Abstract
Besides being important to determine Standard Model parameters such as the CKM matrix elements |V cb | and |V ub |, semileptonic B decays seem also promising to reveal new physics (NP) phenomena, in particular in connection with the possibility of uncovering lepton flavour universality (LFU) violating effects. In this view, it could be natural to connect the tensions in the inclusive versus exclusive determinations of |V cb | to the anomalies in the ratios R(D(*)) of decay rates into τ vs μ, e. However, the question has been raised about the role of the parametrization of the hadronic B → D(*) form factors in exclusive B decay modes. We focus on the fully differential angular distributions of \( \overline{B}\to {D}^{\ast }{\ell}^{-}{\overline{\nu}}_{\ell } \) with D∗ → Dπ or D∗ → Dγ, the latter mode being important in the case of B s → D * s decays. We show that the angular coefficients in the distributions can be used to scrutinize the role of the form factor parametrization and to pin down deviations from SM. As an example of a NP scenario, we include a tensor operator in the b → c semileptonic effective Hamiltonian, and discuss how the angular coefficients allow to construct observables sensitive to this structure, also defining ratios useful to test LFU.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
HFLAV collaboration, Y. Amhis et al., 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].
BaBar collaboration, J.P. Lees et al., Evidence for an excess of \( \overline{B}\to {D}^{\left(\ast \right)}{\tau}^{-}{\overline{\nu}}_{\tau } \) decays, Phys. Rev. Lett. 109 (2012) 101802 [arXiv:1205.5442] [INSPIRE].
BaBar collaboration, J.P. Lees et al., Measurement of an Excess of \( \overline{B}\to {D}^{\left(\ast \right)}{\tau}^{-}{\overline{\nu}}_{\tau } \) Decays and Implications for Charged Higgs Bosons, Phys. Rev. D 88 (2013) 072012 [arXiv:1303.0571] [INSPIRE].
Belle collaboration, M. Huschle et al., Measurement of the branching ratio of \( \overline{B}\to {D}^{\left(\ast \right)}{\tau}^{-}{\overline{\nu}}_{\tau } \) relative to \( \overline{B}\to {D}^{\left(\ast \right)}{\ell}^{-}{\overline{\nu}}_{\ell } \) decays with hadronic tagging at Belle, Phys. Rev. D 92 (2015) 072014 [arXiv:1507.03233] [INSPIRE].
Belle collaboration, Y. Sato et al., Measurement of the branching ratio of \( {\overline{B}}^0\to {D}^{\ast +}{\tau}^{-}{\overline{\nu}}_{\tau } \) relative to B0 → D∗+ℓ−νℓ decays with a semileptonic tagging method, Phys. Rev. D 94 (2016) 072007 [arXiv:1607.07923] [INSPIRE].
Belle collaboration, S. Hirose et al., Measurement of the τ lepton polarization and R(D *) in the decay \( \overline{B}\to {D}^{\ast }{\tau}^{-}{\overline{\nu}}_{\tau } \), Phys. Rev. Lett. 118 (2017) 211801 [arXiv:1612.00529] [INSPIRE].
LHCb collaboration, Measurement of the ratio of branching fractions \( \mathrm{\mathcal{B}}\left({\overline{B}}^0\to {D}^{\ast +}{\tau}^{-}{\overline{\nu}}_{\tau}\right)/\mathrm{\mathcal{B}}\left({\overline{B}}^0\to {D}^{\ast +}{\mu}^{-}{\overline{\nu}}_{\mu}\right) \), Phys. Rev. Lett. 115 (2015) 111803 [arXiv:1506.08614] [INSPIRE].
S. Fajfer, J.F. Kamenik and I. Nisandzic, On the \( B\to {D}^{\ast}\tau {\overline{\nu}}_{\tau } \) Sensitivity to New Physics, Phys. Rev. D 85 (2012) 094025 [arXiv:1203.2654] [INSPIRE].
S. Aoki et al., Review of lattice results concerning low-energy particle physics, Eur. Phys. J. C 77 (2017) 112 [arXiv:1607.00299] [INSPIRE].
