Rescale subleading bvll parameters

[peterstangl]

This pull request simply rescales the hadronic parameters of the subleading hadronic effects in $B\to K^*\ell\ell$. This is just a change of convention without affecting the predictions in flavio.

Expressing the helicity amplitude as

$$H_V^{\lambda} \propto C_9 \tilde V_{L,\lambda} + C_9^\prime \tilde V_{R, \lambda} + \frac{2 m_b m_B}{q^2} \Big( C_7 \tilde T_{L,\lambda} + C_7^\prime \tilde T_{R,\lambda} \Big) - \frac{m_B^2}{q^2} 16\pi^2 h_\lambda(q^2)$$

where $h_\lambda(q^2)$ encode any non-local effects, the subleading effects in the new convention correspond to the shifts

$$\Delta h_0(q^2) = - \frac{1}{16\pi^2} \left( a_0 + b_0 \frac{q^2}{m_B^2} + \dots \right) \tilde T_{L , 0} ~,$$ $$\Delta h_-(q^2) = - \frac{1}{16\pi^2} \left( a_- + b_- \frac{q^2}{m_B^2} + \dots \right) \tilde T_{L , -} ~,$$ $$\Delta h_+(q^2) = - \frac{1}{16\pi^2} \left( a_+ + b_+ \frac{q^2}{m_B^2} + \dots \right) \tilde T_{R , +} ~,$$

with the parameters $a_\lambda$ and $b_\lambda$ defined in flavio. Compared to the previous convention, the new one defines

$$ a_\lambda^\texttt{new} = \frac{2m_b}{m_B} a_\lambda^\texttt{v2.6.2} \simeq 1.6a_\lambda^\texttt{v2.6.2},\quad b_\lambda^\texttt{new} = \frac{2m_b m_B}{\text{GeV}^2} ~ b_\lambda^\texttt{v2.6.2} \simeq 43b_\lambda^\texttt{v2.6.2}~.$$

[Copilot]

Pull request overview

Rescales the nuisance parameters used to model subleading non-factorizable hadronic effects in (B\to K^*\ell\ell) / (B_s\to\phi\ell\ell) at low (q^2), implementing a new convention intended to leave physical predictions unchanged when using the default priors.

Changes:

• Update the low-(q^2) (\Delta C_7^{(\prime)}) polynomial parameterization to use (q^2/m_B^2) and an overall factor (m_B/(2m_b)).
• Rescale the correlated prior widths in parameters_correlated.yml accordingly for the affected (\Delta C_7^{(\prime)}) parameters.
• Minor whitespace cleanup in a YAML comment.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
flavio/physics/bdecays/bvll/subleading.py	Applies the new normalization for the (\Delta C_7^{(\prime)}) polynomial used for subleading low-(q^2) effects.
flavio/data/parameters_correlated.yml	Updates correlated prior widths for the affected nuisance parameters to match the new convention.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.

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