<p>The neutrino research program in the coming decades will require improved precision. A major source of uncertainty is the interaction of neutrinos with nuclei that serve as targets for such experiments. Broadly speaking, this interaction often depends, e.g., for charge-current quasielastic scattering, on the combination of “nucleon physics,” expressed by form factors, and “nuclear physics,” expressed by a nuclear model. It is important to get a good handle on both. We present a fully analytic implementation of the correlated Fermi gas model for electron-nucleus and charge-current quasielastic neutrino-nucleus scattering. The implementation is used to compare separately form factors and nuclear model effects for both electron-carbon and neutrino-carbon scattering data.</p>

United States

Bhubanjyoti Bhattacharya

Sam Carey

Israel

Erez O. Cohen

Gil Paz

Quasielastic lepton-nucleus scattering and the correlated Fermi gas model

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.

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

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

In this Letter, we perform fits to <math><mrow><mi>B</mi><mo>→</mo><mi>P</mi><mi>P</mi></mrow></math> decays, where <math><mrow><mi>B</mi><mo>=</mo><mo>{</mo><msup><mrow><mi>B</mi></mrow><mrow><mn>0</mn></mrow></msup><mo>,</mo><msup><mrow><mi>B</mi></mrow><mrow><mo>+</mo></mrow></msup><mo>,</mo><msubsup><mrow><mi>B</mi></mrow><mrow><mi>s</mi></mrow><mrow><mn>0</mn></mrow></msubsup><mo>}</mo></mrow></math> and the pseudoscalar <math><mi>P</mi><mo>=</mo><mo>{</mo><mi>π</mi><mo>,</mo><mi>K</mi><mo>}</mo></math>, under the assumption of flavor SU(3) symmetry [<math><mrow><msub><mrow><mi>SU</mi><mo>(</mo><mn>3</mn><mo>)</mo></mrow><mrow><mi>F</mi></mrow></msub></mrow></math>]. Although the fits to <math><mi>Δ</mi><mi>S</mi><mo>=</mo><mn>0</mn></math> or <math><mi>Δ</mi><mi>S</mi><mo>=</mo><mn>1</mn></math> decays individually are good, the combined fit is very poor: there is a <math><mn>3.6</mn><mi>σ</mi></math> disagreement with the <math><mrow><msub><mrow><mi>SU</mi><mo>(</mo><mn>3</mn><mo>)</mo></mrow><mi>F</mi></msub></mrow></math> limit of the standard model (<math><mrow><msub><mrow><mi>SM</mi></mrow><mrow><msub><mrow><mi>SU</mi><mo>(</mo><mn>3</mn><mo>)</mo></mrow><mrow><mi>F</mi></mrow></msub></mrow></msub></mrow></math>). One can remove this discrepancy by adding <math><mrow><msub><mrow><mi>SU</mi><mo>(</mo><mn>3</mn><mo>)</mo></mrow><mi>F</mi></msub></mrow></math>-breaking effects, but 1000% <math><mrow><msub><mrow><mi>SU</mi><mo>(</mo><mn>3</mn><mo>)</mo></mrow><mi>F</mi></msub></mrow></math> breaking is required. The above results are rigorous, group theoretically—no dynamical assumptions have been made. When one adds an assumption motivated by QCD factorization, the discrepancy with the <math><mrow><msub><mrow><mi>SM</mi></mrow><mrow><msub><mrow><mi>SU</mi><mo>(</mo><mn>3</mn><mo>)</mo></mrow><mrow><mi>F</mi></mrow></msub></mrow></msub></mrow></math> grows to <math><mn>4.4</mn><mi>σ</mi></math>.