D. Bigi, P. Gambino and S. Schacht, R(D *), |V cb |, and the Heavy Quark Symmetry relations between form factors, JHEP 11 (2017) 061 [arXiv:1707.09509] [INSPIRE].
S. Jaiswal, S. Nandi and S.K. Patra, Extraction of |V cb | from B → D (*) ℓν ℓ and the Standard Model predictions of R(D (*)), JHEP 12 (2017) 060 [arXiv:1707.09977] [INSPIRE].
F.U. Bernlochner, Z. Ligeti, M. Papucci and D.J. Robinson, Combined analysis of semileptonic B decays to D and D * : R(D (*)), |V cb |, and new physics, Phys. Rev. D 95 (2017) 115008 [arXiv:1703.05330] [INSPIRE].
Belle collaboration, S. Hirose et al., Measurement of the τ lepton polarization and R(D *) in the decay \( \overline{B}\to {D}^{*}{\tau}^{-}{\overline{\nu}}_{\tau } \) with one-prong hadronic τ decays at Belle, Phys. Rev. D 97 (2018) 012004 [arXiv:1709.00129] [INSPIRE].
LHCb collaboration, Measurement of the ratio of branching fractions ℬ(B + c → J/ψτ + ν τ )/ℬ(B + c → J/ψμ + ν μ ), Phys. Rev. Lett. 120 (2018) 121801 [arXiv:1711.05623] [INSPIRE].
C.-T. Tran, M.A. Ivanov, J.G. Körner and P. Santorelli, Implications of new physics in the decays B c → (J/ψ, η c )τν, Phys. Rev. D 97 (2018) 054014 [arXiv:1801.06927] [INSPIRE].
I. Caprini, L. Lellouch and M. Neubert, Dispersive bounds on the shape of \( \overline{B}\to {D}^{\left(\ast \right)} \) lepton anti-neutrino form-factors, Nucl. Phys. B 530 (1998) 153 [hep-ph/9712417] [INSPIRE].
Belle collaboration, A. Abdesselam et al., Precise determination of the CKM matrix element |V cb | with \( {\overline{B}}^0\to {D}^{\ast +}{\ell}^{-}{\overline{\nu}}_{\ell } \) decays with hadronic tagging at Belle, arXiv:1702.01521 [INSPIRE].
C.G. Boyd, B. Grinstein and R.F. Lebed, Constraints on form-factors for exclusive semileptonic heavy to light meson decays, Phys. Rev. Lett. 74 (1995) 4603 [hep-ph/9412324] [INSPIRE].
C.G. Boyd, B. Grinstein and R.F. Lebed, Model independent extraction of |V cb | using dispersion relations, Phys. Lett. B 353 (1995) 306 [hep-ph/9504235] [INSPIRE].
C.G. Boyd, B. Grinstein and R.F. Lebed, Model independent determinations of \( \overline{B}\to D \) (lepton), D * (lepton) anti-neutrino form-factors, Nucl. Phys. B 461 (1996) 493 [hep-ph/9508211] [INSPIRE].
D. Bigi, P. Gambino and S. Schacht, A fresh look at the determination of |V cb | from B → D * ℓν, Phys. Lett. B 769 (2017) 441 [arXiv:1703.06124] [INSPIRE].
B. Grinstein and A. Kobach, Model-Independent Extraction of |V cb | from \( \overline{B}\to {D}^{\ast}\ell \overline{\nu} \), Phys. Lett. B 771 (2017) 359 [arXiv:1703.08170] [INSPIRE].
P. Colangelo and F. De Fazio, Tension in the inclusive versus exclusive determinations of |V cb |: a possible role of new physics, Phys. Rev. D 95 (2017) 011701 [arXiv:1611.07387] [INSPIRE].
P. Biancofiore, P. Colangelo and F. De Fazio, Anomalous enhancement observed in \( B\to {D}^{\left(*\right)}\tau {\overline{\nu}}_{\tau } \) decays, Phys. Rev. D 87 (2013) 074010 [arXiv:1302.1042] [INSPIRE].
