flavor Universality tests through angular observables of \( \overline{B} \)→ D(∗) ℓ\( \overline{\nu} \)decay modes, arXiv:1907.02257 [INSPIRE].

  31. A.K. Alok et al., New physics in b → sμ+μ−: CP-violating observables, JHEP11 (2011) 122 [arXiv:1103.5344] [INSPIRE].

    Google Scholar 

  32. LHCb collaboration, Differential branching fraction and angular analysis of the decay B0→ K∗0μ+μ− , JHEP08 (2013) 131 [arXiv:1304.6325] [INSPIRE].

  33. 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].

    ADS  Article  Google Scholar 

  34. R. Brun and F. Rademakers, ROOT: an object oriented data analysis framework, Nucl. Instrum. Meth.A 389 (1997) 81 [INSPIRE].

    ADS  Article  Google Scholar 

  35. M. Cacciari, S. Frixione and P. Nason, The pTspectrum in heavy flavor photoproduction, JHEP03 (2001) 006 [hep-ph/0102134] [INSPIRE].

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

    ADS  Article  Google Scholar 

  37. N. Isgur, D. Scora, B. Grinstein and M.B. Wise, Semileptonic B and D Decays in the Quark Model, Phys. Rev.D 39 (1989) 799 [INSPIRE].

    ADS  Google Scholar 

  38. M. Chrzaszcz, T. Przedzinski, Z. Was and J. Zaremba, TAUOLA of τ lepton decays — Framework for hadronic currents, matrix elements and anomalous decays, Comput. Phys. Commun.232 (2018) 220 [arXiv:1609.04617] [INSPIRE].

    ADS  Article  Google Scholar 

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

  40. A. Poluektov, TensorFlowAnalysis, https://gitlab.cern.ch/poluekt/TensorFlowAnalysis (2019).

  41. M. Abadi et al., TensorFlow: large-scale machine learning on heterogeneous systems, http://tensorflow.org/ (2015).

  42. F. James and M. Roos, Minuit: a system for function minimization and analysis of the parameter errors and correlations, Comput. Phys. Commun.10 (1975) 343 [INSPIRE].

    ADS  Article  Google Scholar 

  43. I. Caprini, L. Lellouch and M. Neubert, Dispersive bounds on the shape of \( \overline{B} \)→ D(∗)lepton anti-neutrino form-factors, Nucl. Phys.B 530 (1998) 153 [hep-ph/9712417] [INSPIRE].

  44. S. Duell et al., HAMMER: reweighting tool for simulated data samples, PoS(ICHEP2016)1074.

  45. Z. Ligeti, M. Papucci and D.J. Robinson, New physics in the visible final states of B → D(∗)τν, JHEP01 (2017) 083 [arXiv:1610.02045] [INSPIRE].

    Google Scholar 

  46. F. Pedregosa et al., Scikit-learn: machine learning in Python, J. Mach. Learn. Res.12 (2011) 2825.

    MathSciNet  MATH  Google Scholar 

  47. LHCb collaboration, Physics case for an LHCb Upgrade II — Opportunities in flavour physics and beyond, in the HL-LHC era, arXiv:1808.08865 [INSPIRE].

  48. B. Shwartz, The Belle II experiment, Nucl. Part. Phys. Proc.260 (2015) 233.

    Article  Google Scholar 

  49. Belle-II collaboration, The Belle II physics book, arXiv:1808.10567 [INSPIRE].

  50. R.J. Barlow and C. Beeston, Fitting using finite Monte Carlo samples, Comput. Phys. Commun.77 (1993) 219 [INSPIRE].

    ADS  Article  Google Scholar 

  51. D. London, CP Violation in \( \overline{B} \)0→ D∗+ ℓ − \( \overline{\nu} \)ℓ, talk given at the 17thConference on Flavor Physics and CP-violation (FPCP 2019), May 6–10, Victoria, Canada (2019), arXiv:1906.07752 [INSPIRE].

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Affiliations

  1. Department of Physics, University of Oxford, Parks Road, Oxford, U.K.

    Donal Hill & Malcolm John

  2. Département de Physique, Ećole Normale Supérieure, 45 Rue d’Ulm, Paris, France

    Wenqi Ke

  3. Centre de Physique des Particules de Marseille, Aix-Marseille University, 163 Avenue de Luminy, Marseille, France

    Anton Poluektov

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  1. Donal Hill
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  2. Malcolm John
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Correspondence to Donal Hill.

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ArXiv ePrint: 1908.04643

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Hill, D., John, M., Ke, W. et al. Model-independent method for measuring the angular coefficients of B0→ D∗−τ+ντ decays. J. High Energ. Phys. 2019, 133 (2019). https://doi.org/10.1007/JHEP11(2019)133

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  • DOI: https://doi.org/10.1007/JHEP11(2019)133

Keywords

  • B physics
  • Flavor physics
  • Tau Physics
  • Beyond Standard Model
  • Hadron- Hadron scattering (experiments)