Canada

Raphaël Berthiaume

Rida Boumris

Alexandre Jean

Suman Kumbhakar

David London

Anomalies in Hadronic <math><mi>B</mi></math> Decays

Under flavor <math><mi>S</mi><mi>U</mi><mo>(</mo><mn>3</mn><mo>)</mo></math> symmetry (<math><mrow><msub><mrow><mi>SU</mi><mo>(</mo><mn>3</mn><mo>)</mo></mrow><mi>F</mi></msub></mrow></math>), the final-state particles in <math><mi>B</mi><mo>→</mo><mi>P</mi><mi>P</mi><mi>P</mi></math> decays (<math><mi>P</mi></math> is a pseudoscalar meson) are treated as identical, and the <math><mi>P</mi><mi>P</mi><mi>P</mi></math> must be in a fully-symmetric (FS) state, a fully-antisymmetric (FA) state, or in one of four mixed states. In this paper, we present the formalism for the FA states. We write the amplitudes for the <math><mrow><mn>22</mn><mi>B</mi><mo>→</mo><mi>P</mi><mi>P</mi><mi>P</mi></mrow></math> decays that can be in an FA state in terms of both the <math><mrow><msub><mrow><mi>SU</mi><mo>(</mo><mn>3</mn><mo>)</mo></mrow><mi>F</mi></msub></mrow></math> reduced matrix elements and diagrams. This shows the equivalence of diagrams and <math><mrow><msub><mrow><mi>SU</mi><mo>(</mo><mn>3</mn><mo>)</mo></mrow><mi>F</mi></msub></mrow></math>. We also give 15 relations among the amplitudes in the <math><mrow><msub><mrow><mi>SU</mi><mo>(</mo><mn>3</mn><mo>)</mo></mrow><mi>F</mi></msub></mrow></math> limit as well as the additional four that appear when the diagrams <math><mi>E</mi><mo>/</mo><mi>A</mi><mo>/</mo><mi>P</mi><mi>A</mi></math> are neglected. We present sets of <math><mi>B</mi><mo>→</mo><mi>P</mi><mi>P</mi><mi>P</mi></math> decays that can be used to extract <math><mi>γ</mi></math> using the FA amplitudes. The value(s) of <math><mi>γ</mi></math> found in this way can be compared with the value(s) found using the FS states.

Mirjam Fines-Neuschild

Andrea Houck

Maxime Imbeault

Charmless <math><mi>B</mi><mo>→</mo><mi>P</mi><mi>P</mi><mi>P</mi></math> decays: The fully antisymmetric final state

We impose <math><mi>U</mi></math>-spin symmetry [<math><mi>S</mi><mi>U</mi><mo>(</mo><mn>2</mn><msub><mo>)</mo><mtext>Uspin</mtext></msub></math>] on the Hamiltonian for <math><mi>B</mi></math> decays. As expected, we find the equality of amplitudes related by the exchange <math><mi>d</mi><mo>↔</mo><mi>s</mi></math>. We also find that the amplitudes for the <math><mi>Δ</mi><mi>S</mi><mo>=</mo><mn>0</mn></math> processes <math><msup><mi>B</mi><mn>0</mn></msup><mo>→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup></math>, <math><msubsup><mi>B</mi><mi>s</mi><mn>0</mn></msubsup><mo>→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>K</mi><mo>−</mo></msup></math>, and <math><msup><mi>B</mi><mn>0</mn></msup><mo>→</mo><msup><mi>K</mi><mo>+</mo></msup><msup><mi>K</mi><mo>−</mo></msup></math> form a <math><mi>U</mi></math>-spin triangle relation. The amplitudes for <math><msubsup><mi>B</mi><mi>s</mi><mn>0</mn></msubsup><mo>→</mo><msup><mi>K</mi><mo>+</mo></msup><msup><mi>K</mi><mo>−</mo></msup></math>, <math><msup><mi>B</mi><mn>0</mn></msup><mo>→</mo><msup><mi>π</mi><mo>−</mo></msup><msup><mi>K</mi><mo>+</mo></msup></math>, and <math><msubsup><mi>B</mi><mi>s</mi><mn>0</mn></msubsup><mo>→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup></math> form a similar <math><mi>Δ</mi><mi>S</mi><mo>=</mo><mn>1</mn></math> triangle relation. And these two triangles are related to one another by <math><mi>d</mi><mo>↔</mo><mi>s</mi></math>. We perform fits to the observables for these six decays. If perfect <math><mi>U</mi></math> spin is assumed, then the fit is very poor. If <math><mi>U</mi></math>-spin-breaking contributions are added, then we find many scenarios that can explain the data. However, in all cases, 100% <math><mi>U</mi></math>-spin breaking is required, considerably larger than the naive expectation of <math><mo>∼</mo><mn>20</mn><mo>%</mo></math>. This is the <math><mi>U</mi></math>-spin puzzle; it may be strongly hinting at the presence of new physics.

