dB/dq^2 predictions for b->sμμ decays

[gmelachr]

Dear authors,

my name is Georgios Melachroinos. At the CMS experiment, we are working on an analysis to measure the differential branching ratios of b->sμμ decays. At the moment, our results are blinded and under review and therefore have been completely removed from the plots. We have superimposed the predictions obtained with Flavio with those from EOS, HEPfit, and SuperIso, as well as available results from LHCb and CMS. While in most cases there is good agreement between EOS, Flavio, and SuperIso, we observe some differences both for the central values and the uncertainties. Therefore, we would like to present to you the predictions we derived using the latest flavio version. Please find attached six plots.

Despite the fact that we use the latest available flavio version, could you please verify that the Flavio predictions are derived using the latest and most precise B->X and Λb0->Λ0 form factors?

Thank you in advance for your help and suggestions.
If it's more convenient, we are of course available for discussion.

Best regards,
Georgios

[peterstangl]

Hi @gmelachr,

I will have more time to reply in more detail next week. Just a few comments for the moment:

• flavio settings and form factor implementations can be easily adjusted and updated by the user. So in this sense there is no unique "flavio prediction", but it depends on the settings. If a prediction is used in a publication, it would be useful to explicitly mention which settings (form factors and input parameters) have been used, even if flavio's default settings are used. In any case, flavio allows you to always adjust the settings and use different form factors if needed.

• In $b\to s\ell\ell$ processes, the theory predictions in flavio should be restricted as follows:

  • At low $q^2$, the predictions are based on the QCD factorization framework that should only be used below $q^2=6~\text{GeV}^2$.
  • At high $q^2$, predictions should not be used for narrow bins.

  See sm predictions from flavio for CMS B0→K*mumu angular analysis #287 (comment) and Questions regarding dBR/dq^2 distribution for B+ ->μμΚ+ decay #198 (comment) for more details.

[DavidMStraub]

Hi @gmelachr, adding to what Peter already wrote: one option would be to mention both the software and the form factor source in the plot label as is sometimes done by LHCb, see e.g. in this plot taken from arXiv:2605.18084

[gmelachr]

Dear David & Peter,

thank you both for the answers.

For these plots, the default Flavio settings are used. Following your comments, we will explicitly state the software version and the settings used, together with the corresponding references available in the Flavio GitHub repository.

We will also follow your recommendations regarding the validity range of the theory predictions and will update the plots to remove the predictions in the region 6<q^2<8 GeV^2. Regarding the high-q^2 region, while integrated predictions could still be considered for sufficiently large bins, we will update the plots not to show theory predictions in this region, in order to remain consistent with recent LHCb publications as well as with the following CMS results:

https://cds.cern.ch/record/2957485/files/BPH-23-003-pas.pdf and https://www.sciencedirect.com/science/article/pii/S0370269325001662?via%3Dihub.

We look forward to your more detailed comments next week.

Best regards,
Georgios