The study of $$ \overline{B}\to {D}^{\ast}\tau {\overline{\nu}}_{\tau } $$ angular distribution can be used to obtain information about new physics (or beyond the Standard Model) couplings, which are motivated by various $\textit{B}$ anomalies. However, the inability to measure precisely the three-momentum of the $\textit{τ}$ lepton hinders such measurements, as the tau decay contains one or more undetected neutrinos. Here, we present a measurable angular distribution of $$ \overline{B}\to {D}^{\ast}\tau {\overline{\nu}}_{\tau } $$ by considering the additional decay $$ \tau \to \ell {\nu}_{\tau }{\overline{\nu}}_{\ell } $$ , where $\textit{ℓ}$ ∈ {$\textit{e}$, $\textit{μ}$}. The full process used is $$ \overline{B}\to {D}^{\ast}\left(\to D\pi \right)\tau \left(\to \ell {\nu}_{\tau }{\overline{\nu}}_{\ell}\right){\overline{\nu}}_{\tau } $$ , in which only the $\textit{ℓ}$ and $\textit{D}$ are reconstructed. A fit to the experimental angular distribution of this process can be used to extract information on new physics parameters. To demonstrate the feasibility of this approach, we generate simulated data for this process and perform a sensitivity study to obtain the expected statistical errors on new physics parameters from experiments in the near future. We obtain a sensitivity of the order of 5% for the right-handed current and around 6% for the tensor current. In addition, we use the recent lattice QCD data on $\textit{B}$ → $\textit{D}$ form factors and obtain correlations between form factors and new physics parameters.

United States

Bhubanjyoti Bhattacharya

Thomas Browder

Alakabha Datta

France

Tejhas Kapoor

Emi Kou

China

Lopamudra Mukherjee

New physics searches via angular distributions of $$ \overline{B}\to {D}^{\ast}\left(\to D\pi \right)\tau \left(\to \ell {\nu}_{\tau }{\overline{\nu}}_{\ell}\right){\overline{\nu}}_{\tau } $$ decays

Two categories of four-fermion SMEFT operators are semileptonic (two quarks and two leptons) and hadronic (four quarks). At tree level, an operator of a given category contributes only to processes of the same category. However, when the SMEFT Hamiltonian is evolved down from the new-physics scale to low energies using the renormalization-group equations (RGEs), due to operator mixing this same SMEFT operator can generate operators of the other category at one loop. Thus, to search for a SMEFT explanation of a low-energy anomaly, or combination of anomalies, one must: (i) identify the candidate semileptonic and hadronic SMEFT operators, (ii) run them down to low energy with the RGEs, (iii) generate the required low-energy operators with the correct Wilson coefficients, and (iv) check that all other constraints are satisfied. In this paper, we illustrate this method by finding all SMEFT operators that, by themselves, provide a combined explanation of the (semileptonic)   <math> <mover> <mi>b</mi> <mo>¯</mo> </mover> <mo>→</mo> <mover> <mi>s</mi> <mo>¯</mo> </mover> <msup> <mi>ℓ</mi> <mo>+</mo> </msup> <msup> <mi>ℓ</mi> <mo>−</mo> </msup> </math>  $$ \overline{b}\to \overline{s}{\ell}^{+}{\ell}^{-} $$  anomalies and the (hadronic) B → πK puzzle.

Jacky Kumar

Canada

Suman Kumbhakar

David London

Uniting low-energy semileptonic and hadronic anomalies within SMEFT

In this work, we explore the effect of neutrino nonstandard interactions (NSI) involving the charm quark at SND@LHC. Using an effective description of new physics in terms of four-fermion operators involving a charm quark, we constrain the Wilson coefficients of the effective interaction from two and three-body charmed meson decays. In our fit, we include charmed meson decays not only to pseudoscalar final states but also to vector final states and include decays to the η and η  ′  final states. We also consider constraints from charmed baryon decays. We then study the effect of new physics in neutrino scattering processes, involving charm production at SND@LHC, for various benchmark new physics couplings obtained from the low energy fits. Finally, we also study the effects of lepton universality violation (LUV) assuming that the new physics coupling is not lepton universal.

