Predictions forB→Kγγ decays

Abstract

We present a phenomenological study of the rare double radiative decay B → Kγγ in the Standard Model (SM) and beyond. Using the operator product expansion (OPE) technique, we estimate the short-distance (SD) contribution to the decay amplitude in a region of the phase space which is around the point where all decay products have energy ∼ m b /3 in the rest frame of the B-meson. At lowest order in 1/Q, where Q is of order m b , the B → Kγγ matrix element is then expressed in terms of the usual B → K form factors known from semileptonic rare decays. The integrated SD branching ratio in the SM in the OPE region turns out to be ∆B(B → Kγγ) OP E SM ≃ 1 × 10 −9 . We work out the di-photon invariant mass distribution with and without the resonant background through B → K{η c , χ c0 } → Kγγ. In the SM, the resonance contribution is dominant in the region of phase space where the OPE is valid. The present experimental upper limit on B s → τ + τ − decays, which constrains the scalar/pseudoscalar Four-Fermi operators with τ + τ − , leaves considerable room for new physics in the one-particle-irreducible contribution to B → Kγγ decays. In this case, we find that the SD B → Kγγ branching ratio can be enhanced by one order of magnitude with respect to its SM value and the SD contribution can lie outside of the resonance peaks. *

Probing photon helicity in radiative B decays via charmonium resonance interference

“…To model the amplitudes M ηc,χ c0 for the B decays to η c (γγ)K and χ c0 (γγ)K we use a general Breit-Wigner Ansatz along the lines described in Ref. [5]. Thus we neglect variations in the amplitudes beyond the Breit-Wigner form.…”

“…Consequently, recent efforts have focused on finding additional observable degrees of freedom related to b → sγ, such as CP asymmetries or the helicity of the emitted photon, in order to subject the SM to ever more stringent tests. In a similar vein, the decay B → X s γγ and its exclusive manifestation B → Kγγ have been studied in this context [3][4][5]. In analogy to b → sl + l − , the diphoton invariant mass spectrum and forward-backward asymmetries have been suggested as probes for new physics beyond the SM [6].…”

(O8,O8) contribution toAsatrian1, Greub2, Kokulu3 2016Phys. Rev. D

“…Also the corresponding exclusive modes, B s → γγ and B → Kγγ, have been examined before, both in the SM [9,[26][27][28][29][30][31][32][33][34] and in its extensions [25,30,31,[35][36][37][38][39][40][41][42][43]. We should add that the long-distance resonant effects were also discussed in the literature (see e.g.…”

“…[9] and the references therein). Finally, the effects of photon emission from the spectator quark in the B-meson were discussed in [26,30,44].…”

Phenomenological study of the double radiative decay $B\rightarrow K \gamma \gamma$

“…At the quark level it receives one-particle-reducible (1PR) contributions from the b → sγ transition plus an additional photon and a one-particle-irreducible (1PI) term from a fermion loop with the two photons emitted from that loop (see Fig 1). At the lowest order, the corresponding amplitude can be written as [1,2]…”