M. Duraisamy and A. Datta, The Full \( B\to {D}^{\ast }{\tau}^{-}\overline{\nu_{\tau }} \) Angular Distribution and CP violating Triple Products, JHEP 09 (2013) 059 [arXiv:1302.7031] [INSPIRE].
S. Bhattacharya, S. Nandi and S.K. Patra, Optimal-observable analysis of possible new physics in B → D (*) τν τ , Phys. Rev. D 93 (2016) 034011 [arXiv:1509.07259] [INSPIRE].
D. Bardhan, P. Byakti and D. Ghosh, A closer look at the R D and \( {R}_{D^{*}} \) anomalies, JHEP 01 (2017) 125 [arXiv:1610.03038] [INSPIRE].
R. Alonso, A. Kobach and J. Martin Camalich, New physics in the kinematic distributions of \( \overline{B}\to {D}^{\left(\ast \right)}{\tau}^{-}\left(\to {\ell}^{-}{\overline{\nu}}_{\ell }{\nu}_{\tau}\right){\overline{\nu}}_{\tau } \), Phys. Rev. D 94 (2016) 094021 [arXiv:1602.07671] [INSPIRE].
D. Bečirević, S. Fajfer, I. Nisandzic and A. Tayduganov, Angular distributions of \( \overline{B}\to {D}^{\left(\ast \right)}\ell {\overline{\nu}}_{\ell } \) decays and search of New Physics, arXiv:1602.03030 [INSPIRE].
Z. Ligeti, M. Papucci and D.J. Robinson, New Physics in the Visible Final States of B → D (*) τν, JHEP 01 (2017) 083 [arXiv:1610.02045] [INSPIRE].
A.K. Alok, D. Kumar, S. Kumbhakar and S.U. Sankar, D ∗ polarization as a probe to discriminate new physics in \( \overline{B}\to {D}^{\ast}\tau \overline{\nu} \), Phys. Rev. D 95 (2017) 115038 [arXiv:1606.03164] [INSPIRE].
M.A. Ivanov, J.G. Körner and C.-T. Tran, Probing new physics in \( {\overline{B}}^0\to {D}^{\left(\ast \right)}{\tau}^{-}{\overline{\nu}}_{\tau } \) using the longitudinal, transverse, and normal polarization components of the tau lepton, Phys. Rev. D 95 (2017) 036021 [arXiv:1701.02937] [INSPIRE].
R. Alonso, J. Martin Camalich and S. Westhoff, Tau properties in B → Dτν from visible final-state kinematics, Phys. Rev. D 95 (2017) 093006 [arXiv:1702.02773] [INSPIRE].
M. Jung and D.M. Straub, Constraining new physics in b → cℓν transitions, arXiv:1801.01112 [INSPIRE].
M. Bauer and M. Neubert, Minimal Leptoquark Explanation for the \( {R}_{D^{\left(\ast \right)}} \) , R K , and (g − 2) g Anomalies, Phys. Rev. Lett. 116 (2016) 141802 [arXiv:1511.01900] [INSPIRE].
D. Bečirević, S. Fajfer, N. Košnik and O. Sumensari, Leptoquark model to explain the B-physics anomalies, R K and R D , Phys. Rev. D 94 (2016) 115021 [arXiv:1608.08501] [INSPIRE].
A. Crivellin, D. Müller and T. Ota, Simultaneous explanation of R(D (*)) and b → sμ + μ − : the last scalar leptoquarks standing, JHEP 09 (2017) 040 [arXiv:1703.09226] [INSPIRE].
D. Buttazzo, A. Greljo, G. Isidori and D. Marzocca, B-physics anomalies: a guide to combined explanations, JHEP 11 (2017) 044 [arXiv:1706.07808] [INSPIRE].
F. Feruglio, P. Paradisi and A. Pattori, On the Importance of Electroweak Corrections for B Anomalies, JHEP 09 (2017) 061 [arXiv:1705.00929] [INSPIRE].