Italy

Switzerland

Elena Graverini

India

Divya Sachdeva

John Waite

Neutrino nonstandard interactions and lepton flavor universality violation at SND@LHC via charm production

We explain recent LHCb measurements of the lepton universality ratios,  $$R_{D^{(*)}}^{\tau /\ell }\equiv \frac{\mathcal {B}(\bar{B} \rightarrow D^{(*)+} \tau ^- \bar{\nu }_\tau )}{\mathcal {B}(\bar{B} \rightarrow D^{(*)+}\ell ^- \bar{\nu }_\ell )}$$  <math> <mrow> <msubsup> <mi>R</mi> <mrow> <msup> <mi>D</mi> <mrow> <mo>(</mo> <mrow></mrow> <mo>∗</mo> <mo>)</mo> </mrow> </msup> </mrow> <mrow> <mi>τ</mi> <mo>/</mo> <mi>ℓ</mi> </mrow> </msubsup> <mo>≡</mo> <mfrac> <mrow> <mi>B</mi> <mo>(</mo> <mover> <mrow> <mi>B</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> <mo>→</mo> <msup> <mi>D</mi> <mrow> <mo>(</mo> <mrow></mrow> <mo>∗</mo> <mo>)</mo> <mo>+</mo> </mrow> </msup> <msup> <mi>τ</mi> <mo>-</mo> </msup> <msub> <mover> <mrow> <mi>ν</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> <mi>τ</mi> </msub> <mo>)</mo> </mrow> <mrow> <mi>B</mi> <mo>(</mo> <mover> <mrow> <mi>B</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> <mo>→</mo> <msup> <mi>D</mi> <mrow> <mo>(</mo> <mrow></mrow> <mo>∗</mo> <mo>)</mo> <mo>+</mo> </mrow> </msup> <msup> <mi>ℓ</mi> <mo>-</mo> </msup> <msub> <mover> <mrow> <mi>ν</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> <mi>ℓ</mi> </msub> <mo>)</mo> </mrow> </mfrac> </mrow> </math>   and  $${R(\Lambda _c^+)}^{\tau /\ell } \equiv \frac{\mathcal {B}(\Lambda _b \rightarrow \Lambda _c^+ \tau ^- \bar{\nu }_{\tau })}{\mathcal {B}(\Lambda _b \rightarrow \Lambda _c^+ \ell ^- \bar{\nu }_{\ell })}$$  <math> <mrow> <msup> <mrow> <mi>R</mi> <mo>(</mo> <msubsup> <mi>Λ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>)</mo> </mrow> <mrow> <mi>τ</mi> <mo>/</mo> <mi>ℓ</mi> </mrow> </msup> <mo>≡</mo> <mfrac> <mrow> <mi>B</mi> <mo>(</mo> <msub> <mi>Λ</mi> <mi>b</mi> </msub> <mo>→</mo> <msubsup> <mi>Λ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <msup> <mi>τ</mi> <mo>-</mo> </msup> <msub> <mover> <mrow> <mi>ν</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> <mi>τ</mi> </msub> <mo>)</mo> </mrow> <mrow> <mi>B</mi> <mo>(</mo> <msub> <mi>Λ</mi> <mi>b</mi> </msub> <mo>→</mo> <msubsup> <mi>Λ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <msup> <mi>ℓ</mi> <mo>-</mo> </msup> <msub> <mover> <mrow> <mi>ν</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> <mi>ℓ</mi> </msub> <mo>)</mo> </mrow> </mfrac> </mrow> </math>   with  $$\ell =\mu $$  <math> <mrow> <mi>ℓ</mi> <mo>=</mo> <mi>μ</mi> </mrow> </math>  , via new physics that affects  $$R_D^{\tau /\ell }$$  <math> <msubsup> <mi>R</mi> <mi>D</mi> <mrow> <mi>τ</mi> <mo>/</mo> <mi>ℓ</mi> </mrow> </msubsup> </math>   and  $$R(\Lambda _c^+)^{\tau /\ell }$$  <math> <mrow> <mi>R</mi> <msup> <mrow> <mo>(</mo> <msubsup> <mi>Λ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <mo>)</mo> </mrow> <mrow> <mi>τ</mi> <mo>/</mo> <mi>ℓ</mi> </mrow> </msup> </mrow> </math>   but not  $$R_{D^*}^{\tau /\ell }$$  <math> <msubsup> <mi>R</mi> <mrow> <msup> <mi>D</mi> <mo>∗</mo> </msup> </mrow> <mrow> <mi>τ</mi> <mo>/</mo> <mi>ℓ</mi> </mrow> </msubsup> </math>  . The scalar operator in the effective theory for new physics is indicated. We find that the forward-backward asymmetry and  $$\tau $$  <math> <mi>τ</mi> </math>   polarization in  $$\bar{B} \rightarrow D^+ \tau ^{-} \bar{\nu }_{\tau }$$  <math> <mrow> <mover> <mrow> <mi>B</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> <mo>→</mo> <msup> <mi>D</mi> <mo>+</mo> </msup> <msup> <mi>τ</mi> <mo>-</mo> </msup> <msub> <mover> <mrow> <mi>ν</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> <mi>τ</mi> </msub> </mrow> </math>   and  $$\Lambda _b \rightarrow \Lambda _c^+ \tau ^- \bar{\nu }_{\tau }$$  <math> <mrow> <msub> <mi>Λ</mi> <mi>b</mi> </msub> <mo>→</mo> <msubsup> <mi>Λ</mi> <mi>c</mi> <mo>+</mo> </msubsup> <msup> <mi>τ</mi> <mo>-</mo> </msup> <msub> <mover> <mrow> <mi>ν</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> <mi>τ</mi> </msub> </mrow> </math>   decays are significantly affected by the scalar interaction. We construct a simple two Higgs doublet model as a realization of our scenario and consider lepton universality in semileptonic charm and top decays, radiative B decay, B-mixing, and  $$Z \rightarrow b \bar{b}$$  <math> <mrow> <mi>Z</mi> <mo>→</mo> <mi>b</mi> <mover> <mrow> <mi>b</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> </math>  .

