Abstract
We study the decay B¯→Xsγ in Randall–Sundrum models with an IR-localised bulk Higgs. The two models under consideration are a minimal model and a model with a custodial protection mechanism. We include the effects of tree- and one-loop diagrams involving 5D gluon and Higgs exchanges as well as QCD corrections arising from the evolution from the Kaluza–Klein scale to the typical scale of the decay. We find the RS corrections to the branching fraction can be sizeable for large Yukawas and moderate KK scales T; for small Yukawas the RS contribution is small enough to be invisible in current experimental data.
Highlights
One of the best studied processes in flavour physics is the inclusive radiative B → Xsγ decay
Since we focus on QCD effects, we do not investigate the phenomenologically interesting decay B → K∗ + −; it receives tree-level contributions from four-fermion operators with both quark and lepton fields, which cannot be generated by gluon exchanges
For diagrams where a Higgs is emitted from an external leg and not from the loop, one further has to distinguish two different contributions: those where the external quark propagator propagates KK modes and so-called off-shell terms that arise if the external propagator is a mass-less zero-mode, but the 1/p2 pole in the propagator is cancelled by powers of p in the numerator, see [31] for a detailed discussion
Summary
One of the best studied processes in flavour physics is the inclusive radiative B → Xsγ decay. Mass and CKM hierarchies can be related to the strength of the Planck or IR brane localisation of the corresponding KK zero-mode wave functions [22] This intimate relationship of geometry and flavour makes the study of flavour physics observables all the more intriguing. Since we focus on QCD effects, we do not investigate the phenomenologically interesting decay B → K∗ + −; it receives tree-level contributions from four-fermion operators with both quark and lepton fields, which cannot be generated by gluon exchanges.
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