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Remarks on the Standard Model predictions for $R (D)$ and $R (D^{*})$

C. S. Kim^*

G. Lopez-Castro^† and S. L. Tostado^‡

A. Vicente^§

Department of Physics and IPAP, Yonsei University, Seoul 120-749, Korea

Departamento de Física, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado Postal 14-740, 07000 México D.F., México

Instituto de Física Corpuscular (CSIC-Universitat de València), Apartado 22085, E-46071 Valencia, Spain

^*cskim@yonsei.ac.kr
^†glopez@fis.cinvestav.mx
^‡stostado@fis.cinvestav.mx
^§avelino.vicente@ific.uv.es

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Phys. Rev. D 95, 013003 – Published 26 January, 2017

DOI: https://doi.org/10.1103/PhysRevD.95.013003

Abstract

Semileptonic $b \to c$ transitions, and in particular the ratios $R (D^{(*)}) = \frac{Γ (B \to D^{(*)} τ ν)}{Γ (B \to D^{(*)} ℓ ν)}$ , can be used to test the universality of the weak interactions. In light of the recent discrepancies between the experimental measurements of these observables by the BABAR, Belle, and LHCb collaborations and the Standard Model predicted values, we study the robustness of the latter. Our analysis reveals that $R (D)$ might be enhanced by lepton mass effects associated to the mostly unknown scalar form factor. In contrast, the Standard Model prediction for $R (D^{*})$ is found to be more robust, because possible pollutions from $B^{*}$ contributions turn out to be negligibly small; this indicates that $R (D^{*})$ is a promising observable for searches of new physics.

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References (60)

