SM prediction for `<dBR/dq2>(Bs->phimumu)`

[rishabh-raturi]

Dear experts,

I'm working on the Bs to phi mu mu analysis in the BPH group of the CMS experiment. I have included the SM predictions using flavio and obtained the attached plot. I would like to verify whether the values I obtained are correct. Below is the code snippet I used:

q2_vals = []
    dBRdq2_vals = []
    dBRdq2_err = []

    q2_min_start = 1.1
    q2_max_end = 19.0
    n_bins = 60
    bin_width = (q2_max_end - q2_min_start) / n_bins

    for i in range(n_bins):
        q2_min = q2_min_start + i * bin_width
        q2_max = q2_min_start + (i+1) * bin_width
        mid = (q2_min + q2_max) / 2

        # Exclude J/psi and psi(2S) regions
        if ( (q2_min < 11.0 and q2_max > 8.0) or (q2_min < 12.5 and q2_max > 11.0) ):
            continue

        dBRdq2 = fl.sm_prediction('<dBR/dq2>(Bs->phimumu)', q2min=q2_min, q2max=q2_max)
        dBRdq2_sigma = fl.sm_uncertainty('<dBR/dq2>(Bs->phimumu)', q2min=q2_min, q2max=q2_max)
        q2_vals.append(mid)
        dBRdq2_vals.append(dBRdq2*1e8)
        dBRdq2_err.append(dBRdq2_sigma * 1e8)

While running, I received the following warnings:

The QCDF corrections should not be trusted for q2 above 6 GeV^2
  warnings.warn("The QCDF corrections should not be trusted for q2 above 6 GeV^2")
UserWarning: The predictions in the region of narrow charmonium resonances are not meaningful
  warnings.warn("The predictions in the region of narrow charmonium resonances are not meaningful")

• Does the code above correctly use flavio to obtain the SM differential branching fraction predictions for Bs to phi mu mu?
• Are the predictions in the q2 region 6.0-8.0 GeV2 and 11.0-12.5 GeV2 indeed not reliable as shown in the warnings?

SummaryPlot_flavio.pdf

Thank you for your time and consideration.

Best regards,
Rishabh

[DavidMStraub]

Hi,

Does the code above correctly use flavio to obtain the SM differential branching fraction predictions for Bs to phi mu mu?

As far as I can tell, yes.

Are the predictions in the q2 region 6.0-8.0 GeV2 and 11.0-12.5 GeV2 indeed not reliable as shown in the warnings?

The underlying theory employs a limit that is not expected to be valid in these regions. In practice, it means the error bars you show may be underestimated in these regions because they do not account for the model uncertainty.

For an actual estimate of the uncertainties, you can check e.g. https://arxiv.org/pdf/2206.03797.

[peterstangl]

Hi @rishabh-raturi,
the situation here is quite similar to the $B\to K$ and $B\to K^*$ decays. Your questions should be addressed in the following two GitHub issues:

• Questions regarding dBR/dq^2 distribution for B+ ->μμΚ+ decay #198
• sm predictions from flavio for CMS B0→K*mumu angular analysis #235

[rishabh-raturi]

Hello @DavidMStraub , @peterstangl,

Apologies for the late reply. Thank you for the feedback and for pointing out the related issues.

Best regards,
Rishabh