Danny Marfatia

Hint of a new scalar interaction in LHCb data?

Belle II has reported the first evidence for <math><msup><mi>B</mi><mo>+</mo></msup><mo>→</mo><msup><mi>K</mi><mo>+</mo></msup><mi>ν</mi><mover><mi>ν</mi><mo>¯</mo></mover></math> with a branching ratio <math><mn>2.7</mn><mi>σ</mi></math> higher than the standard model expectation. We explain this and the MiniBooNE and muon anomalous magnetic moment anomalies in a model with a dark scalar that couples to a slightly heavier sterile Dirac neutrino and that communicates with the visible sector via a Higgs portal. We make predictions for rare kaon and other <math><mi>B</mi></math> meson decays.

<math><mi>B</mi><mo>→</mo><mi>K</mi><mi>ν</mi><mover><mi>ν</mi><mo>¯</mo></mover></math>, MiniBooNE and muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math> anomalies from a dark sector

We study flavor changing neutral current decays of B and K mesons in the dark U(1) D  model, with the dark photon/dark Z mass between 10 MeV and 2 GeV. Although the model provides an improved fit (compared to the standard model) to the differential decay distributions of B → K (∗) ℓ + ℓ −, with ℓ = μ, e, and B  s  → ϕμ + μ  − , the allowed parameter space is ruled out by measurements of atomic parity violation, K + → μ + + invisible decay, and   <math> <msub> <mi>B</mi> <mi>s</mi> </msub> <mo>−</mo> <msub> <mover> <mi>B</mi> <mo>¯</mo> </mover> <mi>s</mi> </msub> </math>  $$ {B}_s-{\overline{B}}_s $$  mixing, among others. To evade constraints from low energy data, we extend the model to allow for (1) additional invisible Z  D  decay, (2) a direct vector coupling of Z  D  to muons, and (3) a direct coupling of Z  D  to both muons and electrons, with the electron coupling fine-tuned to cancel the Z  D  coupling to electrons via mixing. We find that only the latter case survives all constraints.

