New physics effects in leptonic and semileptonic decays

Bečirević, Damir; Jaffredo, Florentin; Peñuelas, Ana Belén Cabrejas; Sumensari, Olcyr

doi:10.1007/jhep05(2021)175

“…However, the decay modes B → πτ ν τ and B → ρτ ν τ could be sensitive to new fundamental interactions beyond the SM (BSM) due to a relatively large mass of τ . As a reference one could look at some eralier studies on these channels [5][6][7][8][9]. On a similar note the observables associated with the purely leptonic decay B → τ ν τ could also be sensitive to new interactions.…”

Section: Introductionmentioning

confidence: 99%

A closer look at observables from exclusive semileptonic B → (π, ρ)ℓνℓ decays

Biswas

¹

,

Nandi

²

2021

J. High Energ. Phys.

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This article analyses the available inputs in B → πℓνℓ and B → ρℓνℓ decays which include the measured values of differential rate in different q2-bins (lepton invariant mass spectrum), lattice, and the newly available inputs on the relevant form-factors from the light-cone sum rules (LCSR) approach. We define different fit scenarios, and in each of these scenarios, we predict a few observables in the standard model (SM). For example, $$ R(M)=\frac{\mathcal{B}\left(B\to M{\ell}_i{\nu}_{\ell_i}\right)}{\mathcal{B}\left(B\to M{\ell}_j{\nu}_{\ell_j}\right)},{R}_{\ell_j}^{\ell_i}(M)=\frac{\mathcal{B}\left(B\to {\ell}_i{\nu}_{\ell_i}\right)}{\mathcal{B}\left(B\to M{\ell}_j{\nu}_{\ell_j}\right)} $$ R M = B B → M ℓ i ν ℓ i B B → M ℓ j ν ℓ j , R ℓ j ℓ i M = B B → ℓ i ν ℓ i B B → M ℓ j ν ℓ j with M = π or ρ and ℓi,j = e, μ or τ. We also discuss the new physics (NP) sensitivities of all these observables and obtain bounds on a few NP Wilson coefficients in b → uτντ decays using the available data. We have noted that the data at present allows sizeable NP contributions in this mode. Also, we have predicted a few angular observables relevant to these decay modes.

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“…ref. [90] for a recent such analysis. We derive these limits by comparing the theoretically predicted event rates with the new physics corrections discussed in section 2 to the experimentally observed ones.…”

Section: Jhep10(2021)086mentioning

confidence: 99%

EFT at FASERν

Falkowski

¹

,

González–Alonso

²

,

Kopp

³

et al. 2021

J. High Energ. Phys.

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We investigate the sensitivity of the FASERν detector to new physics in the form of non-standard neutrino interactions. FASERν, which will be installed 480 m downstream of the ATLAS interaction point, will for the first time study interactions of multi-TeV neutrinos from a controlled source. Our formalism — which is applicable to any current and future neutrino experiment — is based on the Standard Model Effective Theory (SMEFT) and its counterpart, Weak Effective Field Theory (WEFT), below the electroweak scale. Starting from the WEFT Lagrangian, we compute the coefficients that modify neutrino production in meson decays and detection via deep-inelastic scattering, and we express the new physics effects in terms of modified flavor transition probabilities. For some coupling structures, we find that FASERν will be able to constrain interactions that are two to three orders of magnitude weaker than Standard Model weak interactions, implying that the experiment will be indirectly probing new physics at the multi-TeV scale. In some cases, FASERν constraints will become comparable to existing limits — some of them derived for the first time in this paper — already with 150 fb−1 of data.

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“…The ratio R J/ψ has been recently measured by the LHCb collaboration [19] and it shows a 1.8 σ discrepancy with SM results, which are in the range R SM J/ψ ∼ 0.25 − 0.28 [20][21][22][23][24][25][26][27][28][29][30][31][32].B c decays induced by the c → s, d transition at the quark level are also being investigated as a possible source of information on NP [33], taking advantage of the recent results of ref. [34]. In this latter work, the possibilities of extracting constraints on NP by using the current data on the leptonic and semileptonic decays of pseudoscalar mesons, not only driven by the b → c transition, have been exhaustively discussed.…”

Section: Jhep06(2021)118mentioning

confidence: 99%

New physics and the tau polarization vector in b → $$ \mathrm{c}\tau {\overline{\nu}}_{\tau } $$ decays

Penalva

¹

,

Hernández

²

,

Nieves

³

2021

J. High Energ. Phys.

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For a general Hb → $$ {H}_c\tau {\overline{\nu}}_{\tau } $$ H c τ ν ¯ τ decay we analyze the role of the τ polarization vector $$ {\mathcal{P}}^{\mu } $$ P μ in the context of lepton flavor universality violation studies. We use a general phenomenological approach that includes, in addition to the Standard Model (SM) contribution, vector, axial, scalar, pseudoscalar and tensor new physics (NP) terms which strength is governed by, complex in general, Wilson coefficients. We show that both in the laboratory frame, where the initial hadron is at rest, and in the center of mass of the two final leptons, a $$ \overrightarrow{\mathcal{P}} $$ P → component perpendicular to the plane defined by the three-momenta of the final hadron and the τ lepton is only possible for complex Wilson coefficients, being a clear signal for physics beyond the SM as well as time reversal (or CP-symmetry) violation. We make specific evaluations of the different polarization vector components for the Λb → Λc, $$ {\overline{B}}_c $$ B ¯ c → ηc, J/ψ and $$ \overline{B} $$ B ¯ → D(*) semileptonic decays, and describe NP effects in the complete two-dimensional space associated with the independent kinematic variables on which the polarization vector depends. We find that the detailed study of $$ {\mathcal{P}}^{\mu } $$ P μ has great potential to discriminate between different NP scenarios for 0− → 0− decays, but also for Λb → Λc transitions. For this latter reaction, we pay special attention to corrections to the SM predictions derived from complex Wilson coefficients contributions.

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New physics effects in leptonic and semileptonic decays

Cited by 35 publications

References 94 publications

A closer look at observables from exclusive semileptonic B → (π, ρ)ℓνℓ decays

A closer look at observables from exclusive semileptonic B → (π, ρ)ℓνℓ decays

EFT at FASERν

New physics and the tau polarization vector in b → $$ \mathrm{c}\tau {\overline{\nu}}_{\tau } $$ decays

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