2026/07/29 by Shuai Zhao
Physics and Astronomy · #hep-ph #hep-ex
23 pages, 5 figures, 1 table
arxiv created 2026/07/29 · arxiv updated 2026/07/31
We introduce a B-decay tagged energy correlator (BTEC) to resolve the angular structure of energy flow in inclusive B decays in the endpoint region, focusing on the direct-photon contribution to B→ Xsγ. At leading power and at the natural collinear angular scale τ∼ s∼ QΛ\rm QCD, we derive a factorization relation involving the standard hard coefficient and B-meson shape function together with a new measured quark jet function; no new leading-power nonperturbative function is introduced. We calculate the measured jet function at one-loop accuracy and verify that its angular integral reproduces the standard inclusive quark jet function. For the central Bosch--Lange--Neubert--Paz parameter set, an illustrative benchmark gives 3 - 16% migration outside the fixed angular cuts τc=2 - 4~\rm GeV2. With an independently constrained shape function, the angular cumulatives provide a closure test of leading-power endpoint factorization and are sensitive to direct-O7 power corrections and resolved-photon effects. The BTEC thereby adds information on the angular structure of the inclusive recoil jet beyond the ordinary photon spectrum and may improve signal--background discrimination when their energy-flow profiles differ.