On lepton flavor universality in top quark decays

Kamenik, Jernej F.; Katz, Andrey; Stolarski, Daniel

doi:10.1007/jhep01(2019)032

Cited by 12 publications

(11 citation statements)

References 49 publications

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“…Search strategies in this region could include requiring a b tag in the final jets [36]. Some sensitivity is expected also in the top quark decays [108].…”

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confidence: 99%

Mono- τ Signatures at the LHC Constrain Explanations of B -decay Anomalies

2019

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We investigate the crossing-symmetry relation between b → cτ −ν decay and bc → τ −ν scattering to derive direct correlations of new physics in semitauonic B-meson decays and the mono-tau signature at the LHC (pp → τ h X þ MET). Using an exhaustive set of effective operators and heavy mediators we find that the current ATLAS and CMS data constrain scenarios addressing anomalies in B decays. Pure tensor solutions, completed by leptoquark, and right-handed solutions, completed by W 0 R or leptoquark, are challenged by our analysis. Furthermore, the sensitivity that will be achieved in the high-luminosity phase of the LHC will probe all the possible scenarios that explain the anomalies. Finally, we note that the LHC is also competitive in the b → u transitions and bounds in some cases are currently better than those from B decays.Introduction.-Branching fractions of semitauonic Bmeson decays, measured through the ratios R D ðÃÞ ¼ ΓðB → D ðÃÞ τνÞ=ΓðB → D ðÃÞ lνÞ (with l ¼ e or μ), appear to be enhanced with respect to the standard model (SM) by roughly thirty percent, with a global significance of ∼4σ [1][2][3][4][5][6][7][8][9][10][11]. If this is due to new physics (NP), its mass scale is expected to be not far above the TeV scale (see, e.g., [12]). The most immediate question is whether such NP is already ruled out by the existing high-p T searches and, if not, what the road map is for its direct discovery.From a bottom-up perspective the NP interpretation of the R D ðÃÞ anomalies involves two different aspects, (i) new dynamics (i.e., degrees of freedom), and (ii) the flavor structure. Both aspects are relevant when it comes to identifying correlated effects in other observables such as weak hadron or τ decays, electroweak precision observables, and high-p T LHC signatures (see, e.g., [13]).The Lorentz structure of the effective operators that describe the effects of the hypothesized heavy mediators at low energies can be discriminated by using b → cτν decay data alone [14][15][16][17][18][19][20][21][22][23][24]. On the other hand, most flavor data are consistent with the SM, which suggests that such NP must couple mainly to the third generation of quarks and leptons [13,[25][26][27][28][29][30][31][32]. However, in general, and without the guidance of a theory of flavor, models addressing the anomalies have some freedom in the way they implement couplings in

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“…Search strategies in this region could include requiring a b tag in the final jets [36]. Some sensitivity is expected also in the top quark decays [108].…”

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confidence: 99%

Mono- τ Signatures at the LHC Constrain Explanations of B -decay Anomalies

2019

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“…Flavor at low and high p T Jernej. F. Kamenik approximately 10% precision [35], which is sufficient to already constrain NP models addressing R(D ( * ) ) through light (m NP < m t − m b ) mediators [36]. More interestingly, in the future, measurements exploiting the different kinematics of the SM and NP contributions to t → bτν, by measuring the differential LFU ratio as a function of the b-jet energy, could potentially probe LFU in top decays down to sub-percent level.…”

Section: Pos(beauty2019)046mentioning

confidence: 99%

Flavor at low and high $p_T$

Kamenik¹

2020

Proceedings of 18th International Conference on B-Physics at Frontier Machines — PoS(Beauty2019)

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“…In this study, we will therefore focus on new physics that can contribute to this process, and thus couples to top quarks as well as first or second generation leptons. We will ignore new physics JHEP08(2020)036 coupling to τ , but see [36] for a recent work. The impact of contact interactions involving two leptons (electrons or muons) and two b-quarks in di-lepton final state was also recently studied in [37].…”

Section: Jhep08(2020)036mentioning

confidence: 99%

“…If there is new physics of this type, UV considerations as well as strong bounds from µ → eγ indicate that it generically couples dominantly to a single flavour of lepton. Therefore, inspired by [65] and [36], we also consider ratios of measurements in the electron vs. muon channel. These ratios have partial cancellation of systematic errors and place significantly stronger constraints if new physics couples dominantly to one flavour of lepton.…”

Section: Jhep08(2020)036mentioning

confidence: 99%

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Constraining new physics with single top production at LHC

Stolarski

Tonero

2020

J. High Energ. Phys.

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We study effects of beyond the Standard Model physics coupling third generation quarks to leptons of the first two generations. We parametrize these effects by dimension-six effective operators, and we also consider related simplified UV completions: scalar leptoquark and W models. We derive new constraints on these scenarios by using recent ATLAS measurements of differential cross sections of single top production in association with a W boson, and also show how these limits will evolve with future data. We also describe how the limits can be significantly improved by using ratios of differential distributions with different flavours of leptons.

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On lepton flavor universality in top quark decays

Cited by 12 publications

References 49 publications

Mono- τ Signatures at the LHC Constrain Explanations of B -decay Anomalies

Mono- τ Signatures at the LHC Constrain Explanations of B -decay Anomalies

Flavor at low and high $p_T$

Constraining new physics with single top production at LHC

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