English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We calculate the set of O(\alpha_s) corrections to the double differentialdecay width d\Gamma_{77}/(ds_1 \, ds_2) for the process \bar{B} \to X_s \gamma\gamma originating from diagrams involving the electromagnetic dipole operatorO_7. The kinematical variables s_1 and s_2 are defined as s_i=(p_b -q_i)^2/m_b^2, where p_b, q_1, q_2 are the momenta of b-quark and two photons.While the (renormalized) virtual corrections are worked out exactly for acertain range of s_1 and s_2, we retain in the gluon bremsstrahlung processonly the leading power w.r.t. the (normalized) hadronic masss_3=(p_b-q_1-q_2)^2/m_b^2 in the underlying triple differential decay widthd\Gamma_{77}/(ds_1 ds_2 ds_3). The double differential decay width, based onthis approximation, is free of infrared- and collinear singularities whencombining virtual- and bremsstrahlung corrections. The corresponding resultsare obtained analytically. When retaining all powers in s_3, the sum ofvirtual- and bremstrahlung corrections contains uncanceled 1/\epsilonsingularities (which are due to collinear photon emission from the s-quark) andother concepts, which go beyond perturbation theory, like parton fragmentationfunctions of a quark or a gluon into a photon, are needed which is beyond thescope of our paper.

The \bar{B} \to X_s \gamma \gamma decay: NLL QCD contribution of the Electromagnetic Dipole operator O_7