# Maximizing the impact of new physics in $b\to c\tau \nu $ anomalies

## Abstract

Here, we develop a rigorous, semianalytical method for maximizing any $$\mathcal{b → cτν}$$ observable in the full 20-real-dimensional parameter space of the dimension 6 effective Hamiltonian, given some fixed values of $$R_{D^{(*)}}$$. We apply our method to find the maximum allowed values of $$F^L_{D^\ast}$$ and $$R_{J/ψ}$$, two observables which have both come out higher than their Standard Model predictions in recent measurements by the Belle and LHCb Collaborations. While the measurements still have large error bars, they add to the existing $$R_{D^{(*)}}$$ anomaly, and it is worthwhile to consider new physics explanations. It has been shown that none of the existing, minimal models in the literature can explain the observed values of $$F^L_{D^\ast}$$ and $$R_{J/ψ}$$. Using our method, we will generalize beyond the minimal models and show that there is no combination of dimension 6 Wilson operators that can come within 1σ of the observed $$R_{J/ψ}$$ value. By contrast, we will show that the observed value of $$F^L_{D\ast}$$ can be achieved, but only with sizable contributions from tensor and mixed-chirality vector Wilson coefficients.

- Authors:

- Publication Date:

- Research Org.:
- Rutgers Univ., Piscataway, NJ (United States)

- Sponsoring Org.:
- USDOE Office of Science (SC)

- OSTI Identifier:
- 1577394

- Alternate Identifier(s):
- OSTI ID: 1802020

- Grant/Contract Number:
- DOE-SC0010008; SC0010008

- Resource Type:
- Published Article

- Journal Name:
- Physical Review D

- Additional Journal Information:
- Journal Name: Physical Review D Journal Volume: 100 Journal Issue: 11; Journal ID: ISSN 2470-0010

- Publisher:
- American Physical Society

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Astronomy & Astrophysics; Physics

## Citation Formats

```
Asadi, Pouya, and Shih, David. Maximizing the impact of new physics in b → c τ ν anomalies. United States: N. p., 2019.
Web. doi:10.1103/PhysRevD.100.115013.
```

```
Asadi, Pouya, & Shih, David. Maximizing the impact of new physics in b → c τ ν anomalies. United States. https://doi.org/10.1103/PhysRevD.100.115013
```

```
Asadi, Pouya, and Shih, David. Fri .
"Maximizing the impact of new physics in b → c τ ν anomalies". United States. https://doi.org/10.1103/PhysRevD.100.115013.
```

```
@article{osti_1577394,
```

title = {Maximizing the impact of new physics in b → c τ ν anomalies},

author = {Asadi, Pouya and Shih, David},

abstractNote = {Here, we develop a rigorous, semianalytical method for maximizing any $\mathcal{b → cτν}$ observable in the full 20-real-dimensional parameter space of the dimension 6 effective Hamiltonian, given some fixed values of $R_{D^{(*)}}$. We apply our method to find the maximum allowed values of $F^L_{D^\ast}$ and $R_{J/ψ}$, two observables which have both come out higher than their Standard Model predictions in recent measurements by the Belle and LHCb Collaborations. While the measurements still have large error bars, they add to the existing $R_{D^{(*)}}$ anomaly, and it is worthwhile to consider new physics explanations. It has been shown that none of the existing, minimal models in the literature can explain the observed values of $F^L_{D^\ast}$ and $R_{J/ψ}$. Using our method, we will generalize beyond the minimal models and show that there is no combination of dimension 6 Wilson operators that can come within 1σ of the observed $R_{J/ψ}$ value. By contrast, we will show that the observed value of $F^L_{D\ast}$ can be achieved, but only with sizable contributions from tensor and mixed-chirality vector Wilson coefficients.},

doi = {10.1103/PhysRevD.100.115013},

journal = {Physical Review D},

number = 11,

volume = 100,

place = {United States},

year = {2019},

month = {12}

}

https://doi.org/10.1103/PhysRevD.100.115013

*Citation information provided by*

Web of Science

Web of Science

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