N. Cabibbo, Unitary Symmetry and Leptonic Decays, Phys. Rev. Lett. 10, 531 (1963).
M. Kobayashi and T. Maskawa, $C P$ violation in the renormalizable theory of weak interaction, Prog. Theor. Phys. 49, 652 (1973).
H. Na, C. M. Bouchard, G. P. Lepage, C. Monahan, and J. Shigemitsu (HPQCD Collaboration), $B \to D ℓ ν$ form factors at nonzero recoil and extraction of $| V_{c b} |$ , Phys. Rev. D 92, 054510 (2015); Erratum, 93, 119906(E) (2016).
S. Fajfer, J. F. Kamenik, and I. Nišandžić, On the $B \to D^{*} τ {\bar{ν}}_{τ}$ sensitivity to new physics, Phys. Rev. D 85, 094025 (2012).
D. Bigi and P. Gambino, Revisiting $B \to D ℓ ν$ , Phys. Rev. D 94, 094008 (2016).
D. Bečirević, N. Košnik, and A. Tayduganov, $\bar{B} \to D τ {\bar{ν}}_{τ}$ vs. $\bar{B} \to D μ {\bar{ν}}_{μ}$ , Phys. Lett. B 716, 208 (2012).
M. Huschle et al. (Belle Collaboration), Measurement of the branching ratio of $\bar{B} \to D^{(*)} τ^{-} {\bar{ν}}_{τ}$ relative to $\bar{B} \to D^{(*)} ℓ^{-} {\bar{ν}}_{ℓ}$ decays with hadronic tagging at Belle, Phys. Rev. D 92, 072014 (2015),
A. Abdesselam et al. (Belle Collaboration), Measurement of the branching ratio of ${\bar{B}}^{0} \to D^{* +} τ^{-} {\bar{ν}}_{τ}$ relative to ${\bar{B}}^{0} \to D^{* +} ℓ^{-} {\bar{ν}}_{ℓ}$ decays with a semileptonic tagging method, arXiv:1603.06711.
R. Aaij et al. (LHCb Collaboration), Measurement of the Ratio of Branching Fractions $B ({\bar{B}}^{0} \to D^{* +} τ^{-} {\bar{ν}}_{τ}) / B ({\bar{B}}^{0} \to D^{* +} μ^{-} {\bar{ν}}_{μ})$ , Phys. Rev. Lett. 115, 111803 (2015); Publisher’s Note, 115, 159901 (2015).
J. P. Lees et al. (BABAR Collaboration), Evidence for an Excess of $\bar{B} \to D^{(*)} τ^{-} {\bar{ν}}_{τ}$ Decays, Phys. Rev. Lett. 109, 101802 (2012).
Heavy Flavor Averaging Group, http://www.slac.stanford.edu/xorg/hfag/semi/winter16/winter16_dtaunu.html.
S. Fajfer, J. F. Kamenik, I. Nišandžić, and J. Zupan, Implications of Lepton Flavor Universality Violations in $B$ Decays, Phys. Rev. Lett. 109, 161801 (2012).
A. Crivellin, C. Greub, and A. Kokulu, Explaining $B \to D τ ν$ , $B \to D^{*} τ ν$ and $B \to τ ν$ in a 2HDM of type III, Phys. Rev. D 86, 054014 (2012).
A. Celis, M. Jung, X.-Q. Li, and A. Pich, Sensitivity to charged scalars in $B \to D^{(*)} τ ν_{τ}$ and $B \to τ ν_{τ}$ decays, J. High Energy Phys. 01 (2013) 054.
J. A. Bailey et al., Refining New-Physics Searches in $B \to D τ ν$ Decay with Lattice QCD, Phys. Rev. Lett. 109, 071802 (2012).
M. Tanaka and R. Watanabe, New physics in the weak interaction of $\bar{B} \to D^{(*)} τ \bar{ν}$ , Phys. Rev. D 87, 034028 (2013).
P. Ko, Y. Omura, and C. Yu, $B \to D^{(*)} τ ν$ and $B \to τ ν$ in chiral U(1)’ models with flavored multi Higgs doublets, J. High Energy Phys. 03 (2013) 151.
M. Freytsis, Z. Ligeti, and J. T. Ruderman, Flavor models for $\bar{B} \to D^{(*)} τ \bar{ν}$ , Phys. Rev. D 92, 054018 (2015).
A. Crivellin, J. Heeck, and P. Stoffer, A Perturbed Lepton-Specific Two-Higgs-Doublet Model Facing Experimental Hints for Physics Beyond the Standard Model, Phys. Rev. Lett. 116, 081801 (2016).
N. G. Deshpande and A. Menon, Hints of $R$ -parity violation in B decays into $τ ν$ , J. High Energy Phys. 01 (2013) 025.
Y. Sakaki, M. Tanaka, A. Tayduganov, and R. Watanabe, Testing leptoquark models in $\bar{B} \to D^{(*)} τ \bar{ν}$ , Phys. Rev. D 88, 094012 (2013).