South Korea

A. Hammad

Ahmed Rashed

Dark photon and dark Z mediated B meson decays

Recent experimental results in <math><mi>B</mi></math> physics from Belle, BABAR, and LHCb suggest new physics (NP) in the weak <math><mi>b</mi><mo>→</mo><mi>c</mi></math> charged-current processes. Here we focus specifically on the decay modes <math><msup><mover><mi>B</mi><mo>¯</mo></mover><mn>0</mn></msup><mo>→</mo><msup><mi>D</mi><mrow><mo>*</mo><mo>+</mo></mrow></msup><msup><mo>ℓ</mo><mo>−</mo></msup><mover><mi>ν</mi><mo>¯</mo></mover></math> with <math><mo>ℓ</mo><mo>=</mo><mi>e</mi></math> and <math><mi>μ</mi></math>. The world averages of the ratios <math><msub><mi>R</mi><mi>D</mi></msub></math> and <math><msubsup><mi>R</mi><mi>D</mi><mo>*</mo></msubsup></math> currently differ from the Standard Model (SM) predictions by <math><mn>3.4</mn><mi>σ</mi></math> while recently a new anomaly has been observed in the forward-backward asymmetry measurement, <math><mrow><msub><mrow><mi>A</mi></mrow><mrow><mi>FB</mi></mrow></msub></mrow></math>, in <math><msup><mover><mi>B</mi><mo>¯</mo></mover><mn>0</mn></msup><mo>→</mo><msup><mi>D</mi><mrow><mo>*</mo><mo>+</mo></mrow></msup><msup><mi>μ</mi><mo>−</mo></msup><mover><mi>ν</mi><mo>¯</mo></mover></math> decay. It is found that <math><mrow><mi>Δ</mi><msub><mrow><mi>A</mi></mrow><mrow><mi>FB</mi></mrow></msub><mo>=</mo><msub><mrow><mi>A</mi></mrow><mrow><mi>FB</mi></mrow></msub><mo>(</mo><mi>B</mi><mo>→</mo><msup><mrow><mi>D</mi></mrow><mrow><mo>*</mo></mrow></msup><mi>μ</mi><mi>ν</mi><mo>)</mo><mo>−</mo><msub><mrow><mi>A</mi></mrow><mrow><mi>FB</mi></mrow></msub><mo>(</mo><mi>B</mi><mo>→</mo><msup><mrow><mi>D</mi></mrow><mrow><mo>*</mo></mrow></msup><mi>e</mi><mi>ν</mi><mo>)</mo></mrow></math> is around <math><mn>4.1</mn><mi>σ</mi></math> away from the SM prediction in an analysis of 2019 Belle data. In this work we explore possible solutions to the <math><mrow><mi>Δ</mi><msub><mrow><mi>A</mi></mrow><mrow><mi>FB</mi></mrow></msub></mrow></math> anomaly and point out correlated NP signals in other angular observables. These correlations between angular observables must be present in the case of beyond the Standard Model physics. We stress the importance of <math><mi>Δ</mi></math> type observables that are obtained by taking the difference of the observable for the muon and the electron mode. These quantities cancel form-factor uncertainties in the SM and allow for clean tests of NP. These intriguing results also suggest an urgent need for improved simulation and analysis techniques in <math><msup><mover><mi>B</mi><mo>¯</mo></mover><mn>0</mn></msup><mo>→</mo><msup><mi>D</mi><mrow><mo>*</mo><mo>+</mo></mrow></msup><msup><mo>ℓ</mo><mo>−</mo></msup><mover><mi>ν</mi><mo>¯</mo></mover></math> decays. Here we also describe a new Monte Carlo event generator tool based on EVTGEN that we developed to allow simulation of the NP signatures in <math><msup><mover><mi>B</mi><mo>¯</mo></mover><mn>0</mn></msup><mo>→</mo><msup><mi>D</mi><mrow><mo>*</mo><mo>+</mo></mrow></msup><msup><mo>ℓ</mo><mo>−</mo></msup><mi>ν</mi></math>, which arise due to the interference between the SM and NP amplitudes. We then discuss prospects for improved observables sensitive to NP couplings with 1, 5, 50, and <math><mrow><mn>250</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>ab</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math> of Belle II data, which seem to be ideally suited for this class of measurements.

Thomas E. Browder

Quinn Campagna

Shawn Dubey

Alexei Sibidanov

Implications for the <math><mi>Δ</mi><msub><mi>A</mi><mrow><mi>F</mi><mi>B</mi></mrow></msub></math> anomaly in <math><msup><mover><mi>B</mi><mo>¯</mo></mover><mn>0</mn></msup><mo>→</mo><msup><mi>D</mi><mrow><mo>*</mo><mo>+</mo></mrow></msup><msup><mo>ℓ</mo><mo>−</mo></msup><mover><mi>ν</mi><mo>¯</mo></mover></math> using a new Monte Carlo event generator