LHCb collaboration, Test of Lepton Flavor Universality by the measurement of the B 0 → D *− τ + ν τ branching fraction using three-prong τ decays, Phys. Rev. D 97 (2018) 072013 [arXiv:1711.02505] [INSPIRE].
J.G. Körner and G.A. Schuler, Exclusive Semileptonic Heavy Meson Decays Including Lepton Mass Effects, Z. Phys. C 46 (1990) 93 [INSPIRE].
F.J. Gilman and R.L. Singleton, Analysis of Semileptonic Decays of Mesons Containing Heavy Quarks, Phys. Rev. D 41 (1990) 142 [INSPIRE].
M. González-Alonso, J. Martin Camalich and K. Mimouni, Renormalization-group evolution of new physics contributions to (semi)leptonic meson decays, Phys. Lett. B 772 (2017) 777 [arXiv:1706.00410] [INSPIRE].
C.F. Uhlemann and N. Kauer, Narrow-width approximation accuracy, Nucl. Phys. B 814 (2009) 195 [arXiv:0807.4112] [INSPIRE].
C.G. Boyd, B. Grinstein and R.F. Lebed, Precision corrections to dispersive bounds on form-factors, Phys. Rev. D 56 (1997) 6895 [hep-ph/9705252] [INSPIRE].
A. Vaquero Avilés-Casco et al., \( \overline{B}\to {D}^{*}\ell \overline{\nu} \) at Non-Zero Recoil, EPJ Web Conf. 175 (2018) 13003 [arXiv:1710.09817] [INSPIRE].
F.U. Bernlochner, Z. Ligeti, M. Papucci and D.J. Robinson, Tensions and correlations in |V cb | determinations, Phys. Rev. D 96 (2017) 091503 [arXiv:1708.07134] [INSPIRE].
Fermilab Lattice and MILC collaborations, J.A. Bailey et al., Update of |V cb | from the \( \overline{B}\to {D}^{*}\ell \overline{\nu} \) form factor at zero recoil with three-flavor lattice QCD, Phys. Rev. D 89 (2014) 114504 [arXiv:1403.0635] [INSPIRE].
A. Sirlin, Large m W , m Z Behavior of the O(α) Corrections to Semileptonic Processes Mediated by W, Nucl. Phys. B 196 (1982) 83 [INSPIRE].
D. Atwood and W.J. Marciano, Radiative Corrections and Semileptonic B Decays, Phys. Rev. D 41 (1990) 1736 [INSPIRE].
MILC collaboration, J.A. Bailey et al., B → D form factors at nonzero recoil and |V cb | from 2+1-flavor lattice QCD, Phys. Rev. D 92 (2015) 034506 [arXiv:1503.07237] [INSPIRE].
Belle collaboration, W. Dungel et al., Measurement of the form factors of the decay B 0 → D *− ℓ + ν and determination of the CKM matrix element |V cb |, Phys. Rev. D 82 (2010) 112007 [arXiv:1010.5620] [INSPIRE].
M. Neubert, Heavy quark symmetry, Phys. Rept. 245 (1994) 259 [hep-ph/9306320] [INSPIRE].
BELLE-II collaboration, E. Guido, Belle II physics prospects, PoS(FPCP2017)036.
Open Access
This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.
Author information
Authors and Affiliations
Corresponding author
Additional information
ArXiv ePrint: 1801.10468
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.
The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.
To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/.
About this article
Cite this article
Colangelo, P., De Fazio, F. Scrutinizing \( \overline{B}\to {D}^{\ast}\left(D\pi \right){\ell}^{-}{\overline{\nu}}_{\ell } \) and \( \overline{B}\to {D}^{\ast}\left(D\upgamma \right){\ell}^{-}{\overline{\nu}}_{\ell } \) in search of new physics footprints. J. High Energ. Phys. 2018, 82 (2018). https://doi.org/10.1007/JHEP06(2018)082
Received:
Revised:
Accepted:
Published:
DOI: https://doi.org/10.1007/JHEP06(2018)082