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LHCb Meets Theory: X(3872) Line Shape
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Europe/Zurich
6/R-012 - conference room (CERN)
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Description
In 2020 LHCb devoted a few papers to the mass, width & lineshape of the X(3872) state [1,2]. In these papers we performed the measurement of the mass and width of X(3872) state using Breit-Wigner models, and also performed the first fit beyond the naive Breit-Wigner model, using Flatte-like lineshape. It allowed us to make the first estimate for the pole position, scattering length, effective-range and compositeness. These results were heavily discussed, and many improvements have been proposed
Four years after these results, within the LHCb collaboration, we are planning to launch a new analysis of the X(3872) lineshape. With a larger dataset and combining inclusive b-> X(3872)+X and exclusive B+ -> X(3872)K+ decays, we expect better sensitivity to the X(3872) lineshape. In addition, we have accumulated more experience and should now have a better understanding of the data and background. Together with more advanced analysis techniques, we expect better sensitivity and further reduction of uncertainties, specifically the systematic uncertainty.
In view of this analysis, we’d like to have an extended discussion with the theory community on the theory models & parameterization that need to be tested. In this new analysis, if practical, we wish to test several models. To be as inclusive as possible, we’d like to set up such a discussion in the form of mini-workshop from our regular series “LHCb meets theory”. We’d like to have a set of presentations on the different theory-models from their authors. Most useful, we want to get useful feedback with suggestions from the theory community on the planned analysis. We’d like to discuss all the important details, e.g.:
- what constrains are important / one can use on the X(3872) lineshape (branching ratios, unobservable X decay channels)?
- Can results from Ref [3] be used directly, or some reanalysis/refit is needed?
- how to properly account for the finite width of the D* meson in the pole-search procedure? Your input is welcome.
[1] Phys.Rev.D 102 (2020) 9, 092005; arXiv:2005.13419
[2] JHEP 08 (2020) 123; arXiv:2005.13422
[3] Phys.Rev.D 108 (2023) 1, L011103; arXiv:2204.12497
