Global fit to b → cτν transitions

Murgui, Clara; Peñuelas, Ana Belén Cabrejas; Jung, Martin; Pich, Antonio

doi:10.1007/jhep09(2019)103

Cited by 157 publications

(247 citation statements)

References 139 publications

(244 reference statements)

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“…(3.31). A sizeable scalar contribution to b → cτ −ν decays is known to improve the quality of fits [36,38,39,[49][50][51]. We require it to be comparable with the left-handed one, i.e.…”

Section: Constraints On Fn Chargesmentioning

confidence: 99%

Effective theory approach to new physics with flavour: general framework and a leptoquark example

Bordone

Catà

Feldmann

2020

J. High Energ. Phys.

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Extending the Standard Model with higher-dimensional operators in an effective-fieldtheory (EFT) approach provides a systematic framework to study new-physics (NP) effects from a bottom-up perspective, as long as the NP scale is sufficiently large compared to the energies probed in the experimental observables. However, when taking into account the different quark and lepton flavours, the number of free parameters increases dramatically, which makes generic studies of the NP flavour structure infeasible. In this paper, we address this issue in view of the recently observed "flavour anomalies" in B-meson decays, which we take as a motivation to develop a general framework that allows us to systematically reduce the number of flavour parameters in the EFT. This framework can be easily used in global fits to flavour observables at Belle II and LHCb as well as in analyses of flavour-dependent collider signatures at the LHC. Our formalism represents an extension of the well-known minimal-flavour-violation approach, and uses Froggatt-Nielsen charges to define the flavour power-counting. As a relevant illustration of the formalism, we apply it to the flavour structures which could be induced by a U 1 vector leptoquark, which represents one of the possible explanations for the recent hints of flavour non-universality in semileptonic B-decays. We study the phenomenological viability of this specific framework performing a fit to low-energy flavour observables.

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Section: Constraints On Fn Chargesmentioning

confidence: 99%

Effective theory approach to new physics with flavour: general framework and a leptoquark example

Bordone

Catà

Feldmann

2020

J. High Energ. Phys.

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“…the new Belle measurements, see Refs. [33][34][35][36][37]) 1 . On the other hand, particular NP scenarios such as: charged scalars [46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62], leptoquarks (both scalar and vector) , extra gauge bosons [47,94,[98][99][100][101][102][103][104][105][106][107][108][109][110][111], right-handed neutrinos [62,[106][107][108][109][110][111][112][113], R-parity violating (RPV) supersymmetric couplings [31,[114][115]…”

Section: Introductionmentioning

confidence: 99%

Charged current b→cτν¯τ anomalies in a general W′ boson scenario

2019

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The very recent experimental information obtained from Belle experiment, along with the one accumulated by the BABAR and LHCb experiments have shown the existence of anomalies in the ratios R(D) and R(D * ) associated with the charged current transition b → cτντ . Although the Belle measurements are in agreement with the SM predictions, the new experimental world averages still exhibit a tension. In addition, the D * longitudinal polarization FL(D * ) related with the channel B → D * τντ observed by the Belle and the ratio R(J/ψ) measured by the LHCb also show discrepancies with their corresponding SM estimations. In this work, we present a modelindependent study based on the most general effective Lagrangian that yields to a tree-level effective contribution to the transition b → cτντ induced by a general W gauge boson. Instead of considering any specific new physics (NP) realization, we performed an analysis by considering all the different chiral charges to the charm-bottom and τ -ντ interaction terms with a charged W boson that explain the anomalies. We present a phenomenological study of parameter space allowed by the new experimental b → cτντ data and with the mono-tau signature pp → τ h X + MET at the LHC. For comparison, we include some of the W boson NP realizations that have already been studied in the literature.

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“…measured recently by LHCb to be R J/ψ = 0.71 ± 0.17 ± 0.18 [41]. Although the ratio is also measured to be enhanced with respect to the SM prediction R SM J/ψ ≈ 0.25-0.29 [42][43][44][45][46][47][48][49][50][51][52][53][54], the central value of the measurement shows a very large effect that cannot be wellaccommodated with BSM contributions [37]. The observable f D * L , the longitudinal polarisation of the D * in B → D * τ ν, also differs from the SM expectation by ∼ 1.6σ:…”

Section: Charged Current Processesmentioning

confidence: 90%

“…Together these measurements amount to a deviation 3σ [35,37] from SM predictions, which can be significantly reduced in the presence of new physics [36][37][38][39][40].…”

Section: Charged Current Processesmentioning

confidence: 99%

A near-minimal leptoquark model for reconciling flavour anomalies and generating radiative neutrino masses

Bigaran

Gargalionis

Volkas

2019

J. High Energ. Phys.

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We introduce two scalar leptoquarks, the SU(2) L isosinglet denoted φ ∼ (3, 1, −1/3) and the isotriplet ϕ ∼ (3, 3, −1/3), to explain observed deviations from the standard model in semi-leptonic B-meson decays. We explore the regions of parameter space in which this model accommodates the persistent tensions in the decay observables R D ( * ) , R K ( * ) , and angular observables in b → sµµ transitions. Additionally, we exploit the role of these exotics in existing models for one-loop neutrino mass generation derived from ∆L = 2 effective operators. Introducing the vector-like quark χ ∼ (3, 2, −5/6) necessary for lepton-number violation, we consider the contribution of both leptoquarks to the generation of radiative neutrino mass. We find that constraints permit simultaneously accommodating the flavour anomalies while also explaining the relative smallness of neutrino mass without the need for cancellation between leptoquark contributions. A characteristic prediction of our model is a rate of muon-electron conversion in nuclei fixed by the anomalies in b → sµµ and neutrino mass; the COMET experiment will thus test and potentially falsify our scenario. The model also predicts signatures that will be tested at the LHC and Belle II.

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Global fit to b → cτν transitions

Cited by 157 publications

References 139 publications

Effective theory approach to new physics with flavour: general framework and a leptoquark example

Effective theory approach to new physics with flavour: general framework and a leptoquark example

Charged current b→cτν¯τ anomalies in a general W′ boson scenario

A near-minimal leptoquark model for reconciling flavour anomalies and generating radiative neutrino masses

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