Nicolas Payot

<math><mi>U</mi></math>-spin puzzle in <math><mi>B</mi></math> 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

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.

Danny Marfatia

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

At present, the measurements of   <math> <msub> <mi>R</mi> <msup> <mi>D</mi> <mfenced> <mo>∗</mo> </mfenced> </msup> </msub> </math>  $$ {R}_{D^{\left(\ast \right)}} $$  and R  J/ψ  hint at new physics (NP) in   <math> <mi>b</mi> <mo>→</mo> <mi>c</mi> <msup> <mi>τ</mi> <mo>−</mo> </msup> <mover> <mi>v</mi> <mo>¯</mo> </mover> </math>  $$ b\to c{\tau}^{-}\overline{v} $$  decays. The angular distribution of   <math> <mover> <mi>B</mi> <mo>¯</mo> </mover> <mo>→</mo> <msup> <mi>D</mi> <mo>∗</mo> </msup> <mfenced> <mrow> <mo>→</mo> <mi>Dπ</mi> </mrow> </mfenced> <msup> <mi>τ</mi> <mo>−</mo> </msup> <msub> <mover> <mi>v</mi> <mo>¯</mo> </mover> <mi>τ</mi> </msub> </math>  $$ \overline{B}\to {D}^{\ast}\left(\to D\pi \right){\tau}^{-}{\overline{v}}_{\tau } $$  would be useful for getting information about the NP, but it cannot be measured. The reason is that the three-momentum   <math> <msub> <mover> <mi>p</mi> <mo>→</mo> </mover> <mi>τ</mi> </msub> </math>  $$ {\overrightarrow{p}}_{\tau } $$  cannot be determined precisely since the decay products of the τ  −  include an undetected ν  τ . In this paper, we construct a measurable angular distribution by considering the additional decay τ  −  → π  −  ν  τ . The full process is   <math> <mover> <mi>B</mi> <mo>¯</mo> </mover> <mo>→</mo> <msup> <mi>D</mi> <mo>∗</mo> </msup> <mfenced> <mrow> <mo>→</mo> <mi>D</mi> <msup> <mi>π</mi> <mo>′</mo> </msup> </mrow> </mfenced> <msup> <mi>τ</mi> <mo>−</mo> </msup> <mfenced> <mrow> <mo>→</mo> <msup> <mi>π</mi> <mo>−</mo> </msup> <msub> <mi>v</mi> <mi>τ</mi> </msub> </mrow> </mfenced> <msub> <mover> <mi>v</mi> <mo>¯</mo> </mover> <mi>τ</mi> </msub> </math>  $$ \overline{B}\to {D}^{\ast}\left(\to D{\pi}^{\prime}\right){\tau}^{-}\left(\to {\pi}^{-}{v}_{\tau}\right){\overline{v}}_{\tau } $$ , which includes three final-state particles whose three-momenta can be measured: D, π ′, π −. The magnitudes and relative phases of all the NP parameters can be extracted from a fit to this angular distribution. One can measure CP-violating angular asymmetries. If one integrates over some of the five kinematic parameters parametrizing the angular distribution, one obtains (i) familiar observables such as the q 2 distribution and the D ∗ polarization, and (ii) new observables associated with the π  −  emitted in the τ decay: the forward-backward asymmetry of the π  −  and the CP-violating triple-product asymmetry.

Saeed Kamali

A measurable angular distribution for   <math> <mover> <mi>B</mi> <mo>¯</mo> </mover> <mo>→</mo> <msup> <mi>D</mi> <mo>∗</mo> </msup> <msup> <mi>τ</mi> <mo>−</mo> </msup> <msub> <mover> <mi>v</mi> <mo>¯</mo> </mover> <mi>τ</mi> </msub> </math>  $$ \overline{B}\to {D}^{\ast }{\tau}^{-}{\overline{v}}_{\tau } $$  decays