<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>B</mml:mi></mml:mrow><mml:mrow><mml:mi>c</mml:mi></mml:mrow></mml:msub><mml:mo stretchy="false">→</mml:mo><mml:mi>J</mml:mi><mml:mo stretchy="false">/</mml:mo><mml:mi>ψ</mml:mi></mml:mrow></mml:math>
 form factors for the full 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>q</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:math>
 range from lattice QCD

We investigate the viability of extending the Standard Model with S1 and S3 scalar leptoquarks when the flavour structure is parametrized in terms of Froggatt-Nielsen charges. In contrast to a similar analysis with a vector leptoquark, we find essentially two solutions for the charges that fit the experimental constraints, which are dominated by the current tensions in B decays. These two scenarios differ in their estimate of the anomalous magnetic moment of the muon, (g − 2), but they both predict sizeable contributions to τ → μγ, $$ {\overline{B}}_s $$ B ¯ s → τ±μ∓ and B+→ K+τ+μ− decays, whose branching ratios are close to the current experimental limits.

show abstract

“…For our estimate we use the lattice determination of the form factors in ref. [58] and the predictions in ref. [57].…”

Section: Charged Currents Regarding R D ( * ) We Findsupporting

confidence: 63%

Constraining flavour patterns of scalar leptoquarks in the effective field theory

Bordone

Catà

Feldmann

et al. 2021

J. High Energ. Phys.

View full text Add to dashboard Cite

show abstract

“…For theB c → η c , J/ψ transitions, there exist no systematic LQCD calculations, except for the very recent work of the HPQCD collaboration [85] where the SM vector and axial form factors of theB c → J/ψ decay have been determined. Here we use the form factors obtained within the non-relativistic quark model scheme of ref.…”

Section: Jhep06(2021)118mentioning

confidence: 99%

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

Penalva

Hernández

Nieves

2021

J. High Energ. Phys.

View full text Add to dashboard Cite

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.

show abstract

“…The only exceptions to that pattern are the decays D s → φ ν and B c → J/ψ ν which have been studied on the lattice in ref. [4] and [5], respectively.…”

Section: Jhep05(2021)175mentioning

confidence: 99%

“…For the B c → J/ψ transition, the relevant form factors at nonzero recoil have been recently computed by means of LQCD simulations in ref. [5], which allows us to predict the corresponding LFU ratio R (τ /µ) BcJ/ψ , with O(1%) precision [81], see also ref. [82].…”

Section: → πLν and |V CD |mentioning

confidence: 99%

See 1 more Smart Citation

New physics effects in leptonic and semileptonic decays

Bečirević

Jaffredo

Peñuelas

et al. 2021

J. High Energ. Phys.

View full text Add to dashboard Cite

We discuss the possibilities of extracting the constraints on New Physics by using the current data on the leptonic and semileptonic decays of pseudoscalar mesons. In doing so we use a general low energy Lagrangian that besides the vector and axial operators also includes the (pseudo-)scalar and tensor ones. In obtaining constraints on New Physics couplings, we combine the experimental information concerning several decay modes with the accurate and precise lattice QCD results for the hadronic matrix elements. We propose to study new observables that can be extracted from the angular analysis of the semileptonic decays and discuss their values both in the Standard Model and in some specific scenarios of physics beyond the Standard Model.

show abstract

Bc→J/ψ form factors for the full q2 range from lattice QCD

Cited by 49 publications

References 57 publications

Constraining flavour patterns of scalar leptoquarks in the effective field theory

Constraining flavour patterns of scalar leptoquarks in the effective field theory

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

New physics effects in leptonic and semileptonic decays

Contact Info

Product

Resources

About