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In Pursuit of New Physics with B_s Decays

Isard Dunietz·Robert Fleischer·Ulrich Nierste
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Abstract

The presence of a sizeable CP-violating phase in B_s^0-B_s^0-bar mixing would be an unambiguous signal of physics beyond the Standard Model. We analyse various possibilities to detect such a new phase considering both tagged and untagged decays. The effects of a sizeable width difference Delta Gamma between the B_s mass eigenstates, on which the untagged analyses rely, are included in all formulae. A novel method to find this phase from simple measurements of lifetimes and branching ratios in untagged decays is proposed. This method does not involve two-exponential fits, which require much larger statistics. For the tagged decays, an outstanding role is played by the observables of the time-dependent angular distribution of the B_s -> J/psi [-> l^+ l^-] ϕ[-> K^+K^-] decay products. We list the formulae needed for the angular analysis in the presence of both a new CP-violating phase and a sizeable Delta Gamma, and propose methods to remove a remaining discrete ambiguity in the new phase. This phase can therefore be determined in an unambiguous way.

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Isard Dunietz, Robert Fleischer, Ulrich Nierste. 2001-03-06. In Pursuit of New Physics with B_s Decays. https://doi.org/10.1103/physrevd.63.114015

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