I. Doršner, S. Fajfer, N. Košnik, and I. Nišandžić, Minimally flavored colored scalar in $\bar{B} \to D^{(*)} τ \bar{ν}$ and the mass matrices constraints, J. High Energy Phys. 11 (2013) 084.
R. Alonso, B. Grinstein, and J. Martin Camalich, Lepton universality violation and lepton flavor conservation in $B$ -meson decays, J. High Energy Phys. 10 (2015) 184.
M. Bauer and M. Neubert, Minimal Leptoquark Explanation for the $R_{D^{(*)}}$ , $R_{K}$ , and $(g - 2)_{g}$ Anomalies, Phys. Rev. Lett. 116, 141802 (2016).
R. Barbieri, G. Isidori, A. Pattori, and F. Senia, Anomalies in $B$ -decays and $U (2)$ flavour symmetry, Eur. Phys. J. C 76, 67 (2016).
S. Fajfer and N. Košnik, Vector leptoquark resolution of $R_{K}$ and $R_{D^{(*)}}$ puzzles, Phys. Lett. B 755, 270 (2016).
L. Calibbi, A. Crivellin, and T. Ota, Effective Field Theory Approach to $b \to s ℓ ℓ^{(')}$ , $B \to K^{(*)} ν \bar{ν}$ and $B \to D^{(*)} τ ν$ with Third-Generation Couplings, Phys. Rev. Lett. 115, 181801 (2015).
C. Hati, G. Kumar, and N. Mahajan, $\bar{B} \to D^{(*)} τ \bar{ν}$ excesses in ALRSM constrained from $B$ , $D$ decays and $D^{0} - {\bar{D}}^{0}$ mixing, J. High Energy Phys. 01 (2016) 117.
C. Hati, Explaining the diphoton excess in alternative left-right symmetric model, Phys. Rev. D 93, 075002 (2016).
F. F. Deppisch, S. Kulkarni, H. Päs, and E. Schumacher, Leptoquark patterns unifying neutrino masses, flavor anomalies and the diphoton excess, Phys. Rev. D 94, 013003 (2016).
J. Zhu, H.-M. Gan, R.-M. Wang, Y.-Y. Fan, Q. Chang, and Y.-G. Xu, Probing the $R$ -parity violating supersymmetric effects in the exclusive $b \to c ℓ^{-} {\bar{ν}}_{ℓ}$ decays, Phys. Rev. D 93, 094023 (2016).
N. G. Deshpande and X.-G. He, Consequences of $R$ -parity violating interactions for anomalies in $\bar{B} \to D^{(*)} τ \bar{ν}$ and $b \to s μ^{+} μ^{-}$ , arXiv:1608.04817.
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, 115021 (2016).
S. Sahoo, R. Mohanta, and A. K. Giri, Explaining $R_{K}$ and $R_{D^{(*)}}$ anomalies with vector leptoquark, arXiv:1609.04367.
G. Hiller, D. Loose, and K. Schönwald, Leptoquark flavor patterns and $B$ decay anomalies, J. High Energy Phys. 12 (2016) 027.
B. Bhattacharya, A. Datta, J.-P. Guévin, D. London, and R. Watanabe, Simultaneous explanation of the $R_{K}$ and $R_{D^{(*)}}$ puzzles: A model analysis, arXiv:1609.09078.
D. Das, C. Hati, G. Kumar, and N. Mahajan, Towards a unified explanation of $R_{D^{(*)}}$ , $R_{K}$ and $(g - 2)_{μ}$ anomalies in a left-right model with leptoquarks, Phys. Rev. D 94, 055034 (2016).
D. Buttazzo, A. Greljo, G. Isidori, and D. Marzocca, Toward a coherent solution of diphoton and flavor anomalies, J. High Energy Phys. 08 (2016) 035.
X.-G. He and G. Valencia, $B$ decays with $τ$ leptons in nonuniversal left-right models, Phys. Rev. D 87, 014014 (2013).
A. Greljo, G. Isidori, and D. Marzocca, On the breaking of lepton flavor universality in $B$ decays, J. High Energy Phys. 07 (2015) 142.
S. M. Boucenna, A. Celis, J. Fuentes-Martín, A. Vicente, and J. Virto, Non-Abelian gauge extensions for $B$ -decay anomalies, Phys. Lett. B 760, 214 (2016).
S. M. Boucenna, A. Celis, J. Fuentes-Martín, A. Vicente, and J. Virto, Phenomenology of an $S U (2) \times S U (2) \times U (1)$ model with lepton-flavour non-universality, J. High Energy Phys. 12 (2016) 059.