We calculate the complete differential decay distributions for the <math><mi>B</mi></math> meson decays, <math><mrow><mover><mrow><mi>B</mi></mrow><mrow><mo>¯</mo></mrow></mover><mo>→</mo><msup><mrow><mi>D</mi></mrow><mrow><mo>(</mo><mo>*</mo><mo>)</mo></mrow></msup><mo>ℓ</mo><mover><mrow><mi>X</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math>, to a massive right-handed (RH) neutrino in the low-energy effective field theory (LEFT) framework. We find that a massive RH neutrino does not introduce any new angular structures compared to the massless case, but can cause significant distortions in angular observables. We study the phenomenology of low-energy four-fermion operators permitted by the standard model effective field theory (SMEFT) extended with RH neutrinos (SMNEFT). We show that to explain the positive value of the difference in forward-backward asymmetries, <math><mrow><mi>Δ</mi><msub><mrow><mi>A</mi></mrow><mrow><mi>FB</mi></mrow></msub><mo>≡</mo><msubsup><mrow><mi>A</mi></mrow><mrow><mi>FB</mi></mrow><mrow><mi>μ</mi></mrow></msubsup><mo>−</mo><msubsup><mrow><mi>A</mi></mrow><mrow><mi>FB</mi></mrow><mrow><mi>e</mi></mrow></msubsup></mrow></math>, tentatively inferred from Belle data, the RH neutrino must be massive. We also make predictions for <math><msup><mi>q</mi><mn>2</mn></msup></math> dependent angular observables to motivate future measurements.

Israel

Hongkai Liu

<math><mrow><mover><mrow><mi>B</mi></mrow><mrow><mo>¯</mo></mrow></mover><mo>→</mo><msup><mrow><mi>D</mi></mrow><mrow><mo>(</mo><mo>*</mo><mo>)</mo></mrow></msup><mo>ℓ</mo><mover><mrow><mi>X</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math> decays in effective field theory with massive right-handed neutrinos

Model-independent description of nonleptonic decays of charmed mesons is a challenging task due to large nonperturbative effects of strong interactions on the transition amplitudes. We discuss the equivalence of two different flavor-SU(3)-based descriptions of Cabibbo-favored non-leptonic decays of charmed mesons to two-pseudoscalars final states including the η and η′ mesons.

Alexey Petrov

Flavor SU(3) in Cabibbo-favored D-meson decays

We offer a new solution to an old puzzle in the penguin-dominated <math><mi>B</mi><mo>→</mo><mi>π</mi><mi>K</mi></math> decays. The puzzle is the inconsistency among the measurements of the branching ratios and <math><mi>C</mi><mi>P</mi></math> asymmetries of the four <math><mrow><mi>B</mi><mo>→</mo><mi>π</mi><mi>K</mi></mrow></math> decays: <math><mrow><msup><mrow><mi>B</mi></mrow><mrow><mo>+</mo></mrow></msup><mo>→</mo><msup><mrow><mi>π</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mn>0</mn></mrow></msup></mrow></math>, <math><mrow><msup><mrow><mi>B</mi></mrow><mrow><mo>+</mo></mrow></msup><mo>→</mo><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>+</mo></mrow></msup></mrow></math>, <math><mrow><msubsup><mrow><mi>B</mi></mrow><mrow><mi>d</mi></mrow><mrow><mn>0</mn></mrow></msubsup><mo>→</mo><msup><mrow><mi>π</mi></mrow><mrow><mo>−</mo></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>+</mo></mrow></msup></mrow></math>, <math><msubsup><mi>B</mi><mi>d</mi><mn>0</mn></msubsup><mo>→</mo><msup><mi>π</mi><mn>0</mn></msup><msup><mi>K</mi><mn>0</mn></msup></math>. We solve the <math><mi>B</mi><mo>→</mo><mi>π</mi><mi>K</mi></math> puzzle by considering the effect of an axionlike particle (ALP) that mixes with the <math><msup><mi>π</mi><mn>0</mn></msup></math> and has mass close to the <math><msup><mi>π</mi><mn>0</mn></msup></math> mass. We show that the ALP can also explain the anomalies in the electron and muon anomalous magnetic moments.

Soumitra Nandi

Axionlike particles resolve the <math><mrow><mi>B</mi><mo>→</mo><mi>π</mi><mi>K</mi></mrow></math> and <math><mi>g</mi><mo>−</mo><mn>2</mn></math> anomalies