Resolution of R/<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"><mml:msub><mml:mrow><mml:mi>R</mml:mi></mml:mrow><mml:mrow><mml:msup><mml:mrow><mml:mi>D</mml:mi></mml:mrow><mml:mrow><mml:mo>⁎</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:msub></mml:math> puzzle

Alok, Ashutosh Kumar; Kumar, Dinesh; Kumbhakar, Suman; Sankar, S. Uma

doi:10.1016/j.physletb.2018.07.001

Cited by 34 publications

(18 citation statements)

References 21 publications

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“…In [87] it was shown that in the NRQCD approximation one can derive a generalized set of relations using the HQSS, so that the transition form factors of B c → η c and B c → J/ψ decays can be given in terms of a single form factor, even for the case of non-equal fourvelocities v 1 = v 2 , of the initial and the final state heavy mesons. If the following helicity JHEP05(2019)094 basis for the form factors in B c → J/ψ decay is defined 48) and 49) the expressions from [87], stemming from considering NRQCD and HQSS, and relating different decay form factors at the point of zero recoil q 2 max ofQq →Q q transitions can be expressed as [24]:…”

Section: Parametrization Of the Form Factors And The Resultsmentioning

confidence: 99%

“…The constraints on contributions of these NP operators and the corresponding Wilson coefficients are obtained from the experimental results of R D , R D * , polarizations of τ and D * in B → D ( * ) lν decays, as well as on the B c lifetime. There are various studies [43][44][45][46][47][48] performing a global fit on these NP operators considering the presence of only one or two NP operators simultaneously. We have taken the latest constraints on the Wilson coefficients from ref.…”

Section: Jhep05(2019)094mentioning

confidence: 99%

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On lepton flavour universality in semileptonic Bc → ηc, J/ψ decays

Leljak

Melić

Patra

2019

J. High Energ. Phys.

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We discuss B c → η c and B c → J/ψ semileptonic decays within the Standard Model (SM) and beyond. The relevant transition form factors, being the main source of theoretical uncertainties, are calculated in the sum rule approach and are provided in a full q 2 range. We calculate the semileptonic branching fractions and find for the ratios, R ηc | SM = 0.32 ± 0.02, R J/ψ | SM = 0.23 ± 0.01. Both predictions are in agreement with other existing calculations and support the current tension in R J/ψ at 2σ level with the experiment. To extend the potential of testing the SM in the semileptonic B c decays, we consider the forward-backward asymmetry and polarization observables. We also study the 4-fold differential distributions of B c → J/ψ(J/ψ →˜ −˜ +) −ν , where˜ = e, µ, in the presence of different new physics scenarios and find that the new physics effects can significantly modify the angular observables and can also produce effects which do not exist in the SM. Using the constraints on the new physics couplings from the recent combined analysis of BaBar, Belle and LHCb data on semileptonic B → D (*) decays, where the effects of new physics could be visible, we find that these different new physics scenarios are not able to simultaneously explain the current experimental value of R J/ψ .

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Section: Parametrization Of the Form Factors And The Resultsmentioning

confidence: 99%

Section: Jhep05(2019)094mentioning

confidence: 99%

On lepton flavour universality in semileptonic Bc → ηc, J/ψ decays

Leljak

Melić

Patra

2019

J. High Energ. Phys.

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“…There are ongoing discussions of the possible systematic effects and the uncertaina e-mail: patrick.tunney@kcl.ac.uk ties in the SM calculations, so the jury is still out on the significances of these flavour anomalies [12]. In the meantime, it is interesting to explore possible interpretations and look for other phenomenological signatures that might corroborate them [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

Anomaly-free models for flavour anomalies

2018

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We explore the constraints imposed by the cancellation of triangle anomalies on models in which the flavour anomalies reported by LHCb and other experiments are due to an extra U(1) gauge boson Z . We assume universal and rational U(1) charges for the first two generations of lefthanded quarks and of right-handed up-type quarks but allow different charges for their third-generation counterparts. If the right-handed charges vanish, cancellation of the triangle anomalies requires all the quark U(1) charges to vanish, if there are either no exotic fermions or there is only one Standard Model singlet dark matter (DM) fermion. There are non-trivial anomaly-free models with more than one such 'dark' fermion, or with a single DM fermion if right-handed up-type quarks have non-zero U(1) charges. In some of the latter models the U(1) couplings of the first-and secondgeneration quarks all vanish, weakening the LHC Z constraint, and in some other models the DM particle has purely axial couplings, weakening the direct DM scattering constraint. We also consider models in which anomalies are cancelled via extra vector-like leptons, showing how the prospective LHC Z constraint may be weakened because the Z → μ + μ − branching ratio is suppressed relative to other decay modes.

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“…[9,17,18] considered the interpretation of the data in terms of the type-II two-Higgs doublet model (2HDM) and found it to be inconsistent with the data. On the other hand, besides a plethora of model-independent analysis of the present anomaly [19][20][21][22][23][24][25][26][27][28][29][30][31], one can find in the literature potential explanations in terms of W vector bosons [32][33][34], composite states [35,36], and Frogatt-Nielson-type models [37]. Alternatively, a number of authors have considered leptoquarks as a potential source for the anomaly [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54].…”

Section: Introductionmentioning

confidence: 99%

Constraining the minimal flavor violating leptoquark explanation of the RD(*) anomaly

2019

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There has been persistent disagreement between the Standard Model (SM) prediction and experimental measurements of R D ( * ) = B(B → D ( * ) τντ )/B(B → D ( * ) lν l ) (l = e, µ). This anomaly may be addressed by introducing interactions beyond the Standard Model involving new states, such as leptoquarks. Since the processes involved are quark flavor changing, any new states would need to couple to at least two different generations of quarks, requiring a non-trivial flavor structure in the quark sector while avoiding stringent constraints from flavor-changing neutral current processes. In this work, we look at scalar leptoquarks as a possible solution for the R D ( * ) anomaly under the assumption of minimal flavor violation (MFV). We investigate all possible representations for the leptoquarks under the SM quark flavor symmetry group, consistent with asymptotic freedom. We consider constraints on their parameter space from self-consistency of the MFV scenario, perturbativity, the FCNC decay b → sνν and precision electroweak observables. We find that none of the scalar leptoquarks can explain the R D ( * ) anomaly while simultaneously avoiding all constraints within this scenario. Thus scalar leptoquarks with MFV-generated quark couplings do not work as a solution to the R D ( * ) anomaly.

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Resolution of R/RD⁎ puzzle

Cited by 34 publications

References 21 publications

On lepton flavour universality in semileptonic Bc → ηc, J/ψ decays

On lepton flavour universality in semileptonic Bc → ηc, J/ψ decays

Anomaly-free models for flavour anomalies

Constraining the minimal flavor violating leptoquark explanation of the RD(*) anomaly

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