A. Abada, A. M. Teixeira, A. Vicente, and C. Weiland, Sterile neutrinos in leptonic and semileptonic decays, J. High Energy Phys. 02 (2014) 091.
G. Cvetič and C. S. Kim, Rare decays of $B$ mesons via on-shell sterile neutrinos, Phys. Rev. D 94, 053001 (2016).
P. Biancofiore, P. Colangelo, and F. De Fazio, On the anomalous enhancement observed in $B \to D^{(*)} τ {\bar{ν}}_{τ}$ decays, Phys. Rev. D 87, 074010 (2013).
S. Bhattacharya, S. Nandi, and S. K. Patra, Optimal-observable analysis of possible new physics in $B \to D^{(*)} τ ν_{τ}$ , Phys. Rev. D 93, 034011 (2016).
R. Alonso, A. Kobach, and J. Martin Camalich, New physics in the kinematic distributions of $\bar{B} \to D^{(*)} τ^{-} (\to ℓ^{-} {\bar{ν}}_{ℓ} ν_{τ}) {\bar{ν}}_{τ}$ , Phys. Rev. D 94, 094021 (2016).
A. K. Alok, D. Kumar, S. Kumbhakar, and S. U. Sankar, $D^{*}$ polarization as a probe to discriminate new physics in $B \to D^{*} τ \bar{ν}$ , arXiv:1606.03164.
D. Bardhan, P. Byakti, and D. Ghosh, A closer look at the $R_{D}$ and $R_{D^{*}}$ anomalies, arXiv:1610.03038.
Y.-Y. Fan, Z.-J. Xiao, R.-M. Wang, and B.-Z. Li, The $B \to D^{(*)} l ν_{l}$ decays in the pQCD approach with the lattice QCD input, Science bulletin 60, 2009 (2015).
N. Košnik, D. Bečirević, and A. Tayduganov, Testing the Standard Model in $B \to D τ \bar{ν}$ decay with minimal theory input, Proc. Sci., ConfinementX2012 (2012) 244 [arXiv:1301.4037].
K. A. Olive et al. (Particle Data Group Collaboration), Review of particle physics, Chin. Phys. C 38, 090001 (2014).
M. Bordone, G. Isidori, and D. van Dyk, Impact of leptonic $τ$ decays on the distribution of $B \to P μ \bar{ν}$ decays, Eur. Phys. J. C 76, 360 (2016).
Z. Ligeti, M. Papucci, and D. J. Robinson, New physics in the visible final states of $B \to D^{(*)} τ ν$ , arXiv:1610.02045.
Q. Chang, J. Zhu, X.-L. Wang, J.-F. Sun, and Y.-L. Yang, Study of semileptonic BP decays, Nucl. Phys. B909, 921 (2016).
F. Bernardoni, J. Bulava, M. Donnellan, and R. Sommer (ALPHA Collaboration), Precision lattice QCD computation of the $B^{*} B π$ coupling, Phys. Lett. B 740, 278 (2015).
J. M. Flynn, P. Fritzsch, T. Kawanai, C. Lehner, B. Samways, C. T. Sachrajda, R. S. Van de Water, and O. Witzel (RBC and UKQCD Collaborations), The $B^{*} B π$ coupling using relativistic heavy quarks, Phys. Rev. D 93, 014510 (2016).
B. El-Bennich, M. A. Ivanov, and C. D. Roberts, Strong $D^{*} \to D π$ and $B^{*} \to B π$ couplings, Phys. Rev. C 83, 025205 (2011).
A. Flores-Tlalpa, G. López Castro, and G. Sanchez Toledo, Radiative two-pion decay of the tau lepton, Phys. Rev. D 72, 113003 (2005).
W. Dungel et al. (Belle Collaboration), Measurement of the form factors of the decay $B^{0} \to D^{* -} ℓ^{+} ν_{ℓ}$ and determination of the CKM matrix element $| V_{c b} |$ , Phys. Rev. D 82, 112007 (2010).

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Remarks on the Standard Model predictions for $R (D)$ and $R (D^{*})$

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Remarks on the Standard Model predictions for R(D) and R(D*)

Abstract

Physics Subject Headings (PhySH)

Article Text

References (60)

Remarks on the Standard Model predictions for $R (D)$ and $R (D^{*})$